Enables 7-dehydrocholesterol reductase activity. Acts upstream of or within several processes, including blood vessel development; lung development; and sterol biosynthetic process. Predicted to be located in endoplasmic reticulum and nuclear outer membrane. Predicted to be integral component of endoplasmic reticulum membrane. Is expressed in adrenal gland; genitourinary system; and neural retina. Used to study Smith-Lemli-Opitz syndrome. Human ortholog(s) of this gene implicated in Smith-Lemli-Opitz syndrome. Orthologous to human DHCR7 (7-dehydrocholesterol reductase). [provided by Alliance of Genome Resources, Apr 2022]