[Analysis of 59 cases of large vestibular aqueduct syndrome SLC26A4gene mutation frequency and new mutation sites].

Objective:To study the frequency of SLC26A4 gene mutation sites in children with enlarged vestibular aqueduct deafness in Yunnan, report the new mutation sites of SLC26A4 gene, further clarify the mutation spectrum of SLC26A4gene, and explore the association between biallelic and monoallelic mutations of SLC26A4 gene and CT phenotype of inner ear, so as to provide basis for clinical and genetic diagnosis of deafness. Methods:Review the results of temporal bone CT examination of 390 children after cochlear implantation in the Department of Otolaryngology, Kunming Children's Hospital from August 2016 to September 2021. Sanger sequencing of SLC26A4 gene was performed in 59 children with enlarged vestibular aqueduct. According to the genetic test results, the children who underwent temporal bone CT examination were divided into two groups: SLC26A4 biallelic mutation group（homozygous mutation and compound heterozygous mutation）, monoallelic mutation group, and the association with inner ear CT phenotype was analyzed, and the new sites were summarized and analyzed. Results:The c.919-2a>g mutation was the most common mutation in children with enlarged vestibular aqueduct with SLC26A4 gene mutation. Three new variants of SLC26A4 gene were found; CT examination combined with genetic testing found that a part of children with enlarged vestibular aqueduct was associated with SLC26A4 monoallelic mutation or no SLC26A4 gene mutation was detected. Further research is needed to investigate the involvement of other pathogenic factors in the pathogenesis of EVA.

Investigation of genetic and phenotypic heterogeneity in 37 Turkish patients with Kabuki and Kabuki-like phenotype.

Kabuki syndrome (KS) is a rare disorder characterized by distinct face, persistent fingertip pads, and intellectual disability (ID) caused by mutation in KMT2D (56%-76%) or KDM6A (5%-8%). Thirty-seven children aged 1-16 years who followed for median of 6.8 years were included in this study, which aimed to investigate the genetic and clinical characteristics of KS patients. KMT2D and KDM6A were evaluated by sequencing and multiplex-ligation-dependent probe amplification in 32 patients. Twenty-one pathogenic variants in KMT2D, of which 17 were truncated and nine were novel, one frame-shift novel variant in KDM6A were identified. The molecular diagnosis rate was 68.7% (22/32). In the whole-exome sequencing analysis performed in the remaining patients, no pathogenic variant that could cause any disease was detected. All patients had ID; 43.2% were severe and moderate. We observed that facial features that became more prominent with age were enough for a possible diagnosis of KS in infancy. The frequencies of facial features, cardiac and renal anomalies, short stature, microcephaly, and epilepsy did not differ depending on whether they had truncating or nontruncating variants or were in variant-negative KS-like group. This study has expanded clinical features of the disease, as well as identified new variants in genes causing KS.

Identification of unique DNA methylation sites in Kabuki syndrome using whole genome bisulfite sequencing and targeted hybridization capture followed by enzymatic methylation sequencing.

BACKGROUND: Kabuki syndrome (KS) is a congenital malformation syndrome caused by mutations in the KMT2D and KDM6A genes that encode histone modification enzymes. Although KS is considered a single gene disorder, its symptoms vary widely. Recently, disease-specific DNA methylation patterns, or episignatures, have been recognized and used as a diagnostic tool for KS. Because of various crosstalk mechanisms between histone modifications and DNA methylation, DNA methylation analysis may have high potential for investigations into the pathogenesis of KS. RESULTS: In this study, we investigated altered CpG-methylation sites that were specific to KS to find important genes associated with the various phenotypes or pathogenesis of KS. Whole genome bisulfite sequencing (WGBS) was performed to select target CpG islands, and enzymatic conversion technology was applied after hybridization capture to confirm KS-specific episignatures of 130 selected differently methylated target regions (DMTRs) in DNA samples from the 65 participants, 31 patients with KS and 34 unaffected individuals, in this study. We identified 26 candidate genes in 22 DMTRs that may be associated with KS. Our results indicate that disease-specific methylation sites can be identified from a small number of WGBS samples, and hybridization capture followed by enzymatic methylation sequencing can simultaneously test the sites. CONCLUSIONS: Although DNA methylation can be tissue-specific, our results suggest that methylation profiling of DNA extracted from peripheral blood may be a powerful approach to study the pathogenesis of diseases.

