Lathosterolosis: An inborn error of human and murine cholesterol synthesis due to lathosterol 5-desaturase deficiency

Lathosterol 5-desaturase catalyzes the conversion of lathosterol to 7-dehydrocholesterol in the next to last step of cholesterol synthesis. Inborn errors of cholesterol synthesis underlie a group of human malformation syndromes including Smith-Lemli-Opitz syndrome, desmosterolosis, CHILD syndrome, CDPX2 and lathosterolosis. We disrupted the lathosterol 5-desaturase gene (Sc5d) in order to further our understanding of the pathophysiological processes underlying these disorders and to gain insight into the corresponding human disorder. Sc5d^-/- pups were stillborn, had elevated lathosterol and decreased cholesterol levels, had craniofacial defects including cleft palate and micrognathia, and limb patterning defects. Many of the malformations found in Sc5d^-/- mice are consistent with impaired hedgehog signaling, and appear to be a result of decreased cholesterol rather than increased lathosterol. A patient initially described as atypical SLOS with mucolipidosis was shown to have lathosterolosis by biochemical and molecular analysis. We identified a homozygous mutation of SC5D (137A > C, Y46S) in this patient. An unique aspect of the lathosterolosis phenotype is the combination of a malformation syndrome with an intracellular storage defect.