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Journal ArticleDOI

Beyond monogenetic rare variants: tackling the low rate of genetic diagnoses in predominantly antibody deficiency

01 Mar 2021-Cellular & Molecular Immunology (Nature Publishing Group)-Vol. 18, Iss: 3, pp 588-603
TL;DR: The clinical and immunological variability of PAD is defined, how genetic defects identified in PAD have given insight into B-cell immunobiology is considered, and recent technological advances in genomics and the challenges associated with identifying causal variants are addressed.
Abstract: Predominantly antibody deficiency (PAD) is the most prevalent form of primary immunodeficiency, and is characterized by broad clinical, immunological and genetic heterogeneity. Utilizing the current gold standard of whole exome sequencing for diagnosis, pathogenic gene variants are only identified in less than 20% of patients. While elucidation of the causal genes underlying PAD has provided many insights into the cellular and molecular mechanisms underpinning disease pathogenesis, many other genes may remain as yet undefined to enable definitive diagnosis, prognostic monitoring and targeted therapy of patients. Considering that many patients display a relatively late onset of disease presentation in their 2nd or 3rd decade of life, it is questionable whether a single genetic lesion underlies disease in all patients. Potentially, combined effects of other gene variants and/or non-genetic factors, including specific infections can drive disease presentation. In this review, we define (1) the clinical and immunological variability of PAD, (2) consider how genetic defects identified in PAD have given insight into B-cell immunobiology, (3) address recent technological advances in genomics and the challenges associated with identifying causal variants, and (4) discuss how functional validation of variants of unknown significance could potentially be translated into increased diagnostic rates, improved prognostic monitoring and personalized medicine for PAD patients. A multidisciplinary approach will be the key to curtailing the early mortality and high morbidity rates in this immune disorder.
Citations
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TL;DR: APDS2 is a combined immunodeficiency with a variable clinical phenotype and Complications are frequent, such as severe bacterial and viral infections, lymphoproliferation, and lymphoma similar to APDS1/PASLI-CD.
Abstract: Background: Activated phosphoinositide 3-kinase delta syndrome (APDS) 2 a (p110 delta-activating mutations causing senescent T cells, a lymphadenopathy, and immunodeficiency [PASLI]-R1), a recently a described primary immunodeficiency, results from autosomal dominant a mutations in PIK3R1, the gene encoding the regulatory subunit (p85 a alpha, p55 alpha, and p50 alpha) of class IA phosphoinositide 3-kinases. a Objectives: We sought to review the clinical, immunologic, and a histopathologic phenotypes of APDS2 in a genetically defined a international patient cohort. a Methods: The medical and biological records of 36 patients with a genetically diagnosed APDS2 were collected and reviewed. a Results: Mutations within splice acceptor and donor sites of exon 11 of a the PIK3R1 gene lead to APDS2. Recurrent upper respiratory tract a infections (100%), pneumonitis (71%), and chronic lymphoproliferation a (89%, including adenopathy [75%], splenomegaly [43%], and upper a respiratory tract lymphoid hyperplasia [48%]) were the most common a features. Growth retardation was frequently noticed (45%). Other a complications were mild neurodevelopmental delay (31%); malignant a diseases (28%), most of them being B-cell lymphomas; autoimmunity a (17%); bronchiectasis (18%); and chronic diarrhea (24%). Decreased a serum IgA and IgG levels (87%), increased IgM levels (58%), B-cell a lymphopenia (88%) associated with an increased frequency of a transitional B cells (93%), and decreased numbers of naive CD4 and a naive CD8 cells but increased numbers of CD8 effector/memory T cells a were predominant immunologic features. The majority of patients (89%) a received immunoglobulin replacement; 3 patients were treated with a rituximab, and 6 were treated with rapamycin initiated after diagnosis a of APDS2. Five patients died from APDS2-related complications. a Conclusion: APDS2 is a combined immunodeficiency with a variable a clinical phenotype. Complications are frequent, such as severe bacterial a and viral infections, lymphoproliferation, and lymphoma similar to a APDS1/PASLI-CD. Immunoglobulin replacement therapy, rapamycin, and, a likely in the near future, selective phosphoinositide 3-kinase delta a inhibitors are possible treatment options.

