Showing papers in "Human Genetics in 2017"

The Human Gene Mutation Database: towards a comprehensive repository of inherited mutation data for medical research, genetic diagnosis and next-generation sequencing studies

Abstract: The Human Gene Mutation Database (HGMD®) constitutes a comprehensive collection of published germline mutations in nuclear genes that underlie, or are closely associated with human inherited disease. At the time of writing (March 2017), the database contained in excess of 203,000 different gene lesions identified in over 8000 genes manually curated from over 2600 journals. With new mutation entries currently accumulating at a rate exceeding 17,000 per annum, HGMD represents de facto the central unified gene/disease-oriented repository of heritable mutations causing human genetic disease used worldwide by researchers, clinicians, diagnostic laboratories and genetic counsellors, and is an essential tool for the annotation of next-generation sequencing data. The public version of HGMD (http://www.hgmd.org) is freely available to registered users from academic institutions and non-profit organisations whilst the subscription version (HGMD Professional) is available to academic, clinical and commercial users under license via QIAGEN Inc.

Deep intronic mutations and human disease.

Abstract: Next-generation sequencing has revolutionized clinical diagnostic testing. Yet, for a substantial proportion of patients, sequence information restricted to exons and exon-intron boundaries fails to identify the genetic cause of the disease. Here we review evidence from mRNA analysis and entire genomic sequencing indicating that pathogenic mutations can occur deep within the introns of over 75 disease-associated genes. Deleterious DNA variants located more than 100 base pairs away from exon-intron junctions most commonly lead to pseudo-exon inclusion due to activation of non-canonical splice sites or changes in splicing regulatory elements. Additionally, deep intronic mutations can disrupt transcription regulatory motifs and non-coding RNA genes. This review aims to highlight the importance of studying variation in deep intronic sequence as a cause of monogenic disorders as well as hereditary cancer syndromes.

Forensic use of Y-chromosome DNA: a general overview.

Abstract: The male-specific part of the human Y chromosome is widely used in forensic DNA analysis, particularly in cases where standard autosomal DNA profiling is not informative. A Y-chromosomal gene fragment is applied for inferring the biological sex of a crime scene trace donor. Haplotypes composed of Y-chromosomal short tandem repeat polymorphisms (Y-STRs) are used to characterise paternal lineages of unknown male trace donors, especially suitable when males and females have contributed to the same trace, such as in sexual assault cases. Y-STR haplotyping applied in crime scene investigation can (i) exclude male suspects from involvement in crime, (ii) identify the paternal lineage of male perpetrators, (iii) highlight multiple male contributors to a trace, and (iv) provide investigative leads for finding unknown male perpetrators. Y-STR haplotype analysis is employed in paternity disputes of male offspring and other types of paternal kinship testing, including historical cases, as well as in special cases of missing person and disaster victim identification involving men. Y-chromosome polymorphisms are applied for inferring the paternal bio-geographic ancestry of unknown trace donors or missing persons, in cases where autosomal DNA profiling is uninformative. In this overview, all different forensic applications of Y-chromosome DNA are described. To illustrate the necessity of forensic Y-chromosome analysis, the investigation of a prominent murder case is described, which initiated two changes in national forensic DNA legislation both covering Y-chromosome use, and was finally solved via an innovative Y-STR dragnet involving thousands of volunteers after 14 years. Finally, expectations for the future of forensic Y-chromosome DNA analysis are discussed.

Intron retention as a component of regulated gene expression programs

Abstract: Intron retention has long been an exemplar of regulated splicing with case studies of individual events serving as models that provided key mechanistic insights into the process of splicing control. In organisms such as plants and budding yeast, intron retention is well understood as a major mechanism of gene expression regulation. In contrast, in mammalian systems, the extent and functional significance of intron retention have, until recently, remained greatly underappreciated. Technical challenges to the global detection and quantitation of transcripts with retained introns have often led to intron retention being overlooked or dismissed as "noise". Now, however, with the wealth of information available from high-throughput deep sequencing, combined with focused computational and statistical analyses, we are able to distinguish clear intron retention patterns in various physiological and pathological contexts. Several recent studies have demonstrated intron retention as a central component of gene expression programs during normal development as well as in response to stress and disease. Furthermore, these studies revealed various ways in which intron retention regulates protein isoform production, RNA stability and translation efficiency, and rapid induction of expression via post-transcriptional splicing of retained introns. In this review, we highlight critical findings from these transcriptomic studies and discuss commonalties in the patterns prevalent in intron retention networks at the functional and regulatory levels.

The landscape of genetic diseases in Saudi Arabia based on the first 1000 diagnostic panels and exomes.

