Mutations in DHCR7, encoding the penultimate enzyme in the pathway (downregulated 1.46-fold in Piezo1 KO brains) underlie Smith–Lemli–Opitz syndrome (SLOS), which includes symptoms of microcephaly, mental developmental delay, and hearing impairment (Irons et al., 1993). The gene discussed is DHCR7; the disease is microcephaly.