PROX1 and obesity due to melanocortin 4 receptor deficiency: In fact, by using the Prox1+/– mice with defective lymphatic vasculature and lymphatic leakage, we and others have previously shown that these animals develop features characteristic of late-onset obesity resulting from subcutaneous and intra-abdominal fat accumulation, due to the subtle leakage of lymph fluid from defective lymphatics (6, 7, 14).