Sleep disturbance is a common feature of Kabuki syndrome.

Kabuki syndrome (KS) is a rare epigenetic disorder caused by heterozygous loss of function variants in either KMT2D (90%) or KDM6A (10%), both involved in regulation of histone methylation. While sleep disturbance in other Mendelian disorders of the epigenetic machinery has been reported, no study has been conducted on sleep in KS. This study assessed sleep in 59 participants with KS using a validated sleep questionnaire. Participants ranged in age from 4 to 43 years old with 86% of participants having a pathogenic variant in KMT2D. In addition, data on adaptive function, behavior, anxiety, and quality of life were collected using their respective questionnaires. Some form of sleep issue was present in 71% of participants, with night-waking, daytime sleepiness, and sleep onset delay being the most prevalent. Sleep dysfunction was positively correlated with maladaptive behaviors, anxiety levels, and decreasing quality of life. Sleep issues were not correlated with adaptive function. This study establishes sleep disturbance as a common feature of KS. Quantitative sleep measures may be a useful outcome measure for clinical trials in KS. Further, clinicians caring for those with KS should consider sleep dysfunction as an important feature that impacts overall health and well being in these patients.

Genotype-Phenotype Correlations of Pathogenic COCH Variants in DFNA9: A HuGE Systematic Review and Audiometric Meta-Analysis.

Pathogenic missense variants in COCH are associated with DFNA9, an autosomal dominantly inherited type of progressive sensorineural hearing loss with or without vestibular dysfunction. This study is a comprehensive overview of genotype-phenotype correlations using the PRISMA and HuGENet guidelines. Study characteristics, risk of bias, genotyping and data on the self-reported age of onset, symptoms of vestibular dysfunction, normative test results for vestibular function, and results of audiovestibular examinations were extracted for each underlying pathogenic COCH variant. The literature search yielded 48 studies describing the audiovestibular phenotypes of 27 DFNA9-associated variants in COCH. Subsequently, meta-analysis of audiometric data was performed by constructing age-related typical audiograms and by performing non-linear regression analyses on the age of onset and progression of hearing loss. Significant differences were found between the calculated ages of onset and progression of the audiovestibular phenotypes of subjects with pathogenic variants affecting either the LCCL domain of cochlin or the vWFA2 and Ivd1 domains. We conclude that the audiovestibular phenotypes associated with DFNA9 are highly variable. Variants affecting the LCCL domain of cochlin generally lead to more progression of hearing loss when compared to variants affecting the other domains. This review serves as a reference for prospective natural history studies in anticipation of mutation-specific therapeutic interventions.

Sperm-associated antigen 6 (Spag6) mutation leads to vestibular dysfunction in mice.

Spag6 encodes an axoneme central apparatus protein that is required for normal flagellar and cilia motility. Recent findings suggest that Spag6 plays a role in hearing and planar cell polarity (PCP) in the cochlea of the inner ear. However, a role for Spag6 in the vestibule has not yet been explored. In the present study, the function of Spag6 in the vestibule of the inner ear was examined using Spag6-deficient mice. Our results demonstrate a vestibular disorder in the Spag6 mutants, associated with abnormal ultrastructures of vestibular hair cells and Scarpa's ganglion cells, including swollen stereocilia, decreased crista in mitochondria and swollen Scarpa's ganglion cells. Immunostaining data suggests existence of caspase-dependent apoptosis in vestibular sensory epithelium and Scarpa's ganglion cells. Our observations reveal new functions for Spag6 in vestibular function and apoptosis in the mouse vestibule.

