Expression pattern of serine protease inhibitor kazal type 3 (Spink3) during mouse embryonic development.

Recent evidence shows that the serine protease inhibitor Kazal type 3 (Spink3) has more diverse functions than expected. To gain insight into its function, we analyzed the spatiotemporal expression profile of Spink3, using in situ hybridization (ISH) and a Spink3+/lacZ knock-in mouse, in which lacZ was inserted into the Spink3 locus. Spink3lacZ expression was first observed in the foregut, midgut, hindgut and the forebrain/midbrain junction region at 9.5 days post coitus (dpc). In the pancreas, Spink3 mRNA was detected at 11.5 dpc, before formation of the typical shape of the exocrine structure of the pancreas. Acinar cell expression was clearly identified by 13.5 dpc. After differentiation of the intestinal tract, Spink3lacZ expression was observed in the large intestine at 11.5 dpc, followed by expression in the small intestine at 13.5 dpc, before appearance of intestinal digestive enzymes. Spink3 mRNA and Spink3lacZ activity were also detected in other tissues, including the mesonephric tubules and the urogenital ridge at 11.5 dpc, the genital swelling at 13.5 dpc, the ductus epididymis at 17.5 dpc, and the seminal vesicle at 8 weeks. These data suggest that Spink3 may play important roles in proliferation and/or differentiation of various cell types during development.