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Exome sequencing and large-scale analysis of electronic medical record-linked biobank data identify candidate deafness genes.

INTRODUCTION: Rapid advances in whole-exome sequencing (WES) have enabled large-scale detection of pathogenic variants. Although hundreds of genes are implicated in hearing loss, up to half of inherited cases remain unsolved, limiting eligibility for gene therapy trials that require genetic diagnosis. Biobanks and electronic medical records (EMRs) offer opportunities to integrate genomic and clinical data at scale and expand the spectrum of hearing loss genes. Despite clinical value, EMRs often lack key information such as inheritance patterns, posing challenges for accurate interpretation. METHODS: WES was performed on DNA samples from 1038 hearing-impaired patients enrolled in the Maccabi Research and Innovation Center Tipa Biobank. Clinical data were extracted from EMRs. Audiograms were available for all cases, although data on age of onset, family history and mode of inheritance were mostly unavailable. We applied a scalable bioinformatics analysis strategy for high-throughput annotation, filtering and prioritisation of WES variants across more than 1000 patients, designed to accommodate incomplete and heterogeneous clinical records. RESULTS: Using this approach, 15% of cases were solved or potentially solved through known or novel variants in established deafness genes. Homozygous variants in novel candidate genes were identified in 3% of cases. Functional characterisation was performed for promising candidate genes to validate their role in the ear. CONCLUSION: These findings demonstrate that WES can determine disease aetiology in large, genetically heterogeneous populations, even in the context of incomplete clinical data. This approach supports large-scale genetic screening and provides a framework for identifying patients who may benefit from emerging gene-based therapies.

Genetic Testing↗

Telomere variation in Xenopus laevis.

Eukaryotic telomeres are variable at several levels, from the length of the simple sequence telomeric repeat tract in different cell types to the presence or number of telomere-adjacent DNA sequence elements in different strains or individuals. We have investigated the sequence organization of Xenopus laevis telomeres by use of the vertebrate telomeric repeat (TTAGGG)n and blot hybridization analysis. The (TTAGGG)n-hybridizing fragments, which ranged from less than 10 to over 50 kb with frequently cutting enzymes, defined a pattern that was polymorphic between individuals. BAL 31 exonuclease treatment confirmed that these fragments were telomeric. The polymorphic fragments analyzed did not hybridize to 5S RNA sequences, which are telomeric according to in situ hybridization. When telomeric fragments from offspring (whole embryos) were compared to those from the spleens of the parents, the inheritance pattern of some bands was found to be unusual. Furthermore, in one cross, the telomeres of the embryo were shorter than the telomeres of the parents' spleen, and in another, the male's testis telomeres were shorter than those of the male's spleen. Our data are consistent with a model for chromosome behavior that involves a significant amount of DNA rearrangement at telomeres and suggest that length regulation of Xenopus telomeres is different from that observed for Mus spretus and human telomeres.

Animals↗

Evidence against unusual sex concordance and pseudoautosomal inheritance in the catatonic subtype of schizophrenia.

The study is based on sibships with multiply afflicted members derived from a family study of consecutively admitted probands with catatonic schizophrenia. As shown recently, the clinical subtype of periodic catatonia, as defined by Leonhard, is compatible with a major gene effect and genetic anticipation; that is, the age of illness onset of the probands is significantly earlier than that of their parents. In the present study, 83 probands with the clinical subtype of periodic catatonia had 26 afflicted siblings that were distributed among 23 families. We analyzed sex-concordance and pseudoautosomal inheritance patterns. Stratifying the 26 afflicted siblings by sibship size and by the proband's sex, we did not find unusual sex-concordance rates in sibships afflicted with periodic catatonia. Further, there was no association between sex concordance and maternal or paternal origin of the disease. Thus, our results provide strong evidence against pseudoautosomal inheritance or sex-linked transmission in affected sibships in the obviously familial schizophrenic subtype of periodic catatonia.

Adult↗

Genetics of the Costello syndrome.