Neuroimaging in Kabuki syndrome and another KMT2D-related disorder.

Recognition of distinct phenotypic features is an important component of genetic diagnosis. Although CHARGE syndrome, Kabuki syndrome, and a recently delineated KMT2D Ex 38/39 allelic disorder exhibit significant overlap, differences on neuroimaging may help distinguish these conditions and guide genetic testing and variant interpretation. We present an infant clinically diagnosed with CHARGE syndrome but subsequently found to have a de novo missense variant in exon 38 of KMT2D, the gene implicated in both Kabuki syndrome and a distinct KMT2D allelic disorder. We compare her brain and inner ear morphology to a retrospective cohort of 21 patients with classic Kabuki syndrome and to typical CHARGE syndrome findings described in the literature. Thirteen of the 21 Kabuki syndrome patients had temporal bone imaging (5/13 CT, 12/13 MRI) and/or brain MRI (12/13) which revealed findings distinct from both CHARGE syndrome and the KMT2D allelic disorder. Our findings further elucidate the spectrum of inner ear dysmorphology distinguishing Kabuki syndrome and the KMT2D allelic disorder from CHARGE syndrome, suggesting that these three disorders may be differentiated at least in part by their inner ear anomalies.

Kabuki Syndrome-Clinical Review with Molecular Aspects.

Kabuki syndrome (KS) is a rare developmental disorder principally comprised of developmental delay, hypotonia and a clearly defined dysmorphism: elongation of the structures surrounding the eyes, a shortened and depressed nose, thinning of the upper lip and thickening of the lower lip, large and prominent ears, hypertrichosis and scoliosis. Other characteristics include poor physical growth, cardiac, gastrointestinal and renal anomalies as well as variable behavioral issues, including autistic features. De novo or inherited pathogenic/likely pathogenic variants in the KMT2D gene are the most common cause of KS and account for up to 75% of patients. Variants in KDM6A cause up to 5% of cases (X-linked dominant inheritance), while the etiology of about 20% of cases remains unknown. Current KS diagnostic criteria include hypotonia during infancy, developmental delay and/or intellectual disability, typical dysmorphism and confirmed pathogenic/likely pathogenic variant in KMT2D or KDM6A. Care for KS patients includes the control of physical and psychomotor development during childhood, rehabilitation and multi-specialist care. This paper reviews the current clinical knowledge, provides molecular and scientific links and sheds light on the treatment of Kabuki syndrome individuals.

Ophthalmic manifestations in Kabuki (make-up) syndrome: A single-center pediatric cohort and systematic review of the literature.

Kabuki syndrome (KS) is a genetic disorder caused by pathogenic variants in KMT2D or KDM6A, and manifesting with multi-systemic involvement, including recognizable facial features, developmental delay and multiple congenital anomalies. Ophthalmological involvement has been described in varying rates in several studies. We aimed to evaluate the prevalence and nature of ophthalmological findings in a cohort of KS patients in Israel. Medical records of all patients diagnosed with KS in our tertiary center between 2004 and 2020 were retrospectively reviewed. Data collected included physical examination findings, molecular analysis as well as comprehensive ophthalmic characteristics including visual acuity, ocular alignment and motility, ocular adnexa, anterior segments and dilated fundus exams. Finally, an updated systematic review of the literature was performed. Thirteen unrelated patients were included in the study, diagnosed at an age raging from the first months of life to 20 years. Of these, three (23%) showed significant ophthalmological abnormalities, beyond the characteristic structural findings of long palpebral fissures and lower eyelid eversion. These included bilateral posterior colobomata in the first patient; bilateral ptosis, hypermetropia, esotropia, blue sclera and anisocoria in the second; and bilateral congenital cataracts in the third. To conclude, our findings underscore the importance of a comprehensive ophthalmological evaluation as part of the routine multidisciplinary assessment of children suspected/diagnosed with KS.

Exploring the biomechanical responses of human cupula by numerical analysis of temperature experiments.

