Usher syndrome:Genetic diagnosis and current therapeutic approaches

Usher Syndrome(USH)is the most common deaf-blind syndrome,affecting approximately 1 in 6000 people in the deaf population.This genetic condition is characterized by a combination of hearing loss(HL),retinitis pigmentosa,and,in some cases,vestibular areflexia.Among the subtypes of USH,USH type 1 is considered the most severe form,presenting profound bilateral congenital deafness,vestibular areflexia,and early onset RP.USH type 2 is the most common form,exhibiting congenital moderate to severe HL for low frequencies and severe to profound HL for high frequencies.Conversely,type 3 is the rarest,initially manifesting mild symptoms during childhood that become more prominent in the first decades of life.The dual impact of USH on both visual and auditory senses significantly impairs patients'quality of life,restricting their daily activities and interactions with society.To date,9 genes have been confirmed so far for USH:MYO7A,USH1C,CDH23,PCDH15,USH1G,USH2A,ADGRV1,WHRN and CLRN1.These genes are inherited in an autosomal recessive manner and encode proteins expressed in the inner ear and retina,leading to functional loss.Although non-genetic methods can assist in patient triage and disease extension evaluation,genetic and molecular tests play a pivotal role in providing genetic counseling,enabling appropriate gene therapy,and facilitating timely cochlear implantation(CI).The CRISPR/Cas9 system and viral-based gene replacement therapy have recently emerged as highly promising techniques for treating USH.Regarding drug therapy,PTC-124 and Nb54 have been identified as promising drug interventions for genetic HL in USH.Simultaneously,CI has proven to be critical in the restoration of hearing.This review aims to summarize the genetic and molecular diagnosis of USH and highlight the importance of early diagnosis in Cuzzuol BR et al.Diagnosis and current treatments of USH WJO https://www.wjgnet.com 2 January 19,2024 Volume 11 Issue 1 guiding appropriate treatment strategies and improving patient prognosis.

Phenotype of Usher syndrome type Ⅱ assosiated with compound missense mutations of c.721 C>T and c.1969 C>T in MYO7A in a Chinese Usher syndrome family

·AIM: To identify the pathogenic mutations in a Chinese pedigree affected with Usher syndrome type II(USH2).· METHODS: The ophthalmic examinations and audiometric tests were performed to ascertain the phenotype of the family. To detect the genetic defect,exons of 103 known RDs-associated genes including 12 Usher syndrome(USH) genes of the proband were captured and sequencing analysis was performed to exclude known genetic defects and find potential pathogenic mutations. Subsequently, candidate mutations were validated in his pedigree and 100 normal controls using polymerase chain reaction(PCR) and Sanger sequencing.·RESULTS: The patient in the family occurred hearing loss(HL) and retinitis pigmentosa(RP) without vestibular dysfunction, which were consistent with standards of classification for USH2. He carried the compound heterozygous mutations, c.721 C 】T and c.1969 C 】T, in the MYO7 A gene and the unaffected members carried only one of the two mutations. The mutations were not present in the 100 normal controls.· CONCLUSION: We suggested that the compound heterozygous mutations of the MYO7 A could lead to USH2, which had revealed distinguished clinical phenotypes associated with MYO7 A and expanded the spectrum of clinical phenotypes of the MYO7 A mutations.

In silico analysis of a disease-causing mutation in PCDH15 gene in a consanguineous Pakistani family with Usher phenotype

AIM： To map Usher phenotype in a consanguineous Pakistani family and identify disease-associated mutation in a causative gene to establish phenotype-genotype correlation.· METHODS： A consanguineous Pakistani family in which Usher phenotype was segregating as an autosomal recessive trait was ascertained. On the basis of results of clinical investigations of affected members of this family disease was diagnosed as Usher syndrome（USH）. To identify the locus responsible for the Usher phenotype in this family, genomic DNA from blood sample of each individual was genotyped using microsatellite Short Tandem Repeat（STR） markers for the known Usher syndrome loci. Then direct sequencing was performed to find out disease associated mutations in the candidate gene.· RESULTS： By genetic linkage analysis, the USH phenotype of this family was mapped to PCDH15 locus on chromosome 10q21.1. Three different point mutations in exon 11 of PCDH15 were identified and one of them,c.1304AC was found to be segregating with the disease phenotype in Pakistani family with Usher phenotype.This, c.1304 A C transversion mutation predicts an amino-acid substitution of aspartic acid with an alanine at residue number 435（p.D435A） of its protein product.Moreover, in silico analysis revealed conservation of aspartic acid at position 435 and predicated this change as pathogenic.·CONCLUSION：Theidentificationofc.1304ACpathogenic mutation in PCDH15 gene and its association with Usher syndrome in a consanguineous Pakistani family is thefirst example of a missense mutation of PCDH15 causing USH1 phenotype. In previous reports, it was hypothesized that severe mutations such as truncated protein of PCDH15 led to the Usher I phenotype and that missense variants are mainly responsible for non-syndromic hearing impairment.

