The natural history and genotype-phenotype correlations of TMPRSS3 hearing loss: an international, multi-center, cohort analysis.

TMPRSS3-related hearing loss presents challenges in correlating genotypic variants with clinical phenotypes due to the small sample sizes of previous studies. We conducted a cross-sectional genomics study coupled with retrospective clinical phenotype analysis on 127 individuals. These individuals were from 16 academic medical centers across 6 countries. Key findings revealed 47 unique TMPRSS3 variants with significant differences in hearing thresholds between those with missense variants versus those with loss-of-function genotypes. The hearing loss progression rate for the DFNB8 subtype was 0.3 dB/year. Post-cochlear implantation, an average word recognition score of 76% was observed. Of the 51 individuals with two missense variants, 10 had DFNB10 with profound hearing loss. These 10 all had at least one of 4 TMPRSS3 variants predicted by computational modeling to be damaging to TMPRSS3 structure and function. To our knowledge, this is the largest study of TMPRSS3 genotype-phenotype correlations. We find significant differences in hearing thresholds, hearing loss progression, and age of presentation, by TMPRSS3 genotype and protein domain affected. Most individuals with TMPRSS3 variants perform well on speech recognition tests after cochlear implant, however increased age at implant is associated with worse outcomes. These findings provide insight for genetic counseling and the on-going design of novel therapeutic approaches.

Generation of hiPSC line UMi030-A from an individual with the hearing loss-related GJB2 mutation c.109G > A.

Genetic variants in the GJB2 gene which encodes for the Connexin 26 protein account for âˆ¼ 60% of cases of genetic hearing loss. A novel hiPSC line was generated from an individual with the hearing loss-related variant c.109G > A in GJB2 leading to the p.V37I alteration in the Connexin26 protein. These cells will help to delineate the role of GJB2 in hearing loss pathogenesis and serve as a platform for drug discovery and development.

Brain endothelium-derived extracellular vesicles containing amyloid-beta induce mitochondrial alterations in neural progenitor cells.

Aim: Elevated brain deposits of amyloid beta (Aß40) contribute to neuropathology and cognitive dysfunction in Alzheimer's disease (AD). However, the role of the blood-brain barrier (BBB) as an interface for the transfer of Aß40 from the periphery into the brain is not well characterized. In addition, a substantial population of neural progenitor cells (NPCs) resides in close proximity to brain capillaries that form the BBB. The aim of this study is to understand the impact of brain endothelium-derived extracellular vesicles (EV) containing Aß40 on metabolic functions and differentiation of NPCs. Methods: Endothelial EVs were derived from an in vitro model of the brain endothelium treated with 100 nM Aß40 or PBS. We then analyzed the impact of these EVs on mitochondrial morphology and bioenergetic disruption of NPCs. In addition, NPCs were differentiated and neurite development upon exposure to EVs was assessed using the IncuCyte Zoom live cell imaging system. Results: We demonstrate that physiological concentrations of Aß40 can be transferred to accumulate in NPCs via endothelial EVs. This transfer results in mitochondrial dysfunction, disrupting crista morphology, metabolic rates, fusion and fission dynamics of NPCs, as well as their neurite development. Conclusion: Intercellular transfer of Aß40 is carried out by brain endothelium-derived EVs, which can affect NPC differentiation and induce mitochondrial dysfunction, leading to aberrant neurogenesis. This has pathological implications because NPCs growing into neurons are incorporated into cerebral structures involved in learning and memory, two common phenotypes affected in AD and related dementias.

Peripheral vestibular system: Age-related vestibular loss and associated deficits.

Given the interdependence of multiple factors in age-related vestibular loss (e.g., balance, vision, cognition), it is important to examine the individual contributions of these factors with ARVL. While the relationship between the vestibular and visual systems has been well studied (Bronstein et al., 2015), little is known about the association of the peripheral vestibular system with neurodegenerative disorders (Cronin et al., 2017). Further, emerging research developments implicate the vestibular system as an opportunity for examining brain function beyond balance, and into other areas, such as cognition and psychological functioning. Additionally, the bidirectional impact of psychological functioning is understudied in ARVL. Recognition of ARVL as part of a multifaceted aging process will help guide the development of integrated interventions for patients who remain at risk for decline. In this review, we will discuss a wide variety of characteristics of the peripheral vestibular system and ARVL, how it relates to neurodegenerative diseases, and correlations between ARVL and balance, vision, cognitive, and psychological dysfunction. We also discuss clinical implications as well as future directions for research, with an emphasis on improving care for patients with ARVL.

Effect of metronidazole on vaginal microbiota associated with asymptomatic bacterial vaginosis.