The vestibular receptor of cupula acts an important role in maintaining body balance. However, the cupula buried in the semicircular canals (SCCs) will be destroyed if it is detached from the relevant environment. The mechanical properties of human cupula still remain ambiguous. In this paper, we explored the cupula responses changing with temperature by experiments and numerical simulation of SCCs model. We obtained 3 volunteers' nystagmus induced by constant angular acceleration when the temperature of volunteers' SCCs was 36 °C and 37 °C respectively. The slow-phase velocity of 3 volunteers decreased by approximately 3°/s when the temperature of SCCs reduced by 1 °C, which corresponded to the reduction of cupula deformation by 0.3-0.8 µm in the numerical model. Furthermore, we investigated the effects of the variation of endolymphatic properties induced by temperature reduction on cupula deformation through numerical simulation. We found that the decrease of cupula deformation was not caused by the change of endolymphatic properties, but probably by the increase of cupula's elastic modulus. With the temperature reducing by 1 °C, the cupula's elastic modulus may increase by 6-20%, suggesting that the stiffness of cupula is enhanced. This exploration of temperature characteristic of human cupula promotes the research of alleviating vestibular diseases.

Generation and characterization of a P2rx2 V60L mouse model for DFNA41.

P2RX2 encodes the P2X2 receptor, which is an adenosine triphosphate (ATP) gated (purinoreceptor) ion channel. P2RX2 c. 178G > T (p.V60L) mutation was previously identified in two unrelated Chinese families, as the cause of human DFNA41, a form of dominant, early-onset and progressive sensorineural hearing loss. We generated and characterized a knock-in mouse model based on human p.V60L mutation that recapitulates the human phenotype. Heterozygous KI mice started to exhibit hearing loss at 21-day-old and progressed to deafness by 6-month-old. Vestibular dysfunction was also observed in mutant mice. Abnormal morphology of the inner hair cells and ribbon synapses was progressively observed in KI animals suggesting that P2rx2 plays a role in the membrane spatial location of the ribbon synapses. These results suggest that P2rx2 is essential for acoustic information transfer, which can be the molecular mechanism related to hearing loss.

The First Case Report of Kabuki Syndrome from the National Iranian Registry of Primary Immunodeficiencies.

Kabuki syndrome is a rare congenital anomaly/mental retardation syndrome characterized by intellectual disability, developmental delay, short stature, facial dysmorphic features including ectropion of the lateral third of the lower eyelids, long palpebral fissures, and prominent finger pads. Pathogenic variants of KMT2D (MLL2) and KDM6A are found to be the major causes of Kabuki syndrome. Here, we report the first Iranian case with Kabuki syndrome with an IQ of 79, two episodes of viral pneumonia and distinctive facial features, prominent ears, and persistent fetal fingertip pads. These characteristics raised our suspicion of performing whole-exome sequencing (WES), which revealed 2 heterozygous pathogenic missense variants in the KMT2D gene: c.C10024T in exon 34, leading to p.R3342C and c.G15005A in exon 48, leading to p.R5002Q. Hence, the definitive diagnosis of Kabuki syndrome was made based on molecular findings along with the intellectual disability and characteristic facial features.

Hair cell uptake of gentamicin in the developing mouse utricle.

