Showing papers on "Anticipation (genetics) published in 2018"

Repeat expansion diseases.

Abstract: More than 40 diseases, most of which primarily affect the nervous system, are caused by expansions of simple sequence repeats dispersed throughout the human genome. Expanded trinucleotide repeat diseases were discovered first and remain the most frequent. More recently tetra-, penta-, hexa-, and even dodeca-nucleotide repeat expansions have been identified as the cause of human disease, including some of the most common genetic disorders seen by neurologists. Repeat expansion diseases include both causes of myotonic dystrophy (DM1 and DM2), the most common genetic cause of amyotrophic lateral sclerosis/frontotemporal dementia (C9ORF72), Huntington disease, and eight other polyglutamine disorders, including the most common forms of dominantly inherited ataxia, the most common recessive ataxia (Friedreich ataxia), and the most common heritable mental retardation (fragile X syndrome). Here I review distinctive features of this group of diseases that stem from the unusual, dynamic nature of the underlying mutations. These features include marked clinical heterogeneity and the phenomenon of clinical anticipation. I then discuss the diverse molecular mechanisms driving disease pathogenesis, which vary depending on the repeat sequence, size, and location within the disease gene, and whether the repeat is translated into protein. I conclude with a brief clinical and genetic description of individual repeat expansion diseases that are most relevant to neurologists.

Familial Cortical Myoclonic Tremor and Epilepsy, an Enigmatic Disorder: From Phenotypes to Pathophysiology and Genetics. A Systematic Review.

Abstract: Background: Autosomal dominant familial cortical myoclonic tremor and epilepsy (FCMTE) is characterized by distal tremulous myoclonus, generalized seizures, and signs of cortical reflex myoclonus. FCMTE has been described in over 100 pedigrees worldwide, under several different names and acronyms. Pathological changes have been located in the cerebellum. This systematic review discusses the clinical spectrum, treatment, pathophysiology, and genetic findings. Methods: We carried out a PubMed search, using a combination of the following search terms: cortical tremor, myoclonus, epilepsy, benign course, adult onset, familial, and autosomal dominant; this resulted in a total of 77 studies (761 patients; 126 pedigrees) fulfilling the inclusion and exclusion criteria. Results: Phenotypic differences across pedigrees exist, possibly related to underlying genetic differences. A “benign” phenotype has been described in several Japanese families and pedigrees linked to 8q (FCMTE1). French patients (5p linkage; FCMTE3) exhibit more severe progression, and in Japanese/Chinese pedigrees (with unknown linkage) anticipation has been suggested. Preferred treatment is with valproate (mind teratogenicity), levetiracetam, and/or clonazepam. Several genes have been identified, which differ in potential pathogenicity. Discussion: Based on the core features (above), the syndrome can be considered a distinct clinical entity. Clinical features may also include proximal myoclonus and mild progression with aging. Valproate or levetiracetam, with or without clonazepam, reduces symptoms. FCMTE is a heterogeneous disorder, and likely to include a variety of different conditions with mutations of different genes. Distinct phenotypic traits might reflect different genetic mutations. Genes involved in Purkinje cell outgrowth or those encoding for ion channels or neurotransmitters seem good candidate genes.

Spinocerebellar Ataxia Type 17 (SCA17).

Abstract: In 1999, a polyglutamine expansion was identified in the transcription factor TATA-binding protein (TBP) in a patient with ataxia with negative family history. Subsequently, CAG/CAA repeat expansions in the TBP gene were identified in families with spinocerebellar ataxia (SCA), establishing this repeat expansion as the underlying mutation in SCA type 17 (SCA17). There are several characteristic differences between SCA17 and other polyglutamine diseases. First, SCA17 shows a complex and variable clinical phenotype, in some cases overlapping that of Huntington’s disease. Second, compared to the other SCA subtypes caused by expanded trinucleotide repeats, anticipation in SCA17 kindreds is rare because of the characteristic structure of the TBP gene. And thirdly, SCA17 patients often have diagnostic problems that may arise from non-penetrance. Because the gap between normal and abnormal repeat numbers is very narrow, it is difficult to determine a cutoff value for pathologic CAG repeat number in SCA17. Herein, we review the clinical, genetic and pathologic features of SCA17.