Abstract: In this study, we report the experience of the only reference clinical next-generation sequencing lab in Saudi Arabia with the first 1000 families who span a wide-range of suspected Mendelian phenotypes. A total of 1019 tests were performed in the period of March 2016-December 2016 comprising 972 solo (index only), 14 duo (parents or affected siblings only), and 33 trio (index and parents). Multigene panels accounted for 672 tests, while whole exome sequencing (WES) represented the remaining 347 tests. Pathogenic or likely pathogenic variants that explain the clinical indications were identified in 34% (27% in panels and 43% in exomes), spanning 279 genes and including 165 novel variants. While recessive mutations dominated the landscape of solved cases (71% of mutations, and 97% of which are homozygous), a substantial minority (27%) were solved on the basis of dominant mutations. The highly consanguineous nature of the study population also facilitated homozygosity for many private mutations (only 32.5% of the recessive mutations are founder), as well as the first instances of recessive inheritance of previously assumed strictly dominant disorders (involving ITPR1, VAMP1, MCTP2, and TBP). Surprisingly, however, dual molecular diagnosis was only observed in 1.5% of cases. Finally, we have encountered candidate variants in 75 genes (ABHD6, ACY3, ADGRB2, ADGRG7, AGTPBP1, AHNAK2, AKAP6, ASB3, ATXN1L, C17orf62, CABP1, CCDC186, CCP110, CLSTN2, CNTN3, CNTN5, CTNNA2, CWC22, DMAP1, DMKN, DMXL1, DSCAM, DVL2, ECI1, EP400, EPB41L5, FBXL22, GAP43, GEMIN7, GIT1, GRIK4, GRSF1, GTRP1, HID1, IFNL1, KCNC4, LRRC52, MAP7D3, MCTP2, MED26, MPP7, MRPS35, MTDH, MTMR9, NECAP2, NPAT, NRAP, PAX7, PCNX, PLCH2, PLEKHF1, PTPN12, QKI, RILPL2, RIMKLA, RIMS2, RNF213, ROBO1, SEC16A, SIAH1, SIRT2, SLAIN2, SLC22A20, SMDT1, SRRT, SSTR1, ST20, SYT9, TSPAN6, UBR4, VAMP4, VPS36, WDR59, WDYHV1, and WHSC1) not previously linked to human phenotypes and these are presented to accelerate post-publication matchmaking. Two of these genes were independently mutated in more than one family with similar phenotypes, which substantiates their link to human disease (AKAP6 in intellectual disability and UBR4 in early dementia). If the novel candidate disease genes in this cohort are independently confirmed, the yield of WES will have increased to 83%, which suggests that most "negative" clinical exome tests are unsolved due to interpretation rather than technical limitations.

Analysis of implantation and ongoing pregnancy rates following the transfer of mosaic diploid–aneuploid blastocysts

Abstract: Preimplantation genetic testing for aneuploidy (PGT-A) is widely used in IVF and aims to improve outcomes by avoiding aneuploid embryo transfers. Chromosomal mosaicism is extremely common in early development and could affect the efficacy of PGT-A by causing incorrect embryo classification. Recent innovations have allowed accurate mosaicism detection in trophectoderm samples taken from blastocysts. However, there is little data concerning the impact of mosaicism on viability, and the optimal clinical pathway for such embryos is unclear. This study provides new information concerning the extent to which mosaic preimplantation embryos are capable of producing pregnancies and births. Archived trophectoderm biopsy specimens from transferred blastocysts were analyzed using next generation sequencing (NGS). Unlike other PGT-A methods, NGS accurately detects mosaicism in embryo biopsies. 44 mosaic blastocysts were identified. Their clinical outcomes were compared to 51 euploid blastocysts, derived from a well-matched, contemporary control group. Mosaic embryos were associated with outcomes that were significantly poorer than those of the control group: implantation 30.1 versus 55.8% (P = 0.038); miscarriage rate 55.6 versus 17.2% (P = 0.036); and ongoing pregnancy 15.4 versus 46.2% (P = 0.003). 61% of the mosaic errors affected whole chromosomes and 39% were segmental aneuploidies. Embryo viability is compromised by the presence of aneuploid cells. However, a minority of affected embryos can produce successful pregnancies. Hence, such embryos should not necessarily be excluded, but given a lower priority for transfer than those that are fully euploid. It is recommended that pregnancies established after mosaic embryo transfers be subjected to prenatal testing, with appropriate patient counselling.

Emerging genotype–phenotype relationships in patients with large NF1 deletions

Abstract: The most frequent recurring mutations in neurofibromatosis type 1 (NF1) are large deletions encompassing the NF1 gene and its flanking regions (NF1 microdeletions). The majority of these deletions encompass 1.4-Mb and are associated with the loss of 14 protein-coding genes and four microRNA genes. Patients with germline type-1 NF1 microdeletions frequently exhibit dysmorphic facial features, overgrowth/tall-for-age stature, significant delay in cognitive development, large hands and feet, hyperflexibility of joints and muscular hypotonia. Such patients also display significantly more cardiovascular anomalies as compared with patients without large deletions and often exhibit increased numbers of subcutaneous, plexiform and spinal neurofibromas as compared with the general NF1 population. Further, an extremely high burden of internal neurofibromas, characterised by >3000 ml tumour volume, is encountered significantly, more frequently, in non-mosaic NF1 microdeletion patients than in NF1 patients lacking such deletions. NF1 microdeletion patients also have an increased risk of malignant peripheral nerve sheath tumours (MPNSTs); their lifetime MPNST risk is 16–26%, rather higher than that of NF1 patients with intragenic NF1 mutations (8–13%). NF1 microdeletion patients, therefore, represent a high-risk group for the development of MPNSTs, tumours which are very aggressive and difficult to treat. Co-deletion of the SUZ12 gene in addition to NF1 further increases the MPNST risk in NF1 microdeletion patients. Here, we summarise current knowledge about genotype–phenotype relationships in NF1 microdeletion patients and discuss the potential role of the genes located within the NF1 microdeletion interval whose haploinsufficiency may contribute to the more severe clinical phenotype

