Mutation-agnostic RNA interference with engineered replacement rescues Tmc1-related hearing loss.

Hearing loss is the most common sensory deficit, of which genetic etiologies are a frequent cause. Dominant and recessive mutations in TMC1, a gene encoding the pore-forming subunit of the hair cell mechanotransduction channel, cause DFNA36 and DFNB7/11, respectively, accounting for ∼2% of genetic hearing loss. Previous work has established the efficacy of mutation-targeted RNAi in treatment of murine models of autosomal dominant non-syndromic deafness. However, application of such approaches is limited by the infeasibility of development and validation of novel constructs for each variant. We developed an allele-non-specific approach consisting of mutation-agnostic RNAi suppression of both mutant and WT alleles, co-delivered with a knockdown-resistant engineered WT allele with or without the use of woodchuck hepatitis virus post-transcriptional regulatory element (WPRE) to augment transgene expression. This therapeutic construct was delivered into the mature murine model of DFNA36 with an AAV vector and achieved robust hair cell and auditory brainstem response preservation. However, WPRE-enhanced Tmc1 expression resulted in inferior outcomes, suggesting a role for gene dosage optimization in future TMC1 gene therapy development.

Genetic testing hearing loss: The challenge of non syndromic mimics.

Congenital hearing loss is a common cause of morbidity in early childhood. There are multiple reasons for congenital hearing impairment, with genetic contribution becoming increasingly recognized. Sensorineural hearing loss has classically been viewed as either syndromic or non-syndromic. With the advent of DNA sequencing technology such as NextGen sequencing, a subcategory has arisen, that of non-syndromic mimics (NSM)s. NSMs present initially as isolated hearing loss but as the patient ages other phenotypes become evident. Early diagnosis of these conditions is imperative as patients may suffer significant morbidity and mortality from complications from their hearing loss syndrome. An example is QT prolongation in Jervell and Lange-Nielsen Syndrome. The need for genetic testing and proper genetic counseling is necessary for patients with hearing loss and testing should be done as early in life as possible.

International Pediatric Otolaryngology group (IPOG) consensus on the diagnosis and management of pediatric obstructive sleep apnea (OSA).

OBJECTIVE: To develop an expert-based consensus of recommendations for the diagnosis and management of pediatric obstructive sleep apnea. METHODS: A two-iterative Delphi method questionnaire was used to formulate expert recommendations by the members of the International Pediatric Otolaryngology Group (IPOG). RESULTS: Twenty-six members completed the survey. Consensus recommendations (>90% agreement) are formulated for 15 different items related to the clinical evaluation, diagnosis, treatment, postoperative management and follow-up of children with OSA. CONCLUSION: The recommendations formulated in this IPOG consensus statement may be used along with existing clinical practice guidelines to improve the quality of care and to reduce variation in care for children with OSA.

C3(H2O) prevents rescue of complement-mediated C3 glomerulopathy in Cfh-/- Cfd-/- mice.

Therapeutic complement inhibition is a major focus for novel drug development. Of upstream targets, factor D (FD) is appealing because it circulates in plasma at low concentrations and has a single function: to cleave factor B to generate C3 convertase of the alternative pathway (AP). Mice with a targeted deletion of factor H (FH; Cfh-/- mice) develop C3 glomerulopathy (C3G) due to uncontrolled AP activity. To assess the impact of FD inhibition, we studied Cfh-/- Cfd-/- mice. We show that C3G in Cfh-/- mice is not rescued by removing FD. We used serum from Cfh-/- Cfd-/- mice to demonstrate that residual AP function occurs even when both FD and FH are missing and that hemolytic activity is present due to the action of C3(H2O). We propose that uncontrolled tick-over leads to slow activation of the AP in Cfh-/- Cfd-/- mice and that a minimal threshold of FH is necessary if tissue deposition of C3 is to be prevented. The FD/FH ratio dictates serum C3 level and renal C3b deposition. In C3G patients with chronic renal disease, the FD/FH ratio correlates inversely with C3 and C5 serum levels, suggesting that continuous AP control may be difficult to achieve by targeting FD.

Brief Report of Variants Detected in Hereditary Hearing Loss Cases in Iran over a 3-Year Period.

