A number of genes are implicated in human, dog, and mouse PCD, including DNAI1[13], DNAH11[17], DNAH5[18], [19], TXNDC3[38], Spag6[9], Pcdp1[16], CCDC39[15], CCDC40[14], Spef2[10], etc. However, MNS1-deficient mice grew to adulthood, suggesting that hydrocephalus is relatively mild in these mutant mice. This evidence concerns the gene CCDC40 and Hydrocephalus.