ESPNL (espin-like) is an actin-binding protein essential for inner ear hair cell development and auditory function. It binds to actin filaments without cross-linking them and is specifically required for the formation and maintenance of stereocilia, the mechanosensory organelles of hair cells 1. ESPNL serves as a marker gene for differentiating hair cells during inner ear development, with expression specifically detected in this cellular population during in vitro differentiation from stem and progenitor cells 1. The protein is critical for stereociliary staircase formation, a structural organization essential for normal hearing [UniProt annotation]. Beyond its primary role in auditory function, ESPNL has emerged as a potential disease susceptibility gene in epithelial ovarian cancer, with expression quantitative trait locus analysis identifying ESPNL as a putative candidate gene at chromosome 2.3 associated with high-grade serous ovarian cancer risk in East Asian women 2. Additionally, ESPNL was identified as one of eight tumor microenvironment-related prognostic genes in lung adenocarcinoma, where elevated expression correlated with worse overall survival outcomes 3. These findings suggest ESPNL's involvement extends beyond auditory development to potential cancer biology, though the mechanistic basis for these associations requires further investigation.