Figure 1.

Expression of mutant Blk proteins in transgenic mice. (A) Organization of Blk transgenes. The H₂K promoter, Blk cDNA, β-globin splice donor and acceptor sequences, and the Ig heavy chain intronic enhancer are indicated by rectangles. The Y495F mutation is indicated by a vertical line. (B) Expression of constitutively active mutant Blk protein in transgenic mice. Thymocytes (lanes 1–5) or splenic B cells (lanes 6–11) from transgenic mice (lanes 1–4; lanes 6–10) and nontransgenic control animals (lanes 5 and 11) were assayed for Blk by immunoblotting. Individual transgenic mice from which samples were derived are identified across the top. Spleens from Blk(Y495F)-6, -13, -15, and -16 were macroscopically normal; tumor was evident in the spleen from founder animal Blk(Y495F)-29. The apparent sizes (in kDa) and positions of molecular mass standards are indicated at right.