Cochlear implants in genetic deafness

Genetic defects are one of the most important etiologies of severe to profound sensorineural hearing loss and play an important role in determining cochlear implantation outcomes.While the pathogenic mutation types of a number of deafness genes have been cloned,the pathogenesis mechanisms and their relationship to the outcomes of cochlear implantation remain a hot research area.The auditory performance is considered to be affected by the etiology of hearing loss and the number of surviving spiral ganglion cells,as well as others.Current research advances in cochlear implantation for hereditary deafness,especially the relationship among clinic-types,genotypes and outcomes of cochlear implantation,will be discussed in this review.

USH2A mutation and specific driver mutation subtypes are associated with clinical efficacy of immune checkpoint inhibitors in lung cancer

This study aimed to identify subtypes of genomic variants associated with the efficacy of immune checkpoint inhibitors(ICIs)by conducting systematic literature search in electronic databases up to May 31,2021.The main outcomes including overall survival(OS),progression-free survival(PFS),objective response rate(ORR),and durable clinical benefit(DCB)were correlated with tumor genomic features.A total of 1546 lung cancer patients with available genomic variation data were included from 14 studies.The Kirsten rat sarcoma viral oncogene homolog G12C(KRAS^(G12C))mutation combined with tumor protein P53(TP53)mutation revealed the promising efficacy of ICI therapy in these patients.Furthermore,patients with epidermal growth factor receptor(EGFR)classical activating mutations(including EGFRL858Rand EGFRΔ19)exhibited worse outcomes to ICIs in OS(adjusted hazard ratio(HR),1.40;95%confidence interval(CI),1.01-1.95;P=0.0411)and PFS(adjusted HR,1.98;95%CI,1.49-2.63;P<0.0001),while classical activating mutations with EGFR^(T790)Mshowed no difference compared to classical activating mutations without EGFR^(T790)Min OS(adjusted HR,0.96;95%CI,0.48-1.94;P=0.9157)or PFS(adjusted HR,0.72;95%CI,0.39-1.35;P=0.3050).Of note,for patients harboring the Usher syndrome type-2A(USH2A)missense mutation,correspondingly better outcomes were observed in OS(adjusted HR,0.52;95%CI,0.32-0.82;P=0.0077),PFS(adjusted HR,0.51;95%CI,0.38-0.69;P<0.0001),DCB(adjusted odds ratio(OR),4.74;95%CI,2.75-8.17;P<0.0001),and ORR(adjusted OR,3.45;95%CI,1.88-6.33;P<0.0001).Our findings indicated that,USH2A missense mutations and the KRAS^(G12C)mutation combined with TP53 mutation were associated with better efficacy and survival outcomes,but EGFR classical mutations irrespective of combination with EGFR^(T790)Mshowed the opposite role in the ICI therapy among lung cancer patients.Our findings might guide the selection of precise targets for effective immunotherapy in the clinic.

Advances in cochlear implantation for hereditary deafness caused by common mutations in deafness genes

The pathogenic factors of deafness are complex;more than 50%of cases are caused by genetic factors.Between 75%and 80%of cases of hereditary hearing impairment are autosomal recessive,15%to 25%are autosomal dominant,and 1%to 2%are mitochondrial or X-linked.Cochlea implantation is the main method for treating severe and extremely severe bilateral sensorineural deafness and it is widely used in clinical treatment.As clinical cases of cochlea implantation accumulate,differences in the efficacy of implantation in individuals are emerging and attracting attention.In addition to residual hearing level,implantation age,and other factors,gene mutation is an important factor influencing postoperative rehabilitation in patients.With continuous progress in genetic testing technology for deafness,genetic diagnosis has become an important tool in preoperative evaluation and postoperative effect prediction in patients undergoing cochlear implantation.This article reviews the current status and future development of cochlear implantation in the treatment of hereditary deafness resulting from mutations in common deafness-causing genes.