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PubMedDate not supplied

Development of the sensory receptor cells in the utricular macula.

Normal CBA mice were timed for the developmental stage by the vaginal plug technique. The day of copulatory plug observance was designated as gestation day one. The developmental characteristics of the utricular macula sensory epithelium is described on an ultrastructural level from the 15th to the 19th day of gestation (approximate day of birth). The following pertinent observations are reported: (1) the formation of stereocilia begins prior to the 15th day and continues to approximately the 18th day, (2) the formation of the stereocilia suggests a mechanism of gradual transformation of existing cell surface microvilli, (3) the onset of the genesis of stereocilia precedes neuronal contact and cuticular plate formation, (4) stereocilia rootlets are forming before cuticular plate formation, (5) utricular sensory hair cells have undergone significant ultrastructural differentiation prior to the development of synaptic contacts, and (6) nerve chalice formation of type 1 sensory cells begins on the 18th day and is still incomplete at birth.

Animals↗

PubMed2026

CASZ1 regulates the maturation of outer hair cells and is required for hearing in mice.

The transcription factor ATOH1 is a master regulator of mechanosensory hair-cell (HC) development in the ear. Here, we report that its target gene Casz1 regulates the maturation of outer HCs (OHCs). Genetic deletion of Casz1 during (but not after) cochlear development in the mouse caused: hearing loss; disorganization of mechanosensory stereocilia bundles in OHCs; reduced F-actin density in OHC cuticular plates; progressive OHC loss; and mild morphological alterations in inner HCs. This deletion also altered gene expression, delaying downregulation of genes expressed in immature OHCs, including the actin regulator-encoding gene Coro2a, and accelerating upregulation of genes expressed in mature OHCs. Deleting Coro2a in Casz1 mutant mice restored F-actin density in cuticular plates but increased stereocilia bundle disorganization and hearing thresholds, revealing that CORO2A provides an overall beneficial effect. Our data indicate that CASZ1 regulates transcriptional and morphological maturation of OHCs, and that CASZ1 in maturing HCs is necessary for hearing.

CASZ1↗

PubMed1979

Morphologic variations along the length of the monkey vas deferens.

Gross and microscopic morphology of the vas deferens of sexually mature macaque monkeys were studied with special reference to the changes and modifications occurring throughout its entire length. The vas deferens was subdivided into four regional segments designated proximal, middle, distal, and ampulla. Each segment showed morphologic variations and it seemed to correspond roughly to the region located in a different part of the body which it traverses. The longitudinal folds of the epithelium are simple in the proximal region but gradually become more complex towards the distal region. In the ampulla, they often branch and form crypts. Stereocilia of epithelial cells are taller and more uniform in the proximal portion in comparison with the short, irregular stereocilia found in the more distal segment of the vas deferens. The luminal epithelial cells of the proximal part apparently have no granules or cytoplasmic blebbings, while the principal cells in the distal portion contain large numbers of cytoplasmic granules and apical blebs. Cells in the middle segments possess cytological features intermediate to the proximal and distal regions. These structural variations along the length of the vas deferens sug gest that this segment of the excurrent duct of the testis performs functions other than just as a passageway for spermatozoa.

Animals↗

PubMed2023

Spontaneous allelic variant in deafness-blindness gene Ush1g resulting in an expanded phenotype.

Relationships between novel phenotypic behaviors and specific genetic alterations are often discovered using target-specific, directed mutagenesis or phenotypic selection following chemical mutagenesis. An alternative approach is to exploit deficiencies in DNA repair pathways that maintain genetic integrity in response to spontaneously induced damage. Mice deficient in the DNA glycosylase NEIL1 show elevated spontaneous mutations, which arise from translesion DNA synthesis past oxidatively induced base damage. Several litters of Neil1 knockout mice included animals that were distinguished by their backwards-walking behavior in open-field environments, while maintaining frantic forward movements in their home cage environment. Other phenotypic manifestations included swim test failures, head tilting and circling. Mapping of the mutation that conferred these behaviors showed the introduction of a stop codon at amino acid 4 of the Ush1g gene. Ush1gbw/bw null mice displayed auditory and vestibular defects that are commonly seen with mutations affecting inner-ear hair-cell function, including a complete lack of auditory brainstem responses and vestibular-evoked potentials. As in other Usher syndrome type I mutant mouse lines, hair cell phenotypes included disorganized and split hair bundles, as well as altered distribution of proteins for stereocilia that localize to the tips of row 1 or row 2. Disruption to the bundle and kinocilium displacement suggested that USH1G is essential for forming the hair cell's kinocilial links. Consistent with other Usher type 1 models, Ush1gbw/bw mice had no substantial retinal degeneration compared with Ush1gbw /+ controls. In contrast to previously described Ush1g alleles, this new allele provides the first knockout model for this gene.

