Cdk5 controls lymphatic vessel development and function by phosphorylation of Foxc2

The lymphatic system maintains tissue fluid balance, and dysfunction of lymphatic vessels and valves causes human lymphedema syndromes. Yet, our knowledge of the molecular mechanisms underlying lymphatic vessel development is still limited. Here, we show that cyclin-dependent kinase 5 (Cdk5) is an essential regulator of lymphatic vessel development. Endothelial-specific Cdk5 knockdown causes congenital lymphatic dysfunction and lymphedema due to defective lymphatic vessel patterning and valve formation. We identify the transcription factor Foxc2 as a key substrate of Cdk5 in the lymphatic vasculature, mechanistically linking Cdk5 to lymphatic development and valve morphogenesis. Collectively, our findings show that Cdk5–Foxc2 interaction represents a critical regulator of lymphatic vessel development and the transcriptional network underlying lymphatic vascular remodeling. The mechanisms regulating lymphatic vessel development and function are still largely unknown. Here, the authors show that the protein kinase Cdk5 is required for lymphatic vessel development by regulating the activity of the transcription factor Foxc2 and its target genes.