26 citations

Journal Article
TL;DR: In this paper, the authors performed genetic linkage analysis in consanguineous families affected by hypogammaglobulinemia and concluded that mutations in LRBA cause an immune deficiency characterized by defects in B cell activation and autophagy and susceptibility to apoptosis.
Abstract: Most autosomal genetic causes of childhood-onset hypogammaglobulinemia are currently not well understood. Most affected individuals are simplex cases, but both autosomal-dominant and autosomal-recessive inheritance have been described. We performed genetic linkage analysis in consanguineous families affected by hypogammaglobulinemia. Four consanguineous families with childhood-onset humoral immune deficiency and features of autoimmunity shared genotype evidence for a linkage interval on chromosome 4q. Sequencing of positional candidate genes revealed that in each family, affected individuals had a distinct homozygous mutation in LRBA (lipopolysaccharide responsive beige-like anchor protein). All LRBA mutations segregated with the disease because homozygous individuals showed hypogammaglobulinemia and autoimmunity, whereas heterozygous individuals were healthy. These mutations were absent in healthy controls. Individuals with homozygous LRBA mutations had no LRBA, had disturbed B cell development, defective in vitro B cell activation, plasmablast formation, and immunoglobulin secretion, and had low proliferative responses. We conclude that mutations in LRBA cause an immune deficiency characterized by defects in B cell activation and autophagy and by susceptibility to apoptosis, all of which are associated with a clinical phenotype of hypogammaglobulinemia and autoimmunity.

16 citations

15 Jul 2016
TL;DR: PTEN loss-of-function mutations can cause APDS-like immunodeficiency because of aberrant PI3K pathway activation in lymphocytes.
Abstract: BACKGROUND Activated phosphatidylinositol 3-kinase δ syndrome (APDS) is a recently discovered primary immunodeficiency disease (PID). Excess phosphatidylinositol 3-kinase (PI3K) activity linked to mutations in 2 PI3K genes, PIK3CD and PIK3R1, causes APDS through hyperphosphorylation of AKT, mammalian target of rapamycin (mTOR), and S6. OBJECTIVE This study aimed to identify novel genes responsible for APDS. METHODS Whole-exome sequencing was performed in Japanese patients with PIDs. Immunophenotype was assessed through flow cytometry. Hyperphosphorylation of AKT, mTOR, and S6 in lymphocytes was examined through immunoblotting, flow cytometry, and multiplex assays. RESULTS We identified heterozygous mutations of phosphatase and tensin homolog (PTEN) in patients with PIDs. Immunoblotting and quantitative PCR analyses indicated that PTEN expression was decreased in these patients. Patients with PTEN mutations and those with PIK3CD mutations, including a novel E525A mutation, were further analyzed. The clinical symptoms and immunologic defects of patients with PTEN mutations, including lymphocytic AKT, mTOR, and S6 hyperphosphorylation, resemble those of patients with APDS. Because PTEN is known to suppress the PI3K pathway, it is likely that defective PTEN results in activation of the PI3K pathway. CONCLUSION PTEN loss-of-function mutations can cause APDS-like immunodeficiency because of aberrant PI3K pathway activation in lymphocytes.

14 citations

24 Mar 2017
TL;DR: In this paper, the authors describe four patients from two unrelated families of different ethnicities with a primary immunodeficiency, predominantly manifesting as susceptibility to Epstein-Barr virus (EBV)related diseases.
Abstract: In this study, we describe four patients from two unrelated families of different ethnicities with a primary immunodeficiency, predominantly manifesting as susceptibility to Epstein-Barr virus (EBV)–related diseases. Three patients presented with EBV-associated Hodgkin’s lymphoma and hypogammaglobulinemia; one also had severe varicella infection. The fourth had viral encephalitis during infancy. Homozygous frameshift or in-frame deletions in CD70 in these patients abolished either CD70 surface expression or binding to its cognate receptor CD27. Blood lymphocyte numbers were normal, but the proportions of memory B cells and EBV-specific effector memory CD8+ T cells were reduced. Furthermore, although T cell proliferation was normal, in vitro–generated EBV-specific cytotoxic T cell activity was reduced because of CD70 deficiency. This reflected impaired activation by, rather than effects during killing of, EBV-transformed B cells. Notably, expression of 2B4 and NKG2D, receptors implicated in controlling EBV infection, on memory CD8+ T cells from CD70-deficient individuals was reduced, consistent with their impaired killing of EBV-infected cells. Thus, autosomal recessive CD70 deficiency is a novel cause of combined immunodeficiency and EBV-associated diseases, reminiscent of inherited CD27 deficiency. Overall, human CD70–CD27 interactions therefore play a nonredundant role in T and B cell–mediated immunity, especially for protection against EBV and humoral immunity.

