Non-syndromic Deafness Research Articles

Insight into the Natural History of Pathogenic Variant c.919-2A>G in the SLC26A4 Gene Involved in Hearing Loss: The Evidence for Its Common Origin in Southern Siberia (Russia).

Pathogenic variants in the SLC26A4 gene leading to nonsyndromic recessive deafness (DFNB4), or Pendred syndrome, are some of the most common causes of hearing loss worldwide. Earlier, we found a high proportion of SLC26A4-related hearing loss with prevailing pathogenic variant c.919-2A>G (69.3% among all mutated SLC26A4 alleles that have been identified) in Tuvinian patients belonging to the indigenous Turkic-speaking Siberian people living in the Tyva Republic (Southern Siberia, Russia), which implies a founder effect in the accumulation of c.919-2A>G in Tuvinians. To evaluate a possible common origin of c.919-2A>G, we genotyped polymorphic STR and SNP markers, intragenic and flanking SLC26A4, in patients homozygous for c.919-2A>G and in healthy controls. The common STR and SNP haplotypes carrying c.919-2A>G were revealed, which convincingly indicates the origin of c.919-2A>G from a single ancestor, supporting a crucial role of the founder effect in the c.919-2A>G prevalence in Tuvinians. Comparison analysis with previously published data revealed the identity of the small SNP haplotype (~4.5 kb) in Tuvinian and Han Chinese carriers of c.919-2A>G, which suggests their common origin from founder chromosomes. We assume that c.919-2A>G could have originated in the geographically close territories of China or Tuva and subsequently spread to other regions of Asia. In addition, the time intervals of the c.919-2A>G occurrence in Tuvinians were roughly estimated.

Identification a novel pathogenic LRTOMT mutation in Mauritanian families with nonsyndromic deafness.

Although recessive mutations in GJB2 are the common genetic etiology of sensorineural hearing impairment (SNHI), variants in LRTOMT gene were also identified, mostly in Middle East and North African populations. Using Sanger sequencing we screened the exon 7 of LRTOMT in a cohort of 128 unrelated Mauritanian children with congenital deafness. Only one biallelic missense mutation, predicted as pathogenic (c.179T > C;p.Leu60Pro) was found at homozygous state in four families. This variant, not reported before, showed a deleterious effect by SIFT (score: 0.01) and a disease-causing effect by Mutation Taster (prob: 1). Exploration of the encoded protein 3D structure revealed a disruption from an organized α helix (in the normal protein structure) into a random conformation. Early fitting of a cochlear implant seemed to improve the audition ability of the mutation carrier. Further screening using a panel of deafness genes may expose other variants underlying hearing impairment in our population.

Preliminary investigation of the diagnosis and gene function of deep learning PTPN11 gene mutation syndrome deafness.

Syndromic deafness caused by PTPN11 gene mutation has gradually come into the public's view. In the past, many people did not understand its application mechanism and role and only focused on non-syndromic deafness, so the research on syndromic deafness is not in-depth and there is a large degree of lack of research in this area. In order to let the public know more about the diagnosis and gene function of deafness caused by PTPN11 gene mutation syndrome, this paper used deep learning technology to study the diagnosis and gene function of deafness caused by syndrome with the concept of intelligent medical treatment, and finally drew a feasible conclusion. This paper provided a theoretical and practical basis for the diagnosis of deafness caused by PTPN11 gene mutation syndrome and the study of gene function. This paper made a retrospective analysis of the clinical data of 85 deaf children who visited Hunan Children's Hospital,P.R. China from January 2020 to December 2021. The conclusion were as follows: Children aged 1-6years old had multiple syndrome deafness, while children under 1year old and children aged 6-12years old had relatively low probability of complex deafness; girls were not easy to have comprehensive deafness, but there was no specific basis to prove that the occurrence of comprehensive deafness was necessarily related to gender; the hearing loss of patients with Noonan Syndrome was mainly characterized by moderate and severe damage and abnormal inner ear and auditory nerve; most of the mutation genes in children were located in Exon1 and Exon3, with a total probability of 57.65%. In the course of the experiment, it was found that deep learning was effective in the diagnosis of deafness with PTPN11 gene mutation syndrome. This technology could be applied to medical diagnosis to facilitate the diagnosis and treatment of more patients with deafness with syndrome. Intelligent medical treatment was also becoming a hot topic nowadays. By using this concept to analyze and study the pathological characteristics of deafness caused by PTPN11 gene mutation syndrome, it not only promoted patients to find diseases in time, but also helped doctors to diagnose and treat such diseases, which was of great significance to patients and doctors. The study of PTPN11 gene mutation syndrome deafness was also of great significance in genetics. The analysis of its genes not only enriched the gene pool, but also provided reference for future research.

