Expression of OCI-5/glypican 3 during intestinal morphogenesis: regulation by cell shape in intestinal epithelial cells.

OCI-5, the rat homologue of human glypican 3 (GPC3), is believed to be involved in morphogenesis and growth control during development. The finding that GPC3 is mutated in patients with the Simpson-Golabi-Behmel overgrowth syndrome is consistent with this idea. In this report, using RNA in situ hybridization, expression of OCI-5 in the developing intestine is detected in both endoderm- and mesenchyme-derived cells in a phased manner related to age and proximal/distal position. To investigate the mechanism of its regulation during intestinal development, OCI-5 expression was studied in the primitive rat intestinal epithelial cell line IEC-18. The expression of the OCI-5 transcript is increased in IEC-18 cells at confluence, in low calcium media, and during spheroid culture, all conditions which result in the cells acquiring a more rounded cell shape. In contrast, cytoskeletal disruption with colchicine causes cells to flatten and spread and abolishes both the confluence- and the low calcium-dependent induction of OCI-5. Treatment with vanadate, a phosphatase inhibitor, causes cells to acquire a spindle-shaped morphology and prevents OCI-5 induction in all situations. Nuclear run-on analysis demonstrates that the rate of OCI-5 transcription is increased at confluence, in low calcium media, and during spheroid culture of IEC-18, and decreased by treatment of cells with colchicine. Together, these data suggest that OCI-5 expression is regulated in IEC-18 by cell shape. The pattern of expression of OCI-5 in the developing intestine is consistent with it playing a role in epithelial-mesenchymal interactions during intestinal morphogenesis, when cell shape changes are likely to occur.