(a) RT-PCR analysis of NUMB isoforms in day 7 dental pulp cells. RT-PCR analysis of mRNA extracted from day 7 dental pulp culture shows two PCR bands corresponding to 2 kb and 1.8 kb obtained using primers designed to amplify the longest NUMB reading frame. (b) The alignment of the sequence obtained from 1.8 kb and the 2 kb PCR fragments. The 2 kb PCR fragment contains 236 bp insertion in the phosphotyrosine binding domain (PTB) 201 bp downstream of the initiation start site.