Fig. 3. Hoxb13 is required for secretion of major ventral prostate proteins. The lack of ventral secretory protein expression is specific to Hoxb13 homozygous mutants. (A) SDS-PAGE of secretory proteins. Hoxb13 homozygous mutants do not express p25 a 25-40 kDa glycoprotein or p12 a 6 kDa serine protease inhibitor (lane 3). Hoxd13 mutants do not exhibit defects in their ventral prostatic secretory protein profile. In the absence of Hoxd13, one copy of Hoxb13 is sufficient for expression of both p12 and p25 (lane 4). (B) The Hoxb13 mutation appears to affect secretory function of only the ventral prostate. SDS-PAGE of secretory proteins from anterior prostates (AP) ventral prostates (VP). (C) Hoxb13 homozygous mutant ventral prostates do not produce secretory protein mRNA. Semi-quantitative RT-PCR using primers for the two major ventral secretory proteins p12 and p25, reveals absence of these mRNAs in ventral prostates from Hoxb13 homozygous mutants. Heart and liver RNAs are used as negative controls, GAPDH is an internal loading control. Molecular mass markers indicated by bars on the left of A and B are 188, 98, 62, 49, 38, 28, 17, 14, and 6 kDa.