Targeted deletion of Sost distal enhancer increases bone formation and bone mass

• Published in: Proceedings of the National Academy of Sciences - PNAS 2012-08, Vol.109 (35), p.14092-14097
• Main Authors: Collette, Nicole M, Genetos, Damian C, Economides, Aris N, Xie, LiQin, Shahnazari, Mohammad, Yao, Wei, Lane, Nancy E, Harland, Richard M, Loots, Gabriela G
• Format: Article
• Language: English
• Subjects: adults; Age Factors; Animals; antagonists; Biological Sciences; bone density; Bone diseases; Bone formation; Bone Remodeling - genetics; Bones; Cells; Chondrocytes; Craniofacial Abnormalities - genetics; Craniofacial Abnormalities - metabolism; Enhancer Elements, Genetic - genetics; Female; Femur; Femur - cytology; Femur - physiology; Gene Deletion; Glycoproteins - genetics; Glycoproteins - metabolism; Homeostasis; homozygosity; humans; Hyperostosis - genetics; Hyperostosis - metabolism; Lac Operon; Male; Mandible - abnormalities; Mandible - metabolism; MEF2 Transcription Factors; Mice; Mice, Transgenic; Modulated signal processing; Mutation; Myogenic Regulatory Factors - genetics; Myogenic Regulatory Factors - metabolism; Osteoblasts; Osteochondrodysplasias; Osteocytes; Osteocytes - physiology; Osteosclerosis - genetics; Osteosclerosis - metabolism; patients; Phenotypes; Rodents; Signal transduction; Signal Transduction - genetics; skeleton; Skull - abnormalities; Skull - metabolism; Syndactyly - genetics; Syndactyly - metabolism; transcription (genetics); transcription factors; transcriptional activation; Transcriptional Activation - genetics
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1207188109

The Wnt antagonist Sost has emerged as a key regulator of bone homeostasis through the modulation of Lrp4/5/6 Wnt coreceptors. In humans, lack of Sclerostin causes sclerosteosis and van Buchem (VB) disease, two generalized skeletal hyperostosis disorders that result from hyperactive Wnt signaling. Unlike sclerosteosis, VB patients lack SOST coding mutations but carry a homozygous 52 kb noncoding deletion that is essential for the transcriptional activation of SOST in bone. We recently identified a putative bone enhancer, ECR5 , in the VB deletion region, and showed that the transcriptional activity of ECR5 is controlled by Mef2C transcription factor in vitro. Here we report that mice lacking ECR5 or Mef2C through Col1-Cre osteoblast/osteocyte-specific ablation result in high bone mass (HBM) due to elevated bone formation rates. We conclude that the absence of the Sost -specific long-range regulatory element ECR5 causes VB disease in rodents, and that Mef2C is the main transcription factor responsible for ECR5 -dependent Sost transcriptional activation in the adult skeleton.