A QTL on Chr 5 modifies hearing loss associated with the fascin-2 variant of DBA/2J mice

Two Loci Contribute to Age-Related Hearing Loss Resistance in the Japanese Wild-Derived Inbred MSM/Ms Mice

An MSM/Ms strain was established using Japanese wild mice, which exhibit resistance to several phenotypes associated with aging, such as obesity, inflammation, and tumorigenesis, compared to common inbred mouse strains. MSM/Ms strain is resistant to age-related hearing loss, and their auditory abilities are sustained for long durations. The age-related hearing loss 3 (ahl3) locus contributes to age-related hearing in MSM/Ms strain. We generated ahl3 congenic strains by transferring a genomic region on chromosome 17 from MSM/Ms mice into C57BL/6J mice. Although C57BL/6J mice develop age-related hearing loss because of the ahl allele of the cadherin 23 gene, the development of middle- to high-frequency hearing loss was significantly delayed in an ahl3 congenic strain. Moreover, the novel age-related hearing loss 10 (ahl10) locus associated with age-related hearing resistance in MSM/Ms strain was mapped to chromosome 12. Although the resistance effects in ahl10 congenic strain were slightly weaker than those in ahl3 congenic strain, slow progression of age-related hearing loss was confirmed in ahl10 congenic strain despite harboring the ahl allele of cadherin 23. These results suggest that causative genes and polymorphisms of the ahl3 and ahl10 loci are important targets for the prevention and treatment of age-related hearing loss.

Fascin-1: Updated biological functions and therapeutic implications in cancer biology

Filopodia are cellular protrusions that respond to a variety of stimuli. Filopodia are formed when actin is bound to the protein Fascin, which may play a crucial role in cellular interactions and motility during cancer metastasis. Significantly, the noncanonical features of Fascin-1 are gradually being clarified, including the related molecular network contributing to metabolic reprogramming, chemotherapy resistance, stemness ac-tivity, and tumor microenvironment events. However, the relationship between biological characteristics and pathological features to identify effective therapeutic strategies needs to be studied further. The pur-pose of this review article is to provide a broad overview of the latest molecular networks and multiomics research regarding fascins and cancer. It also highlights their direct and indirect effects on available cancer treatments. With this multidisciplinary approach, researchers and clinicians can gain the most relevant in-formation on the function of fascins in cancer progression, which may facilitate clinical applications in the future.

c.753A>G genome editing of a Cdh23ahl allele delays age-related hearing loss and degeneration of cochlear hair cells in C57BL/6J mice

C57BL/6J mice have long been studied as a model of age-related hearing loss (ARHL). In C57BL/6J mice, ARHL begins in the high-frequency range at 3 months of age and spreads toward low frequencies by 10 months of age. We previously confirmed that c.753A>G genome editing of an ahl allele (c.753A) in the cadherin 23 gene (Cdh23) suppressed the onset of ARHL until 12 months of age. We further investigated the hearing phenotypes of the original and genome-edited C57BL/6J-Cdh23^+/+ (c.753G/G) mice until 24 months of age. The hearing tests revealed that most of the C57BL/6J mice maintained good hearing levels until 14 months of age following genome editing of a Cdh23^ahl allele. However, the hearing levels of the C57BL/6J-Cdh23^+/+ mice gradually declined, and severe ARHL developed with increasing age. ARHL in the C57BL/6J mice was correlated with degeneration of the stereocilia in cochlear hair cells. The stereocilia degeneration was rescued in the C57BL/6J-Cdh23^+/+ mice at 12 months of age, but the stereocilia bundles exhibited abnormal phenotypes similar to those of the original C57BL/6J mice at more advanced ages. Therefore, genome editing of Cdh23^ahl did not completely suppress ARHL in C57BL/6J mice. We also compared the hearing levels of C57BL/6J-Cdh23^+/+ mice with those of C3H/HeN and MSM/Ms mice, which carry the Cdh23⁺ allele. The severity and onset patterns of ARHL in the C57BL/6J-Cdh23^+/+ mice differed from those observed in other Cdh23^+/+ mice. Therefore, we hypothesize that other susceptible and/or resistant alleles of ARHL exist in the genetic backgrounds of these mice.

