Genetically modified pigs:Emerging animal models for hereditary hearing loss

Hereditary hearing loss(HHL),a genetic disorder that impairs auditory function,significantly affects quality of life and incurs substantial economic losses for society.To investigate the underlying causes of HHL and evaluate therapeutic outcomes,appropriate animal models are necessary.Pigs have been extensively used as valuable large animal models in biomedical research.In this review,we highlight the advantages of pig models in terms of ear anatomy,inner ear morphology,and electrophysiological characteristics,as well as recent advancements in the development of distinct genetically modified porcine models of hearing loss.Additionally,we discuss the prospects,challenges,and recommendations regarding the use pig models in HHL research.Overall,this review provides insights and perspectives for future studies on HHL using porcine models.

Autosomal dominant non-syndromic hearing loss caused by a novel mutation in MYO7A:A case report and review of the literature

BACKGROUND Variants in the MYO7A gene commonly result in Usher syndrome,and in rare cases lead to autosomal dominant non-syndromic deafness(DFNA11).Currently,only nine variants have been reported to be responsible for DFNA11 and their clinical phenotypes are not identical.Here we present a novel variant causing DFNA11 identified in a three-generation Chinese family.CASE SUMMARY The proband was a 53-year-old Han male who presented with post-lingual bilateral symmetrical moderate sensorineural hearing loss.We learned from the patient’s medical history collection that multiple family members also had similar hearing loss,generally occurring around the age of 40.Subsequent investigation by high-throughput sequencing identified a novel MYO7A variant.To provide evidence supporting that this variant is responsible for the hearing loss in the studied family,we performed Sanger sequencing on 11 family members and found that the variant co-segregated with the deafness phenotype.In addition,the clinical manifestation of the 11 affected family members was found to be lateonset bilateral slowly progressive hearing loss,inherited in this family in an autosomal dominant manner.None of the affected family members had visual impairment or vestibular symptoms;therefore,we believe that this novel MYO7A variant is responsible for the rare DFNA11 in this family.CONCLUSION We report a novel variant leading to DFNA11 which further enriches the collection of MYO7A variants,and our review of the nine previous variants that have been identified to cause DFNA11 provides a reference for clinical genetic counseling.

NON-SYNDROMIC HEARING LOSS AND HIGH- THROUGHPUT STRATEGIES TO DECIPHER ITS GENETIC HETEROGENEITY

Hearing loss (HL) is the most common sensory disorder, affecting all age groups, ethnicities, and gen-ders. According to World Health Organization (WHO) estimates in 2005, 278 million people worldwide have moderate to profound HL in both ears. Results of the 2002 National Health Interview Survey indicate that nearly 31 million of all non-institutionalized adults (aged 18 and over) in the United States have trouble hearing. Epidemiological studies have estimated that approximately 50%of profound HL can be attributed to genetic causes. With over 60 genes implicated in nonsyndromic hearing loss, it is also an extremely het-erogeneous trait. Recent progress in identifying genes responsible for hearing loss enables otolaryngologists and other clinicians to apply molecular diagnosis by genetic testing. The advent of the $1000 genome has the potential to revolutionize the identification of genes and their mutations underlying genetic disorders. This is especially true for extremely heterogeneous Mendelian conditions such as deafness, where the muta-tion, and indeed the gene, may be private. The recent technological advances in target-enrichment methods and next generation sequencing offer a unique opportunity to break through the barriers of limitations im-posed by gene arrays. These approaches now allow for the complete analysis of all known deafness-causing genes and will result in a new wave of discoveries of the remaining genes for Mendelian disorders. This re-view focuses on describing genotype-phenotype correlations of the most frequent genes including GJB2, which is responsible for more than half of cases, followed by other common genes and on discussing the im-pact of genomic advances for comprehensive genetic testing and gene discovery in hereditary hearing loss.

Impact of next-generation sequencing on molecular diagnosis of inherited non-syndromic hearing loss

Hearing loss is one of the most common birth defects,with inherited genetic defects play an important role,contributing to about 60%of deafness occurring in infants.However,hearing impairment is genetically heterogeneous,with both common and rare forms occurring due to mutations in estimated 500 genes.Due to the large number and presumably low mutation frequencies of those genes,it would be highly expensive and time-consuming to address this issue by conventional gene-by-gene Sanger sequencing.Next-generation sequencing is a revolutionary technology that allows the simultaneous screening of mutations in a large number of genes.It is cost effective compared to classical strategies of linkage analysis and direct sequencing when the number or size of genes is large,and thus has become a highly efficient strategy for identifying novel causative genes and mutations involved in heritable disease.In this review, we describe major NGS methodologies currently used for genetic disorders and highlight applications of these technologies in studies of molecular diagnosis and the discovery of genes implicated in non-syndromic hearing loss.

