Which ISH ASBT mRNA statement is correct?

• A. Detected only in ileum
• B. Detected in colon and ileum only
• C. Not detected in any segment
• D. Detected throughout ALL intestinal segments (discordance with protein) – minimal in duodenum/jejunum → ileum marked to diffuse → mild to moderate in cecum and colon

Answer: (D)

The main idea here is that mRNA presence detected by in situ hybridization can be broader than where the protein is actually abundant. For ASBT, the mRNA is detectable across all intestinal segments, but its level varies: minimal in the proximal small intestine (duodenum/jejunum), stronger in the ileum, and mild to moderate in the cecum and colon. This shows a discordance between mRNA distribution and the protein’s localization or abundance, which often reflects post-transcriptional regulation, mRNA/stability differences, or protein trafficking and turnover.

So the statement that ASBT mRNA is detected throughout all intestinal segments with a gradient from minimal in the proximal small intestine to higher in the ileum and moderate in the colon fits this pattern best.