Expression and Function of NUMB in Odontogenesis

• Published in: BioMed research international 2013-01, Vol.2013 (2013), p.1-11
• Main Authors: George, Anne, Song, Yiqiang, Ravindran, Sriram, Gao, Qi, Ramachandran, Amsaveni, Li, Haitao, Evans, Carla A.
• Format: Article
• Language: English
• Subjects: Animals; Cell Differentiation - genetics; Cell Line; Cellular proteins; Dental Pulp - metabolism; Gene Expression Regulation; Humans; Membrane Proteins - genetics; Membrane Proteins - isolation & purification; Membrane Proteins - metabolism; Mice; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - isolation & purification; Nerve Tissue Proteins - metabolism; Odontoblasts - metabolism; Odontogenesis; Physiological aspects; Receptor, Notch1 - genetics; Receptor, Notch1 - metabolism; RNA, Messenger - genetics; RNA, Messenger - isolation & purification; Signal Transduction; Stem cells
• ISSN: 2314-6133; 2314-6141
• DOI: 10.1155/2013/182965

NUMB is a multifunctional protein implicated to function in self-renewal and differentiation of progenitors in several tissues. To characterize the transcripts and to analyze the expression pattern of NUMB in odontogenesis, we isolated 2 full-length clones for NUMB from mouse dental pulp mRNA. One novel sequence contained 200 bp insertion in the phosphotyrosine binding domain (PTB). Confocal microscopy analysis showed strong NUMB expression in human dental pulp stem cells (hDPSC) and preameloblasts. Western blot analysis indicated that NUMB isoforms were differentially expressed in various dental tissues. Immunohistochemical analysis showed that in postnatal mouse tooth germs, NUMB was differentially expressed in the preameloblasts, odontoblasts, cervical loop region, and in the dental pulp stem cells during development. Interestingly, overexpression of NUMB in HAT-7, a preameloblast cell line, had dramatic antagonizing effects on the protein expression level of activated Notch 1. Further analysis of the Notch signaling pathway showed that NUMB significantly downregulates sonic hedgehog (Shh) expression in preameloblasts. Therefore, we propose that NUMB maintains ameloblast progenitor phenotype at the cervical loop by downregulating the activated Notch1 protein and thereby inhibiting the mRNA expression of Shh.