Genetic mutations in RNA-binding proteins and their roles in ALS

Abstract: Mutations in genes that encode RNA-binding proteins (RBPs) have emerged as critical determinants of neurological diseases, especially motor neuron disorders such as amyotrophic lateral sclerosis (ALS). RBPs are involved in all aspects of RNA processing, controlling the life cycle of RNAs from synthesis to degradation. Hallmark features of RBPs in neuron dysfunction include misregulation of RNA processing, mislocalization of RBPs to the cytoplasm, and abnormal aggregation of RBPs. Much progress has been made in understanding how ALS-associated mutations in RBPs drive pathogenesis. Here, we focus on several key RBPs involved in ALS—TDP-43, HNRNP A2/B1, HNRNP A1, FUS, EWSR1, and TAF15—and review our current understanding of how mutations in these proteins cause disease.

Genome-wide meta-analyses of nonsyndromic orofacial clefts identify novel associations between FOXE1 and all orofacial clefts, and TP63 and cleft lip with or without cleft palate

Abstract: Nonsyndromic orofacial clefts (OFCs) are a heterogeneous group of common craniofacial birth defects with complex etiologies that include genetic and environmental risk factors. OFCs are commonly categorized as cleft lip with or without cleft palate (CL/P) and cleft palate alone (CP), which have historically been analyzed as distinct entities. Genes for both CL/P and CP have been identified via multiple genome-wide linkage and association studies (GWAS); however, altogether, known variants account for a minority of the estimated heritability in risk to these craniofacial birth defects. We performed genome-wide meta-analyses of CL/P, CP, and all OFCs across two large, multiethnic studies. We then performed population-specific meta-analyses in sub-samples of Asian and European ancestry. In addition to observing associations with known variants, we identified a novel genome-wide significant association between SNPs located in an intronic TP63 enhancer and CL/P (p = 1.16 × 10−8). Several novel loci with compelling candidate genes approached genome-wide significance on 4q21.1 (SHROOM3), 12q13.13 (KRT18), and 8p21 (NRG1). In the analysis of all OFCs combined, SNPs near FOXE1 reached genome-wide significance (p = 1.33 × 10−9). Our results support the highly heterogeneous nature of OFCs and illustrate the utility of meta-analysis for discovering new genetic risk factors.

Expanding the genetic heterogeneity of intellectual disability.

Abstract: Intellectual disability (ID) is a common morbid condition with a wide range of etiologies. The list of monogenic forms of ID has increased rapidly in recent years thanks to the implementation of genomic sequencing techniques. In this study, we describe the phenotypic and genetic findings of 68 families (105 patients) all with novel ID-related variants. In addition to established ID genes, including ones for which we describe unusual mutational mechanism, some of these variants represent the first confirmatory disease-gene links following previous reports (TRAK1, GTF3C3, SPTBN4 and NKX6-2), some of which were based on single families. Furthermore, we describe novel variants in 14 genes that we propose as novel candidates (ANKHD1, ASTN2, ATP13A1, FMO4, MADD, MFSD11, NCKAP1, NFASC, PCDHGA10, PPP1R21, SLC12A2, SLK, STK32C and ZFAT). We highlight MADD and PCDHGA10 as particularly compelling candidates in which we identified biallelic likely deleterious variants in two independent ID families each. We also highlight NCKAP1 as another compelling candidate in a large family with autosomal dominant mild intellectual disability that fully segregates with a heterozygous truncating variant. The candidacy of NCKAP1 is further supported by its biological function, and our demonstration of relevant expression in human brain. Our study expands the locus and allelic heterogeneity of ID and demonstrates the power of positional mapping to reveal unusual mutational mechanisms.

Spermatogenic failure and the Y chromosome

Abstract: The Y chromosome harbors a number of genes essential for testis development and function. Its highly repetitive structure predisposes this chromosome to deletion/duplication events and is responsible for Y-linked copy-number variations (CNVs) with clinical relevance. The AZF deletions remove genes with predicted spermatogenic function en block and are the most frequent known molecular causes of impaired spermatogenesis (5–10% of azoospermic and 2–5% of severe oligozoospermic men). Testing for this deletion has both diagnostic and prognostic value for testicular sperm retrieval in azoospermic men. The most dynamic region on the Yq is the AZFc region, presenting numerous NAHR hotspots leading to partial losses or gains of the AZFc genes. The gr/gr deletion (a partial AZFc deletion) negatively affects spermatogenic efficiency and it is a validated, population-dependent risk factor for oligozoospermia. In certain populations, the Y background may play a role in the phenotypic expression of partial AZFc rearrangements and similarly it may affect the predisposition to specific deletions/duplication events. Also, the Yp contains a gene array, TSPY1, with potential effect on germ cell proliferation. Despite intensive investigations during the last 20 years on the role of this sex chromosome in spermatogenesis, a number of clinical and basic questions remain to be answered. This review is aimed at providing an overview of the role of Y chromosome-linked genes, CNVs, and Y background in spermatogenesis.