12 citations

References
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Journal ArticleDOI
TL;DR: Because of the increased complexity of analysis and interpretation of clinical genetic testing described in this report, the ACMG strongly recommends thatclinical molecular genetic testing should be performed in a Clinical Laboratory Improvement Amendments–approved laboratory, with results interpreted by a board-certified clinical molecular geneticist or molecular genetic pathologist or the equivalent.

17,834 citations


"Beyond monogenetic rare variants: t..." refers background in this paper

  • ...4).(179) Subsequently, the functional impact of a variant is predicted using publicly available algorithms to predict pathogenicity in silico including sorting intolerant from tolerant (SIFT), polymorphism phenotyping v2 (PolyPhen2), and combined annotationdependent depletion (CADD) (Fig....

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  • ...Consideration of the known information about the gene product and the predicted impact on protein function can indicate whether a VUS may be pathogenic.(179) In gene discovery, inheritance patterns can indicate the type of defects that can be expected, i....

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  • ...4; Table 2).(179,190) Benign and likely benign (categories 1 and 2) variants are disregarded, whereas pathogenic (category 5) variants are given a confirmatory diagnosis (Fig....

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  • ...4), a process typically done on the basis of available information, as discussed below.(179) Variants are assessed on the basis of their allele frequency in the general population using population databases including 1000 Genomes and gnomAD,(180,181) with an allele frequency of <0....

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Journal ArticleDOI
TL;DR: A new method and the corresponding software tool, PolyPhen-2, which is different from the early tool polyPhen1 in the set of predictive features, alignment pipeline, and the method of classification is presented and performance, as presented by its receiver operating characteristic curves, was consistently superior.
Abstract: To the Editor: Applications of rapidly advancing sequencing technologies exacerbate the need to interpret individual sequence variants. Sequencing of phenotyped clinical subjects will soon become a method of choice in studies of the genetic causes of Mendelian and complex diseases. New exon capture techniques will direct sequencing efforts towards the most informative and easily interpretable protein-coding fraction of the genome. Thus, the demand for computational predictions of the impact of protein sequence variants will continue to grow. Here we present a new method and the corresponding software tool, PolyPhen-2 (http://genetics.bwh.harvard.edu/pph2/), which is different from the early tool PolyPhen1 in the set of predictive features, alignment pipeline, and the method of classification (Fig. 1a). PolyPhen-2 uses eight sequence-based and three structure-based predictive features (Supplementary Table 1) which were selected automatically by an iterative greedy algorithm (Supplementary Methods). Majority of these features involve comparison of a property of the wild-type (ancestral, normal) allele and the corresponding property of the mutant (derived, disease-causing) allele, which together define an amino acid replacement. Most informative features characterize how well the two human alleles fit into the pattern of amino acid replacements within the multiple sequence alignment of homologous proteins, how distant the protein harboring the first deviation from the human wild-type allele is from the human protein, and whether the mutant allele originated at a hypermutable site2. The alignment pipeline selects the set of homologous sequences for the analysis using a clustering algorithm and then constructs and refines their multiple alignment (Supplementary Fig. 1). The functional significance of an allele replacement is predicted from its individual features (Supplementary Figs. 2–4) by Naive Bayes classifier (Supplementary Methods). Figure 1 PolyPhen-2 pipeline and prediction accuracy. (a) Overview of the algorithm. (b) Receiver operating characteristic (ROC) curves for predictions made by PolyPhen-2 using five-fold cross-validation on HumDiv (red) and HumVar3 (light green). UniRef100 (solid ... We used two pairs of datasets to train and test PolyPhen-2. We compiled the first pair, HumDiv, from all 3,155 damaging alleles with known effects on the molecular function causing human Mendelian diseases, present in the UniProt database, together with 6,321 differences between human proteins and their closely related mammalian homologs, assumed to be non-damaging (Supplementary Methods). The second pair, HumVar3, consists of all the 13,032 human disease-causing mutations from UniProt, together with 8,946 human nsSNPs without annotated involvement in disease, which were treated as non-damaging. We found that PolyPhen-2 performance, as presented by its receiver operating characteristic curves, was consistently superior compared to PolyPhen (Fig. 1b) and it also compared favorably with the three other popular prediction tools4–6 (Fig. 1c). For a false positive rate of 20%, PolyPhen-2 achieves the rate of true positive predictions of 92% and 73% on HumDiv and HumVar, respectively (Supplementary Table 2). One reason for a lower accuracy of predictions on HumVar is that nsSNPs assumed to be non-damaging in HumVar contain a sizable fraction of mildly deleterious alleles. In contrast, most of amino acid replacements assumed non-damaging in HumDiv must be close to selective neutrality. Because alleles that are even mildly but unconditionally deleterious cannot be fixed in the evolving lineage, no method based on comparative sequence analysis is ideal for discriminating between drastically and mildly deleterious mutations, which are assigned to the opposite categories in HumVar. Another reason is that HumDiv uses an extra criterion to avoid possible erroneous annotations of damaging mutations. For a mutation, PolyPhen-2 calculates Naive Bayes posterior probability that this mutation is damaging and reports estimates of false positive (the chance that the mutation is classified as damaging when it is in fact non-damaging) and true positive (the chance that the mutation is classified as damaging when it is indeed damaging) rates. A mutation is also appraised qualitatively, as benign, possibly damaging, or probably damaging (Supplementary Methods). The user can choose between HumDiv- and HumVar-trained PolyPhen-2. Diagnostics of Mendelian diseases requires distinguishing mutations with drastic effects from all the remaining human variation, including abundant mildly deleterious alleles. Thus, HumVar-trained PolyPhen-2 should be used for this task. In contrast, HumDiv-trained PolyPhen-2 should be used for evaluating rare alleles at loci potentially involved in complex phenotypes, dense mapping of regions identified by genome-wide association studies, and analysis of natural selection from sequence data, where even mildly deleterious alleles must be treated as damaging.