Identification of novel missense mutation related with non-syndromic sensorineural deafness, DFNA11 in korean family by NGS.

Hereditary hearing loss is one of the most common genetically heterogeneous defects in human. About 70% of hereditary hearing loss is defined as non-syndromic hearing loss showing loss of hearing ability without any other symptoms. Up to date, the identified genes associated with non-syndromic hearing loss are 128, including 52 genes for DFNA and 76 genes for DFNB. Because of high levels of heterogeneity, it is difficult to identify the causative factors for hearing loss using Sanger sequencing. Our aim was to detect causative factors and investigate pathogenic mutations, which co-segregates within the candidate family. We used Next Generation Sequencing technique to investigate whole-exome sequences of a Korean family with non-syndromic hereditary hearing loss. The family showed autosomal dominant inheritance pattern. We identified a novel missense variation, c.1978G > A in MYO7A gene, in the family with the autosomal dominant inheritance pattern. c.1978G > A produced Gly660Arg in the motor head domain of Myosin VIIA disrupt the ATP- and actin-binding motif function. This study is the first to report pathogenic mutations within MYO7A gene in Korean family and our data would facilitate diagnosing the primary cause of hereditary hearing loss in Korean.

Genetic mapping and pedigree analysis of non-syndromic congenital deafness in Surabaya, Indonesia

Background: Genetic mutations cause 50-75% of congenital deafness. Congenital deafness is a disease divided into syndromic and non-syndromic types. Type B special schools facilitate children with deafness in Surabaya. This study aimed to identify a mutation gene that causes non-syndromic hearing impairment in school students. Methods: This research was an analytic observational study using a cross-sectional method applying simple random sampling of non-syndromic deaf children. The applied tests were pure tone audiometry, polymerase chain reaction (PCR), and hybridization tests. Subjects were evaluated on the pedigree route and then analyzed. Results: A total of 138 participants with non-syndromic hearing loss were enrolled in this study and 49 patients met the inclusion criteria. The subject’s average age was 16.16 years, with more male subjects than female. The hybridization results obtained six genetic mutations, one subject with mtDNA 1555, one subject with GJB2-299, two subjects with SLC26A4-IVS(7)2, and 3 subjects with unknown mutations. In pedigree analysis, the same genetic mutation was found in two generations of subjects with mtDNA 1555 and GJB2-299 mutations, and mutations of more than one genetic type were found in two generations of subjects with the SLC26A4-IVS(7)2 mutation. Conclusions: This study obtained six genetic mutations in non-syndromic congenital deaf children. Non-syndromic congenital deafness in Indonesia was found to have genetic mutations as a health risk. The risk was heredity with diverse inheritance patterns.

Mutation-agnostic RNA interference with engineered replacement rescues Tmc1-related hearing loss.

