Figure 2.

Polaris and Tg737 expression in mutant and wild-type samples. (A) Analysis of Polaris expression in mutant kidney extracts reveals that expression of the 95-kDa protein is abolished; however, the levels of the 75-kDa isoform increased. The small shift in the size of the 75-kDa isoform in the mutant sample is due to slightly aberrant running during electrophoresis. (B) Level of expression of the smaller protein isoform was inversely correlated with the level of expression of the 95-kDa product in 94D Tg737^orpk mutant collecting duct cell line. (C) As seen in the collecting duct cell line, expression of the 95-kDa Polaris peptide reduced the level of the putative 75-kDa isoform. (D) Western blot analysis revealed that expression of both the ∼95 kDa and ∼75 kDa proteins are abolished in e8.0 Tg737^Δ2-3β-Gal mutant embryos. (E) Northern analysis was conducted on Poly(A⁺) selected RNA from wild-type, Tg737^orpk heterozygous, and Tg737^orpk homozygous mutant testis. Tg737 expression was detected as two prominent transcripts corresponding to 2.8 and 3.2 kb in both wild-type and heterozygous samples. In mutants, the 3.2-kb transcript is lost, whereas expression of the smaller transcript persists. Similar results are obtained in other tissues except that higher molecular weight transcripts are also present.