The Fam50a positively regulates ameloblast differentiation via interacting with Runx2

Abstract

Differentiated ameloblasts secret enamel matrix proteins such as amelogenin, ameloblastin, and enamelin. Expression levels of these proteins are regulated by various factors. To find a new regulatory factor for ameloblast differentiation, we performed 2D-PAGE analysis using mouse ameloblast lineage cell line (mALCs) cultured with mineralizing medium. Of identified proteins, family with sequence similarity 50 member A (Fam50a) was significantly increased during differentiation of mALCs. Fam50a protein was also highly expressed in secretory ameloblasts of mouse tooth germs. In mALCs cultures, forced expression of Fam50a up-regulated the expression of enamel matrix protein genes such as amelogenin, ameloblastin, and enamelin. In addition, up-regulation of Fam50a also increased ALP activity and mineralized nodule formation in a dose-dependent manner. In contrast, knockdown of Fam50a decreased expression levels of enamel matrix protein genes, ALP activity, and mineralized nodule formation. By fluorescence microscopy, endogenous Fam50a protein was found to be localized to the nucleus of ameloblasts. In addition, Fam50a synergistically increased Ambn transactivation by Runx2. Moreover, Fam50a increased binding affinity of Runx2 to Ambn promoter by physically interacting with Runx2. Taken together, these results suggest Fam50a might be a new positive regulator of ameloblast differentiation.

Hypoplastic AI with Highly Variable Expressivity Caused by ENAM Mutations

“…Could some degree of insufficient ENAM be compensated by other genetic factors regulating the expression of ENAM from a normal allele? FAM50A and beta-catenin/LEF1 were shown to regulate the differentiation of ameloblast or expression of enamelin expression (Tian et al 2010; Kim et al 2018). We tried to identify variants in these factors within the exome sequencing data in this and previous studies, but there were no variants.…”

Regulatory mechanisms of jaw bone and tooth development

“…Two factors downstream of Bmp signaling, Runx2 and Osterix, are also related to ameloblast differentiation. In vitro culture of mouse ameloblast lineage cells (mALCs) revealed that Runx2 physically interacts with Fam50a to increase its binding affinity to the ameloblastin (Ambn) promoter (Kim et al, 2018). Tooth morphogenesis initially progresses normally in Osterix null mice; however, markers of mature ameloblasts (Enam, Amelx, Mmp20, Amtn, Klk4) have limited expression in incisors and molar tissues of these mice, and they lack enamel matrix (Bae et al, 2018).…”

Coupling of spliceosome complexity to intron diversity

“…This strain is deleted for CNAG_02260, which encodes the Cryptococcal ortholog of FAM50A. While FAM50A is a spliceosomal protein in humans, it has also been linked to transcription (Kim et al, 2018) suggesting a pleiotropic role. Consistent with this, we observed that many genes display transcript level changes in this mutant, while few global transcript changes were observed for the other gene deletion strains, save for the Δ rrp6 strain, which increased the levels of ∼250 mRNAs, consistent with its predicted role in nuclear RNA turnover (Figure 2D).…”

“…This strain is deleted for CNAG_02260, which encodes the Cryptococcal ortholog of FAM50A. While FAM50A is a spliceosomal protein in humans, it has also been linked to transcription (Kim et al, 2018) suggesting a pleiotropic role.…”