Ju Yang

Mutations in apoptosis-inducing factor cause X-linked recessive auditory neuropathy spectrum disorder

Background Auditory neuropathy spectrum disorder (ANSD) is a form of hearing loss in which auditory signal transmission from the inner ear to the auditory nerve and brain stem is distorted, giving rise to speech perception difficulties beyond that expected for the observed degree of hearing loss. For many cases of ANSD, the underlying molecular pathology and the site of lesion remain unclear. The X-linked form of the condition, AUNX1, has been mapped to Xq23-q27.3, although the causative gene has yet to be identified. Methods We performed whole-exome sequencing on DNA samples from the AUNX1 family and another small phenotypically similar but unrelated ANSD family. Results We identified two missense mutations in AIFM1 in these families: c.1352G>A (p.R451Q) in the AUNX1 family and c.1030C>T (p.L344F) in the second ANSD family. Mutation screening in a large cohort of 3 additional unrelated families and 93 sporadic cases with ANSD identified 9 more missense mutations in AIFM1. Bioinformatics analysis and expression studies support this gene as being causative of ANSD. Conclusions Variants in AIFM1 gene are a common cause of familial and sporadic ANSD and provide insight into the expanded spectrum of AIFM1-associated diseases. The finding of cochlear nerve hypoplasia in some patients was AIFM1-related ANSD implies that MRI may be of value in localising the site of lesion and suggests that cochlea implantation in these patients may have limited success.

Reference of Temperature and Time during tempering process for non-stoichiometric FTO films

In order to enhance the mechanical strength of Low-E glass, Fluorine-doped tin oxide (FTO) films have to be tempered at high temperatures together with glass substrates. The effects of tempering temperature (600 °C ~ 720 °C) and time (150 s ~ 300 s) on the structural and electrical properties of FTO films were investigated. The results show all the films consist of non-stoichiometric, polycrystalline SnO2 without detectable amounts of fluoride. 700 °C and 260 s may be the critical tempering temperature and time, respectively. FTO films tempered at 700 °C for 260 s possesses the resistivity of 7.54 × 10−4 Ω•cm, the average transmittance in 400 ~ 800 nm of ~80%, and the calculated emissivity of 0.38. Hall mobility of FTO films tempered in this proper condition is mainly limited by the ionized impurity scattering. The value of [O]/[Sn] at the film surface is much higher than the stoichiometric value of 2.0 of pure crystalline SnO2.

Reproductive management through integration of PGD and MPS-based noninvasive prenatal screening/diagnosis for a family with GJB2-associated hearing impairment

A couple with a proband child of GJB2 (encoding the gap junction protein connexin 26)-associated hearing impairment and a previous pregnancy miscarriage sought for a reproductive solution to bear a healthy child. Our study aimed to develop a customized preconception-to-neonate care trajectory to fulfill this clinical demand by integrating preimplantation genetic diagnosis (PGD), noninvasive prenatal testing (NIPT), and noninvasive prenatal diagnosis (NIPD) into the strategy. Auditory and genetic diagnosis of the proband child was carried out to identify the disease causative mutations. The couple then received in-vitro-fertilization treatment, and eight embryos were obtained for day 5 biopsy. PGD was performed by short-tandem-repeat linkage analysis and Sanger sequencing of GJB2 gene. Transfer of a GJB2c.235delC heterozygous embryo resulted in a singleton pregnancy. At the 13th week of gestation, genomic DNA (gDNA) from the trio family and cell-free DNA (cfDNA) from maternal plasma were obtained for assessment of fetal chromosomal aneuploidy and GJB2 mutations. NIPT and NIPD showed the absence of chromosomal aneuploidy and GJB2-associated disease in the fetus, which was later confirmed by invasive procedures and postnatal genetic/auditory diagnosis. This strategy successfully prevented the transmission of hearing impairment in the newborn, thus providing a valuable experience in reproductive management of similar cases and potentially other monogenic disorders.

A POU3F4 Mutation Causes Nonsyndromic Hearing Loss in a Chinese X-linked Recessive Family

Background: The molecular genetic research showed the association between X-linked hearing loss and mutations in POU3F4. This research aimed to identify a POU3F4 mutation in a nonsyndromic X-linked recessive hearing loss family. Methods: A series of clinical evaluations including medical history, otologic examinations, family history, audiologic testing, and a high-resolution computed tomography scan were performed for each patient. Bidirectional sequencing was carried out for all polymerase chain reaction products of the samples. Moreover, 834 controls with normal hearing were also tested. Results: The pedigree showed X-linkage recessive inheritance pattern, and pathogenic mutation (c.499C>T) was identified in the proband and his family member, which led to a premature termination prior to the entire POU domains. This mutation co-segregated with hearing loss in this family. No mutation of POU3F4 gene was found in 834 controls. Conclusions: A nonsense mutation is identified in a family displaying the pedigree consistent with X-linked recessive pattern in POU3F4 gene. In addition, we may provide molecular diagnosis and genetic counseling for this family.

SIX2 haploinsufficiency causes conductive hearing loss with ptosis in humans

The ossicles represent one of the most fundamental morphological features in evolutionary biology of the mammalians. The mobile ossicular morphology abnormalities result in the severe conductive hearing loss. Development and patterning of the middle ear malformation depend on genetic and environmental causes. However, the genetic basis for the risk of congenital ossicle malformation is poorly understood. We show here nine affected individuals in a Chinese pedigree who had bilateral conductive hearing loss with ptosis. We performed whole-genome sequencing and array comparative genomic hybridization (CGH) analysis on DNA samples from the Chinese pedigree. We confirmed the presence of a novel 60 kb heterozygous deletion in size, encompassing SIX2 in our family. Mutation screening in 169 sporadic cases with external ear and middle ear malformations identified no pathogenic variant or polymorphism. We suggest SIX2 haploinsufficiency as a potential congenital factor could be attributed to developmental malformation of the middle ear ossicles and upper eyelid. To the best of our knowledge, this is the first report to provide a description of copy number variation in the SIX2 gene resulting in syndromic conductive hearing loss.