Induced pluripotent stem cells:Landscape for studying and treating hereditary hearing loss

Hearing loss(HL) is one of the most widespread sensory disorders,affecting approximately 1 in 500 newborns.Heritable diseases of the inner ear are the leading causes of prelingual HL.Treating of hereditary HL and understanding its underlying mechanisms remain difficult challenges to otolaryngologists.As stem cells are capable of self-renewal and differentiation,they are ideally suited both for disease modeling and regenerative medicine.Recently,description of induced pluripotent stem cells(iPSCs) has allowed the field of disease modeling and personalized therapy to become far more accessible and physiologically relevant,as iPSCs can be generated from patients of any genetic background.This review briefly describes the advantages of iPSCs technology and discusses potential applications of this powerful biological tool in studying and treating hereditary HL.

The genetic load for hereditary hearing impairment in Chinese population and its clinical implication

Objective To understand the genetic load in the Chinese population for improvement in diagnosis, prevention and rehabilitation of deafness. Methods DNA samples, immortalized cell lines as well as detailed clinical and audiometric data were collected through a national genetic resources collecting network. Two conventional genetic approaches were used in the studies. Linkage analysis in X chromosome and autosomes with microsatellite markers were performed in large families for gene mapping and positional cloning of novel genes. Candidate gene approach was used for screening the mtDNA 12SrRNA, GJB2 and SLC26A4 mutations in population -based samples. Results A total of 2,572 Chinese hearing loss families or sporadic cases were characterized in the reported studies, including seven X-linked, one Y-linked, 28 large and multiplex autosomal dominant hearing loss families, 607 simplex autosomal recessive hereditary hearing loss families, 100 mitochondrial inheritance families, 147 GJB2 induced hearing loss cases, 230 cases with enlarged vestibular aqueduct (EVA) syndrome, 169 sporadic cases with auditory neuropathy, and 1,283 sporadic sensorineural hearing loss cases. Through linkage analysis or sequence analysis, two X-linked families were found transmitting two novel mutations in the POU3F4 gene, while another X -linked family was mapped onto a novel locus, nominated as AUNX1 (auditory neuropathy, X-linked locus 1). The only Y-linked family was mapped onto the DFNY1 locus(Y-linked locus 1, DFNY1). Eight of the 28 autosomal dominant families were linked to various autosomal loci. In population genetics studies, 2,567 familial cases and sporadic patients were subjected to mutation screening for three common hearing loss genes: mtDNA 12S rRNA 1555G, GJB2 and SLC26A4. The auditory neuropathy cases in our samples were screened for OTOF gene mutations. Conclusions These data show that the Chinese population has a genetic load on hereditary hearing loss. Establishing personalized surveillance and prevention models for hearing loss based on genetic research will provide the opportunity to decrease the prevalence of deafness in the Chinese population.

<i>GJB2</i>Gene Related Nonsyndromic Hearing Loss in Mazandaran Province, North of Iran

Introduction: Congenital hearing loss is the most common sensory deficit in the world and mutations in GJB2 gene are the most common cause of deafness in many populations. Frequency of GJB2 mutations is estimated about 16% in Iran and varies among different provinces with a decreasing trend from north to south. The aim of this study was to investigate the frequency of GJB2 mutations in Mazandaran province, north of Iran, among non-syndromic hearing loss patients. Methods: 262 patients from 204 families participated in this study. After genomic DNA extraction, GJB2 gene analysis was carried out using DNA sequencing of both coding and non-coding regions by ABI 3130XL genetic analyzer. Results: 30.15% of all subjects showed mutations in GJB2 gene. Four mutations, including c.35delG (Gly12Valfs*), IVSI-1 + 1G > A, c.95G > A (Arg32His) and c.224 G > A (Arg75Gln) comprises 69.89% of all mutations in this study c.35delG and IVSI-1 were the most common mutations among patients respectively. Codon 75 mutation (c.224G > A. p: Arg75Gln) with autosomal dominant inheritance was seen in 7 cases from 3 families. 22 patients showed only one mutation in GJB2 gene and in 126 (48.09%) individuals, parents had a consanguineous marriage. Discussion: Frequency of GJB2 gene related hearing loss among patients was higher than average (16%) in this province. This study also showed a dominant inheritance pattern of GJB2 gene in this area. Consanguineous marriage also showed highly frequent among parents. More investigation needs to clarify cause of hearing loss in those 22 patients with one mutation in GJB2 gene, either two gene inheritance or another gene may be responsible for hearing loss.