11,571 citations


"Beyond monogenetic rare variants: t..." refers background in this paper

  • ...3).(181,184,185) Variants resulting in a premature stop codon or deletion, for example, strongly predict pathogenicity....

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Journal ArticleDOI
Monkol Lek, Konrad J. Karczewski1, Konrad J. Karczewski2, Eric Vallabh Minikel2, Eric Vallabh Minikel1, Kaitlin E. Samocha, Eric Banks1, Timothy Fennell1, Anne H. O’Donnell-Luria2, Anne H. O’Donnell-Luria3, Anne H. O’Donnell-Luria1, James S. Ware, Andrew J. Hill1, Andrew J. Hill4, Andrew J. Hill2, Beryl B. Cummings1, Beryl B. Cummings2, Taru Tukiainen1, Taru Tukiainen2, Daniel P. Birnbaum1, Jack A. Kosmicki, Laramie E. Duncan1, Laramie E. Duncan2, Karol Estrada1, Karol Estrada2, Fengmei Zhao2, Fengmei Zhao1, James Zou1, Emma Pierce-Hoffman1, Emma Pierce-Hoffman2, Joanne Berghout5, David Neil Cooper6, Nicole A. Deflaux7, Mark A. DePristo1, Ron Do, Jason Flannick2, Jason Flannick1, Menachem Fromer, Laura D. Gauthier1, Jackie Goldstein2, Jackie Goldstein1, Namrata Gupta1, Daniel P. Howrigan2, Daniel P. Howrigan1, Adam Kiezun1, Mitja I. Kurki1, Mitja I. Kurki2, Ami Levy Moonshine1, Pradeep Natarajan, Lorena Orozco, Gina M. Peloso1, Gina M. Peloso2, Ryan Poplin1, Manuel A. Rivas1, Valentin Ruano-Rubio1, Samuel A. Rose1, Douglas M. Ruderfer8, Khalid Shakir1, Peter D. Stenson6, Christine Stevens1, Brett Thomas1, Brett Thomas2, Grace Tiao1, María Teresa Tusié-Luna, Ben Weisburd1, Hong-Hee Won9, Dongmei Yu, David Altshuler1, David Altshuler10, Diego Ardissino, Michael Boehnke11, John Danesh12, Stacey Donnelly1, Roberto Elosua, Jose C. Florez1, Jose C. Florez2, Stacey Gabriel1, Gad Getz1, Gad Getz2, Stephen J. Glatt13, Christina M. Hultman14, Sekar Kathiresan, Markku Laakso15, Steven A. McCarroll2, Steven A. McCarroll1, Mark I. McCarthy16, Mark I. McCarthy17, Dermot P.B. McGovern18, Ruth McPherson19, Benjamin M. Neale1, Benjamin M. Neale2, Aarno Palotie, Shaun Purcell8, Danish Saleheen20, Jeremiah M. Scharf, Pamela Sklar, Patrick F. Sullivan21, Patrick F. Sullivan14, Jaakko Tuomilehto22, Ming T. Tsuang23, Hugh Watkins17, Hugh Watkins16, James G. Wilson24, Mark J. Daly1, Mark J. Daly2, Daniel G. MacArthur1, Daniel G. MacArthur2 
18 Aug 2016-Nature
TL;DR: The aggregation and analysis of high-quality exome (protein-coding region) DNA sequence data for 60,706 individuals of diverse ancestries generated as part of the Exome Aggregation Consortium (ExAC) provides direct evidence for the presence of widespread mutational recurrence.
Abstract: Large-scale reference data sets of human genetic variation are critical for the medical and functional interpretation of DNA sequence changes. Here we describe the aggregation and analysis of high-quality exome (protein-coding region) DNA sequence data for 60,706 individuals of diverse ancestries generated as part of the Exome Aggregation Consortium (ExAC). This catalogue of human genetic diversity contains an average of one variant every eight bases of the exome, and provides direct evidence for