Applying polygenic risk scoring for psychiatric disorders to a large family with bipolar disorder and major depressive disorder

Abstract: Psychiatric disorders are thought to have a complex genetic pathology consisting of interplay of common and rare variation. Traditionally, pedigrees are used to shed light on the latter only, while here we discuss the application of polygenic risk scores to also highlight patterns of common genetic risk. We analyze polygenic risk scores for psychiatric disorders in a large pedigree (n ~ 260) in which 30% of family members suffer from major depressive disorder or bipolar disorder. Studying patterns of assortative mating and anticipation, it appears increased polygenic risk is contributed by affected individuals who married into the family, resulting in an increasing genetic risk over generations. This may explain the observation of anticipation in mood disorders, whereby onset is earlier and the severity increases over the generations of a family. Joint analyses of rare and common variation may be a powerful way to understand the familial genetics of psychiatric disorders.

Molecular Mechanisms and Therapeutic Strategies in Spinocerebellar Ataxia Type 7.

Abstract: Spinocerebellar Ataxia type 7 (SCA7, OMIM # 164500) is an autosomal dominant neurodegenerative disorder characterized by adult onset of progressive cerebellar ataxia and blindness. SCA7 is part of the large family of autosomal dominant cerebellar ataxias (ADCAs), and was estimated to account for 1-11.7% of ADCAs in diverse populations. The frequency of SCA7 is higher where local founder effects were observed as in Scandinavia, Korea, South Africa and Mexico. SCA7 is pathomechanistically related to the group of CAG/polyglutamine (polyQ) expansion disorders, which includes other SCAs (1-3, 6 and 17), Huntington's disease, spinal bulbar muscular atrophy and dentatorubro pallidoluysian atrophy. Two distinctive characteristics of SCA7 are the strong anticipation by which earlier onset and more severe symptoms are observed in successive generations of affected families, and the loss of visual acuity due to cone-rod dystrophy of the retina. The pathology is caused by an unstable CAG repeat expansion coding for a polyQ stretch in Ataxin-7 (ATXN7). PolyQ expansion in ATXN7 confers toxic properties and leads to selective neuronal degeneration in the cerebellum, the brain stem and the retina. Herein, we summarize the genetic, clinical and pathological features of SCA7 and review our current knowledge of pathomechanisms and preclinical studies.

Clinical and Genetic Features of Patients with Juvenile Amyotrophic Lateral Sclerosis with Fused in Sarcoma (FUS) Mutation

Abstract: BACKGROUND Juvenile amyotrophic lateral sclerosis (JALS) is a rare form of motor neuron disease and occurs before 25 years of age. Only a few cases of juvenile-onset ALS have been reported. MATERIAL AND METHODS To study genetic and clinicopathological features in Chinese patients with juvenile ALS, we retrospectively reviewed ALS patients in our hospital and screened out 2 patients with disease onset before the age of 25. Genetic analysis was carried out with next-generation sequencing (NGS) to identify ALS causative genes. Sanger sequencing was used to validate identified variants. The clinical, electrophysiological, and pathological data were summarized. RESULTS A novel frameshift mutation c.1510dupG (p.G505Wfs*12) was found in Patient One using next-generation sequencing (NGS). Patient Two had a reported pathogenic mutation c.C1483T(p.R495X) with NGS. The mother of Patient Two carried the same mutation as her son and disease onset was at 1.5 years after the death of her son. CONCLUSIONS We identified a novel frameshift mutation associated with JALS. JALS and generally typical ALS, with the same FUS mutation, can appear in a family and present a phenomenon of anticipation. For diagnosis of central nervous system degeneration in adolescents with bulbar symptoms, great attention should be paid to JALS.