Hearing loss is the most common sensory deficit, of which genetic etiologies are a frequent cause. Dominant and recessive mutations in TMC1, a gene encoding the pore-forming subunit of the hair cell mechanotransduction channel, cause DFNA36 and DFNB7/11, respectively, accounting for ∼2% of genetic hearing loss. Previous work has established the efficacy of mutation-targeted RNAi in treatment of murine models of autosomal dominant non-syndromic deafness. However, application of such approaches is limited by the infeasibility of development and validation of novel constructs for each variant. We developed an allele-non-specific approach consisting of mutation-agnostic RNAi suppression of both mutant and WT alleles, co-delivered with a knockdown-resistant engineered WT allele with or without the use of woodchuck hepatitis virus post-transcriptional regulatory element (WPRE) to augment transgene expression. This therapeutic construct was delivered into the mature murine model of DFNA36 with an AAV vector and achieved robust hair cell and auditory brainstem response preservation. However, WPRE-enhanced Tmc1 expression resulted in inferior outcomes, suggesting a role for gene dosage optimization in future TMC1 gene therapy development.

PMON145 The Role of Pou3f4 in Pituitary Development and Disease

Abstract Mutations in the pituitary specific transcription factor Prophet of Pit-1 (PROP1) are the most common genetic etiology of combined pituitary hormone deficiency (CPHD), which affects 1 in 8,000 newborns worldwide. CPHD is associated with short stature, attributable to growth hormone (GH) deficiency and/or thyroid stimulating hormone (TSH) deficiency. Pathogenic lesions impair pituitary development and differentiation of endocrine cells. Prop1-mutant mice show increased expression of genes including SRY-Box Transcription Factor 21 (Sox21) and Pou Domain, Class 3, Transcription Factor 4 (Pou3f4). POU3F4 is expressed in the developing inner ear and restricts the proliferation and lineage potential of neural stem cells. Genetic defects cause non-syndromic X-linked deafness (DFNX2) in humans and mice. The function of POU3F4 in pituitary development is largely unknown and the implications of its overexpression in Prop1-mutant pituitaries remain unexplored. Therefore, we aim to address the role of Pou3f4 in pituitary development and determine the contributions of Pou3f4 upregulation to pituitary disease by utilizing Pou3f4-mutant mice as well as double mutant mice lacking both Prop1 and Pou3f4. Utilizing immunofluorescent analysis at critical timepoints during pituitary development, we have characterized the timeline for endogenous POU3F4 expression. Initial expression is detected at e11.5 in differentiating cells on the ventral side of Rathke's pouch and is restricted to the proliferating anterior lobe at e13.5, continuing postnatally, similar to previously published expression data. POU3F4 expression then decreases and becomes gradually restricted to the periluminal stem cell niche at e15.5 and p0. We further validated the upregulation of POU3F4 in histological sections of Prop1-mutant mice at e15 and p0, finding increased expression in the developing anterior lobe of mutants compared to wildtypes. Single-cell regulatory network inference and clustering (SCENIC) analyses, which utilize single-cell transcription factor co-expression with potential direct downstream targets that contain the corresponding transcription factors’ binding sequence to infer active transcription networks, predict increased activity of the Pou3f4 gene regulatory network in a subpopulation of Sox2-expressing stem cells in Prop1-mutant mice. Preliminary analyses indicate that Pou3f4 mutant have normal morphology at P1, together with grossly normal expression of Sox2 and Pou1f1. We are performing quantitative PCR to determine possible compensatory mechanisms in response to loss of Pou3f4 expression. To investigate whether any Prop1-mutant phenotypes, including dysmorphology and ectopic expression of Sox21 and Otog, are attributable to Pou3f4 upregulation, we are studying Pou3f4;Prop1 mice. We will determine the impacts of POU3F4 upregulation on cellular morphology, stem cell maintenance and endocrine cell differentiation. The mechanisms of action in the regulation of stem cell differentiation constitutes a gap in our current understanding of the pathogenesis of CPHD. These studies will provide novel insights into the mechanistic function of Pou3f4 during embryonic pituitary development and potential novel etiologies of CPHD in human patients. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.

A CDH23 missense variant in Beauceron dogs with non-syndromic deafness.