Although Costello syndrome is considered to be an autosomal recessive disorder, review of 20 families demonstrated that the 37 sibs of the probands were all normal. In 6 families on whom pedigrees were not available, 2 affected sib-pairs were born. Even if there were no normal offspring in these latter families, the occurrence of the Costello syndrome in only 2 of 39 sibs virtually excludes an autosomal recessive inheritance pattern (P = 0.999). Moreover, a significant increase of mean paternal age (38.0 yr) and paternal-maternal age difference (7.36 yr) suggests sporadic autosomal dominant mutations as a likely cause. The 2 reported cases of affected sibs born to healthy parents may be explained by gonadal mosaicism, although heterogeneity with a small proportion of recessively inherited cases cannot be excluded.

Abnormalities, Multiple↗

Genetic polymorphism of IgG in mink. II. A genetic analysis of allotypes.

Population distribution and inheritance pattern were analyzed in mink IgG allotypes: L1 (L chains), H2, H3, H4, H6, H7, and H8 (the constant region of the H chains, i.e. C gamma-allotypes) and conformational allotype 5 with unknown chain localization. Contrary to expectation, neither allelism, nor close linkage were demonstrated for these allotypes. The major feature of the inheritance of H2, H3, and H4 C gamma-allotypes, as well as allotype 5, was significant excess of negative (without these allotypes) progeny in the F1 generation from monohybrid cross. The explanation offered for this departure of the C gamma-allotypes from normal Mendelian genetics suggests widespread latencies of their expression in mink.

Animals↗

Jarcho-Levin syndrome: four new cases and classification of subtypes.

The Jarcho-Levin syndrome is a condition manifested by vertebral body and related rib malformations. We report on four new cases and review 57 cases from the literature. Analysis of the 61 cases suggests that there are two major subtypes (spondylocostal dysostosis and spondylothoracic dysostosis) with different survival rates, associated malformations, and inheritance patterns. Individuals with spondylothoracic dysostosis have vertebral body malformations and ribs which flare in a fanlike pattern but which are not significantly malformed. This is an autosomal recessive trait, and the patients have a higher mortality rate and greater incidence of neural tube defects. Individuals with spondylocostal dysostosis have vertebral malformations, frequent dramatic rib malformations, and short stature, but do not have a fanlike thoracic configuration. Most cases of spondylocostal dysostosis are inherited in an autosomal recessive fashion, although in a few families it is a dominant trait which is correlated with better survival. Respiratory compromise previously accounted for the high mortality in these conditions, but improvements in respiratory technology have increased survival. Appropriate classification of these similar phenotypes will improve counseling concerning recurrence risk, management, and prognosis.

Abnormalities, Multiple↗

Familial megacecum and colon in the rat: a new model of gastrointestinal neuromuscular dysfunction.

Gastrointestinal motility disorders are of considerable clinical importance in humans and animals. Abnormalities of smooth muscle and the enteric nervous system have been described. We have identified and characterized a new mutant stock of rats that develops severe megacecum and colon with pseudo-obstruction, Familial Megacecum and Colon (FMC). The inheritance pattern of FMC was characterized by selective breeding. Gastrointestinal motility was evaluated radiographically. Complete pathologic evaluations, including ultrastructural examination and staining of colonic segments for acetylcholinesterase, peripherin, vasoactive intestinal peptide, substance P, nitric oxide synthase, and somatostatin, were performed. Spontaneous contractility and contractile force in isolated colonic muscle strips were examined. Familial megacecum and colon is inherited as an autosomal recessive trait. The markedly dilated cecum and proximal portion of the colon are followed by a short, funnel-shaped segment and distal portion of the colon with normal or slightly reduced lumen. Although clinical features and gross anatomic changes of the colon resemble those of Hirschsprung's disease in humans and animals, aganglionosis is not a feature of FMC. An increase in somatostatin staining was observed in dilated regions of bowel. The spontaneous contractile frequency and contractile force were diminished in the affected colon. Familial megacecum and colon is a new mutant, distinct from previously described hereditary and targeted mutant rodent models that develop megacecum and colon as a result of distal colonic dysfunction. The functional or morphologic defect(s) that result in colonic dysfunction in rats with FMC was not determined. The disease may result from an absence or overexpression of a single or group of neurotransmitters or their respective neurons, receptor abnormalities, or defects in the intestinal pacemaker system.

Animals↗

Familial temporal lobe epilepsy autosomal dominant inheritance in a large pedigree from southern Italy.

