SLOS is caused by mutations in DHCR7 on chromosome 11  (Fitzky et al., 1998, Wassif et al., 1998, Waterham et al., 1998), which encodes for 7-dehydrocholesterol reductase (DHCR7), an enzyme that catalyzes the final step in cholesterol biosynthesis (Irons et al., 1993).

IRONS, M., ELIAS, E. R., SALEN, G., TINT, G. S. & BATTA, A. K. 1993. Defective cholesterol biosynthesis in Smith-Lemli-Opitz syndrome. Lancet, 341, 1414.

DOI: https://doi.org/10.1016/0140-6736(93)90983-N

FITZKY, B. U., WITSCH-BAUMGARTNER, M., ERDEL, M., LEE, J. N., PAIK, Y. K., GLOSSMANN, H., UTERMANN, G. & MOEBIUS, F. F. 1998. Mutations in the Delta7-sterol reductase gene in patients with the Smith-Lemli-Opitz syndrome. Proc Natl Acad Sci U S A, 95, 8181-6.

*The DOI below sends to the general Proc Natl Acad Sci (PNAS) page. Not sure if you would just want to list this or I have this NCBI overview that has a PDF of it listed. Link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC20950/

DOI: https://doi.org/10.1073/pnas.95.14.818

WASSIF, C. A., MASLEN, C., KACHILELE-LINJEWILE, S., LIN, D., LINCK, L. M., CONNOR, W. E., STEINER, R. D. & PORTER, F. D. 1998. Mutations in the human sterol delta7-reductase gene at 11q12-13 cause Smith-Lemli-Opitz syndrome. Am J Hum Genet, 63, 55-62.

DOI: https://doi.org/10.1086/301936

WATERHAM, H. R., WIJBURG, F. A., HENNEKAM, R. C., VREKEN, P., POLL-THE, B. T., DORLAND, L., DURAN, M., JIRA, P. E., SMEITINK, J. A., WEVERS, R. A. & WANDERS, R. J. 1998. Smith-Lemli-Opitz syndrome is caused by mutations in the 7-dehydrocholesterol reductase gene. Am J Hum Genet, 63, 329-38.

DOI: https://doi.org/10.1086/301982

Smith-Lemli-Opitz syndrome

Link: https://rarediseases.org/rare-diseases/smith-lemli-opitz-syndrome/