Congenital coat-colour-related deafness is common among certain canine breeds especially those exhibiting extreme white spotting or merle patterning. We identified a non-syndromic deafness in Beauceron dogs characterised by a bilateral hearing loss in puppies that is not linked to coat colour. Pedigree analysis suggested an autosomal recessive transmission. By combining homozygosity mapping with whole genome sequencing and variant filtering in affected dogs we identified a CDH23:c.700C>T variant. The variant, located in the CHD23 (cadherin related 23) gene, was predicted to induce a CDH23:p.(Pro234Ser) change in the protein. Proline-234 of CDH23 protein is highly conserved across different vertebrate species. In silico tools predicted the CDH23:p.(Pro234Ser) change to be deleterious. CDH23 encodes a calcium-dependent transmembrane glycoprotein localised near the tips of hair-cell stereocilia in the mammalian inner ear. Intact function of these cilia is mandatory for the transformation of the acoustical wave into a neurological signal, leading to sensorineural deafness when impaired. By genotyping a cohort of 90 control Beauceron dogs sampled in France, we found a 3.3% carrier frequency. The CDH23:c.[700C>T] allele is easily detectable with a genetic test to avoid at-risk matings.

GJB2 and GJB6 gene transcripts in the human cochlea: A study using RNAscope, confocal, and super-resolution structured illumination microscopy.

BackgroundGap junction (GJ) proteins, connexin26 and 30, are highly prevalent in the human cochlea (HC), where they are involved in transcellular signaling, metabolic supply, and fluid homeostasis. Their genes, GJB2 and GJB6, are both located at the DFNB1 locus on chromosome 13q12. Mutations in GJB2 may cause mild to profound non-syndromic deafness. Here, we analyzed for the first time the various expressions of GJB2 and GJB6 gene transcripts in the different cell networks in the HC using the RNAscope technique.Materials and methodsArchival paraformaldehyde-fixed sections of surgically obtained HC were used to label single mRNA oligonucleotides using the sensitive multiplex RNAscope® technique with fluorescent-tagged probes. Positive and negative controls also included the localization of ATP1A1, ATP1A2, and KCNJ10 gene transcripts in order to validate the specificity of labeling.ResultsConfocal and super-resolution structured illumination microscopy (SR-SIM) detected single gene transcripts as brightly stained puncta. The GJB2 and GJB6 gene transcripts were distributed in the epithelial and connective tissue systems in all three cochlear turns. The largest number of GJB2 and GJB6 gene transcripts was in the outer sulcus, spiral ligament, and stria vascularis (SV). Oligonucleotides were present in the supporting cells of the organ of Corti (OC), spiral limbus fibrocytes, and the floor of the scala vestibuli. Multiplex gene data suggest that cells in the cochlear lateral wall contain either GJB2 or GJB6 gene transcripts or both. The GJB6, but not GJB2, gene transcripts were found in the intermediate cells but none were found in the marginal cells. There were no GJB2 or GJB6 gene transcripts found in the hair cells and only a few in the spiral ganglion cells.ConclusionBoth GJB2 and GJB6 mRNA gene transcripts were localized in cells in the adult HC using RNAscope® in situ hybridization (ISH) and high resolution microscopy. Generally, GJB6 dominated over GJB2, except in the basal cells. Results suggest that cells may contain either GJB2 or GJB6 gene transcripts or both. This may be consistent with specialized GJ plaques having separate channel permeability and gating properties. A reduction in the number of GJB2 gene transcripts was found in the basal turn. Such information may be useful for future gene therapy.

Genetic Load of Alternations of Transcription Factor Genes in Non-Syndromic Deafness and the Associated Clinical Phenotypes: Experience from Two Tertiary Referral Centers.