Intratympanic injection of gentamicin has proven to be an effective therapy for intractable vestibular dysfunction. However, most studies to date have focused on the cochlea, so little is known about the distribution and uptake of gentamicin by the counterpart of the auditory system, specifically vestibular hair cells (HCs). Here, with a combination of in vivo and in vitro approaches, we used a gentamicin-Texas Red (GTTR) conjugate to investigate the mechanisms of gentamicin vestibulotoxicity in the developing mammalian utricular HCs. In vivo, GTTR fluorescence was concentrated in the apical cytoplasm and the cellular membrane of neonatal utricular HCs, but scarce in the nucleus of HCs and supporting cells. Quantitative analysis showed the GTTR uptake by striolar HCs was significantly higher than that in the extrastriola. In addition, the GTTR fluorescence intensity in the striola was increased gradually from 1 to 8 days, peaking at 8-9 days postnatally. In vitro, utricle explants were incubated with GTTR and candidate uptake conduits, including mechanotransduction (MET) channels and endocytosis in the HC, were inhibited separately. GTTR uptake by HCs could be inhibited by quinine, a blocker of MET channels, under both normal and stressed conditions. Meanwhile, endocytic inhibition only reduced GTTR uptake in the CoCl2 hypoxia model. In sum, the maturation of MET channels mediated uptake of GTTR into vestibular HCs. Under stressed conditions, MET channels play a pronounced role, manifested by channel-dependent stress enhanced GTTR permeation, while endocytosis participates in GTTR entry in a more selective manner.

Could the MED13 mutations manifest as a Kabuki-like syndrome?

MED13-related disorder is a new neurodevelopmental disorder recently described in literature, which belongs to the group of CDK8-kinase module genes-associated conditions. It is characterized by variable intellectual disability and/or developmental delays, especially in language. Autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), eye or vision problems, hypotonia, mild congenital hearth abnormalities and dysmorphisms have been described among individuals with MED13 mutations. We report the case of a 13-year-old girl who received a previous clinical diagnosis of Kabuki syndrome (KS) without mutations in classic KS genes. After a whole exome sequencing (WES) analysis a de novo missense mutation in MED13 (c.C979T; p.Pro327Ser) was found. This variant has been once described in literature as accountable for a novel neurodevelopmental disorder. The aim of this report is to improve clinical delineation of MED13-related condition and to explore differences and similarities between KS spectrum and MED13-related disorders.

Using Xenopus to analyze neurocristopathies like Kabuki syndrome.

Neurocristopathies are human congenital syndromes that arise from defects in neural crest (NC) development and are typically associated with malformations of the craniofacial skeleton. Genetic analyses have been very successful in identifying pathogenic mutations, however, model organisms are required to characterize how these mutations affect embryonic development thereby leading to complex clinical conditions. The African clawed frog Xenopus laevis provides a broad range of in vivo and in vitro tools allowing for a detailed characterization of NC development. Due to the conserved nature of craniofacial morphogenesis in vertebrates, Xenopus is an efficient and versatile system to dissect the morphological and cellular phenotypes as well as the signaling events leading to NC defects. Here, we review a set of techniques and resources how Xenopus can be used as a disease model to investigate the pathogenesis of Kabuki syndrome and neurocristopathies in a wider sense.

Clinical and molecular characterization study of Chinese Kabuki syndrome in Hong Kong.

Kabuki syndrome (OMIM #147920 and 300867) is a rare genetic disorder characterized by a distinctive facial gestalt, intellectual disability and multiple congenital anomalies. We summarized the clinical features and molecular findings of the Kabuki syndrome (KS) patients diagnosed in Hong Kong between January 1991 and December 2019. There were 21 molecularly confirmed KS. Twenty of them were due to pathogenic KMT2D variants and one patient had KDM6A deletion. Nine KMT2D variants were novel. The clinical phenotype of our Chinese KS patients was largely comparable with that reported in patients of other ethnicities. This study expands the mutation spectrum but also provide important natural history information of Chinese KS in literature.

Does vestibular rehabilitation improve postural control of subjects with chronic subjective dizziness?

Postural control is the ability to maintain equilibrium and orientation in a gravitational environment. Patients with chronic subjective dizziness have some troubles with their postural stability. The present study aimed to assess the benefit of home-based vestibular rehabilitation in patients with chronic subjective dizziness using computerized dynamic posturography. Therefore, 100 subjects, between 19 to 86 years, diagnosed with dizziness were included in the study. Computerized dynamic posturography was performed to assess postural stability. Vestibular rehabilitation programs included exercises tailored to the particular needs of each patient. After vestibular rehabilitation, patients were re-examined using the same tests. Posturographic data were analyzed and compared for before and after vestibular rehabilitation findings. The mean composite scores before the intervention (58,92 ±11,64) was significantly (p<0.01) lower than the mean composite scores after vestibular rehabilitation (73,83 ± 8,26). This result is found to be statistically significant. In conclusion it could be suggested that the effectiveness of vestibular rehabilitation could be verified by means of computerized dynamic posturography as a concrete method.