Lethal form of spinocerebellar ataxia type 7 with early onset in childhood

Abstract: Progressive cerebellar ataxias are well-known hereditary neurological disorders. Among them, spinocerebellar ataxia type 7 (SCA7) is inherited as an autosomal dominant trait and is ascribed to the expansion of a CAG trinucleotide repeat within the ATXN7 gene. An anticipation phenomenon can occur during paternal transmission and sometimes is responsible for a severe infantile form. The specificity of SCA7 is the retinal involvement with retinitis pigmentosa and cone rod dystrophy. We describe a familial form with two siblings who died of a severe infantile form. Diagnosis was made in their father, who had a recent history of macular atrophy and presented with gait disturbance thereafter. Retrospectively, substantial triplet repeat expansion was confirmed in the two affected infants. These infantile forms are rare and difficult to diagnose in the absence of suggestive family symptoms.

Etiology and Prevention of Multisystem Organ Failure

Abstract: Anticipation, identification, and treatment of organ failure syndromes is the work of the critical care physician and is necessary for intensive care unit survival. This chapter describes organ failure syndromes during burn convalescence.

Anticipation in a family with primary familial brain calcification caused by an SLC20A2 variant.

Abstract: Aim of the study To describe a family with primary familial brain calcification (PFBC) due to SLC20A2 variant showing possible genetic anticipation. Materials and methods We conducted historical, genealogical, clinical, and radiologic studies of a family with PFBC. Clinical evaluations including neurological examination and head computed tomography (CT) scans of a proband and her father were performed. They provided additional information regarding other family members. To identify a causative gene variant, we performed whole-exome sequencing for the proband followed by segregation analysis in other affected members using direct sequencing. Results In this family, nine affected members were identified over four generations. The proband suffered from chronic daily headache including thunderclap headache. We identified an SLC20A2 (c.509delT, p.(Leu170*)) variant in three affected members over three generations. Interestingly, the age of onset became younger as the disease passed through successive generations, suggestive of genetic anticipation. Conclusions and clinical implications For clinical purpose, it is important to consider thunderclap headache and genetic anticipation in PFBC caused by SLC20A2 variants. Further investigation is required to validate our observation.

Trinucleotide repeat diseases - anticipation diseases

Abstract: Dynamic mutations involve expansion of the number of repeat units consisting of three or more nucleotides in tandem (i.e. adjacent to one another) present in a gene or in its neighborhood. These repeats may occur in different genes and may code for different aminoacids. According to expansions sizes, it is possible to have unaffected individuals that are carriers of a pre-mutation. Instability of triplet repeat size can lead to gradual expansion through generations, a phenomenon called anticipation. Genetic anticipation is characterized by the reduction in the age of disease onset and by a worsening of symptoms in affected individuals in successive generations. This work describes dynamic mutations giving emphasis on triplet repeats diseases, making the parallel with disease anticipation. Treatment strategies that have been developed during the last years are also discussed.

TRIO gene segregation in a family with cerebellar ataxia

Abstract: Aim of the study To report a family with a novel TRIO gene mutation associated with phenotype of cerebellar ataxia. Materials and methods Seven family members of Caribbean descent were recruited through our ataxia research protocol; of the family members, the mother and all 3 children were found to be affected with severe young-onset and rapidly progressive truncal and appendicular ataxia leading to early disability. Array comparative genomic hybridization, mitochondrial DNA analysis, and whole-exome sequencing were performed on 3 of the family members (mother and 2 daughters). Results While the maternal grandmother, great uncle and great aunt were unaffected, the mother and 3 children displayed cognitive dysfunction, severe ataxia, spasticity, and speech disturbances. Age of onset ranged between 3 and 17 years, with average current disease duration of 21 years. Whole-exome sequencing showed a variant p.A1214V in exon 22 of the TRIO gene in 3 of the family members. Array comparative genomic hybridization and mitochondrial DNA analysis were normal. The same variant was later discovered in all but one family member. Conclusions and clinical implications The TRIO p.A1214V variant is associated with cerebellar ataxia in the studied family; it was present in all affected and unaffected family members. Phenotype is severe and broad. Anticipation seems to be present (based on 2 affected generations). It is warranted to screen additional familial early-onset and rapidly progressive ataxia cases for this genotype. TRIO gene mutations may well represent a novel spinocerebellar ataxia subtype.

