Identification Of The Causative Genes For Three Families With Autosomal Dominant Hereditary Hearing Loss And One Family With Auditory Neuropathy

Deafness is one of the most common clinical hereditary disorders. More than60-80%of individuals can be attributed to genetic causes and about20-40%of cases are causedby environmental factors. Most of hereditary hearing impairment is caused bymonogenic mutations. Exome sequencing approach is exerted in the identification of thecausal genes of three families with autosomal dominant hereditary hearing loss.And wealso indentified the causative gene of a auditory neuropathy with Candidate genescreening methods.We identified one novel deafness gene WYF1, a novel causativenonsense mutation p.E375X in DFNA5, and two novel pathogenic mutations p.L517Pand p.I1967del in OTOF. Currently we are doing preliminary functional studies toexplore the pathogenic mechanism of WYF1defect using zebrafish model.Part IClinical Characteristics and Identification of Causative Genes of Three ChineseFamilies with Autosomal Dominant Hereditary Sensorineural Hearing LossFamily FJ-C199is a five-generation Chinese family mainly with progressiveautosomal dominant hereditary hearing loss and tinnitus,and some affected individualsare accompanied with strabismus or nystagmus. The age at onset ranged from9to50years old. The characteristics of audiological assessments of the affected individualscorrespond with that of autosomal dominant hereditary hearing loss.This family ischaracterized by hearing loss,so its hearing loss and nysagmus maybe caused byrespective causative genes;however, it can not be ruled out the possibility that the twophenotypes is of a syndrome, because all individuals with nystagmus is affected withhearing loss and without segregation.Whole exome sequencing and sanger sequencing identified heterozygous framshiftmutation p.D326AfsX42in WYF1in all affected members, and none of the clinicallyunaffected family members carried this varian.WYF1is a transcriptional factor,expressed in the otic vesicle and optic vesicle of mouse，chick and zebrafish.Nineaffected individuals who carried WYF1mutation showed speech delay,accompanied with malformed ears or hearing loss,some with abnormal eye development.Family GD-H238is a five-generation Chinese family, comprising19affectedmembers with hearing impairment. Audiological assessments of the affected individualsrevealed symmetrical, bilateral, progressive, sensorineural hearing loss, which mainlyaffected high frequencies in the initial phase, but the onset age was significantlydifferent (10-30years old and60years old, respectively). The pedigree suggests thatgroup A applies in accordance with typical DFNA, while the group B showed dominanthereditary presbycusis.Whole exome sequencing of Group A of this family identified a novel nonsensemutation in exon8of DFNA5. Sanger sequencing suggested that this mutationco-segregated with the hearing loss phenotype, and it is the pathogenic mutation of thisfamily.Four known DFNA5pathogenic mutation all located in intron7of DFNA5.Thep.E375X mutation we found is the first pathogenic mutation in exon8. This finding willplay an important role in the exploration of the pathogenic mechanism of DFNA5.Family HB-Z177is a five-generation Chinese family with autosomal dominanthereditary hearing loss. Senven affected individuals alive showed late-onset hearingimpairment．The age at onset ranged10-30years old. Audiological assessments of theaffected individuals revealed bilateral, progressive, moderate or severe sensorineuralhearing loss.Whole exome sequencing identified six known deafness gene mutationsand many other variants, three candidates of the six mutations and four suspectedvariants have been tested in the whole family and were ruled out as the causal mutation.So hearing loss might be caused by mutation on a novel one. For the rapid screening ofthe novel causative gene, it is better to choose more than two samples to do the wholeexome sequencing.Part IIStudy of Pathogenic Mechanism of Autosomal Dominant Deafness Gene WYF1WYF1is a transcriptional factor,expressed in the otic vesicle and optic vesicle ofmouse，chick and zebrafish. To examine WYF1function during ear development,twomorpholino antisense oligonucleotides were created; one blocking the translational startsite of WYF1and the other interfering with WYF1mRNA splicing. Injection of either ofthese morpholinos resulte in otoliths fusion and smaller eyes, suggesting that WYF1play a significant role in the development of ear and eye. Part IIIIdentification of Two Novel Mutations in OTOF of a Family With AutosomalRecessive Hereditary Auditory NeuropathyFamily AH-X306is a auditoty neurapathy family, with four affected members,which is of autosomal recessive hereditary hearing loss mode. With the candidate genemethods, we identified two novel mutations in OTOF, p.L517P and p.I1967del, and thehomologous p.L517P mutation result in a severer hearing loss than the compoundheterozygous mutations p.L517P and p.I1967del in OTOF.