Expression of insulin‐like growth factor binding proteins during mouse cochlear development

Abstract

Background: Insulin-like growth factor (IGF) signaling plays important roles in growth and cellular differentiation in the cochlear sensory epithelium. However, the roles of IGF binding proteins (IGFBPs), a family of IGF modulators, remain to be elucidated in this system. To begin to examine the role of IGFBPs, we used reverse transcription polymerase chain reaction (RT-PCR) and in situ hybridization to determine the temporal and spatial patterns of expression for Igfbps within the developing mouse cochlea. Results: RT-PCR analysis indicates that Igfpb2-5 are expressed in the cochlea between embryonic day (E) 13.5 and postnatal day (P) 0. In addition, the expression of each Igfbp significantly increased between E13.5 and P0. In situ hybridization indicates that Igfbp2, 3, 4, and 5 have distinct and complementary expression patterns in the developing cochlea. Moreover, expression patterns of Igfbp3 and 5 demonstrate contrasting gradients along the basal-to-apical axis of the cochlea. Conclusions: Igfbp2-5 are expressed in distinct and complementary patterns during cochlear development. These data suggest that IGFBPs may act to precisely regulate activation of IGF signaling in the developing cochlea in a cell type-specific manner, contributing to cellular patterning and differentiation in the cochlea. Temporal and spatial expression patterns of Igfbps in the developing mouse cochlea were studied. Igfbp2-5 are expressed during cochlear development, and the expression of each Igfbp increases significantly between E13.5 and P0. Igfbp2-5 are expressed in unique and distinct patterns during cochlear development.

FGF20‐FGFR1 signaling through MAPK and PI3K controls sensory progenitor differentiation in the organ of Corti

“…42 By contrast, our experiments were initiated at E14.5 after progenitor cell cycle exit, 4 demonstrating an additional role for PI3K in HC differentiation. In addition, treating E13.5 wild-type cochleae with 40 μM LY294002 in the previous study resulted in fewer HCs compared to our treatments starting on E14.5, 44 further supporting a role for PI3K in both differentiation and progenitor cell proliferation. The results presented here demonstrate an interaction between PI3K and FGF20, potentially placing PI3K signaling downstream of FGF20.…”

Characterization of the development of the mouse cochlear epithelium at the single cell level

“…For additional confirmation, we identified genes that were expressed in specific cell groups within KO ( Supplementary Fig. 2) and then compared their distribution along tSNE1 with published positional data 11,18,19 . Based on these results, the different clusters arising from KO were renamed to reflect their position along the medial-lateral axis (Fig.…”

Hormone Therapy: Challenges for Treating Hearing Impairments

“…Most of it is bound to IGF-1-binding proteins (IGFBP) which regulate the amount of free IGF-1 and therefore its activity. IGFBPs 2-5 are expressed in the cochlea during embryonic and postnatal days, indicating that they play a role in cochlear development through cell pattern and differentiation [7]. Decreased IGF-1 levels are associated with different types of hearing loss, including ARHL.…”

“…The function of different hormones on the ear appears early, during the embryonic development, therefore playing a prominent role in the genesis of hearing, leading to a correct processing of the auditory function [5][6][7]. This is the reason by which some hormonal dysfunctions lead to auditory alterations.…”