An epithelial morphogenetic program for maximal urine concentration (opens in new tab)

Mammals achieve the highest urine concentrations of any vertebrate, a feat that hinges on generating steep osmotic gradients within the renal medulla. Interestingly, the region with the highest osmolality, the inner medulla, is unique to mammals. Among the nephron’s segments, the ascending thin limb (aTL) is the sole element exclusive to this zone and is thought to mediate passive salt reabsorption. However, the architecture and functional impact of the aTL have remained obscure. Here we unco...