Mouse Knockout of the Cholesterogenic Cytochrome P450 Lanosterol 14α-Demethylase (Cyp51) Resembles Antley-Bixler Syndrome

Abstract

Antley-Bixler syndrome (ABS) represents a group of heterogeneous disorders characterized by skeletal, cardiac, and urogenital abnormalities that have frequently been associated with mutations in fibroblast growth factor receptor 2 or cytochrome P450 reductase genes. In some ABS patients, reduced activity of the cholesterogenic cytochrome P450 CYP51A1, an ortholog of the mouse CYP51, and accumulation of lanosterol and 24,25-dihydrolanosterol has been reported, but the role of CYP51A1 in the ABS etiology has remained obscure. To test whether Cyp51 could be involved in generating an ABS-like phenotype, a mouse knock-out model was developed that exhibited several prenatal ABS-like features leading to lethality at embryonic day 15. Cyp51؊/؊ mice had no functional Cyp51 mRNA and no immunodetectable CYP51 protein. The two CYP51 enzyme substrates (lanosterol and 24,25-dihydrolanosterol) were markedly accumulated. Cholesterol precursors downstream of the CYP51 enzymatic step were not detected, indicating that the targeting in this study blocked de novo cholesterol synthesis. This was reflected in the up-regulation of 10 cholesterol synthesis genes, with the exception of 7-dehydrocholesterol reductase. Lethality was ascribed to heart failure due to hypoplasia, ventricle septum, and epicardial and vasculogenesis defects, suggesting that Cyp51 deficiency was involved in heart development and coronary vessel formation. As the most likely downstream molecular mechanisms, alterations were identified in the sonic hedgehog and retinoic acid signaling pathways. Cyp51 knock-out mice provide evidence that Cyp51 is essential for embryogenesis and present a potential animal model for studying ABS syndrome in humans.

Male germ cell-specific knockout of cholesterogenic cytochrome P450 lanosterol 14α-demethylase (Cyp51)

“…The sole statistical signifi cance was displayed by the gene Lss , which was upregulated, albeit only by 1.3-fold, in the round spermatids of the ko mice. A trend of upregulating other cholesterogenic genes in the Cyp51 ko germ cells is probably a response to upregulate cholesterol biosynthesis, a phenomenon also observed in the previous full-knockout embryos ( 8 ).…”

“…Most of the clues indicating the potential role of MAS in spermatogenesis originate from the study of MAS-synthesizing cytochrome P450 lanosterol 14 ␣ -demethylase (CYP51), encoded by the gene Cyp51 in the mouse. CYP51 catalyzes the conversion of lanosterol and 24,25-dihydrolanosterol (DHL) to FF-MAS and has recently been shown as essential for embryo development ( 8 ). FF-MAS is further converted to T-MAS by transmembrane 7 superfamily member 2 (TM7SF2) with sterol-⌬ 14-reductase activity.…”

“…The mouse genotyping protocols were as described ( 8 ) or as recommended by The Jackson Laboratory for Stra8 -Cre + transgenic mice. Adult males at a minimum age of 10 weeks were used in all experiments and were euthanized with CO 2 .…”

Genomic analysis of pediatric cataract in Saudi Arabia reveals novel candidate disease genes

“…Unfortunately, mice that completely lack this gene die at midgestation, so it is not possible to discern a potential lenticular phenotype. 30 Perhaps the most challenging novel candidate is MFSD6L, which we identified in a family with cataract and severe psychomotor retardation. Very little is known about this gene other than that it encodes a multipass membrane protein that bears similarity to Major Facilitator Superfamily Domain-Containing Protein 6, which is known to be mutated in neuronal ceroid lipofuscinosis, a progressive disease that affects the brain and eye.…”

Sterols in spermatogenesis and sperm maturation

“…1 ). The essential role of Cyp51 in de novo cholesterol synthesis and embryo development in vivo has recently been demonstrated by our group ( 20 ). In addition to its role in cholesterol synthesis, Cyp51 is thought to have an essential role in reproduction as an enzyme producing the intermediate FF-MAS.…”