Update of the genotype and phenotype of KMT2D and KDM6A by genetic screening of 100 patients with clinically suspected Kabuki syndrome.

Kabuki syndrome is characterized by a variable degree of intellectual disability, characteristic facial features, and complications in various organs. Many variants have been identified in two causative genes, that is, lysine methyltransferase 2D (KMT2D) and lysine demethylase 6A (KDM6A). In this study, we present the results of genetic screening of 100 patients with a suspected diagnosis of Kabuki syndrome in our center from July 2010 to June 2018. We identified 76 variants (43 novel) in KMT2D and 4 variants (3 novel) in KDM6A as pathogenic or likely pathogenic. Rare variants included a deep splicing variant (c.14000-8C>G) confirmed by RNA sequencing and an 18% mosaicism level for a KMT2D mutation. We also characterized a case with a blended phenotype consisting of Kabuki syndrome, osteogenesis imperfecta, and 16p13.11 microdeletion. We summarized the clinical phenotypes of 44 patients including a patient who developed cervical cancer of unknown origin at 16 years of age. This study presents important details of patients with Kabuki syndrome including rare clinical cases and expands our genetic understanding of this syndrome, which will help clinicians and researchers better manage and understand patients with Kabuki syndrome they may encounter.

MRI utricle diameter asymmetry is significantly greater in dogs with idiopathic vestibular syndrome compared with unaffected dogs.

Idiopathic vestibular syndrome (IVS) is the most common cause of acute unilateral peripheral vestibular dysfunction in older dogs. The purpose of this retrospective, cross-sectional study was to characterize morphological changes in the utricle of dogs affected by IVS, using MRI. To evaluate differences between affected and unaffected utricles, the ratio of the largest to the smallest utricle diameter was obtained, as measured on transverse T2-weighted images, and defined as the utricle asymmetricity ratio (UAR). Out of 137 patients diagnosed with IVS after excluding other vestibular diseases by MRI, 101 were eligible for inclusion. Additionally, 31 older dogs with no signs of vestibular disorders or other intracranial diseases were included as a control group. The disease group was divided into two subgroups in which the direction of head tilt and nystagmus symptoms versus the decreased utricle diameters were consistent or inconsistent. The medians of UARs of the IVS and control groups were 0.83 (range 0.37-1.00) and 0.98 (0.70-1.00), respectively. The medians of the UARs of the consistent and inconsistent IVS subgroups were 0.82 (0.37-0.99) and 0.90 (0.74-1.00), respectively. The UAR of the IVS group was significantly decreased than that of the control group and UAR of the consistent sub-group was significantly decreased than that of the inconsistent sub-group (P < .01). In conclusion, significant asymmetry of utricle diameter was identified in dogs with IVS versus unaffected dogs. We propose that canine IVS may possibly be correlated with structural atrophy of the vestibular system.

Gender differences in audio-vestibular disorders.

In the last years, the attention to the role of gender in physiopathology and pharmacology of diseases in several medical disciplines is rising; however, the data on the relationship between gender and audio-vestibular disorders are still inconclusive and sometimes confusing. With this letter to the editor, we would like to review the role of gender in audio-vestibular disorders. Literature data show that anatomic variances of the inner ear do exist in men and women and that the different physiology and/or hormonal influence between genders could produce different clinical outcome of routine audiological and vestibular tests. Beyond the epidemiological gender-related differences, the clinical data suggest that the gender has a potential role as an etiopathogenetic factor in audio-vestibular disorders and it is probably responsible for the different clinical features observed between male and female subjects.