Immunoblots showing β-gal and Vav proteins in tissue extracts. The tissue extracts derived from HS21/5 vav-βgalmice, nontransgenic (negative control) mice, or Rosa26 (positive control) animals. The blots were probed with monoclonal antibodies to p95^Vav or β-gal and, as a loading control, antibody to Hsp70, and bands were shown with a sheep antimouse Ig reagent. ThelacZ-neo gene fusion in Rosa26 animals consistently yields a 146-kD polypeptide (β-geo) and a smaller product (125 kD), perhaps related to the two transcripts observed in these mice.26