Renal dysplasia unrelated to claudin-16 deficiency in Japanese Black cattle.

Renal lesions of the type usually found in claudin-16 (CL-16) defective Japanese Black cattle (homozygous for CL-16 deficiency) were identified in six animals of this breed, aged 28-59 months, which were either heterozygous for CL-16 deficiency (type 1) or normal, as judged by a DNA-based test associated with the CL-16 gene. Histopathologically, all six cases showed elongated focal lesions which ran through the cortex to terminate in the outer zone of the medulla. The lesions contained components that included: (1) immature tubules, (2) small irregularly shaped tubules with thickening of the basement membrane, (3) mesenchymal cells in an increased interstitium, (4) small atrophic glomeruli, and (5) immature glomeruli. The glomeruli were noticeably reduced in number, and large glomeruli with an increased number of mesangial cells were observed throughout the entire cortical area. Cystic dilation of tubules and flattening of the epithelium were noted in all areas of the kidney. Histopathologically, the renal lesions in the six cases were indistinguishable from those reported previously in cattle homozygous for CL-16 deficiency. These findings demonstrate that such renal lesions in Japanese Black cattle are not necessarily associated with homozygous deletion of the CL-16 gene.