APOL1 variants increase risk for FSGS and HIVAN but not IgA nephropathy.

A chromosome 22q13 locus strongly associates with increased risk for idiopathic focal segmental glomerulosclerosis (FSGS), HIV-1-associated nephropathy (HIVAN), and hypertensive ESRD among individuals of African descent. Although initial studies implicated MYH9, more recent analyses localized the strongest association within the neighboring APOL1 gene. In this replication study, we examined the six top-most associated variants in APOL1 and MYH9 in an independent cohort of African Americans with various nephropathies (44 with FSGS, 21 with HIVAN, 32 with IgA nephropathy, and 74 healthy controls).

Temporary reduction of distortion product otoacoustic emissions (DPOAEs) immediately following auditory brainstem response (ABR).

The hearing status of an experimental animal is typically assessed in the laboratory setting by the combined use of auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAEs), carried out in succession, with the former assay preceding the latter. This study reports a cautionary finding that the use of this accepted regimen yields a reduced DPOAE response. When the DPOAEs were performed after ABR testing, transient reduction of the DPOAE amplitudes was observed at all frequencies in both the inbred, C57/B6 and FVB/N, and the outbred, SW mouse strains.

In vitro expression and characterization of MYH9 mutant alleles linked to hereditary hearing loss.

Objective: To assess whether MYH9 mutant alleles linked to hereditary hearing loss induce disruption of cellular functions and associated phenotype following transient expression within cultured human cell lines.

Study Design: Dominantly inherited MYH9 mutant alleles, MYH9(R702C) and MYH9(R705H), were integrated within eukaryotic expression vector and then transfected into cultured human cell lines for transient expression and analysis. The transfected cells were assessed for transgene-induced alterations of the cellular phenotype, including NMHC-IIA-dependent cell shape, actin cytoskeleton integrity, and inhibition of cytokinesis.

Clinical and molecular genetic analysis of a family with macrothrombocytopenia and early onset sensorineural hearing loss.

A kindred with inherited macrothrombocytopenia (MTCP) and sensorineural hearing loss (SNHL) from Ghent, Belgium was identified. Currently, joint expression of MTCP and hearing loss are linked to mutations within MYH9 only. Thus, we tested the hypothesis that a mutation within MYH9 is responsible for the autosomal dominant inheritance of MTCP and hearing loss in the Ghent family.

MYH9-siRNA and MYH9 mutant alleles: expression in cultured cell lines and their effects upon cell structure and function.

MYH9 encodes a class II nonmuscle myosin heavy chain-A (NMHC-IIA), a widely expressed 1960 amino acid polypeptide, with translated molecular weight of 220 kDa. From studies of type II myosin in invertebrates and analogy with the skeletal and smooth muscle myosin II, NMHC-IIA is considered to be involved in diverse cellular functions, including cell shape, motility and division. The current study assessed the consequences of two separate, naturally occurring MYH9 dominant mutant alleles, MYH9(R702C) and MYH9(R705H) linked to syndromic and nonsyndromic hearing loss, respectively, upon diverse NMHC-IIA related functions in two separate cultured cell lines.

Localization in stereocilia, plasma membrane, and mitochondria suggests diverse roles for NMHC-IIa within cochlear hair cells.

NMHC-IIa, a nonmuscle myosin heavy chain isoform encoded by MYH9, is expressed in sensory hair cells and its dysfunction is associated with syndromic and nonsyndromic hearing loss. In this study, we investigate the ultrastructural distribution of NMHC-IIa within murine hair cells to elucidate its potential role in hair cell function. Using previously characterized anti-mouse NMHC-IIa antibody detected with immunogold labelling, NMHC-IIa was observed in the stereocilia, in the cytosol along the plasma membrane, and within mitochondria.

Alternative splice variants of MYH9.

MYH9 encodes a class II nonmuscle myosin heavy chain-A (NMHC-IIA), a widely expressed 1960 amino acid polypeptide, with a translated molecular weight of 220 kDa. The relatively large number of exons (40) that encode NMHC-IIA and the splice variants that have been documented for its two isoforms, MYH10 and MYH14, strongly suggest existence of alternative splicing for MYH9. In the current study, we perform a targeted search for Myh9 splice variants in two separate regions of the heavy chain that encode loop 1 and loop 2 subdomains within which alternative exons in MYH10 and MYH14 splice variants have been identified.

Generation and characterization of mice with Myh9 deficiency.

Mutant alleles of MYH9 encoding a class II non-muscle myosin heavy chain-A (NMMHC-IIA) have been linked to hereditary megathrombocytopenia with or without additional clinical features that include sensorineural deafness, cataracts, and nephritis. To assess its biological role in the affected targets, particularly the inner ear, we have generated and characterized mice with Myh9 deficiency. These mice were generated using the XA136 ES cell line (BayGenomics, http://baygenomics.

Expression of Myh9 in the mammalian cochlea: localization within the stereocilia.

Mutations of non-muscle myosin Type IIA or MYH9 are linked to syndromic or nonsyndromic hearing loss. The biologic function of MYH9 in the auditory organ and the pathophysiology of its dysfunction remain to be determined. The mouse represents an excellent model for investigating the biologic role of MYH9 in the cells and tissues affected by its dysfunction.

Audiologic testing and molecular analysis of 12S rRNA in patients receiving aminoglycosides.

Background: Pathogenic mutations in the mitochondrial genome are associated with a wide variety of maternally inherited human diseases including sensorineural hearing loss (HL). A specific mutation, m.1555A>G in the mitochondrial 12S rRNA gene, is associated with predisposition to aminoglycoside ototoxicity and HL.

