Craniofacial bone anomalies related to cholesterol synthesis defects.

DHCR7 and SC5D are enzymes crucial for cholesterol biosynthesis, and mutations in their genes are associated with developmental disorders, which are characterized by craniofacial deformities. We have recently reported that a loss of either Dhcr7 or Sc5d results in a failure in osteoblast differentiation. However, it remains unclear to what extent a loss of function in either DHCR7 or SC5D affects craniofacial skeletal formation. Here, using micro computed tomography (μCT), we found that the bone phenotype differs in Dhcr7-/- and Sc5d-/- mice in a location-specific fashion. For instance, in Sc5d-/- mice, although craniofacial bones were overall affected, some bone segments, such as the anterior part of the premaxilla, the anterior-posterior length of the frontal bone, and the main body of the mandible, did not present significant differences compared to WT controls. By contrast, in Dhcr7-/- mice, while craniofacial bones were not much affected, the frontal bone was larger in width and volume, and the maxilla and palatine bone were hypoplastic, compared to WT controls. Interestingly the mandible in Dhcr7-/- mice was mainly affected at the condylar region, not the body. Thus, these results help us understand which bones and how greatly they are affected by cholesterol metabolism aberrations in Dhcr7-/- and Sc5d-/- mice.