Identification of a novel mutation of PJVK in the Chinese non-syndromic hearing loss population with low prevalence of the PJVK mutations

Abstract Conclusion: To our knowledge, this is the first report of PJVK gene mutation in a Chinese non-syndromic sensorineural hearing loss (NSHL) family. Our data indicate that the PJVK gene contributes to hearing impairment in the Chinese population, but it is not a major cause. Objective: To investigate the contribution of PJVK mutations to NSHL in the Chinese population. Methods: We screened for the PJVK gene in a sample of 65 autosomal recessive NSHL families without GJB2, SLC26A4, or mitochondrial 12S rRNA gene mutations. Seven pairs of PCR primers were designed to amplify all of the exons and their flanking regions of the PJVK gene. The PCR products were sequenced and analyzed for identification of mutations. Results: In all, we identified one novel frameshift mutation, c.930_931del AC (p.C312W fsX19), co-segregating with the phenotype in one consanguineous family with a prevalence of 1.5% (1/65). The p.C312W fsX19 mutation was just positioned in the zinc-fingers domain, which was important to the function of pejvakin, and resulted in a stop codon after 19 additional amino acids. It was not identified in the controls and was considered as the causative mutation of family 804566 with autosomal recessive, non-syndromic, prelingual sensorineural hearing impairment.

Clinical Auditory Phenotypes Associated with GATA3 Gene Mutations in Familial Hypoparathyroidism-deafness-renal Dysplasia Syndrome

Background: Hypoparathyroidism-deafness-renal dysplasia (HDR) syndrome is an autosomal dominant disorder primarily caused by haploinsufficiency of GATA binding protein 3 (GATA3) gene mutations, and hearing loss is the most frequent phenotypic feature. This study aimed at identifying the causative gene mutation for a three-generation Chinese family with HDR syndrome and analyzing auditory phenotypes in all familial HDR syndrome cases. Methods: Three affected family members underwent otologic examinations, biochemistry tests, and other clinical evaluations. Targeted genes capture combining next-generation sequencing was performed within the family. Sanger sequencing was used to confirm the causative mutation. The auditory phenotypes of all reported familial HDR syndrome cases analyzed were provided. Results: In Chinese family 7121, a heterozygous nonsense mutation c.826C>T (p.R276*) was identified in GATA3. All the three affected members suffered from sensorineural deafness and hypocalcemia; however, renal dysplasia only appeared in the youngest patient. Furthermore, an overview of thirty HDR syndrome families with corresponding GATA3 mutations revealed that hearing impairment occurred earlier in the younger generation in at least nine familial cases (30%) and two thirds of them were found to carry premature stop mutations. Conclusions: This study highlights the phenotypic heterogeneity of HDR and points to a possible genetic anticipation in patients with HDR, which needs to be further investigated.

Further evidence for “gain-of-function” mechanism of DFNA5 related hearing loss

To report two DFNA5 pathogenic splice-site variations and a novel benign frameshift variation to further support the gain-of-function mechanism of DFNA5 related hearing impairment, targeted genes capture and next generation sequencing were performed on selected members from Family 1007208, 1007081 and a sporadic case with sensorineural hearing loss. Reverse transcriptase polymerase chain reaction was conducted on the proband from Family 1007208 to test how the splice-site variation affects the transcription in RNA level. A novel heterozygous splice-site variation c.991-3 C > A in DFNA5 was found in Family 1007208; a known hotspot heterozygous splice-site variation c.991-15_991_13delTTC was identified in Family 1007081. Both the splice-site variations were segregated with the late onset hearing loss phenotype, leading to the skipping of exon 8 at RNA level. In addition, a novel DFNA5 frameshift variation c.116_119delAAAA was found in the sporadic case, but was not segregated with the hearing impairment phenotype. In conclusion, we identified one novel and one known pathogenic DFNA5 splice-site variation in two Chinese Families, as well as a novel DFNA5 frameshift variation c.116_119delAAAA in a sporadic case, which does not the cause for the hearing loss case. Both the two pathogenic splice-site variations and the nonpathogenic frameshift variation provide further support for the specific gain-of-function mechanism of DFNA5 related hearing loss.

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

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 ACTG1 and ACTB are ubiquitously expressed. ACTG1 (OMIM #604717), which is linked to the DFNA20/26 locus, was identified 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). All previously reported NSHL cases with ACTG1 pathogenic mutations had a family history of hearing impairment, indicating an autosomal dominant pattern of inheritance. De novo mutations account for some cases of Baraitser-Winter syndrome, although none have been reported in NSHL cases. In this study we discuss two sporadic, juvenile cases with NSHL. Both were three-year-old boys whose parents noticed hearing impairment. All parents had normal hearing (Figure 1A), and each child had passed their newborn hearing

Identification of four TMC1 variations in different Chinese families with hereditary hearing loss

Variants in TMC1 (transmembrane channel‐like 1) can cause both autosomal dominant and recessive hearing loss in human population. Mice with Tmc1 variants have been shown to be ideal animal models for gene therapy. In this article, we report four TMC1 variants in four different Chinese families and the follow‐up auditory phenotype of a previously reported family.