Id1 induces the proliferation of cochlear sensory epithelial cells via the nuclear factor‐κB/cyclin D1 pathway in vitro

Abstract

Inhibitors of differentiation (Id) play an essential role in the neurogenesis of the central nervous system. However, the expression and function of Id in the development of cochlear sensory epithelial cells have yet to be elucidated. In this study, we demonstrate the Id1 gene was expressed in the rapidly growing otocyst on embryonic day 12 (E12) and in the organ of Corti, spiral ganglions, and stria vascularis on postnatal day 1 (P1) by cellular and molecular biologic techniques. Knockdown of the Id1 gene with short interfering RNA (siRNA) in a cochlear sensory epithelial cell line (OC1) significantly reduced its proliferation, whereas overexpression of Id1 in OC1 significantly increased the proliferation of OC1, suggesting a role of Id1 in the development of cochlear sensory epithelial cells. The proliferative action of Id1 on OC1 was mediated by nuclear factor-kappaB (NF-kappaB) and cyclin D1 (a downstream molecule of NF-kappaB). Blockage of the NF-kappaB activity with pyrrolidine dithiocarbamate (PDTC) or enhancement of the NF-kappaB activity with p65 (a subunit of NF-kappaB) in OC1 significantly inhibited or increased, respectively, the cell proliferation and transcription of cyclin D1 induced by Id1. Truncation of the NF-kappaB binding site in the cyclin D1 promoter fully abrogated the transcription of cyclin D1, suggesting that the cyclin D1 transcription is dependent on NF-kappaB. We concluded from this study that Id1 induces the proliferation of OC1 via the NF-kappaB/cyclin D1 pathway.

TWIST Family of Basic Helix-Loop-Helix Transcription Factors Mediate Human Mesenchymal Stem Cell Growth and Commitment

“…In general, Id proteins are considered positive regulators of cell cycling and inhibitors of cellular differentiation [30]. Overexpression of Id proteins in embryonic-derived fibroblasts facilitates cell cycle S-phase under serum-deprived conditions [34], where Id-1 has been reported to induce the proliferation of cochlear sensory epithelial cells via the NF-kappaB/cyclin D1 pathway [35]. Furthermore, various cancer cell lines appear to require Id-1 and Id-2 expression for their growth, survival, and metastasis via regulation of p53 and PI3K/Akt/NF-kappaB signaling pathways in a similar fashion to that described for Twist-1 and Dermo-1 [36][37][38][39][40].…”

“…Chondrogenic differentiation was assessed in high density (0.5-1 Â 10 5 cells per well) cultures in 96-well plates with 10 ng/ml TGF-b1 for 48 hours as described previously [5]. Glycosaminoglycan synthesis was measured in quadruplicate wells by 35 SO 4 incorporation using a TopCount NXT Microplate Scintillation & Luminescence counter (Perkin Elmer Life and Analytical Sciences, Downers Grove, IL, http://las.perkinelmer.com/). Pellet cultures were prepared using 1 Â 10 6 cells per sample as previously described [5,27].…”

EGF Mediates Survival of Rat Cochlear Sensory Cells via an NF-κB Dependent Mechanism In Vitro

“…PDTC was chosen because it had been widely used as an inhibitor of NF-B, especially in neurons [19] and cochlear sensory epithelial cells [20]. The NF-B reporter, provided by Dr. Keith Brown at the National Institute of Allergy and Infectious Diseases, contains three repeats of B sites for the immunoglobulin -light chain [21].…”

“…The data presented in this study represent signal molecules related to the EGFR signaling pathway. The microarray database, published previously [20,25], was interrogated with respect to genes of interest in the present study.…”

The Helix-Loop-Helix Protein Id1 Requires Cyclin D1 to Promote the Proliferation of Mammary Epithelial Cell Acini

“…Several potential mechanisms of cell cycle modulation by Id1 have been identified (6,7), including effects on cyclin-dependent kinase (CDK) inhibitors (8,9) and on cyclin D1 expression (2,10).…”