Letter regarding "An attempt to throw light on congenital hip disease terminology and anticipation of clinical outcomes when treated with total hip arthroplasty", by Hartofilakidis G et al.

Abstract: Dear Editor, We read the article by G. Hartofilakidis and colleagues with great interest. In their publication, the authors underline the importance of understanding the difference between 3 types of congenital hip disease. Correct interpretation of this classification can help in the acceptance of a solution for some challenging situations. Unfortunately, however, morphological and radiographic images are so widely used that these have been described in the popular Hartofilakidis classification. Type A (dysplasia): “The femoral head is contained within the original acetabulum despite the degree of subluxation.” In adults, the border between the original acetabulum and the superior osteophyte is difficult to find. The same is true for the inferior osteophyte of the femoral head. We think that type A needs elaboration regarding the femoral head position. Type B (low dislocation): “The femoral head articulates with a false acetabulum that partially covers the true acetabulum to varying degrees.” Letter regarding “An attempt to throw light on congenital hip disease terminology and anticipation of clinical outcomes when treated with total hip arthroplasty”, by Hartofilakidis G et al

Review of diagnostic criteria for multiple sclerosis

Abstract: Multiple sclerosis (MS) is a chronic, autoimmune disease of the central nervous system, leading to inflammatory demyelination and damage to neurons and their axons. The essence of MS is the occurrence of neurological symptoms associated with the occurance of demyelinating lesions disseminated in time (DIT) and space (DIS) (i.e. occurring within various CNS structures, in particular: pyramidal and cerebellar pathways). The aim of the article was to present the evolution of diagnostic criteria of multiple sclerosis in the years 1965-2017. Analysis of the changing criteria reveal that over the last several years, the time necessary to diagnose the disease, previously associated with the anticipation of subsequent symptoms of MS, now is definitely shorter, and the diagnosis can be made before the next relapse of MS, including cerebrospinal fluid examination.

Renal disease and the parturient on dialysis

Abstract: Historically, pregnancy in women on dialysis was rare and carried significant risks to mother and fetus. Despite this, pregnancy in these patients has become more common and presents specific challenges, especially with anticipation of worsening kidney function with pregnancy. Optimal management includes more frequent dialysis sessions and planned delivery at around 37 weeks’ gestation.

Applying polygenic risk scoring for psychiatric disorders to a large family with Bipolar Disorder and Major Depressive Disorder

Abstract: We aim to investigate the application of polygenic risk scoring within a family context. Polygenic risk profiles could aid in unraveling the role that common variation confers on disease risk within a pedigree that would have traditionally been viewed through the prism of monogenic inheritance only. We illustrate our discussion by analyzing polygenic risk scores for schizophrenia, major depressive disorder and bipolar disorder in a large pedigree (n~260) in which 30% of family members suffer from major depressive disorder or bipolar disorder. We apply polygenic risk scores to study patterns of assortative mating and anticipation, whereby it appears increased polygenic risk for psychiatric disorders is contributed by affected individuals who married into the family, resulting in an increasing genetic risk over generations in the family. This may explain the observation of anticipation in mood disorders, whereby onset is earlier and the severity of a disease increases over the generations of a family. Joint analyses of both rare and common variation may be the most powerful way to understand the familial genetics of mood and psychiatric disorders.

Neurodegenerative triplet repeat expansion disorders: A review

Abstract: Epigenetic alterations are the major causes of triplet repeat expansion. The repetitive DNA expands of its normal length results in sever neurodegenerative conditions. The common types of triplet repeat expansion (TNE) disorders are: Huntington disease, Friedreich ataxia, myotonic dystrophy, SBMA and SCA1 out of which Huntington disease, SBMA and SCA1 are categorized as a poly glutamine disorder due to the repeat of CAG. In contrast, the friedreich ataxia is occurred due to expansion of the GAA whereas myotonic dystrophy is due to the expansion of CTG. The triplet disease follows the mechanism of anticipation in which the onset of the disease increases with age. Conclusively, no clear mechanism can explain the origin of the disease. The pre mutation can be expanded in full mutation in successive generations and the number of repeats increased with each generation. TNE can observe in both somatic as well as germ line tissues.