EXPRESSION OF ANOCTAMIN-1 IN HUMAN GASTROINTESTINAL TRACT DURING EMBRYONIC AND FETAL DEVELOPMENT

<p>Anoctamin 1 (ANO1, TMEM16A) is a transmembrane protein belonging to the ANO family, with a role in the formation of calcium-activated chloride channels (CaCC). It is included in the regulation of physiological processes such as muscle contraction, gastrointestinal motility, secretion, and electrical excitability. Also, recent data suggest that ANO1 is a specific marker for interstitial cells of Cajal (ICC). The aim of the paper was to examine the spatial and temporal distribution of ANO1 in the human stomach, small intestine, and large intestine during embryofetal development as a potential marker for the differentiation of ICC and smooth muscle cells. As a material, we used 2 embryos and samples from 21 fetuses. The tissue samples were routinely processed into paraffin blocks, and 5 µm-thick sections were immunostained for ANO1. Our results show that ANO1 appears during embryonic development (8<sup>th</sup> week), and its expression continues through the fetal stages. Epithelial, endothelial and ICC cells consistently expressed ANO1 in all examined samples. Smooth muscle cells showed strong expression in muscularis propria, however by the 25<sup>th</sup> week this immunopositivity was absent from outer muscle layers in stomach and large intestine. In conclusion, ANO1 can be considered as a reliable marker for following the differentiation of SMC and ICC during embryonic and fetal development.</p>