<i>FAM20A</i> is Dispensable for Dentinogenesis and Osteogenesis

Abstract

Family with sequence similarity 20, member A (Fam20a) encodes a pseudokinase which is regarded to facilitate the role of Fam20c in phosphorylating secreted proteins. Fam20c deficiency causes Raine Syndrome in human and impaired the amelogeneis, dentiogenesis and osteogenesis in mice. Mutations in Fam20a are associated with Amelogenesis Imperfecta and Enamel-Renal Syndrome in human. Similarly, abrogation of Fam20a in ectoderm caused Amelogeneis Imperefeca in mice, however, the global knock-out of Fam20a in mice showed few anomaly in dentin and bone. In this study, the Fam20a LacZ mice showed that at the E17.5, the LacZ staining was located in the osteogenic lining of calvarium and mandibular bone, odontoblasts, ameloblasts, the gingival and subcutaneous fibroblasts. During the postnatal life, the LacZ staining was detected in the osteogenic and gingival cells in mandibular bone, as well as the osteogenic and the marrow cells in long bone, but excluded from the joint cartilage. Both the LacZ staining in the mandibular and long bone became faint with the life increased. To address if Fam20a is required for the role of Fam20c during the dentinogenesis and osteogenesis, we first examined the mandibular bone and femur of the Wnt1-cre;Fam20a f/f , Osr2-cre;Fam20a f/f and Col1-cre; Fam20a f/f mice. The gross views and X-ray plain images showed no difference in the tissue morphology and mineralization density between these conditional knock-out mice and their controls. Our findings suggested that Fam20a was not required by Fam20c during dentinogenesis and osteogenesis.