Ectopic expression of the homeobox gene Cux-1 rescues calcineurin inhibition in mouse embryonic kidney cultures.
Cux-1 is a murine homeobox gene structurally related to Drosophila cut. Cux-1 is highly expressed in the nephrogenic zone of the developing kidney, where its expression coincides with cell proliferation. Cux-1 functions as a transcriptional repressor of the cyclin kinase inhibitors (CKI) p21 and p27. Cux-1 DNA binding activity is negatively regulated by phosphorylation, and dephosphorylation of Cux-1 results in increased DNA binding. Transgenic mice ectopically expressing Cux-1 develop renal hyperplasia associated with the down-regulation of the CKI p27. Calcineurin A (CnA) alpha (-/-) mice display renal hypoplasia associated with the ectopic expression of p27. CnA is a serine/threonine phosphatase activated by intracellular calcium. Inhibiting CnA with cyclosporin A (CsA) leads to nephron deficit in rat metanephric organ cultures and apoptosis in various renal cell lines. To determine whether the ectopic expression of p27 in CnA-alpha -/- kidneys results from the down-regulation of Cux-1, metanephroi from embryonic Cux-1 transgenic and wild-type mice were harvested and cultured with CsA for 5 days. CsA treatment significantly inhibited growth of wild-type metanephroi. In contrast, CsA-treated Cux-1 transgenic kidney cultures were not growth inhibited, but showed high levels of cell proliferation in the nephrogenic zone. Moreover, in CsA-treated Cux-1 transgenic kidney cultures, p27 was not expressed in the nephrogenic zone, but only up-regulated in maturing glomeruli and tubules. Taken together, our results demonstrate that ectopic expression of Cux-1 can rescue the effects of CsA inhibition of CnA and suggest that Cux-1 may be regulated by calcineurin A.
Alcalay
Neal I
NI
Department of Anatomy and Cell Biology, The Kidney Institute, University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
Brantley
Jennifer G
JG
Sharma
Madhulika
M
Gooch
Jennifer L
JL
Vanden Heuvel
Gregory B
GB
D000818:Animals; D019703:Calcineurin / Q000378:metabolism; D065095:Calcineurin Inhibitors; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D016572:Cyclosporine / Q000494:pharmacology; D005260:Female; D015870:Gene Expression; D005801:Genes, Homeobox; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D007166:Immunosuppressive Agents / Q000494:pharmacology; D007668:Kidney / Q000196:embryology* / Q000201:enzymology / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D008957:Models, Genetic; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D009924:Organ Culture Techniques; D011247:Pregnancy; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*
D065095:Calcineurin Inhibitors; C000624101:Cux1 protein, mouse; D018398:Homeodomain Proteins; D007166:Immunosuppressive Agents; D009687:Nuclear Proteins; D012097:Repressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016572:Cyclosporine; D019703:Calcineurin