To further elucidate the inheritance pattern and range of phenotypic manifestations of benign familial temporal lobe epilepsy (FTLE), we report a large family recently identified in southern Italy. There were 8 patients (4 men), ranging in age from 31 to 68 years in three generations. One affected patient was deceased at the time of the study. Genealogical study strongly supported autosomal dominant inheritance with incomplete penetrance, as three unaffected individuals transmitted the disease. Clinical anticipation could not be assessed because of the ascertainment method. Male to male transmission occurred. Identifiable antecedents for seizures were present in only two patients, who had a simple febrile convulsion and a closed head trauma, respectively. Migraine was overrepresented in this family. Onset of seizures ranged from 17 to 52 years (mean: 27 years). All patients had weekly simple partial seizures suggestive of temporal origin with vegetative or experiential phenomena. Very rare partial complex seizures occurred in 6/7 patients. One had two generalized nocturnal seizures as well. Two had previously been misdiagnosed as having gastritis or panic attacks, and one had not been diagnosed. Interictal anteromesiotemporal spiking was seen in 5/7 patients, and occurred mostly during NREM sleep. Neurological examination, brain CT or MR scans were normal. Antiepileptic medication always controlled the seizures.

Adult↗

Exploring the c.406 C > T variant in TNNI3 gene: pathogenic insights into restrictive cardiomyopathy.

BACKGROUND: Restrictive cardiomyopathy (RCM) is a rare cardiac disorder characterized by diastolic dysfunction and myocardial stiffness, frequently associated with genetic variants. We aimed to explore the genetic basis of RCM in a diagnosed patient through comprehensive genetic analysis. METHODS: Whole exome sequencing (WES) was conducted on the proband, followed by Sanger sequencing for variant confirmation and familial segregation analysis. In silico tools and structural protein modeling were employed to assess the functional impact of the identified variant. RESULTS: The c.406 C > T variant, classified as likely pathogenic, results in a truncated TNNI3 protein. Bioinformatics analysis highlighted significant structural disruptions, likely impairing sarcomere function. The patient presented with growth retardation, progressive dyspnea, and echocardiographic findings consistent with RCM. Both parents were heterozygous carriers, supporting an autosomal recessive inheritance pattern. The homozygosity of the novel variant identified in this study is a critical factor in the genotype-phenotype correlation observed in this case. CONCLUSION: This study identified the novel c.406 C > T variant in TNNI3 as a potential pathogenic driver of RCM, emphasizing the critical role of genetic evaluations in early diagnosis and management of inherited cardiomyopathies. Further studies are warranted to explore therapeutic interventions targeting TNNI3-related pathologies.

Humans↗

Pattern dystrophy of the retinal pigment epithelium.

The authors describe a family in which one member had pattern dystrophy of the retinal pigment epithelium. The proband also had neovascular membranes which resulted in decreased visual acuity. Two other family members had abnormal electro-oculographic findings, but a clinical normal-appearing fundus that could represent an early stage of the disease. The incidence of this condition in this family indicates autosomal dominance as the inheritance pattern of this dystrophy.

Adult↗

Complex segregation analysis of nonsyndromic cleft lip and palate.

This study was undertaken to examine the inheritance pattern of nonsyndromic cleft lip with or without cleft palate (CL/P). Complex segregation analysis using the unified model as in POINTER and the regressive model as in REGD programs were applied to analyze a midwestern U.S. Caucasian population of 79 families ascertained through a proband with CL/F. In REGD, the dominant or codominant Mendelian major locus models of inheritance were the most parsimonious fit. In POINTER, besides the Mendelian major locus model, the multifactorial threshold (MF/T) model and the mixed model were also consistent with the observed data. However, the high heritability parameter of .93 (SD .063) in the MF/T model suggests that any random exogenous factors are unlikely to be the underlying mechanisms, and the mixed model indicates that this high heritability is accounted for by a major dominant locus component. These findings indicate that the best explanation for the etiology of CL/P in this study population is a putative major locus associated with markedly decreased penetrance. Molecular studies may provide further insight into the genetic mechanism underlying CL/P.

Cleft Lip↗

Autosomal dominant pattern dystrophy of the retina associated with a 4-base pair insertion at codon 140 in the peripherin/RDS gene.

