DHCR7 and Smith-Lemli-Opitz syndrome: To ask if Dhcr7 plays important roles in neural precursor (progenitor) development as seen in human patients with SLOS, we intercrossed Dhcr7+/- mice and prepared single embryo cultures from E12.5 Dhcr7-/- (knockout or KO) or Dhcr7+/+ embryos.