遗传性耳聋基因治疗专家共识(2023,上海)

遗传性耳聋是常见的致残性疾病之一,临床尚无有效治疗药物。近年,基因治疗在临床前遗传性耳聋动物模型中获得显著疗效,推动了多项耳聋基因治疗临床试验的启动和开展。然而,目前尚无针对耳聋基因治疗的相关规范或共识。复旦大学附属眼耳鼻喉科医院作为国际首个成功开展遗传性耳聋基因治疗临床试验的单位,积累了一定经验。基于此,并参考其他疾病基因治疗共识,联合上海市多家单位的耳科学、听力学、遗传学、基因治疗及康复学等专家,在适用人群选择、围手术期准备、基因治疗药物注射及其安全性和有效性评估、治疗后康复等方面制订本共识,为相关从业人员提供参考和依据,以规范遗传性耳聋基因治疗的临床开展。

A novel de novo mutation of ACTG1 in two sporadic non-syndromic hearing loss cases

Dear Editor,Actins are a family of essential cytoskeletal proteins involved in nearly all cellular processes（Lambrechts et al.,2004）.Of the six human genes that encode actins,only ACTG1and ACTB are ubiquitously expressed.ACTG1（OMIM#604717）,which is linked to the DFNA20/26 locus,wasidentified in autosomal dominant, non-syndromic hearing loss （NSHL） cases （Baek et al., 2012; Liu et al., 2008; Park et al., 2013; Yuan et al., 2016）. In addition, some ACTG1 （OMIM #614583） mutations are associated with Baraitser-Winter syndrome, which is characterized by developmental delay, facial dysmorphologies, brain malformations, colobomas, and variable hearing loss （Riviere et al., 2012）.

一个Alport综合征家庭的临床特征及遗传病因学分析

目的分析一个Alport综合征家庭的临床特征及遗传学病因。方法选取2019年12月于南通大学附属医院耳鼻咽喉科门诊就诊的一个AS耳聋家庭(NT103),该家庭家系成员包括父母姐妹4例,其中姐姐为AS患者(Ⅱ-1),其余人临床表现均无异常。对Alport综合征家庭进行详尽临床资料的收集和评估;采用基于家庭为单位,结合定向捕获技术二代测序的策略分析测序结果;对可疑致病基因的变异位点进行家庭内Sanger测序验证,依据美国医学遗传学与基因组学学会(American College of Medical Genetics and Genomics,ACMG)指南确定变异致病性。结果该Alport综合征家庭的先证者表现为持续性血尿伴感音神经性聋但无眼部异常。定向捕获及Sanger测序显示,患者(Ⅱ-1)携带COL4A3复合杂合错义突变,c.4793T>G,p.L1598R/c.4981C>T,p.R1661C分别来自父母双亲,且在家系其他成员中共分离。根据ACMG指南,该Alport综合征家庭先证者携带的COL4A3基因复合杂合突变位点,判定为疑似致病变异。结论本研究丰富了COL4A3临床表型谱及基因突变谱。此外,对于疑似Alport综合征的患者,提倡常规开展基因检测以实现Alport综合征患者的早期个体化精准诊治。

New SNP variants of MARVELD2(DFNB49) associated with non-syndromic hearing loss in Chinese population

Non-syndromic hearing loss(NSHL)is a common defect in humans.Variants of MARVELD2 at the DFNB49 locus have been shown to cause bilateral,moderate to profound NSHL.However,the role of MARVELD2 in NSHL susceptibility in the Chinese population has not been studied.Here we conducted a case-control study in an eastern Chinese population to profile the spectrum and frequency of MARVELD2 variants,as well as the association of MARVELD2 gene variants with NSHL.Our results showed that variants identified in the Chinese population are significantly different from those reported in Slovak,Hungarian,and Czech Roma,as well as Pakistani families.We identified 11 variants in a cohort of 283 NSHL cases.

PLS1基因突变致非综合征型耳聋的研究进展

PLS1基因(OMMI:602734)编码PLS1蛋白。PLS1蛋白是一种肌动蛋白捆绑蛋白,在横结肠、小肠末端和内耳细胞中均有表达,参与微绒毛的组成,有助于维持静纤毛的稳定性。研究发现,PLS1基因突变将导致其表达的PLS1蛋白被破坏,从而导致不同程度的轻度至重度进行性高频感音性耳聋。目前,在世界范围内已经报道了数例PLS1基因碱基替换突变突变导致常染色体显性非综合征型耳聋的病例。我们对PLS1基因突变导致非综合征型遗传性耳聋的研究进展予以综述。