Vaginal dysbiosis-induced by an overgrowth of anaerobic bacteria is referred to as bacterial vaginosis (BV). The dysbiosis is associated with an increased risk for acquisition of sexually transmitted infections. Women with symptomatic BV are treated with oral metronidazole (MET), but its effectiveness remains to be elucidated. This study used whole-genome sequencing (WGS) to determine the changes in the microbiota among women treated with MET. WGS was conducted on DNA obtained from 20 vaginal swabs collected at four time points over 12 months from five randomly selected African American (AA) women. The baseline visit included all women who were diagnosed with asymptomatic BV and were untreated. All subjects were tested subsequently once every 2 months and received a course of MET for each BV episode during the 12 months. The BV status was classified according to Nugent scores (NSs) of vaginal smears. The microbial and resistome profiles were analysed along with the sociodemographic metadata. Despite treatment, none of the five participants reverted to normal vaginal flora - two were consistently positive for BV, and the rest experienced episodic cases of BV. WGS analyses showed Gardnerella spp. as the most abundant organism. After treatment with MET, there was an observed decline of Lactobacillus and Prevotella species. One participant had a healthy vaginal microbiota based on NS at one follow-up time point. Resistance genes including tetM and lscA were detected. Though limited in subjects, this study shows specific microbiota changes with treatment, presence of many resistant genes in their microbiota, and recurrence and persistence of BV despite MET treatment. Thus, MET may not be an effective treatment option for asymptomatic BV, and whole metagenome sequence would better inform the choice of antibiotics.

Usher Syndrome in the Inner Ear: Etiologies and Advances in Gene Therapy.

Hearing loss is the most common sensory disorder with ~466 million people worldwide affected, representing about 5% of the population. A substantial portion of hearing loss is genetic. Hearing loss can either be non-syndromic, if hearing loss is the only clinical manifestation, or syndromic, if the hearing loss is accompanied by a collage of other clinical manifestations. Usher syndrome is a syndromic form of genetic hearing loss that is accompanied by impaired vision associated with retinitis pigmentosa and, in many cases, vestibular dysfunction. It is the most common cause of deaf-blindness. Currently cochlear implantation or hearing aids are the only treatments for Usher-related hearing loss. However, gene therapy has shown promise in treating Usher-related retinitis pigmentosa. Here we review how the etiologies of Usher-related hearing loss make it a good candidate for gene therapy and discuss how various forms of gene therapy could be applied to Usher-related hearing loss.

Stem Cells and Gene Therapy in Progressive Hearing Loss: the State of the Art.

Progressive non-syndromic sensorineural hearing loss (PNSHL) is the most common cause of sensory impairment, affecting more than a third of individuals over the age of 65. PNSHL includes noise-induced hearing loss (NIHL) and inherited forms of deafness, among which is delayed-onset autosomal dominant hearing loss (AD PNSHL). PNSHL is a prime candidate for genetic therapies due to the fact that PNSHL has been studied extensively, and there is a potentially wide window between identification of the disorder and the onset of hearing loss. Several gene therapy strategies exist that show potential for targeting PNSHL, including viral and non-viral approaches, and gene editing versus gene-modulating approaches. To fully explore the potential of these therapy strategies, a faithful in vitro model of the human inner ear is needed. Such models may come from induced pluripotent stem cells (iPSCs). The development of new treatment modalities by combining iPSC modeling with novel and innovative gene therapy approaches will pave the way for future applications leading to improved quality of life for many affected individuals and their families.

Long-range cis-regulatory elements controlling GDF6 expression are essential for ear development.

Molecular mechanisms governing the development of the mammalian cochlea, the hearing organ, remain largely unknown. Through genome sequencing in 3 subjects from 2 families with nonsyndromic cochlear aplasia, we identified homozygous 221-kb and 338-kb deletions in a noncoding region on chromosome 8 with an approximately 200-kb overlapping section. Genomic location of the overlapping deleted region started from approximately 350 kb downstream of GDF6, which codes for growth and differentiation factor 6. Otic lineage cells differentiated from induced pluripotent stem cells derived from an affected individual showed reduced expression of GDF6 compared with control cells. Knockout of Gdf6 in a mouse model resulted in cochlear aplasia, closely resembling the human phenotype. We conclude that GDF6 plays a necessary role in early cochlear development controlled by cis-regulatory elements located within an approximately 500-kb region of the genome in humans and that its disruption leads to deafness due to cochlear aplasia.

Diagnostic and therapeutic applications of genomic medicine in progressive, late-onset, nonsyndromic sensorineural hearing loss.

The progressive, late-onset, nonsyndromic, sensorineural hearing loss (PNSHL) is the most common cause of sensory impairment globally, with presbycusis affecting greater than a third of individuals over the age of 65. The etiology underlying PNSHL include presbycusis, noise-induced hearing loss, drug ototoxicity, and delayed-onset autosomal dominant hearing loss (AD PNSHL). The objective of this article is to discuss the potential diagnostic and therapeutic applications of genomic medicine in PNSHL. Genomic factors contribute greatly to PNSHL. The heritability of presbycusis ranges from 25 to 75%. Current therapies for PNSHL range from sound amplification to cochlear implantation (CI). PNSHL is an excellent candidate for genomic medicine approaches as it is common, has well-described pathophysiology, has a wide time window for treatment, and is amenable to local gene therapy by currently utilized procedural approaches. AD PNSHL is especially suited to genomic medicine approaches that can disrupt the expression of an aberrant protein product. Gene therapy is emerging as a potential therapeutic strategy for the treatment of PNSHL. Viral gene delivery approaches have demonstrated promising results in human clinical trials for two inherited causes of blindness and are being used for PNSHL in animal models and a human trial. Non-viral gene therapy approaches are useful in situations where a transient biologic effect is needed or for delivery of genome editing reagents (such as CRISPR/Cas9) into the inner ear. Many gene therapy modalities that have proven efficacious in animal trials have potential to delay or prevent PNSHL in humans. The development of new treatment modalities for PNSHL will lead to improved quality of life of many affected individuals and their families.