BACKGROUND: Diagnosis of hereditary hearing loss (HHL) as a heterogeneous disorder is very important especially in countries with high rates of consanguinity where the autosomal recessive pattern of inheritance is prevalent. Techniques such as next-generation sequencing, a comprehensive genetic test using targeted genomic enrichment and massively parallel sequencing (TGE + MPS), have made the diagnosis more cost-effective. The aim of this study was to determine HHL variants with comprehensive genetic testing in our country. METHODS: Fifty GJB2 negative individuals with HHL were referred to the Kariminejad-Najmabadi Pathology and Genetics Center, Tehran, one of the reference diagnostic genetic laboratories in Iran, during a 3-year period between 2014 and 2017. They were screened with the OtoSCOPE test, the targeted genomic enrichment and massively parallel sequencing (TGE + MPS) platform after a detailed history had been taken along with clinical evaluation. RESULTS: Among 32 out of 50 GJB2 negative patients (64%), 34 known pathogenic and novel variants were detected of which 16 (47%) were novel, identified in 10 genes of which the most prevalent were CDH23, MYO7A and MYO15A. CONCLUSION: These results provide a foundation from which to make appropriate recommendations for the use of comprehensive genetic testing in the evaluation of Iranian patients with hereditary hearing loss.

Old gene, new phenotype: splice-altering variants in CEACAM16 cause recessive non-syndromic hearing impairment.

BACKGROUND: Hearing loss is a genetically and phenotypically heterogeneous disorder. OBJECTIVES: The purpose of this study was to determine the genetic cause underlying the postlingual progressive hearing loss in two Iranian families. METHODS: We used OtoSCOPE, a next-generation sequencing platform targeting >150 genes causally linked to deafness, to screen two deaf probands. Data analysis was completed using a custom bioinformatics pipeline, and variants were functionally assessed using minigene splicing assays. RESULTS: We identified two homozygous splice-altering variants (c.37G>T and c.662-1G>C) in the CEACAM16 gene, segregating with the deafness in each family. The minigene splicing results revealed the c.37G>T results in complete skipping of exon 2 and loss of the AUG start site. The c.662-1G>C activates a cryptic splice site inside exon 5 resulting in a shift in the mRNA reading frame. CONCLUSIONS: These results suggest that loss-of-function mutations in CEACAM16 result in postlingual progressive hearing impairment and further support the role of CEACAM16 in auditory function.

Heterogeneity of Hereditary Hearing Loss in Iran: a Comprehensive Review.

A significant contribution to the causes of hereditary hearing impairment comes from genetic factors. More than 120 genes and 160 loci have been identified to be involved in hearing impairment. Given that consanguine populations are more vulnerable to most inherited diseases, such as hereditary hearing loss (HHL), the genetic picture of HHL among the Iranian population, which consists of at least eight ethnic subgroups with a high rate of intermarriage, is expected to be highly heterogeneous. Using an electronic literature review through various databases such as PubMed, MEDLINE, and Scopus, we review the current picture of HHL in Iran. In this review, we present more than 39 deafness genes reported to cause non-syndromic HHL in Iran, of which the most prevalent causative genes include GJB2, SLC26A4, MYO15A, and MYO7A. In addition, we highlight some of the more common genetic causes of syndromic HHL in Iran. These results are of importance for further investigation and elucidation of the molecular basis of HHL in Iran and also for developing a national diagnostic tool tailored to the Iranian context enabling early and efficient diagnosis of hereditary hearing impairment.

Advances in Molecular and Cellular Therapies for Hearing Loss.

Development of effective therapeutics for hearing loss has proven to be a slow and difficult process, evidenced by the lack of restorative medicines and technologies currently available to the otolaryngologist. In large part this is attributable to the limited regenerative potential in cochlear cells and the secondary degeneration of the cochlear architecture that commonly follows sensorineural hearing impairment. Therapeutic advances have been made using animal models, particularly in regeneration and remodeling of spiral ganglion neurons, which retract and die following hair cell loss. Natural regeneration in avian and reptilian systems provides hope that replacement of hair cells is achievable in humans. The most exciting recent advancements in this field have been made in the relatively new areas of cellular replacement and gene therapy. In this review we discuss recent developments in gene- and cell-based therapy for hearing loss, including detailed analysis of therapeutic mechanisms such as RNA interference and stem cell transplantation, as well as in utero delivery to the mammalian inner ear. We explore the advantages and limitations associated with the use of these strategies for inner ear restoration.

The use of genetic testing in the evaluation of hearing impairment in a child.

PURPOSE OF REVIEW: To review the role of genetic testing in the evaluation of hearing impairment in children. RECENT FINDINGS: The introduction of genetic testing has greatly enhanced the evaluation of deafness and hearing impairment in children. It can save time and money as well as providing patients, their families, and their physicians with important information; however, this testing is different from the medical testing that pediatricians typically order. SUMMARY: For patients and families to realize the benefits of genetic testing it must be done early in the evaluation process and must be accompanied by appropriate pretest and posttest counseling.