陕西宝鸡地区新生儿耳聋基因筛查结果分析

目的分析陕西省宝鸡地区新生儿常见遗传性耳聋基因突变情况,为遗传性耳聋患者的临床治疗提供参考依据。方法选取2021年1月至2023年4月在陕西宝鸡市妇幼保健院出生的1985例新生儿作为研究对象,采用微阵列芯片杂交法检测4种遗传性耳聋基因(GJB2、GJB3、SLC26A4和线粒体mt DNA 12S rRNA)15个位点,将耳聋基因检测结果进行统计分析。同时将陕西宝鸡地区新生儿耳聋基因突变情况与国内其他地区进行比较。结果1985例新生儿中检出耳聋基因突变108例(5.44%)其中GJB2携带率最高,为2.67%,SLC26A4携带率为2.02%,GJB3携带率为0.40%,线粒体mt DNA 12S rRNA携带率为0.35%;以GJB2(c.235 del C)突变率(1.86%)最高,其次为SLC26A4(c.IVS7-2 A>G)突变率(1.56%)。与国内其他地区比较,陕西宝鸡地区除线粒体mt DNA 12S rRNA(m.1555 A>G)突变率无差异外,GJB2(c.235 del C)、GJB3(c.538 C>T)、SLC26A4(c.IVS-27-2A>G)突变率均有差异。结论陕西宝鸡地区新生儿携带的耳聋基因突变以GJB2为主,该研究有助于及早查明该地区新生儿听力损失的病因,从而对遗传性耳聋患者进行早期干预。

缝隙连接蛋白26突变导致遗传性耳聋的研究进展

缝隙连接蛋白26(Cx26)是耳蜗中最丰富的缝隙连接蛋白之一,由GJB2基因编码,对耳蜗的发育与听力形成至关重要,Cx26突变患者可表现出不同程度的听力损失。学界曾普遍认为钾离子循环障碍是引起耳聋的主要机制,但近年的研究发现GJB2基因突变相关听力损失中的钾离子循环障碍与耳蜗的病理表型并不直接相关,而耳蜗的发育障碍与氧化应激系统在其中起着关键作用。文章总结了Cx26突变引起相关听力损失的病理生理机制,包括钾离子循环障碍、内耳发育障碍、氧化应激系统失衡等。阐明Cx26突变导致听力损失的病理机制有助于开发针对遗传性耳聋的预防和治疗策略。

耳聋基因检测在产前筛查中的应用

目的探讨耳聋基因检测项目在产前筛查中应用的价值。方法选取2020年4月-2023年9月自愿来吉林市妇产医院检测耳聋基因项目的2980名听力正常的孕妇以及部分孕妇的配偶(137人),采用导流杂交法检测我国4种易感耳聋基因的9个位点,包括GJB2-235、GJB2-299、GJB2-35、GJB2-176,SLC26A4-IVS7(-2)、SLC26A4-2168,GJB3-538,mtDNA1555、mtDNA1494。通过所得阳性数据计算各个基因位点所占阳性百分比。确认受检孕妇为耳聋基因携带者后,对其配偶采用相同的流程进行检测,并对所得数据进行分析。结果2980名听力正常的孕妇中检测出耳聋基因携带者共148例,阳性检出率4.97%。其中携带GJB2基因突变者82例,占比2.75%;携带SLC26A4基因突变者57例,占比1.92%;携带GJB3基因突变者6例,占比0.20%;携带mtDNA基因突变者3例,占比0.10%。148名耳聋基因携带者中有137名配偶参加了检测。其中有2例为耳聋易感基因携带者,1例为GJB2-235杂合突变,1例为SLC26A4-IVS7(-2)杂合突变。结论听力正常的孕妇仍有耳聋易感基因的携带者,其中以GJB2-235杂合突变和SLC26A4-IVS7(-2)杂合突变为主。

Novel ATL1 mutation in a Chinese family with hereditary spastic paraplegia: A case report and review of literature