Sensorineural hearing loss is one of the most common inherited sensory disorders. Functional classifications of deafness genes have shed light on genotype- and mechanism-based pharmacological approaches and on gene therapy strategies. In this study, we characterized the clinical phenotypes and genotypes of non-syndromic deafness caused by transcription factor (TF) gene variants, one of the functional classifications of genetic hearing loss. Of 1280 probands whose genomic DNA was subjected to molecular genetic testing, TF genes were responsible for hearing loss in 2.6%. Thirty-three pathogenic variants, including nine novel variants, accounting for non-syndromic deafness were clustered in only four TF genes (POU3F4, POU4F3, LMX1A, and EYA4), which is indicative of a narrow molecular etiologic spectrum of TF genes, and the functional redundancy of many other TF genes, in the context of non-syndromic deafness. The audiological and radiological characteristics associated with the four TF genes differed significantly, with a wide phenotypic spectrum. The results of this study reveal the genetic load of TF gene alterations among a cohort with non-syndromic hearing loss. Additionally, we have further refined the clinical profiles associated with TF gene variants as a basis for a personalized, genetically tailored approach to audiological rehabilitation.

Template-independent genome editing in the Pcdh15av-3j mouse, a model of human DFNB23 nonsyndromic deafness.

Although frameshift mutations lead to 22% of inherited Mendelian disorders in humans, there is no efficient invivo gene therapy strategy available to date, particularly in nondividing cells. Here, we show that nonhomologous end-joining (NHEJ)-mediated nonrandom editing profiles compensate the frameshift mutation in the Pcdh15 gene and restore the lost mechanotransduction function in postmitotic hair cells of Pcdh15av-3J mice, an animal model of human nonsyndromic deafness DFNB23. Identified by an exvivo evaluation system in cultured cochlear explants, the selected guide RNA restores reading frame in approximately 50% of indel products and recovers mechanotransduction in more than 70% of targeted hair cells. Invivo treatment shows that half of the animals gain improvements in auditory responses, and balance function is restored in the majority of injected mutant mice. These results demonstrate that NHEJ-mediated reading-frame restoration is a simple and efficient strategy in postmitotic systems.

P-548 IMPORTANCE OF EXPANDED CARRIER SCREENING AMONG OOCYTE DONORS - questions and concerns

Abstract Study question To examine the utility of a range of expanded screening panels for oocyte donors. Summary answer Expanded carrier screening with NGS data identified that 86% of gamete donors were carriers of at least one condition while 302 genes were tested. What is known already The level of genetic testing for oocyte donors is not regulated in most countries. The use of expanded carrier screening is recommended more widely. If the egg donor is a carrier, there is a 50% chance that the offspring will also be carriers. Expanded carrier screening is performed to determine the potential effects of positive carrier status, which guarantees safety for future pregnancy. From practical experience, more genes are tested for a donor, more potential mutations are detected. Study design, size, duration A cohort of 92 potential oocyte donor applicants aged 18-30 years old, who were qualified for oocyte donation after full screening, tested negative on an initial cystic fibrosis carrier test for 11 most common CFTR mutations (PCR panel), was further screened with expanded commercial carrier testing panel (302 genes) using next-generation sequencing (NGS) data. Participants/materials, setting, methods A cohort of 92 potential oocyte donor applicants aged 18-30 years old, who tested negative on an initial cystic fibrosis carrier test for 11 most common CFTR mutations (PCR panel), was further screened with expanded commercial carrier testing panel (302 genes) using next-generation sequencing (NGS) data. Main results and the role of chance Genotyping results for all donors were analyzed; 38% (35/92) of donors were identified as carriers for one condition, 34% (31/92)- for two conditions, 7% (6/92)- for three conditions and 7% (6/92)- for four conditions, including cystic fibrosis. Among the most prevalent conditions in our study were: Hemochromatosis: Type 1: HFE Related- 22%, Cystic Fibrosis: CFTR-related conditions 11%, Biotinidase deficiency– 7,6%, 21-Hydroxilase-Deficient Congenital Nonclassical Adrenal Hyperplasia- 6,5%, Krabbe disease – 6,5%, Usher syndrome: USH2A-related conditions – 6,5%, Nonsyndromic deafness: GJB2- related conditions- 5,4% and Smith-Lemli-Opitz syndrome (5,4%). Limitations, reasons for caution Each donor was consented for genetic testing Wider implications of the findings This study shows a need to provide the explicit requirement for oocyte donor genetic testing and guidelines to satisfy quality and safety and not reduce the number of donors carries of mutations, but to implement a practice of genetic matching. Trial registration number not applicable