the presence of widespread mutational recurrence. We have used this catalogue to calculate objective metrics of pathogenicity for sequence variants, and to identify genes subject to strong selection against various classes of mutation; identifying 3,230 genes with near-complete depletion of predicted protein-truncating variants, with 72% of these genes having no currently established human disease phenotype. Finally, we demonstrate that these data can be used for the efficient filtering of candidate disease-causing variants, and for the discovery of human 'knockout' variants in protein-coding genes.

8,758 citations


"Beyond monogenetic rare variants: t..." refers background in this paper

  • ...Pipeline for identification of causal variants The diagnostic challenge in WES and WGS is the selection of a causative variant from thousands of NGS reads (up to 50,000 per exome for WES) and hundreds of variants within the standard human genome sequence.(161,177,178) The large number of gene variants identified need to be filtered (Fig....

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Journal ArticleDOI
TL;DR: This protocol describes the use of the 'Sorting Tolerant From Intolerant' (SIFT) algorithm in predicting whether an AAS affects protein function.
Abstract: The effect of genetic mutation on phenotype is of significant interest in genetics. The type of genetic mutation that causes a single amino acid substitution (AAS) in a protein sequence is called a non-synonymous single nucleotide polymorphism (nsSNP). An nsSNP could potentially affect the function of the protein, subsequently altering the carrier's phenotype. This protocol describes the use of the 'Sorting Tolerant From Intolerant' (SIFT) algorithm in predicting whether an AAS affects protein function. To assess the effect of a substitution, SIFT assumes that important positions in a protein sequence have been conserved throughout evolution and therefore substitutions at these positions may affect protein function. Thus, by using sequence homology, SIFT predicts the effects of all possible substitutions at each position in the protein sequence. The protocol typically takes 5–20 min, depending on the input. SIFT is available as an online tool ( http://sift-dna.org ).

6,154 citations


"Beyond monogenetic rare variants: t..." refers background in this paper

  • ...3).(181,184,185) Variants resulting in a premature stop codon or deletion, for example, strongly predict pathogenicity....

    [...]

Journal ArticleDOI
21 Oct 2004-Nature
TL;DR: The current human genome sequence (Build 35) as discussed by the authors contains 2.85 billion nucleotides interrupted by only 341 gaps and is accurate to an error rate of approximately 1 event per 100,000 bases.
Abstract: The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers approximately 99% of the euchromatic genome and is accurate to an error rate of approximately 1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human genome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead.

3,989 citations