We found that the expression of Rab27a and nSMase 2, the two key enzymes that regulate exosome secretion and release, was upregulated in postnatal Pkd1 homozygous PN24 cells and cystic kidneys (Fig. 7a, b), suggesting that exosome biogenesis/release may be increased in Pkd1 mutant renal epithelial cells and tissues. This evidence concerns the gene SMPD3 and Renal cyst.