Mutations in MINAR2 encoding membrane integral NOTCH2-associated receptor 2 cause deafness in humans and mice

Discovery of deafness genes and elucidating their functions have substantially contributed to our understanding of hearing physiology and its pathologies. Here we report on DNA variants in MINAR2, encoding membrane integral NOTCH2-associated receptor 2, in four families underlying autosomal recessive nonsyndromic deafness. Neurologic evaluation of affected individuals at ages ranging from 4 to 80 y old does not show additional abnormalities. MINAR2 is a recently annotated gene with limited functional understanding. We detected three MINAR2 variants, c.144G > A (p.Trp48*), c.412_419delCGGTTTTG (p.Arg138Valfs*10), and c.393G > T, in 13 individuals with congenital- or prelingual-onset severe-to-profound sensorineural hearing loss (HL). The c.393G > T variant is shown to disrupt a splice donor site. We show that Minar2 is expressed in the mouse inner ear, with the protein localizing mainly in the hair cells, spiral ganglia, the spiral limbus, and the stria vascularis. Mice with loss of function of the Minar2 protein (Minar2tm1b/tm1b) present with rapidly progressive sensorineural HL associated with a reduction in outer hair cell stereocilia in the shortest row and degeneration of hair cells at a later age. We conclude that MINAR2 is essential for hearing in humans and mice and its disruption leads to sensorineural HL. Progressive HL observed in mice and in some affected individuals and as well as relative preservation of hair cells provides an opportunity to interfere with HL using genetic therapies.

Analysis of TMIE gene mutations including the first large deletion of exon 1 with autosomal recessive non-syndromic deafness

BackgroundTransmembrane inner ear (TMIE) protein is an essential component of the mechanotransduction complex. In collaboration with other components, TMIE aids the maintenance and function of the sensory hair cells. Autosomal recessive deafness-6 (DFNB6) is caused by mutated TMIE, a gene in the high genetic heterogeneity spectrum of deafness. Hearing loss has a significant impact on the global economy and the quality of life of affected persons, their families, and society. Here, three unrelated families with TMIE variants are presented. All three cases were found while studying the genetic causes of an Iranian cohort of subjects with cochlear implants.MethodsWhole exome sequencing was performed to find possible genetic etiology in probands of families after a comprehensive medical evaluation for hearing loss. Co-segregation analysis in probands and other family members was performed by Sanger sequencing. The variants were interpreted per the American College of Medical Genetics and Genomics guidelines.ResultsThree different variants associated with TMIE were confirmed as reasons for autosomal recessive non-syndromic deafness. The first novel ~ 10-kb deletion surrounding exon 1 of TMIE along with two previously reported variants co-segregated with families including a frameshift variant c.122_125dup (p.Pro43fs) and a missense variant c.250 C > T; p.(Arg84Trp) in exons 2, and 3, respectively.ConclusionThis study increases the mutational spectrum of the TMIE gene and highlights the importance of the large deletion of this gene as a reason for hearing loss. Moreover, an efficient and simple multiplex PCR assay was developed to determine the exact breakpoints of the TMIE deletion.

The Reduction in Microtubule Arrays Caused by the Dysplasia of the Non-Centrosomal Microtubule-Organizing Center Leads to a Malformed Organ of Corti in the Cx26-Null Mouse.