OBJECTIVE: To define the phenotype of a retinal dystrophy associated with a 4-base pair insertion at codon 140 of the peripherin/RDS gene. PATIENTS: Six affected members spanning two generations of a single family were examined. Five were studied in detail electrophysiologically and psychophysically. METHODS: Psychophysical testing included color vision testing, photopic and scotopic static threshold perimetry, and dark adaptometry. Electrophysiological testing included flash and pattern electroretinography, as well as electrooculography. RESULTS: Clinical findings ranged from subtle pigmentary changes at the level of the retinal pigment epithelium to more widespread pigmentary changes associated with choroidal neovascularization. Those with severe fundus changes exhibited greater abnormalities in psychophysical and electrophysiological testing than those with minimal fundus changes. CONCLUSIONS: This particular peripherin/RDS gene mutation is associated with dominantly inherited pattern dystrophy of the retina. The phenotypic expression is variable in a manner not explained by age.

Aged↗

Genetic linkage study of family members of a patient with adult polycystic kidney disease.

OBJECTIVE: To study the feasibility of making an early diagnosis of adult polycystic kidney disease by using genetic linkage analysis in Hong Kong. DESIGN: Genetic linkage study. SETTING: University teaching hospital, Hong Kong. PARTICIPANTS: Six members of a Chinese family with a history of adult polycystic kidney disease. MAIN OUTCOME MEASURES: The inheritance pattern of adult polycystic kidney disease, as detected by polyacrylamide gel electrophoresis of polymerase chain reaction products using radioactively labelled primers specific to six microsatellite DNA markers that are closely linked to the PKD1 gene on chromosome 16. RESULTS: Four of the six members of the family studied were shown to be positive for disease-linked markers, and the inheritance of adult polycystic kidney disease could be traced in this family with a higher degree of precision (93.7%) using genetic linkage analysis, than could be predicted otherwise. CONCLUSION: The success of genetic linkage analysis in providing an early diagnosis of adult polycystic kidney disease is dependent on having a sufficient number of family members whose disease status has been established by imaging methods to allow the disease-linked marker haplotype to be determined. The establishment of a genetic data bank for families with adult polycystic kidney disease should be considered to maximise the effectiveness of this diagnostic approach.

Journal Article↗

The molecular basis for apoptotic defects in patients with CD95 (Fas/Apo-1) mutations.

Heterozygous mutations of the receptor CD95 (Fas/Apo-1) are associated with defective lymphocyte apoptosis and a clinical disease characterized by lymphadenopathy, splenomegaly, and systemic autoimmunity. From our cohort of 11 families, we studied eight patients to define the mechanisms responsible for defective CD95-mediated apoptosis. Mutations in and around the death domain of CD95 had a dominant-negative effect that was explained by interference with the recruitment of the signal adapter protein, FADD, to the death domain. The intracellular domain (ICD) mutations were associated with a highly penetrant Canale-Smith syndrome (CSS) phenotype and an autosomal dominant inheritance pattern. In contrast, mutations affecting the CD95 extracellular domain (ECD) resulted in failure of extracellular expression of the mutant protein or impaired binding to CD95 ligand. They did not have a dominant-negative effect. In each of the families with an ECD mutation, only a single individual was affected. These observations were consistent with differing mechanisms of action and modes of inheritance of ICD and ECD mutations, suggesting that individuals with an ECD mutation may require additional defect(s) for expression of CSS.

Apoptosis↗

A single base pair polymorphism in the WT1 gene detected by single-strand conformation polymorphism analysis.

The Wilms' tumor predisposition gene, WT1, was analysed exon-by-exon in a variety of tumours using the single-strand conformation polymorphism (SSCP) technique. A consistent variation in the usual band pattern for exon 7 was detected in this survey. On sequencing, a silent mutation was noted in codon 313 resulting in an A-->G transition in an arginine codon. The A-->G transition destroys an AflIII restriction enzyme recognition site, which provides a rapid means of identifying heterozygotes at this locus. Analysis of the segregation of this polymorphism in families demonstrated a co-dominant inheritance pattern. In an analysis of 21 randomly selected individuals 25% were heterozygous at this locus, which makes this polymorphism useful in a variety of genetic analyses.

Base Sequence↗

Patterns of parental transmission and familial aggregation models in bipolar affective disorder.

