A novel copy number variant in the murine Cdh23 gene gives rise to profound deafness and vestibular dysfunction.

Hearing loss is the most common congenital sensory deficit worldwide and exhibits high genetic heterogeneity, making molecular diagnoses elusive for most individuals. Detecting novel mutations that contribute to hearing loss is crucial to providing accurate personalized diagnoses, tailored interventions, and improving prognosis. Copy number variants (CNVs) are structural mutations that are understudied, potential contributors to hearing loss. Here, we present the Abnormal Wobbly Gait (AWG) mouse, the first documented mutant exhibiting waltzer-like locomotor dysfunction, hyperactivity, circling behaviour, and profound deafness caused by a spontaneous CNV deletion in cadherin 23 (Cdh23). We were unable to identify the causative mutation through a conventional whole-genome sequencing (WGS) and variant detection pipeline, but instead found a linked variant in hexokinase 1 (Hk1) that was insufficient to recapitulate the AWG phenotype when introduced into C57BL/6J mice using CRISPR-Cas9. Investigating nearby deafness-associated genes revealed a pronounced downregulation of Cdh23 mRNA and a complete absence of full-length CDH23 protein, which is critical for the development and maintenance of inner ear hair cells, in whole head extracts from AWG neonates. Manual inspection of WGS read depth plots of the Cdh23 locus revealed a putative 10.4 kb genomic deletion of exons 11 and 12 that was validated by PCR and Sanger sequencing. This study underscores the imperative to refine variant detection strategies to permit identification of pathogenic CNVs easily missed by conventional variant calling to enhance diagnostic precision and ultimately improve clinical outcomes for individuals with genetically heterogenous disorders such as hearing loss.

Scanning efficacy of p-Chips implanted in the wing and leg of the Big Brown Bat (Eptesicus fuscus).

Individual marking techniques are critical for studying animals, especially in the wild. Current marking methods for bats (Order Chiroptera) have practical limitations and some can cause morbidity. We tested the p-Chip (p-Chip Corp.)-a miniaturized, laser light-activated microtransponder-as a prospective marking technique in a captive research colony of Big Brown Bats (Eptesicus fuscus). We assessed long-term readability and postimplantation effects of p-Chips injected subcutaneously above the second metacarpal (wing; n = 30) and the tibia (leg; n = 13 in both locations). Following implantation (Day 0), p-Chips were scanned with a hand-held ID reader (wand) on postimplantation days (PIDs) 1, 8, 15, 22, 32, 60, 74, 81, 88, 95, and over 1 year later (PID 464). For each trial, we recorded: (1) animal handling time; (2) scan time; (3) number of wand flashes; (4) p-Chip visibility; and (5) overall condition of the bat. Average scan times for p-Chips implanted in both the wing and leg increased over the duration of the study; however, the number of wand flashes decreased, suggesting that efficacy of p-Chip recording increased with user experience. Importantly, over 464 days both the visibility and readability of p-Chips in the wing remained high and superior to tags in the leg, establishing the second metacarpal as the preferred implantation site. Observed morbidity and mortality in captive bats with p-Chips was similar to baseline values for bats without these tags. Because scan efficiency on PID 464 was comparable with earlier days, this indicates that p-Chips implanted in the wing may be suitable as a long-term marking method. Our provisional results suggest that p-Chips are viable for extended field testing to see if they are suitable as an effective alternative to traditional methods to mark bats.

Las técnicas de marcaje individual son fundamentales para el estudio de los animales, especialmente en la naturaleza. Los métodos actuales de marcaje de murciélagos (Chiroptera) tienen limitaciones prácticas y algunos pueden causar morbilidad. Probamos el p-Chip (p-Chip Corp.)­un microtranspondedor miniaturizado activado por luz láser­como técnica de marcaje prospectivo en una colonia en cautiverio de murciélagos morenos (Eptesicus fuscus). Se evaluó la legibilidad a largo plazo y los efectos pos-implantación de los p-Chips inyectados subcutáneamente sobre el segundo metacarpiano (ala; n = 30) y la tibia (pata; n = 13 en ambas localizaciones). Tras la implantación (día 0), se escanearon los p-Chips con un lector de identificación manual (vara) en los días posteriores a la inyección (PID) 1, 8, 15, 22, 32, 60, 74, 81, 88, 95, y más de un año después (PID 464). En cada ensayo se registró: (1) el tiempo total de manipulación del animal; (2) el tiempo de exploración; (3) el número de destellos de proximidad del lector; (4) la visibilidad del p-Chip; y (5) el estado general del murciélago. Los promedios del tiempo de escaneado de los p-Chips implantados tanto en el ala como en la pata aumentaron a lo largo del estudio; sin embargo, el número de destellos del lector disminuyó, lo que sugiere que la eficacia del registro del p-Chip aumentó con la experiencia del usuario. A lo largo de 464 días, tanto la visibilidad como la legibilidad de los p-Chips en el ala siguieron siendo altas y superiores a las de las etiquetas en la pata, lo que estableció el segundo metacarpiano como el lugar preferido de implantación. La morbilidad y mortalidad observadas en murciélagos en cautiverio con p-Chips fue similar a los valores de referencia de los murciélagos sin estas marcas. Dado que la eficacia del escaneado en el PID 464 fue comparable a la de días anteriores, es probable que los p-Chips implantados en el ala sean adecuados como método de marcado a largo plazo. Nuestros resultados provisionales sugieren que los p-Chips son viables para pruebas de campo prolongadas como alternativa prospectiva a los métodos tradicionales de marcaje de murciélagos.