Biological therapy for the inner ear.

Biological therapy for the inner ear has the potential to revolutionise the treatment of sensorineural hearing loss, the most common form of deafness. Progress in the molecular understanding of hearing and hearing loss, combined with advances in the fields of both gene and cellular therapy for the inner ear, is providing a robust foundation from which clinical translation is plausible. Potential areas of interest in gene therapy and its preclinical application to deafness are reviewed, and experimental progress that has occurred in cellular therapy for the inner ear is examined.

Role of cytomegalovirus, Epstein-Barr virus, and human herpes virus-8 in benign lymphoepithelial cysts of the parotid gland.

Objective: To provide background and evaluate the role of herpesviruses in benign lymphoepithelial cysts (BLC) of the parotid gland.

Study Design: Case series derived from review of pathology specimens.

Methods: Radiolabeled polymerase chain reaction (PCR) analysis was used to detect for the presence of cytomegalovirus (CMV), Epstein-Barr virus (EBV), and human herpes virus 8 (HHV-8) DNA sequences in 14 paraffin embedded specimens and 1 freshly aspirated BLC specimen.

Molecular pathogenesis of skull base tumors.

Objective: To review contemporary molecular biological literature related to skull base tumor biology and tumorigenesis.

Data Sources: PUBMED and Ovid literature searches were performed using keyword search. Only English language articles published between 1965 and December 4, 2003 were chosen.

GJB2 gene mutations in cochlear implant recipients: prevalence and impact on outcome.

Objective: To determine the prevalence of GJB2 gene mutations in patients undergoing cochlear implantation (CI) and their impact on rehabilitative outcome following implantation.

Design: Prospective determination of GJB2 mutation by sequence analysis by denaturing high-performance liquid chromatography and its correlation with outcome following CI.

Settings: Two tertiary academic medical centers.

Quantitative analysis of fungal DNA in chronic rhinosinusitis.

Objectives/hypothesis: Fungi have been recognized as important pathogens in sinusitis; however, they are equally present in patients with and without sinusitis. The authors postulated that the quantity of fungal DNA in the nose is determinant of disease, is greater in patients with chronic rhinosinusitis, and is directly correlated to their quality of life.

Study Design: Prospective recruitment of patients with chronic rhinosinusitis.

Cloning and developmental expression of nonmuscle myosin IIA (Myh9) in the mammalian inner ear.

MYH9 encoding a nonmuscle myosin heavy chain has been linked to nonsyndromic and syndromic forms of autosomal dominant hereditary hearing loss, suggesting a critical biological role of this motor protein in the auditory organ. While Myh9 expression has been described in the adult mouse, critical parameters pertaining to its developmental expression remain to be characterized. The current study describes cloning of the mouse Myh9 cDNA and the temporal onset and spatial distribution of Myh9 expression in the inner ear of the developing fetus, the neonate, and the adult.

Genomic structure, cochlear expression, and mutation screening of KCNK6, a candidate gene for DFNA4.

KCNK6 encodes a tandem pore domain potassium channel, TWIK-2, that maps to chromosome 19. Both STS and linkage maps established KCNK6 as a positional candidate gene for DFNA4, a form of autosomal dominant nonsyndromic hereditary hearing loss. Identification and characterization of Kcnk6 expression within the mammalian cochlea established the gene as a functional candidate for DFNA4.

Macrothrombocytopenia and progressive deafness is due to a mutation in MYH9.

Background: In 1992, a family with hereditary macrothrombocytopenia and progressive sensorineural hearing impairment without renal dysfunction was described. Recently, mutations in MYH9, a nonmuscle myosin heavy chain, have been found in several forms of hereditary macrothrombocytopenia.

Hypothesis: The hereditary macrothrombocytopenia and hearing loss in the previously reported family is due to a mutation in MYH9 gene.

Aquaporin 4 expression in the mammalian inner ear and its role in hearing.

Aquaporin 4 (Aqp4), a member of a family of water transport proteins, is a candidate for playing a critical role in inner ear fluid homeostasis. In this study, we assess cross-species Aqp4 expression in the inner ear, sequence conservation in the 5'-UTR, and hearing in Aqp4 knockout mice. A single Aqp4 isoform was expressed in a highly conserved pattern within the supporting epithelia surrounding the sensory cells of the auditory and vestibular sensory organs and the glial cells surrounding the auditory nerve of the mouse and rat.

Aquaporin-2 expression in the mammalian cochlea and investigation of its role in Meniere's disease.

The expression pattern of aquaporin-2 (AQP2), a vasopressin regulated member of the aquaporin gene family, in the cochlea and its potential role in Meniere's disease was investigated. RT-PCR screen of multiple rat tissues identified AQP2 transcripts in the cochlea, testis and kidney and an absence of tissue-specific splice variants. The level of AQP2 transcript in the cochlea was 10-fold lower relative to its expression in the testis and kidney.

In vitro and in vivo assessment of the ability of adeno-associated virus-brain-derived neurotrophic factor to enhance spiral ganglion cell survival following ototoxic insult.

Objectives/hypothesis: Auditory dysfunction following ototoxic insult results from loss of cochlear hair cells. Secondary degeneration of auditory neurons ensues from withdrawal of neurotrophic support from hair cells and can be prevented with administration of neurotrophins. Administration of adeno-associated virus containing the gene for brain-derived neurotrophic factor will promote spiral ganglion neuron survival after the destruction of hair cells.