Mice↗

PubMed2026

TECTB Variants Reveal Tectorial Membrane Vulnerability in Dominant Non-Syndromic Hearing Loss.

Identifying new genes responsible for non-syndromic hearing loss remains a critical goal as many patients still lack a molecular diagnosis despite comprehensive genetic testing. The tectorial membrane (TM) is a specialized acellular matrix of the inner ear, essential for stimulating mechanosensitive hair cell stereocilia bundles and maintaining frequency tuning and auditory sensitivity. Although mutations in genes encoding several non-collagenous proteins found in the TM (TECTA, CEACAM16, OTOG, OTOGL) have been identified as deafness genes, definitive evidence implicating β-tectorin (TECTB) has been lacking. Here, we present multiple lines of genetic and experimental evidence linking heterozygous missense variants in TECTB (NM_058222.3:c.674G>A, p.Cys225Tyr and NM_058222.3:c.853C>T, p.Arg285Cys), with hearing loss. Each variant affects highly conserved residues within or directly flanking the zona pellucida domain. Using a Tectb-C225Y knock-in mouse model, we show that homozygous animals exhibit severe hearing loss and profound disruption of TM morphology, while heterozygous animals display decreased staining density within the TM and increased susceptibility to noise-induced hearing loss, despite normal auditory thresholds. These findings identify TECTB as a novel human deafness gene, further elucidate its contribution to maintaining TM integrity and resilience against environmentally-related auditory decline.

beta‐tectorin (TECTB)↗

PubMed1979

Fine structure of the monkey epididymis: a correlated thin-section and freeze-cleave study.

The epithelium of the monkey epididymis was studied by means of freeze-fracture techniques and conventional electron microscopy. For the study of transepithelial permeability lanthanum hydroxide was used as an intercellular tracer. The epididymal epithelium consists mainly of tall columnar cells. The long stereocilia at the apical surface, similarly to microvilli, exhibit after freeze-fracture, two distinct faces: the E face, concave and with fewer membrane-associated particles, and the complementary convex P face. In the lumen unusual groups of smooth-surfaced vacuoles are present. A tight junctional network, which shows some permeability to the lanthanum tracer, is located at the apical end of the cells. Supranuclear cross-fractures clearly show the well developed Golgi cisternae and numerous vacuole profiles. The highly infolded, centrally located nucleus exhibits, after freeze-fracture, an even distribution of nuclear pores. In the perinuclear region the rough endoplasmic reticulum, which also presents pores, displays a sheet-like organization. The basal cytoplasm is filled by numerous globular profiles of membrane-bounded granules. Freeze-cleave exposes large cytoplasmic areas where the types and amount of organelles indicate an intense metabolic activity.

Animals↗

PubMed1977

[Peptidases. I. Histochemical investigations with 2-naphthylamides and hexazonium-p-rosanilin (author's transl)].

Using fresh frozen (with and without semipermeable membranes), freeze-dried or sections from aldehyde fixed material and hexazotized p-rosaniline for simultaneous coupling more than 20 different unsubstituted or substituted L-amino acid naphthylamides are split especially in the microvilli and/or stereocilia of the small intestine, kidney and epididymis from rats. Further sites of positive reactions can be revealed by L-alanyl, L-leucyl, L-lysyl, alpha,L-glutamyl, gamma,L-glutamyl, L-asparaginyl, N-benzoyl-L-arginyl, N-carbobenzoxy-L-arginyl and N-benzoyl-L-phenylalanyl 2-naphthylamide. Among the substituted and unsubstituted peptide 2-naphthylamides L-prolyl-L-arginyl 2-naphthylamide is not hydrolysed in visible amounts; L-arginyl-L-arginyl, L-alanyl-L-arginyl-L-arginyl, L-alanyl-L-leucyl-L-tyrosyl, L-histidyl-L-seryl, L-seryl-L-tyrosyl and L-glycy-L-phenylalanyl 2-naphthylamide are metabolized in the renal and intestinal brush border; the reaction pattern obtained with N-carbobenzoxy-L-glycyl-L-glycyl-L-arginyl 2-naphthylamide differs from that of N-carbobenzoxy-L-arginyl 2-naphthylamide. In addition L-glycyl-L-prolyl, L-leucyl-L-alanyl, L-lysyl-L-alanyl and L-alanyl-L-phenylalanyl-L-prolyl 2-naphthylamide are also split in the lysosomes of many organs and the secretion granules of gland cells.

