Immunolocalization of DCAMKL-1, a putative intestinal stem cell marker, in normal colonic tissue

Doublecortin and CaM kinase-like-1 (DCAMKL-1) is a microtubule-associated protein kinase which has been recently proposed as a gastrointestinal stem cell marker. The aim of our study was to characterize DCAMKL-1 expression in normal human colon by immunohistochemistry. DCAMKL-1 immunostaining was performed on histologically normal colorectal biopsies from 14 patients. Immunoreactivity was found in over 60% of colonic crypts and was represented by strong cytoplasmic staining, anti-luminal in distribution, and was reminiscent of cytoplasmic orientation of neuroendocrine cells. The highest number (48.5%) of DCAMKL-1 positive cells was found in the first 4 cells from the crypt base. Seventy percent of DCAMKL-1 positive cells were located in the lower third of the crypt, 26% in the middle third and 4% in the upper third. Therefore, in normal colonic mucosa, expression of DCAMKL-1 is not confined to the stem cell compartment. When we compared DCAMKL-1 immunostaining with that of the leucine-rich-repeat-containing G-protein-coupled receptor 5 (Lgr5), an intestinal stem cell marker, and chromogranin-A (CgA), an enteroendocrine cell marker, we found that DCAMKL-1 positive cells co-stained with Lgr5 only at the crypt base, but co-stained with CgA throughout the crypt. Our findings suggest that DCAMKL-1 marks a subset of colorectal stem cells, as well as a subset of enteroendocrine cells.