Global skin colour prediction from DNA.

Abstract: Human skin colour is highly heritable and externally visible with relevance in medical, forensic, and anthropological genetics. Although eye and hair colour can already be predicted with high accuracies from small sets of carefully selected DNA markers, knowledge about the genetic predictability of skin colour is limited. Here, we investigate the skin colour predictive value of 77 single-nucleotide polymorphisms (SNPs) from 37 genetic loci previously associated with human pigmentation using 2025 individuals from 31 global populations. We identified a minimal set of 36 highly informative skin colour predictive SNPs and developed a statistical prediction model capable of skin colour prediction on a global scale. Average cross-validated prediction accuracies expressed as area under the receiver-operating characteristic curve (AUC) ± standard deviation were 0.97 ± 0.02 for Light, 0.83 ± 0.11 for Dark, and 0.96 ± 0.03 for Dark-Black. When using a 5-category, this resulted in 0.74 ± 0.05 for Very Pale, 0.72 ± 0.03 for Pale, 0.73 ± 0.03 for Intermediate, 0.87±0.1 for Dark, and 0.97 ± 0.03 for Dark-Black. A comparative analysis in 194 independent samples from 17 populations demonstrated that our model outperformed a previously proposed 10-SNP-classifier approach with AUCs rising from 0.79 to 0.82 for White, comparable at the intermediate level of 0.63 and 0.62, respectively, and a large increase from 0.64 to 0.92 for Black. Overall, this study demonstrates that the chosen DNA markers and prediction model, particularly the 5-category level; allow skin colour predictions within and between continental regions for the first time, which will serve as a valuable resource for future applications in forensic and anthropologic genetics.

ADAR RNA editing in human disease; more to it than meets the I.

Abstract: We review the structures and functions of ADARs and their involvements in human diseases. ADAR1 is widely expressed, particularly in the myeloid component of the blood system, and plays a prominent role in promiscuous editing of long dsRNA. Missense mutations that change ADAR1 residues and reduce RNA editing activity cause Aicardi-Goutieres Syndrome, a childhood encephalitis and interferonopathy that mimics viral infection and resembles an extreme form of Systemic Lupus Erythmatosus (SLE). In Adar1 mouse mutant models aberrant interferon expression is prevented by eliminating interferon activation signaling from cytoplasmic dsRNA sensors, indicating that unedited cytoplasmic dsRNA drives the immune induction. On the other hand, upregulation of ADAR1 with widespread promiscuous RNA editing is a prominent feature of many cancers and particular site-specific RNA editing events are also affected. ADAR2 is most highly expressed in brain and is primarily required for site-specific editing of CNS transcripts; recent findings indicate that ADAR2 editing is regulated by neuronal excitation for synaptic scaling of glutamate receptors. ADAR2 is also linked to the circadian clock and to sleep. Mutations in ADAR2 could contribute to excitability syndromes such as epilepsy, to seizures, to diseases involving neuronal plasticity defects, such as autism and Fragile-X Syndrome, to neurodegenerations such as ALS, or to astrocytomas or glioblastomas in which reduced ADAR2 activity is required for oncogenic cell behavior. The range of human disease associated with ADAR1 mutations may extend further to include other inflammatory conditions while ADAR2 mutations may affect psychiatric conditions.

Alternative splicing: the pledge, the turn, and the prestige : The key role of alternative splicing in human biological systems.

Abstract: Alternative pre-mRNA splicing is a tightly controlled process conducted by the spliceosome, with the assistance of several regulators, resulting in the expression of different transcript isoforms from the same gene and increasing both transcriptome and proteome complexity. The differences between alternative isoforms may be subtle but enough to change the function or localization of the translated proteins. A fine control of the isoform balance is, therefore, needed throughout developmental stages and adult tissues or physiological conditions and it does not come as a surprise that several diseases are caused by its deregulation. In this review, we aim to bring the splicing machinery on stage and raise the curtain on its mechanisms and regulation throughout several systems and tissues of the human body, from neurodevelopment to the interactions with the human microbiome. We discuss, on one hand, the essential role of alternative splicing in assuring tissue function, diversity, and swiftness of response in these systems or tissues, and on the other hand, what goes wrong when its regulatory mechanisms fail. We also focus on the possibilities that splicing modulation therapies open for the future of personalized medicine, along with the leading techniques in this field. The final act of the spliceosome, however, is yet to be fully revealed, as more knowledge is needed regarding the complex regulatory network that coordinates alternative splicing and how its dysfunction leads to disease.

