Integrin α6Bβ1 is involved in kidney tubulogenesis in vitro

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Abstract
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 expression of integrins α6β1 and α6β4, two known laminin receptors, during kidney development. Integrin β1 subunit could be detected by immunofluorescence on all cell types of embryonic mouse kidney, but we could not detect integrin β4 subunit in embryonic kidney by immunofluorescence or by in situ hybridization. The presence of integrin α6 subunit in all epithelia of embryonic kidney was demonstrated by immunofluorescence and by in situ hybridization. RT-PCR showed that α6B is the major splice variant in embryonic kidney. During in vitro conversion of nephrogenic mesenchyme to epithelial tubules, a strong increase in the expression of the 6 kb mRNA for α6 integrin subunit was seen by northern blotting at the onset of epithelial morphogenesis, on day two of culture. Immunoprecipitation of extracts from embryonic kidney with antibodies against α6 subunit yielded bands corresponding to the expected size of β1 integrin subunit but not of β4 subunit. Monoclonal antibodies against either α6 or β1 subunit but not against E-cadherin blocked kidney tubulogenesis in vitro. This suggests that integrin α6Bβ1 is involved in kidney tubulogenesis in vitro. Another possibility is that the antibodies against integrin α6 and β1 subunit cause abnormal signalling by the integrin.