Indications that such interactions exist and are highly relevant at least for the function of TBX18 in the developing ureter in vivo were recently provided by the identification of mutations in TBX18 in patients with congenital anomalies of the kidney and the urinary tract (CAKUT), including ureter-pelvic and vesico-ureteric junction obstruction and hydronephrosis. The gene discussed is TBX18; the disease is hydronephrosis.