The molecular pathogenesis of schwannomatosis, a paradigm for the co-involvement of multiple tumour suppressor genes in tumorigenesis

Abstract: Schwannomatosis is characterized by the predisposition to develop multiple schwannomas and, less commonly, meningiomas. Despite the clinical overlap with neurofibromatosis type 2 (NF2), schwannomatosis is not caused by germline NF2 gene mutations. Instead, germline mutations of either the SMARCB1 or LZTR1 tumour suppressor genes have been identified in 86% of familial and 40% of sporadic schwannomatosis patients. In contrast to patients with rhabdoid tumours, which are due to complete loss-of-function SMARCB1 mutations, individuals with schwannomatosis harbour predominantly hypomorphic SMARCB1 mutations which give rise to the synthesis of mutant proteins with residual function that do not cause rhabdoid tumours. Although biallelic mutations of SMARCB1 or LZTR1 have been detected in the tumours of patients with schwannomatosis, the classical two-hit model of tumorigenesis is insufficient to account for schwannoma growth, since NF2 is also frequently inactivated in these tumours. Consequently, tumorigenesis in schwannomatosis must involve the mutation of at least two different tumour suppressor genes, an occurrence frequently mediated by loss of heterozygosity of large parts of chromosome 22q harbouring not only SMARCB1 and LZTR1 but also NF2. Thus, schwannomatosis is paradigmatic for a tumour predisposition syndrome caused by the concomitant mutational inactivation of two or more tumour suppressor genes. This review provides an overview of current models of tumorigenesis and mutational patterns underlying schwannomatosis that will ultimately help to explain the complex clinical presentation of this rare disease.

Loss of chromosome Y (LOY) in blood cells is associated with increased risk for disease and mortality in aging men.

Abstract: Recent discoveries have shown that harboring cells without the Y chromosome in the peripheral blood is associated with increased risk for all-cause mortality and disease such as different forms of cancer, Alzheimer’s disease, as well as other conditions in aging men. In the entire world, the life expectancy of men is shorter compared to women, a sex difference that has been known for centuries, but the underlying mechanism(s) are not well understood. As a male-specific genetic risk factor, an increased risk for pathology and mortality associated with mosaic loss of chromosome Y (LOY) in blood cells could help to explain that men on average live shorter lives compared to women. This review primarily focuses on observed associations between LOY in blood and various diseases in aging men. Other topics covered are known risk factors for LOY, methods to detect LOY, and a discussion regarding mechanisms such as immunosurveillance, that could possibly explain how an acquired mutation in blood cells can be associated with disease processes in other organs.

CRISPR/Cas9 in zebrafish: an efficient combination for human genetic diseases modeling.

Abstract: The next-generation sequencing identifies a growing number of candidate genes associated with human genetic diseases, which inevitably requires efficient methods to validate the causal links between genotype and phenotype. Recently, zebrafish, with sufficiently high-throughput capabilities, has become a favored option to study human pathogenesis. In addition, CRISPR/Cas9-based approaches have radically reduced the efforts to introduce targeted genome engineering in various organisms. Here, we systemically review the basic considerations in the design of gene editing in zebrafish with CRISPR/Cas9, and explore the potential of the combination of these two to support efficient functional analysis of human genetic variants.

World-wide distributions of lactase persistence alleles and the complex effects of recombination and selection.

Abstract: The genetic trait of lactase persistence (LP) is associated with at least five independent functional single nucleotide variants in a regulatory region about 14 kb upstream of the lactase gene [-13910*T (rs4988235), -13907*G (rs41525747), -13915*G (rs41380347), -14009*G (rs869051967) and -14010*C (rs145946881)]. These alleles have been inferred to have spread recently and present-day frequencies have been attributed to positive selection for the ability of adult humans to digest lactose without risk of symptoms of lactose intolerance. One of the inferential approaches used to estimate the level of past selection has been to determine the extent of haplotype homozygosity (EHH) of the sequence surrounding the SNP of interest. We report here new data on the frequencies of the known LP alleles in the 'Old World' and their haplotype lineages. We examine and confirm EHH of each of the LP alleles in relation to their distinct lineages, but also show marked EHH for one of the older haplotypes that does not carry any of the five LP alleles. The region of EHH of this (B) haplotype exactly coincides with a region of suppressed recombination that is detectable in families as well as in population data, and the results show how such suppression may have exaggerated haplotype-based measures of past selection.

Novel phenotypes and loci identified through clinical genomics approaches to pediatric cataract.

Abstract: Pediatric cataract is highly heterogeneous clinically and etiologically. While mostly isolated, cataract can be part of many multisystem disorders, further complicating the diagnostic process. In this study, we applied genomic tools in the form of a multi-gene panel as well as whole-exome sequencing on unselected cohort of pediatric cataract (166 patients from 74 families). Mutations in previously reported cataract genes were identified in 58% for a total of 43 mutations, including 15 that are novel. GEMIN4 was independently mutated in families with a syndrome of cataract, global developmental delay with or without renal involvement. We also highlight a recognizable syndrome that resembles galactosemia (a fulminant infantile liver disease with cataract) caused by biallelic mutations in CYP51A1. A founder mutation in RIC1 (KIAA1432) was identified in patients with cataract, brain atrophy, microcephaly with or without cleft lip and palate. For non-syndromic pediatric cataract, we map a novel locus in a multiplex consanguineous family on 4p15.32 where exome sequencing revealed a homozygous truncating mutation in TAPT1. We report two further candidates that are biallelically inactivated each in a single cataract family: TAF1A (cataract with global developmental delay) and WDR87 (non-syndromic cataract). In addition to positional mapping data, we use iSyTE developmental lens expression and gene-network analysis to corroborate the proposed link between the novel candidate genes and cataract. Our study expands the phenotypic, allelic and locus heterogeneity of pediatric cataract. The high diagnostic yield of clinical genomics supports the adoption of this approach in this patient group.

