Monday 14 November 2011
Excess exogenous retinoic acid (RA) has been well documented to have teratogenic effects in the limb and craniofacial skeleton. Malformations that have been observed in this context include craniosynostosis, a common developmental defect of the skull that occurs in 1 in 2500 individuals and results from premature fusion of the cranial sutures.
Genetically based alterations in RA signaling interfere with human development.
Human null and hypomorphic mutations have been identified in the gene encoding the RA-degrading enzyme CYP26B1 that lead to skeletal and craniofacial anomalies, including fusions of long bones, calvarial bone hypoplasia, and craniosynostosis.
Analyses of murine embryos exposed to a chemical inhibitor of Cyp26 enzymes and zebrafish lines with mutations in cyp26b1 suggest that the endochondral bone fusions are due to unrestricted chondrogenesis at the presumptive sites of joint formation within cartilaginous templates, whereas craniosynostosis is induced by a defect in osteoblastic differentiation.
Ultrastructural analysis, in situ expression studies, and in vitro quantitative RT-PCR experiments of cellular markers of osseous differentiation indicate that the most likely cause for these phenomena is aberrant osteoblast-osteocyte transitioning.
Studies reveals a physiological role for RA in partitioning skeletal elements and in the maintenance of cranial suture patency.
Craniosynostosis and Multiple Skeletal Anomalies in Humans and Zebrafish Result from a Defect in the Localized Degradation of Retinoic Acid.
Craniosynostosis and Multiple Skeletal Anomalies in Humans and Zebrafish Result from a Defect in the Localized Degradation of Retinoic Acid. Laue K, Pogoda HM, Daniel PB, van Haeringen A, Alanay Y, von Ameln S, Rachwalski M, Morgan T, Gray MJ, Breuning MH, Sawyer GM, Sutherland-Smith AJ, Nikkels PG, Kubisch C, Bloch W, Wollnik B, Hammerschmidt M, Robertson SP. Am J Hum Genet. 2011 Oct 18. PMID: 22019272