Null Mutation of the Fascin2 Gene by TALEN Leading to Progressive Hearing Loss and Retinal Degeneration in C57BL/6J Mice

Fascin2 (FSCN2) is an actin cross-linking protein that is mainly localized in retinas and in the stereocilia of hair cells. Earlier studies showed that a deletion mutation in human FASCIN2 (FSCN2) gene could cause autosomal dominant retinitis pigmentosa. Recent studies have indicated that a missense mutation in mouse Fscn2 gene (R109H) can contribute to the early onset of hearing loss in DBA/2J mice. To explore the function of the gene, Fscn2 was knocked out using TALEN (transcription activator-like effector nucleases) on the C57BL/6J background. Four mouse strains with deletions of 1, 4, 5, and 41 nucleotides in the target region of Fscn2 were developed. F1 heterozygous (Fscn2^+/- ) mice carrying the same deletion of 41 nucleotides were mated to generate the Fscn2^-/- mice. As a result, the Fscn2^-/- mice showed progressive hearing loss, as measured in the elevation of auditory brainstem-response thresholds. The hearing impairment began at age 3 weeks at high-stimulus frequencies and became most severe at age 24 weeks. Moreover, degeneration of hair cells and loss of stereocilia were remarkable in Fscn2^-/- mice, as revealed by F-actin staining and scanning electron microscopy. Furthermore, compared to the controls, the Fscn2^-/- mice displayed significantly lower electroretinogram amplitudes and thinner retinas at 8, 16, and 24 weeks. These results demonstrate that, in C57BL/6Jmice, Fscn2 is essential for maintaining ear and eye function and that a null mutation of Fscn2 leads to progressive hearing loss and retinal degeneration.

Otoprotective effects of mouse nerve growth factor in DBA/2J mice with early-onset progressive hearing loss

As it displays progressive hair-cell loss and degeneration of spiral ganglion neurons (SGNs) characterized by early-onset progressive hearing loss (ePHL), DBA/2J is an inbred mouse strain widely used in hearing research. Mouse nerve growth factor (mNGF), as a common exogenous nerve growth factor (NGF), has been studied extensively for its ability to promote neuronal survival and growth. To determine whether mNGF can ameliorate progressive hearing loss (PHL) in DBA/2J mice, saline or mNGF was given to DBA/2J mice of either sex by daily intramuscular injection from the 1st to the 9th week after birth. At 5, 7, and 9 weeks of age, in comparison with vehicle groups, mNGF groups experienced decreased auditory-evoked brainstem response (ABR) thresholds and increased distortion product otoacoustic emission (DPOAE) amplitudes, the prevention of hair cell loss, and the inhibition of apoptosis of SGNs. Downregulation of Bak/Bax and Caspase genes and proteins in cochleae of mice receiving the mNGF treatment was detected by real-time PCR, Western blot, and immunohistochemistry. This suggests that the Bak-dependent mitochondrial apoptosis pathway may be involved in the otoprotective mechanism of mNGF in progressive hearing loss of DBA/2J mice. Our results demonstrate that mNGF can act as an otoprotectant in the DBA/2J mice for the early intervention of PHL and, thus, could become of great value in clinical applications. © 2017 Wiley Periodicals, Inc.

Application of Mouse Models to Research in Hearing and Balance

Laboratory mice (Mus musculus) have become the major model species for inner ear research. The major uses of mice include gene discovery, characterization, and confirmation. Every application of mice is founded on assumptions about what mice represent and how the information gained may be generalized. A host of successes support the continued use of mice to understand hearing and balance. Depending on the research question, however, some mouse models and research designs will be more appropriate than others. Here, we recount some of the history and successes of the use of mice in hearing and vestibular studies and offer guidelines to those considering how to apply mouse models.

Recessive mutations of TMC1 associated with moderate to severe hearing loss

TMC1 encodes a protein required for the normal function of mechanically activated channels that enable sensory transduction in auditory and vestibular hair cells. TMC1 protein is localized at the tips of the hair cell stereocilia, the site of conventional mechanotransduction. In many populations, loss-of-function recessive mutations of TMC1 are associated with profound deafness across all frequencies tested. In six families reported here, variable moderate-to-severe or moderate-to-profound hearing loss co-segregated with STR (short tandem repeats) markers at the TMC1 locus DFNB7/11. Massively parallel and Sanger sequencing of genomic DNA revealed each family co-segregating hearing loss with a homozygous TMC1 mutation: two reported mutations (p.R34X and p.R389Q) and three novel mutations (p.S596R, p.N199I, and c.1404 + 1G > T). TMC1 cDNA sequence from affected subjects homozygous for the donor splice site transversion c.1404 + 1G > T revealed skipping of exon 16, deleting 60 amino acids from the TMC1 protein. Since the mutations in our study cause less than profound hearing loss, we speculate that there is hypo-functional TMC1 mechanotransduction channel activity and that other even less damaging variants of TMC1 may be associated with more common mild-to-severe sensorineural hearing loss.