Mutations in the GJB2 gene account for approximately 20–50% of all non-syndromic hereditary deafness cases. The malformed organ of Corti (OC) was observed in different Cx26-null mouse models, which was mainly caused by the developmental arrest of pillar cells (PCs). However, the mechanism of developmental abnormalities in PCs caused by Cx26 deletion is still unclear. In this study, the ultrastructure of PCs at different postnatal days was observed in Cx26-null mice. Knockout of cochlear Cx26 led to the malformed assembly of non-centrosomal microtubule-organizing centers (MTOCs) far from the centrosome rather than near the centrosome. Additionally, the microtubule (MT) arrays emitted by abnormal non-centrosomal MTOCs were significantly reduced. In addition, we found that the protein expression of calmodulin-regulated, spectrin-associated protein2 (camsap2), a microtubule minus-end targeting protein associated with the organization of non-centrosomal MTs, was decreased in juvenile PCs in the Cx26-null group. Our results indicated that the malformation of non-centrosomal MTOCs in cochlear PCs might lead to the corresponding MTs’ failure to be captured and anchored in Cx26-null mice, which results in the deformity of OC. Additionally, this abnormal developmental process might be correlated with the reduced expression of camsap2 caused by Cx26 deletion in the early developmental stage.

TBC1D24-related familial infantile multifocal myoclonus: Description of a new Chinese pedigree with a 20 year follow up

IntroductionDisorders associated with mutations in the Tre2/Bub2/Cdc16 (TBC)1 domain family member 24 gene (TBC1D24) present a wide range of phenotypes, ranging from mild to fatal seizure diseases, non-syndromic deafness, and complex syndromes such as deafness, onychodystrophy, osteodystrophy, and mental retardation(DOOR syndrome). In this study, we introduce three siblings of a previously unreported Chinese family with familial infantile myoclonic epilepsy caused by a homozygous TBC1D24 mutation. MethodsGenomic DNA was extracted from whole blood of the proband, his parents, and sisters. TBC1D24 exomes were sequenced by whole exome sequencing then analyzed by genetic analysis with Sanger sequencing validation. The patients were followed up for more than 20 years to summarize their clinical features. ResultsGenetic analysis identified a homozygous TBC1D24 mutation (c.241_252del12) in the proband and his sisters. Prediction models suggest that the mutation leads to an alteration in the properties and structure of the TBC1D24 protein, especially in the folding direction of the loop region, which is likely to decrease protein activity. The patients manifested with early-onset myoclonic epilepsy, were prone to status epilepticus, and seizures only occurred during wakefulness. Imaging characteristics included cerebellar atrophy and abnormal cerebellar signals. ConclusionWe report a pedigree case of infantile myoclonic epilepsy caused by a homozygous TBC1D24 mutation. Our long-term clinical follow-up not only enriches the clinical phenotype of the disease, but also provides a clinical experience for the early diagnosis and clinical treatment of the disease.

Calcium- and Integrin-Binding Protein 2 (CIB2) in Physiology and Disease: Bright and Dark Sides.

Calcium- and integrin-binding protein 2 (CIB2) is a small EF-hand protein capable of binding Mg2+ and Ca2+ ions. While its biological function remains largely unclear, an increasing number of studies have shown that CIB2 is an essential component of the mechano-transduction machinery that operates in cochlear hair cells. Mutations in the gene encoding CIB2 have been associated with non-syndromic deafness. In addition to playing an important role in the physiology of hearing, CIB2 has been implicated in a multitude of very different processes, ranging from integrin signaling in platelets and skeletal muscle to autophagy, suggesting extensive functional plasticity. In this review, we summarize the current understanding of biochemical and biophysical properties of CIB2 and the biological roles that have been proposed for the protein in a variety of processes. We also highlight the many molecular aspects that remain unclarified and deserve further investigation.

Abstract TP179: Candidate Genes For Small Vessel Ischemic Stroke: A Gwas Pilot Study