The study of human Y chromosome variation through ancient DNA

Abstract: High throughput sequencing methods have completely transformed the study of human Y chromosome variation by offering a genome-scale view on genetic variation retrieved from ancient human remains in context of a growing number of high coverage whole Y chromosome sequence data from living populations from across the world. The ancient Y chromosome sequences are providing us the first exciting glimpses into the past variation of male-specific compartment of the genome and the opportunity to evaluate models based on previously made inferences from patterns of genetic variation in living populations. Analyses of the ancient Y chromosome sequences are challenging not only because of issues generally related to ancient DNA work, such as DNA damage-induced mutations and low content of endogenous DNA in most human remains, but also because of specific properties of the Y chromosome, such as its highly repetitive nature and high homology with the X chromosome. Shotgun sequencing of uniquely mapping regions of the Y chromosomes to sufficiently high coverage is still challenging and costly in poorly preserved samples. To increase the coverage of specific target SNPs capture-based methods have been developed and used in recent years to generate Y chromosome sequence data from hundreds of prehistoric skeletal remains. Besides the prospects of testing directly as how much genetic change in a given time period has accompanied changes in material culture the sequencing of ancient Y chromosomes allows us also to better understand the rate at which mutations accumulate and get fixed over time. This review considers genome-scale evidence on ancient Y chromosome diversity that has recently started to accumulate in geographic areas favourable to DNA preservation. More specifically the review focuses on examples of regional continuity and change of the Y chromosome haplogroups in North Eurasia and in the New World.

The Y chromosome as the most popular marker in genetic genealogy benefits interdisciplinary research

Abstract: The Y chromosome is currently by far the most popular marker in genetic genealogy that combines genetic data and family history. This popularity is based on its haploid character and its close association with the patrilineage and paternal inherited surname. Other markers have not been found (yet) to overrule this status due to the low sensitivity and precision of autosomal DNA for genetic genealogical applications, given the vagaries of recombination, and the lower capacities of mitochondrial DNA combined with an in general much lower interest in maternal lineages. The current knowledge about the Y chromosome and the availability of markers with divergent mutation rates make it possible to answer questions on relatedness levels which differ in time depth; from the individual and familial level to the surnames, clan and population level. The use of the Y chromosome in genetic genealogy has led to applications in several well-established research disciplines; namely in, e.g., family history, demography, anthropology, forensic sciences, population genetics and sex chromosome evolution. The information obtained from analysing this chromosome is not only interesting for academic scientists but also for the huge and lively community of amateur genealogists and citizen-scientists, fascinated in analysing their own genealogy or surname. This popularity, however, has also some drawbacks, mainly for privacy reasons related to the DNA donor, his close family and far-related namesakes. In this review paper we argue why Y-chromosomal analysis and its genetic genealogical applications will still perform an important role in future interdisciplinary research.

The role of RNA alternative splicing in regulating cancer metabolism

Abstract: Tumor cells alter their metabolism by a wide array of mechanisms to promote growth and proliferation. Dysregulated expression and/or somatic mutations of key components of the glycolytic pathway/TCA cycle as well as other metabolic pathways allow tumor cells to improve their ability to survive harsh conditions such as hypoxia and the presence of reactive oxygen species, as well as the ability to obtain nutrients to increase lipids, protein, and nucleic acids biogenesis. Approximately 95% of the human protein encoding genes undergo alternative splicing (AS), a regulated process of gene expression that greatly diversifies the proteome by creating multiple proteins from a single gene. In recent years, a growing body of evidence suggests that unbalanced AS, the formation of certain pro-tumorigenic isoforms and the reduction of anti-tumorigenic isoforms, is implicated in a variety of cancers. It is becoming increasingly clear that cancer-associated AS contributes to increased growth and proliferation, partially due to effects on metabolic reprogramming. Here, we summarize the known roles of AS in regulating cancer metabolism. We present evidence supporting the idea that AS, in many types of cancer, acts as a molecular switch that alters metabolism to drive tumorigenesis. We propose that the elucidation of misregulated AS and its downstream effects on cancer metabolism emphasizes the need for new therapeutic approaches aiming to modulate the splicing machinery to selectively target cancer cells.