Two recent studies [McMahon et al., 1995: Am J Hum Genet 56:1277-1286; Gershon et al., 1996: Am J Med Genet (Neuropsychiatr Genet) 67:202-207] reported an excess of maternal transmission in bipolar affective disorder in multiply affected families. In a sample of 130 families ascertained through a bipolar proband without regard to psychiatric family history we analysed the frequency of maternal (MAT) and paternal (PAT) transmissions, the morbid risk (MR) in relatives of transmitting mothers and fathers and the inheritance patterns in families with MAT vs. PAT transmission of the disease. In the total sample of 130 families we identified 39 families where the disease was transmitted from the paternal side (PAT families) and 35 families where the disease was transmitted from the maternal side (MAT families). Counting PAT and MAT transmissions in these unilineal families we found nearly equal numbers for both transmission types under a narrow (BP: bipolar disorder, schizoaffective-bipolar type disorder) and a broad definition (AFF: BP, recurrent unipolar depression) of the phenotype. The MRs for narrow and broad phenotypes were not significantly different in any type of PAT relative in PAT families vs. MAT relatives in MAT families. However, in PAT families there were two times more affected females than males with both disease models, while in MAT families there was no MR difference by relatives' sex. The transmission of BP was compatible with the Mendelian major gene model in PAT families and with the multifactorial model in MAT families. Extension of the relatives' phenotype led to borderline non-Mendelian major effects in PAT families and reproduced the multifactorial model in MAT families.

Bipolar Disorder↗

An inherited enzymatic defect in porphyria cutanea tarda: decreased uroporphyrinogen decarboxylase activity.

Uroporphyrinogen decarboxylase activity was measured in liver and erythrocytes of normal subjects and in patients with porphyria cutanea tarda and their relatives. In patients with porphyria cutanea tarda, hepatic uroporphyrinogen decarboxylase activity was significantly reduced (mean 0.43 U/mg protein; range 0.25-0.99) as compared to normal subjects (mean 1.61 U/mg protein; range 1.27-2.42). Erythrocyte uroporphyrinogen decarboxylase was also decreased in patients with porphyria cutanea tarda. The mean erythrocyte enzymatic activity in male patients was 0.23 U/mg Hb (range 0.16-0.30) and in female patients was 0.17 U/mg Hb (range 0.15-0.18) as compared with mean values in normal subjects of 0.38 U/mg Hb (range 0.33-0.45) in men and 0.26 U/mg Hb (range 0.18-0.36) in women. With the erythrocyte assay, multiple examples of decreased uroporphyrinogen decarboxylase activity were detected in members of three families of patients with porphyria cutanea tarda. In two of these families subclinical porphyria was also recognized. The inheritance pattern was consistant with an autosomal dominant trait. The difference in erythrocyte enzymatic activity between men and women was not explained but could have been due to estrogens. This possibility was supported by the observation that men under therapy with estrogens for carcinoma of the prostate had values in the normal female range. It is proposed that porphyria cutanea tarda results from the combination of an inherited defect in uroporphyrinogen decarboxylase and an acquired factor, usually siderosis associated with alcoholic liver disease.

5-Aminolevulinate Synthetase↗

Peripheral absolute threshold spectral sensitivity in retinitis pigmentosa.

Dark-adapted spectral sensitivities were measured in the peripheral retinas of 38 patients diagnosed as having typical retinitis pigmentosa (RP) and in 3 normal volunteers. The patients included those having autosomal dominant and autosomal recessive inheritance patterns. Results were analysed by comparisons with the CIE standard scotopic spectral visibility function and with Judd's modification of the photopic spectral visibility function, with consideration of contributions from changes in spectral transmission of preretinal media. The data show 3 general patterns. One group of patients had absolute threshold spectral sensitivities that were fit by Judd's photopic visibility curve. Absolute threshold spectral sensitivities for a second group of patients were fit by a normal scotopic spectral visibility curve. The third group of patients had absolute threshold spectral sensitivities that were fit by a combination of scotopic and photopic spectral visibility curves. The autosomal dominant and autosomal recessive modes of inheritance were represented in each group of patients. These data indicate that RP patients have normal rod and/or cone spectral sensitivities, and support the subclassification of patients described previously by Massof and Finkelstein.

Adolescent↗