Kölliker's Organ Functions as a Developmental Hub in Mouse Cochlea Regulating Spiral Limbus and Tectorial Membrane Development

Kölliker's organ is a transient developmental structure in the mouse cochlea that undergoes significant remodeling postnatally. Utilizing an epithelial-specific conditional deletion mouse model of <i>Prdm16</i> (marker and regulator of Kölliker's organ), we show that <i>Prdm16</i> is required for interdental cell development, and thereby the development of the limbal domain of the tectorial membrane and its medial anchorage to the spiral limbus. Additionally, we show that Kölliker's organ is involved in normal tectorial membrane collagen fibril development and maturation. Interestingly, mesenchymal cells of the spiral limbus underneath <i>Prdm16</i>-deficient Kölliker's organ failed to produce interstitial matrix proteins, resulting in a hypoplastic and truncated spiral limbus, indicating a non-cell autonomous role of <i>Prdm16</i> in regulating spiral mesenchymal matrix development. Single-cell RNA sequencing identified differentially expressed genes in <i>Prdm16</i>-deficient Kölliker's organ suggesting a role for connective tissue growth factor (CTGF) downstream <i>Prdm16</i> in epithelial-mesenchymal signaling involved in spiral limbus matrix deposition. <i>Prdm16</i>-deficient mice showed a hearing deficit, as indicated by elevated auditory brainstem response thresholds at most frequencies, consistent with the cochlear structural defects. Both sexes were studied. This work establishes <i>Prdm16</i> as a deafness gene in mice through its role in regulating Kölliker's organ development. Such understanding recognizes Kölliker's organ as a developmental hub regulating multiple surrounding cochlear structures.