Submitted July 13, 2007
Accepted December 12, 2007
Sox18 and Sox7 play redundant roles in vascular development
Solei Cermenati, Silvia Moleri, Simona Cimbro, Paola Corti, Luca Del Giacco, Roberta Amodeo, Elisabetta Dejana, Peter Koopman, Franco Cotelli, and Monica Beltrame*
Dipartimento di Scienze Biomolecolari e Biotecnologie, Universita' degli Studi di Milano, Milan, Italy
Dipartimento di Biologia, Universita' degli Studi di Milano, Milan, Italy
IFOM, FIRC Institute of Molecular Oncology, Milan, Italy
Institute for Molecular Bioscience, The University of Queensland, Brisbane, Australia
* Corresponding author; email: monica.beltrame{at}unimi.it.
Mutations in SOX18 cause the human Hypotrichosis-Lymphedema-Telangiectasia (HLT) syndrome. Their murine counterparts are the spontaneous ragged mutants, showing combined defects in hair follicle, blood vessel and lymphatic vessel development. Mice null for Sox18 display only mild coat defects, suggesting a dominant negative effect of Sox18/ragged mutations and functional redundancy between Sox18 and other Sox-F proteins. We addressed this point in zebrafish. The zebrafish homologues of Sox18 and of Sox7 are expressed in angioblasts and in the endothelial component of nascent blood vessels in embryos. Knockdown of either gene, using moderate doses of specific morpholinos, had minimal effects on vessels. In contrast, simultaneous knockdown of both genes resulted in multiple fusions between the major axial vessels. With combined use of transgenic lines and molecular markers, we could show that endothelial cells are specified, but fail to acquire a correct arteriovenous identity. Venous endothelial cell differentiation was more severely affected than arterial. Thus, sox7 and sox18 play redundant but collectively essential roles in the establishment of proper arteriovenous identity in zebrafish. Our data suggest that a defect in arteriovenous identity could be responsible for the formation of telangiectases in HLT patients.