CRISPR/Cas9-mediated somatic and germline gene correction to restore hemostasis in hemophilia B mice

Abstract: Hemophilia B (HB) is an X-linked disorder caused by defects of F9 encoded coagulation factor IX, which is an ideal model for gene therapy Most existing HB gene therapies are based on viral mediated gene supplementation, which could increase immunoreaction In this study, CRISPR/Cas9 system was used for gene correction in an F9 mutant HB mouse model in both adult mice (in vivo) and in germline cells (ex vivo) In vivo, naked Cas9-sgRNA plasmid and donor DNA were delivered to HB mice livers to recover the mutation via hydrodynamic tail vein (HTV) injection 625% of the HTV-treated mice showed a detectable gene correction (>1%) in the F9 alleles of hepatocytes, which was sufficient to remit the coagulation deficiency Ex vivo, three different forms of Cas9 were microinjected into germline cells of HB mice to investigate their efficiency and safety in gene correction Cas9 protein showed higher gene recovery rates, less embryo toxicity, and lower mosaic repair percentage, making it more suitable for germline gene therapy Our study strongly supports that CRISPR/Cas9-mediated genome editing is feasible in gene therapy of genetic disorders

Dosage effects of ZP2 and ZP3 heterozygous mutations cause human infertility

Abstract: The zona pellucida (ZP) is an extracellular matrix universally surrounding mammalian eggs, which is essential for oogenesis, fertilization, and pre-implantation embryo development. Here, we identified two novel heritable mutations of ZP2 and ZP3, both occurring in an infertile female patient with ZP-abnormal eggs. Mouse models with the same mutations were generated by CRISPR/Cas9 gene editing system, and oocytes obtained from female mice with either single heterozygous mutation showed approximately half of the normal ZP thickness compared to wild-type oocytes. Importantly, oocytes with both heterozygous mutations showed a much thinner or even missing ZP that could not avoid polyspermy fertilization, following the patient’s pedigree. Further analysis confirmed that precursor proteins produced from either mutated ZP2 or ZP3 could not anchor to oocyte membranes. From these, we conclude that ZP mutations have dosage effects which can cause female infertility in humans. Finally, this patient was treated by intracytoplasmic sperm injection (ICSI) with an improved culture system and successfully delivered a healthy baby.

Mutations in chromatin regulators functionally link Cornelia de Lange syndrome and clinically overlapping phenotypes.

Abstract: The coordinated tissue-specific regulation of gene expression is essential for the proper development of all organisms. Mutations in multiple transcriptional regulators cause a group of neurodevelopmental disorders termed "transcriptomopathies" that share core phenotypical features including growth retardation, developmental delay, intellectual disability and facial dysmorphism. Cornelia de Lange syndrome (CdLS) belongs to this class of disorders and is caused by mutations in different subunits or regulators of the cohesin complex. Herein, we report on the clinical and molecular characterization of seven patients with features overlapping with CdLS who were found to carry mutations in chromatin regulators previously associated to other neurodevelopmental disorders that are frequently considered in the differential diagnosis of CdLS. The identified mutations affect the methyltransferase-encoding genes KMT2A and SETD5 and different subunits of the SWI/SNF chromatin-remodeling complex. Complementary to this, a patient with Coffin-Siris syndrome was found to carry a missense substitution in NIPBL. Our findings indicate that mutations in a variety of chromatin-associated factors result in overlapping clinical phenotypes, underscoring the genetic heterogeneity that should be considered when assessing the clinical and molecular diagnosis of neurodevelopmental syndromes. It is clear that emerging molecular mechanisms of chromatin dysregulation are central to understanding the pathogenesis of these clinically overlapping genetic disorders.

A genome-wide study of Hardy-Weinberg equilibrium with next generation sequence data.

Abstract: Statistical tests for Hardy–Weinberg equilibrium have been an important tool for detecting genotyping errors in the past, and remain important in the quality control of next generation sequence data. In this paper, we analyze complete chromosomes of the 1000 genomes project by using exact test procedures for autosomal and X-chromosomal variants. We find that the rate of disequilibrium largely exceeds what might be expected by chance alone for all chromosomes. Observed disequilibrium is, in about 60% of the cases, due to heterozygote excess. We suggest that most excess disequilibrium can be explained by sequencing problems, and hypothesize mechanisms that can explain exceptional heterozygosities. We report higher rates of disequilibrium for the MHC region on chromosome 6, regions flanking centromeres and p-arms of acrocentric chromosomes. We also detected long-range haplotypes and areas with incidental high disequilibrium. We report disequilibrium to be related to read depth, with variants having extreme read depths being more likely to be out of equilibrium. Disequilibrium rates were found to be 11 times higher in segmental duplications and simple tandem repeat regions. The variants with significant disequilibrium are seen to be concentrated in these areas. For next generation sequence data, Hardy–Weinberg disequilibrium seems to be a major indicator for copy number variation.

