Fig. 5. Transmission electron micrographs of the MD and the surrounding TAL cells of Brn1^+/+ (left) and Brn1^-/- (right) kidneys. MD cells of the Brn1^+/+ kidney exhibit characteristic features, including multiple luminal microvilli and basal and lateral membrane foldings. TAL cells of the Brn1^+/+ kidney display characteristic morphology, such as lateral extension, abundant microvilli, basal and lateral membrane foldings and cellular interdigitation. The putative TAL cells and MD cells of the Brn1^-/- kidney are indistinguishable from each other, exhibiting immature morphology, including simple cell membranes, sparse luminal microvilli, and small and sparse mitochondria with the cytoplasm. Scale bar: 2 µm.