[page 250] [European Journal of Histochemistry 2012; 56:e40]

MUC1 is a transmembrane glycoprotein, api-cally expressed in most epithelial cells, used in the differential diagnosis of carcinomas and for discrimination of tumors of non-epithelial ori-gin showing epithelioid features. Little atten-tion has been paid so far though, on its possible significance in embryonic tissues. A prelimi-nary study from our group revealed MUC1 expression in the cap mesenchymal cells during human nephrogenesis, suggesting a role for MUC1 in the process of mesenchymal-to-epithelial transition. This study aimed at inves-tigating the expression pattern of MUC1 in var-ious developing structures of human fetal kid-ney. Expression of MUC1 was examined in kid-neys of 5 human fetuses. MUC1 immunoreac-tivity was detected in ureteric bud tips, in col-lecting tubules, in cap mesenchymal cells undergoing the initial phases of mesenchymal-to-epithelial transition, in renal vesicles, comma-bodies, and S-shaped bodies. Our previ-ous preliminary report suggested a role for MUC1 in the initial phases of the process of mesenchymal-to-epithelial transition. The pres-ent data suggest that MUC1 expression charac-terizes multiple structures during human nephrogenesis, from the ureteric bud, to the initial phases of mesenchymal-to-epithelial transition and that MUC1 should be added to the genes activated during the process of mes-enchymal-to-epithelial transition in the cap mesenchyme of human kidney