Genetic and phenotypic dissection of 1q43q44 microdeletion syndrome and neurodevelopmental phenotypes associated with mutations in ZBTB18 and HNRNPU

Abstract: Subtelomeric 1q43q44 microdeletions cause a syndrome associating intellectual disability, microcephaly, seizures and anomalies of the corpus callosum. Despite several previous studies assessing genotype-phenotype correlations, the contribution of genes located in this region to the specific features of this syndrome remains uncertain. Among those, three genes, AKT3, HNRNPU and ZBTB18 are highly expressed in the brain and point mutations in these genes have been recently identified in children with neurodevelopmental phenotypes. In this study, we report the clinical and molecular data from 17 patients with 1q43q44 microdeletions, four with ZBTB18 mutations and seven with HNRNPU mutations, and review additional data from 37 previously published patients with 1q43q44 microdeletions. We compare clinical data of patients with 1q43q44 microdeletions with those of patients with point mutations in HNRNPU and ZBTB18 to assess the contribution of each gene as well as the possibility of epistasis between genes. Our study demonstrates that AKT3 haploinsufficiency is the main driver for microcephaly, whereas HNRNPU alteration mostly drives epilepsy and determines the degree of intellectual disability. ZBTB18 deletions or mutations are associated with variable corpus callosum anomalies with an incomplete penetrance. ZBTB18 may also contribute to microcephaly and HNRNPU to thin corpus callosum, but with a lower penetrance. Co-deletion of contiguous genes has additive effects. Our results confirm and refine the complex genotype-phenotype correlations existing in the 1qter microdeletion syndrome and define more precisely the neurodevelopmental phenotypes associated with genetic alterations of AKT3, ZBTB18 and HNRNPU in humans.

Gene-based analyses reveal novel genetic overlap and allelic heterogeneity across five major psychiatric disorders

Abstract: Studies using genome-wide association (GWA) single nucleotide polymorphism (SNP) level data have indicated genetic overlap across the five major disorders in the Psychiatric Genomics Consortium (PGC): attention deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), bipolar disorder (BPD), major depressive disorder (MDD), and schizophrenia (SCZ). However, such SNP-level analyses reveal little about the underlying biology and are reliant on correlated SNP effects across disorders. In contrast to SNPs, genes are more closely related to biology and gene-based tests can incorporate allelic heterogeneity. This study aimed to extend genetic overlap analysis across the five disorders from SNP level to gene level using a novel gene-based approach. Gene-based tests for association were performed using PGC GWA summary results for the five disorders in samples including 33,332 cases and 27,888 controls of European ancestry. After accounting for non-independence of gene-based test results, we determined whether the proportion of genes with association across multiple disorders was more than expected by chance. Similar to previous SNP-level analyses, we observed significant pairwise genetic overlap between ASD, BPD, MDD and SCZ. However, our approach also produced evidence for genetic overlap between ADHD and ASD, ADHD and BPD, and ADHD and MDD. Combining gene-based association results across disorders, 36 genes produced genome-wide significant P values (<3.2 × 10−6). Pathway analysis of genes with P values <1.0 × 10−3 highlighted magnesium ion binding and transport, as well as signal peptide processing, and provide insight into the biological mechanisms underlying these major psychiatric disorders.

Revisiting the male genetic landscape of China: a multi-center study of almost 38,000 Y-STR haplotypes

Abstract: China has repeatedly been the subject of genetic studies to elucidate its prehistoric and historic demography. While some studies reported a genetic distinction between Northern and Southern Han Chinese, others showed a more clinal picture of small differences within China. Here, we investigated the distribution of Y chromosome variation along administrative as well as ethnic divisions in the mainland territory of the People's Republic of China, including 28 administrative regions and 19 recognized Chinese nationalities, to assess the impact of recent demographic processes. To this end, we analyzed 37,994 Y chromosomal 17-marker haplotype profiles from the YHRD database with respect to forensic diversity measures and genetic distance between groups defined by administrative boundaries and ethnic origin. We observed high diversity throughout all Chinese provinces and ethnicities. Some ethnicities, including most prominently Kazakhs and Tibetans, showed significant genetic differentiation from the Han and other groups. However, differences between provinces were, except for those located on the Tibetan plateau, less pronounced. This discrepancy is explicable by the sizeable presence of Han speakers, who showed high genetic homogeneity all across China, in nearly all studied provinces. Furthermore, we observed a continuous genetic North-South gradient in the Han, confirming previous reports of a clinal distribution of Y chromosome variation and being in notable concordance with the previously observed spatial distribution of autosomal variation. Our findings shed light on the demographic changes in China accrued by a fast-growing and increasingly mobile population.

Y chromosome palindromes and gene conversion.

Abstract: The presence of large and near-identical inverted repeat sequences (called palindromes) is a common feature of the constitutively haploid sex chromosomes of different species. Despite the fact palindromes originated in a non-recombining context, they have evolved a strong recombinational activity in the form of abundant arm-to-arm gene conversion. Their independent appearance in different species suggests they can have a profound biological significance that has yet to be fully clarified. It has been theorized that natural selection may have favored palindromic organization of male-specific genes and that the establishment of intra-palindrome gene conversion has strong adaptive significance. Arm-to-arm gene conversion allows the efficient removal of deleterious mutations, increases the fixation rate of beneficial mutations and has played an important role in modulating the equilibrium between gene loss and acquisition during Y chromosome evolution. Additionally, a palindromic organization of duplicates could favor the formation of unusual chromatin structures and could optimize the use of gene conversion as a mechanism to maintain the structural integrity of male-specific genes. In this review, we describe the structural features of palindromes on mammalian sex chromosomes and summarize different hypotheses regarding palindrome evolution and the functional benefits of arm-to-arm gene conversion on the unique haploid portion of the nuclear genome.