We have previously shown that mouse models with mutations in CPA genes ciliary and flagellar associated protein 221 (CFAP221), ciliary and flagellar associated protein 54 (CFAP54), and sperm flagellar protein 2 (SPEF2) each have a PCD phenotype that includes hydrocephalus, male infertility, and airway abnormalities26–30. Here, SPEF2 is linked to Hydrocephalus.