Fig. 1. Expression of Dab1 p80 and p45. (A) Schematic of p80 and p45 protein structures, showing PTB domain, tyrosine phosphorylation sites (p.Tyr), two regions of high sequence identity to Dab2 (DH1 and DH2), and predicted sites for Cdk5 phosphorylation and AP2 binding. (B) SDS PAGE analysis of samples from wild-type, Dab1^p45/+ heterozygous and Dab1^p45/p45 homozygous cerebral hemispheres sampled at E16.5. Brain lysates were analyzed directly (lanes 3-5) or after immunoprecipitation with anti-Dab1(B3) antibody (lanes 6-11). The 555-codon and 271-codon Dab1 mRNAs were translated in vitro and analyzed in parallel (lanes 1 and 2, respectively). Proteins were detected by western blotting with anti-Dab1(B3) antibody (lanes 1-8) or anti-phosphotyrosine (4G10) (lanes 9-11). Bands below p80 and p45 in lanes 1 and 2 represent internal initiation sites. Bands above p80 and p45 in lanes 3-11 may represent phosphorylated forms. Asterisks mark nonspecific bands. (C) Relative levels of expression of p80 and p45. Dab1^p45/WT brains were harvested at P19 and E16.5. Serial threefold dilutions of each brain lysate were analyzed by SDS PAGE and western blotting with anti-Dab1(B3) antibody. (D) Effect of Reln mutation on expression of p80 and p45. Littermate embryos from a Dab1^p45/+ Reln^–/+ intercross were harvested at E16.5 and cerebral hemispheres were analyzed for Dab1 content. Tubulin was used as a loading control. Genotypes were Dab1^+/+ (top two panels) or Dab1^p45/p45 (bottom two panels), and wild type, heterozygous or mutant for Reln. Molecular mass standards were 95, 70, 54 and 47 kDa.

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