Fig. 5. Mist1 and Cx32 are co-expressed in most secretory exocrine cell types. (A) RT-PCR analysis of several different tissues from wild type (WT) mice reveals that Mist1 and Cx32 transcripts are co-expressed in all serous exocrine cell types. The liver, which is not a serous exocrine organ, expresses the Cx32 gene but not the Mist1 gene. (B) RNA blot hybridization reveals that all serous exocrine tissues show a large decrease in Cx32 mRNA levels from Mist1^KO mice when compared to WT control samples. (C-J) Cx32 (green, arrows) and ß-gal (red) immunofluorescence on Mist1^Het and Mist1^KO samples from the pancreas (C,D), lacrimal gland (E,F), submandibular gland (G,H) and liver (I,J). In all Mist1^KO secretory exocrine cells in which the Mist1 locus is transcriptionally active (indicated by the presence of ß-gal protein in C-H, red), Cx32 immunoreactivity is greatly reduced. Mist1^KO liver cells, which do not express Mist1, maintain high levels of Cx32. Nuclei in the liver panels are stained with the DNA fluorochrome DAPI (blue).