What they found
TL;DR (mlx-community/Qwen3.5-35B-A3B-4bit): Mutations in the Tmc1 gene reduce calcium entry into hair cells, which triggers a decrease in the PMCA2 calcium pump and leads to cell death and deafness. The study shows that PMCA2 levels are regulated by calcium-dependent turnover and stabilization by Neuroplastin, with changes becoming permanent after postnatal day 11.
Mutations in transmembrane channel-like protein 1 (TMC1), the pore-forming component of the mechano-electrical transducer (MET) channel in auditory hair cells, cause cell death and deafness in 3-wk old mice. We studied mice with mutations Tmc1 p.T416K, p.M412K, p.D528N, and p.D569N, which possessed functional MET channels at postnatal day (P)6 but became deaf before P21. These Tmc1 mutants had channels with reduced Ca2+ permeability and lower expression of the PMCA2 calcium pump in outer hair cell (OHC) stereocilia. The reduction in PMCA2 density was directly correlated with reduced Ca2+ entry via the MET channel. Over the first postnatal week, PMCA2 expression decreased in cochlear cultures containing lowered extracellular Ca2+, but after P11, PMCA2 density was insensitive to Ca2+ changes. The lower PMCA2 density in mutants was maintained into adulthood and may contribute to hair cell death. Before the onset of hearing, PMCA2 continuously turns over, and its insertion into stereocilia from an identified vesicular compartment is regulated by cytoplasmic [Ca2+]. PMCA2 turnover was strongly inhibited by the endocytosis blocker, Pitstop2, and by PtdIns(4,5)P2 blockers like phenylarsine oxide (PAO), which was shown to elevate stereociliary [Ca2+]. We argue the effects of PAO on mechanotransduction may be partly due to this Ca2+ increase. OHC bundles also expressed Neuroplastin (NPTN), a PMCA2 accessory protein, whose development paralleled PMCA2, and we propose it stabilizes the pump complex in stereocilia. NPTN expression was delayed about 2 d relative to PMCA2 and was less Ca2+ sensitive, implying it originates from a different internal pool of vesicles.
How this applies to our program
This paper suggests that STRC/DFNB16 mutations may similarly disrupt calcium homeostasis and pump regulation, leading to hair cell degeneration. Investigating whether STRC mutations alter PMCA2 turnover or Neuroplastin interaction could reveal new mechanisms for preventing deafness.
Key numbers
- 3-week-old mice become deaf
- P6 functional MET channels
- P21 onset of deafness
Links
Connections
[source]auto-indexed 2026-08-05 by strc-lit-watch