Background: The genetic basis of small vessel stroke (SVS) is poorly understood. Few genetic loci have been identified that may provide insights into SVS pathogenesis. We sought to identify genetic associations with incident SVS. Methods: A GWAS analysis was performed on a prospective cohort of patients enrolled in the American Stroke Association- Bugher Small Vessel Intracranial Disease Whole Genome Association Study which included patients from 4 hospitals in North Carolina recruited between December 2007-August 2012. Patients with SVS in the prior 2 years confirmed clinically and on neuroimaging were compared to a control group who had no previous history of stroke. A logistic regression model with SVS as the outcome and single nucleotide polymorphisms (SNPs) as the main predictor was performed and adjusted for baseline demographics and clinical characteristics, including age, race/ethnicity, sex, tobacco use, history of hypertension, diabetes, hyperlipidemia, atrial fibrillation, history of stroke/TIA, and principal components. Because of the relatively small sample size, SNPs with p-values <1E-4 were considered significant. Results: The cohort included 139 patients who had SVS and 64 controls. Among this cohort, 50% were men and 38% African-American. The mean age of the study group was 63-years. Sixteen SNPs in 9 genes met the statistical cutoff for association with SVS. These were involved in extracellular matrix integrity (CHD23, CLDN14, SPTBN1), neuronal differentiation (DSCAML1), cholesterol transport (GRAMD1B), transcriptional regulation (JARID2, LINC02111, LINC01993) and voltage-gated potassium channel (KCND2). Conclusion: In this pilot GWAS study, several loci variations were associated with SVS. Although this study is hypothesis generating, previous studies have also shown an association of SVS with genes involved in extracellular matrix integrity. In addition, we found it interesting that SNPs in both CLDN14 and CDH23 genes, which have been linked to non-syndromic sensorineural deafness, are also more common in SVS. Some forms of sensorineural deafness have been associated with cognitive impairment and stroke, and if a genetic association is confirmed, it would suggest a common pathophysiology may link the two conditions.

Report of rare and novel mutations in candidate genes in a cohort of hearing-impaired patients.

BackgroundMany hearing‐impaired patients carry mutations in rare or novel genes undetected in regular genetic hot regions/genes screening.MethodsWe collected clinical and genetic data from subjects with hearing loss who visited our department for genetic counseling. Next‐generation sequencing was conducted after 154 deafness‐related genes were captured using a designed genes panels in 14 unrelated families (37 participants). The results were filtered and assessed with in silico tools, in combination with pedigree mapping.ResultsTen mutations in regular deafness genes (GJB2, SLC26A4) and uncommon genes (OTOF, MYO7A, MYO15A, and KARS) were detected, which constituted 57.2% of yielded rate. In particular, two patients with nonsyndromic deafness carried biallelic KARS mutations. In addition, we identified an unreported digenic mutational inheritance in GRP98/USH2A genes in a proband with isolated hearing loss. Functional analyses and molecular modeling suggested the damaging consequence of these variants on encoded proteins. According to the variant pathogenicity guidelines, the 17 identified variants in total were classified as “pathogenic” or “likely pathogenic.”ConclusionThe candidate mutations in deafness genes were suggested to be co‐segregated in at least 57.2% of the studied pedigrees. This is the new report of rare/novel mutations causing inherited hearing loss in Chinese.

Genetic profiles of non-syndromic severe-profound hearing loss in Chinese Hans by whole-exome sequencing

Hereditary hearing loss is highly heterogeneous. Despite over 120 non-syndromic deafness genes have been identified, there are still some of novel genes and variants being explored. In the study, we investigated 105 Chinese Han children with non-syndromic, prelingual, severe-profound hearing loss by whole-exome sequencing on DNA samples. The most common deafness gene was GJB2, mainly in variant c.235delC (p.Leu79CysfsTer3). 14 children were identified with pathogenic mutations in three genes, GJB2, SLC26A4, and OTOF. Two mutations have been identified to be pathogenic and not recorded previously, including c.4691G > A (p.Trp1564Ter) and c.3928_3930dup (p.Lys1310dup) in OTOF. The rare variants c.1349G > A (p.Arg450His) and c.456 T > G (p.Asn152Lys) in GSDME, and c.1595G > T (p.Ser532Ile) in SLC26A4 were detected. The frequency of nonsense variant c.2359G > T (p.Glu787Ter) in OTOA was very high in 17 cases. Four of them were identified to be digenic inheritance, including GJB2 and COL4A4, GJB2 and EYA1, GJB2 and COL4A5, and GJB2 and DFNA5. The findings showed that a novel pathogenic variant and rare variants may be associated with severe and profound hearing loss.