INTEGRIN ALPHA-6B-BETA-1 IS INVOLVED IN KIDNEY TUBULOGENESIS IN-VITRO

Laminin-1 has previously been shown to be of major importance for the development of kidney tubules, Antibodies against fragments E8 and E3 of laminin-1 perturb kidney development in vitro. We here studied expr ession of integrins alpha 6 beta 1 and alpha 6 beta 4, two known lamin in receptors, during kidney development. Integrin pi subunit could be detected by immunofluorescence on all cell types of embryonic mouse ki dney, but we could not detect integrin beta 4 subunit in embryonic kid ney by immunofluorescence or by in situ hybridization, The presence of integrin alpha 6 subunit in all epithelia of embryonic kidney was dem onstrated by immunofluorescence and by in situ hybridization. RT-PCR s howed that alpha 6B is the major splice variant in embryonic kidney, D uring in vitro conversion of nephrogenic mesenchyme to epithelial tubu les, a strong increase in the expression of the 6 kb mRNA for alpha 6 integrin subunit was seen by northern blotting at the onset of epithel ial morphogenesis, on day two of culture. Immunoprecipitation of extra cts from embryonic kidney with antibodies against alpha 6 subunit yiel ded bands corresponding to the expected size of pr integrin subunit bu t not of beta 4 subunit. Monoclonal antibodies against either alpha 6 or beta 1 subunit but not against E-cadherin blocked kidney tubulogene sis in vitro. This suggests that integrin alpha 6B beta 1 is involved in kidney tubulo-genesis in vitro, Another possibility is that the ant ibodies against integrin alpha 6 and beta 1 subunit cause abnormal sig nalling by the integrin.