PDE4D and asthma: Also among the genes that correlated with MUC16 in IL13-treated cells were 5 of 11 genes previously identified by GWAS as associated with risk of childhood asthma: PDE4D, PTPRD, RBFOX1, ROBO2, and RYR2 [78]; MUC16 also correlated with ROBO1, which encodes an interaction partner of ROBO2. The top-ranked GWAS gene, RYR2, encodes a calcium channel thought to play an important role in asthma pathogenesis [78].