BACKGROUND Hereditary spastic paraplegias (HSPs) refer to a group of heterogeneous neurodegenerative diseases characterized by lower limbs spasticity and weakness. So far, over 72 genes have been found to cause HSP (SPG1-SPG72). Among autosomal dominant HSP patients, spastic paraplegia 4 (SPG4/SPAST) gene is the most common pathogenic gene, and atlastin-1 (ATL1) is the second most common one. Here we reported a novel ATL1 mutation in a Chinese spastic paraplegia 3A (SPG3A) family, which expands the clinical and genetic spectrum of ATL1 mutations. CASE SUMMARY A 9-year-old boy with progressive spastic paraplegia accompanied by right hearing loss and mental retardation for five years was admitted to our hospital.Past history was unremarkable. The family history was positive, and his grandfather and mother had similar symptoms. Neurological examinations revealed hypermyotonia in his lower limbs, hyperreflexia in knee reflex, bilateral positive Babinski signs and scissors gait. The results of blood routine test, liver function test, blood glucose test, ceruloplasmin test and vitamin test were all normal. The serum lactic acid level was significantly increased. The testing for brainstem auditory evoked potential demonstrated that the right side hearing was impaired while the left was normal. Magnetic resonance imaging showed mild atrophy of the spinal cord. The gene panel test revealed that the proband carried an ATL1 c.752A>G p.Gln251Arg (p.Q251R) mutation, and Sanger sequencing confirmed the existence of family co-segregation. CONCLUSION We reported a novel ATL1 Q251R mutation and a novel clinical phenotype of hearing loss in a Chinese SPG3A family.

Preimplantation genetic diagnosis of hereditary hearing loss:a narrative review

Preimplantation genetic diagnosis(PGD)uses molecular biological techniques to genetically diagnose embryos beforein vitro fertilization.The information obtained through PGD can help clinicians select healthy embryos for implantation,prevent the transmission of inherited diseases and help affected families have healthy children.This paper reviews the development of PGD technology,the history of its application to hereditary hearing loss,and the general process of how PGD is applied to screen for hereditary hearing loss.The aim of this review is to demonstrate the reliability of PGD in the primary prevention of hereditary hearing loss,assist clinicians in counseling patients at risk of transmitting an inherited disease,and explore the journey from PGD toin vitro fertilization.Given that the application of PGD technology to hereditary hearing loss varies in different countries and regions,there is still a long way to go before PGD is routinely applied for the primary prevention of hereditary hearing loss.

Research progress in pathogenic genes of hereditary non-syndromic mid-frequency deafness

Hearing impairment is considered as the most prevalent impairment worldwide. Almost 600 million people in the world suffer from mild or moderate hearing impairment, an estimated 10% of the human population. Genetic factors play an important role in the pathogenesis of this disorder. Hereditary hearing loss is divided into syndromic hearing loss （associated with other anomalies） and non-syndromic hearing loss （not associated with other anomalies）. Approximately 80% of genetic deafness is non-syndromic. On the basis of the frequency of hearing loss, hereditary non-syndromic hearing loss can be divided into high-, mid-, low-, and total-frequency hearing loss. An audiometric finding of mid-frequency sensorineural hearing loss, or a ＂bowl-shaped＂ audiogram, is uncommon. Up to now, merely 7 loci have been linked to mid-frequency hearing loss. Only four genetic mid- frequency deafness genes, namely, DFNA10 （EYA4）, DFNA8/12 （TECTA）, DFNA13 （COLIIA2）, DFNA44 （CCDC50）, have been reported to date. This review summarizes the research progress of the four genes to draw attention to mid-frequency deafness genes.

Deafness genes for nonsyndromic hearing loss and current studies in China

Objectives To review the identified deafness genes related to nonsyndromic hearing loss (NSHL) and summarize their expressions and functions in the cochlea and to introduce the current studies of molecular genetics on NSHL in China Methods The presented data are based on a review of the literature as well as the author's experience with NSHL and communications with other researchers in China over the past 3 years Results Currently, 23 deafness genes related to NSHL have been cloned and identified Some genes are associated with both NSHL and syndromic hearing loss (SHL), in both dominant and recessive deafness Deafness genes have a highly specific expression pattern in the inner ear Some functional categories are starting to emerge from a characterization of deafness genes There are interacting genes in the genetic background that influence the extent of hearing impairment The GJB3 gene, which is associated with high frequency hearing impairment, was cloned in a Chinese laboratory Mutations in some genes, such as GJB2 and mitochondrial 12S rRNA, have been screened in Chinese patients with NSHL Mapping new deafness gene loci as well as identifying new genes and their functions is an active area of study in China Conclusions It is challenging for us to continue identifying new deafness genes and analyze gene functions By identifying genes responsible for monogenic hearing impairment, more insight may be gained into the molecular process of hearing and the pathology of hearing loss

性连锁遗传性耳聋基因研究进展

耳聋是严重影响人类社会交流及生活质量的感觉神经缺陷疾病之一。约50%的耳聋是由遗传因素导致的,伴性染色体连锁遗传是重要的遗传方式,本文就与性染色体有关的聋病基因AIFM1、GPRASP2、COL4A5、NDP、TIMM8A/DDP、PRPS1、POU3F4、SMPX、COL4A6和TBLIY的概况、功能以及致聋机制等进行文献复习。