Amides↗

PubMed2026

Differential contributions of mt-Tr and Cs variants to developmental cochlear defects and mitochondrial dysfunction in A/J mice.

A/J mice exhibit early-onset hearing loss linked to Cdh23, mitochondrial tRNA-Arg (mt-Tr), and citrate synthase (Cs) variants. Although developmental cochlear defects have been identified in juvenile A/J mice, the hierarchical contributions of mt-Tr versus Cs remain unclear. Using reciprocal intercross-derived strains to decouple mitochondrial haplotypes from nuclear factors, we demonstrate that the mitochondrial background is the primary determinant of auditory dysfunction. Mice with A/J mtDNA (AXB strains) displayed significantly higher ABR thresholds, accelerated hair cell attrition, and severe stereocilia dysmorphology compared to those with B6 mtDNA (BXA strains), occurring largely independently of the Cs genotype. While the Cs mutation exacerbated hearing loss, its impact was secondary to that of the dominant mitochondrial background. Systemic behavioral assessments and mitochondrial assays confirmed that A/J mitochondria exert a more profound metabolic impact than the Cs mutation. Our findings establish that the mitochondrial genomic background, with the mt-Tr locus as a prominent candidate variant, serves as the principal driver of developmental cochlear defects and early-onset hearing loss in A/J mice, while the nuclear Cs mutation acts as a synergistic modifier. This study underscores the critical role of mitonuclear crosstalk in inner ear maturation and provides new insights into the etiology of hereditary hearing loss.

Animals↗

PubMed2025

Biallelic MINAR2 variant is associated with nonsyndromic severe to profound sensorineural hearing loss.

MINAR2 is essential for normal hearing by regulating cholesterol localization in stereocilia in hair cells. MINAR2 knockout results in rapidly progressive sensorineural hearing loss (SNHL) in mice and zebrafish models. Recently, biallelic variants in MINAR2 have been reported to cause SNHL in four unrelated families with nonsyndromic severe to profound SNHL. Here we provide a second report of an additional family with SNHL. The index patient presented with nonsyndromic severe to profound SNHL. The family history was remarkable for a 20-year-old male sibling with nonsyndromic severe to profound SNHL. Both patients did not have any neurological involvement. Trio whole-exome sequencing of the index and his parents revealed a homozygous nonsense variant in MINAR2 (NM_001257308.2:c.319A>T; p.(Lys107*) in the index. Parents were heterozygous for the same variant. This variant introduces an early stop codon and probably results in a loss of function because of the predicted nonsense-mediated decay. Our study provides the first independent confirmation of the MINAR2-related SNHL.

Journal Article↗

PubMed2026

Hearing loss associated with CDC42 in mice and humans (Takenouchi-Kosaki syndrome): CDC42 and RHOQ synergistically function in cochlear hair cells.

CDC42 is involved in multiple signaling pathways, including actin organization and polarity. We previously reported progressive sensorineural hearing loss (SNHL) in inner ear hair cell (HC)-specific Cdc42-knockout (Atoh1-Cre+/-;Cdc42flox/flox) mice. However, the phenotype was milder than expected, suggesting possible redundancy with other Rho-family GTPases. Thereafter, Takenouchi-Kosaki syndrome (TKS), caused by de novo CDC42 mutations and manifesting as SNHL, was reported, in which the p.Y64C mutation was speculated to be constitutively active. However, the relationship between CDC42 status and hearing phenotypes in TKS remains unclear. Using cell models, mouse models, and patient data, we propose that impaired and/or dysregulated cycling between GDP/inactive and GTP/active forms, through either loss-of-function or constitutive activation, can lead to SNHL. Furthermore, to test redundancy, we generated HC-specific Cdc42;RhoQ double-knockout (Atoh1-Cre+/-;Cdc42flox/flox;RhoQflox/flox) mice, which revealed synergistic roles of CDC42 and RHOQ in cochlear HCs. Supporting this synergy, MDCK cells with CDC42 and RHOQ double knockdown showed greater phospho-cofilin, a key regulator of actin turnover, elevation than single knockdowns.

CDC42↗