Kölliker's Organ Functions as a Developmental Hub in Mouse Cochlea regulating spiral limbus and tectorial membrane development.

Abstract

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 Prdm16 (marker and regulator of Kölliker's organ), we show that Prdm16 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 Prdm16-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 Prdm16 in regulating spiral mesenchymal matrix development. Single cell RNA sequencing identified differentially expressed genes in Prdm16-deficient Kölliker's organ suggesting a role for connective tissue growth factor (CTGF) downstream Prdm16 in epithelial-mesenchymal signaling involved in spiral limbus matrix deposition. Prdm16-deficient mice showed a hearing deficit, as indicated by elevated auditory brain stem response thresholds at most frequencies, consistent with the cochlear structural defects. Both sexes were studied. This work establishes Prdm16 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.Significance Statement In this study, we show that the Kölliker's organ functions as a developmental hub that orchestrates the development of tectorial membrane and spiral limbus during cochlear development. Utilizing a mouse model of conditional deletion of Prdm16 (marker and regulator of Kölliker's organ), we establish Prdm16's necessity for hearing in mice through its many roles during cochlear development including permitting interdental cell development and thereby the formation of the tectorial membrane limbal domain, secreting collagens essential for tectorial membrane matrix development, and signaling to the underlying mesenchyme to secrete extracellular matrix and develop the spiral limbus.