FAM20C Plays an Essential Role in the Formation of Murine Teeth

Wang, Xiaofang; Wang, Shuzhen; Lu, Yongbo; Gibson, Monica Prasad; Liu, Ying; Yuan, Baozhi; Feng, Jian Q.; Qin, Chunlin

doi:10.1074/jbc.m112.386862

Cited by 61 publications

(63 citation statements)

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“…Most individuals with Raine syndrome die within a few weeks after birth; however, nonlethal cases with dental abnormalities and clinical features of hypophosphatemia have been reported (17,18). Loss of Fam20C in mice also results in severe bone and tooth anomalies, as well as hypophosphatemia (19)(20)(21).Two other closely related Fam20C paralogs, Fam20A and Fam20B, are present in humans (22). Fam20B is ubiquitously expressed and phosphorylates xylose within the tetrasaccharide linkage region of proteoglycans (23).…”

mentioning

confidence: 99%

Crystal structure of the Golgi casein kinase

Xiao

Tagliabracci

Wen

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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The family with sequence similarity 20 (Fam20) kinases phosphorylate extracellular substrates and play important roles in biomineralization. Fam20C is the Golgi casein kinase that phosphorylates secretory pathway proteins within Ser-x-Glu/pSer motifs. Mutations in Fam20C cause Raine syndrome, an osteosclerotic bone dysplasia. Here we report the crystal structure of the Fam20C ortholog from Caenorhabditis elegans. The nucleotide-free and Mn/ ADP-bound structures unveil an atypical protein kinase-like fold and highlight residues critical for activity. The position of the regulatory αC helix and the lack of an activation loop indicate an architecture primed for efficient catalysis. Furthermore, several distinct elements, including the presence of disulfide bonds, suggest that the Fam20 family diverged early in the evolution of the protein kinase superfamily. Our results reinforce the structural diversity of protein kinases and have important implications for patients with disorders of biomineralization.P rotein phosphorylation is a fundamental mechanism that regulates numerous physiological processes (1, 2). Protein kinases have evolved to function as dynamic switches relaying signals in response to various stimuli by transferring a phosphate from ATP to target proteins (3-5). Most phosphoproteins are found within the cell, residing in the nuclei and cytosol; however, secreted proteins, including casein and other members of the secretory calciumbinding phosphoprotein family, are phosphorylated as well (6). We recently identified a family of kinases that reside in the secretory pathway and function to phosphorylate extracellular substrates (7,8). One member of this family, Fam20C (family with sequence similarity 20, member C), is the physiological casein kinase that phosphorylates multiple secreted proteins within a Ser-x-Glu/pSer motif (7, 9, 10). The importance of this discovery is underscored by the fact that some 75% of the phosphoproteins identified in human serum and cerebrospinal fluid contain phosphate within this motif (11-13). Furthermore, mutations in FAM20C cause Raine syndrome, a deadly osteosclerotic bone dysplasia characterized by generalized osteosclerosis, ectopic calcifications, and characteristic facial features (14-16). Most individuals with Raine syndrome die within a few weeks after birth; however, nonlethal cases with dental abnormalities and clinical features of hypophosphatemia have been reported (17,18). Loss of Fam20C in mice also results in severe bone and tooth anomalies, as well as hypophosphatemia (19)(20)(21).Two other closely related Fam20C paralogs, Fam20A and Fam20B, are present in humans (22). Fam20B is ubiquitously expressed and phosphorylates xylose within the tetrasaccharide linkage region of proteoglycans (23). This phosphorylation event may influence glycosaminoglycan biosynthesis (24). Genetic deletion of Fam20B in mice results in embryonic lethality at E13.5, and mutations in Danio rerio result in reduced cartilage matrix production and skeletal defects (19,25). The substra...

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confidence: 99%

Crystal structure of the Golgi casein kinase

Xiao

Tagliabracci

Wen

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…In addition, the K14-Cre;Fam20C fl/fl mice, in which Fam20C was inactivated in all epithelium-derived tissues including the tooth cervical loop, did not show a shorter length in the dental roots (Figs. 1A, 3E-3H), suggesting that the short-root phenotype in the Sox2-Cre;Fam20C fl/fl mice (Wang et al, 2012b) was more likely associated with the dentin defects and/or phosphate homeostasis. In this respect, future study with the Wnt1-Cre transgene to specifically inactivate FAM20C in the odontoblasts/dentin may help clarify this postulation.…”

Section: K14-cre;fam20cmentioning

confidence: 99%

“…The RNA probes for dentin matrix protein 1 (DMP1) and dentin sialophosphoprotein (DSPP) were prepared as previously described (Wang et al, 2012b). The RNA probes for ameloblastin (AMBN) and amelotin (AMTN) were obtained by PCR with mouse incisor cDNA as a template and were synthesized as previously described (Wang et al, 2012b).…”

Section: In Situ Hybridization (Ish)mentioning

confidence: 99%

“…In humans, loss-of-function mutations are associated with lethal osteosclerotic bone dysplasia (Raine Syndrome) (Simpson et al, 2007), while ubiquitous or mineralized tissuespecific inactivation of FAM20C in mice leads to hypophosphatemic rickets (Wang et al, 2012a) and severe tooth defects (Wang et al, 2012b). These genetic findings highlight the critical role of FAM20C in the development of mineralized tissues.…”

Section: Introduction Fmentioning

confidence: 99%

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The Specific Role of FAM20C in Amelogenesis

et al. 2013

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Previously, we showed that Sox2-Cre;Fam20C fl/fl mice in which Fam20C was ubiquitously inactivated had severe defects in dentin, enamel, and bone, along with hypophosphatemia. It remains to be determined if the enamel defects in the mice with universal inactivation of Family with sequence similarity 20-C (FAM20C) were associated with the dentin defects and whether hypophosphatemia in the knockout mice contributed to the enamel defects. In this study, we crossed Fam20C fl/fl mice with keratin 14-Cre (K14-Cre) transgenic mice to specifically inactivate Fam20C in the epithelial cells, including the dental epithelial cells that are responsible for forming tooth enamel. X-ray, backscattered scanning electron microscopic, and histological analyses showed that the K14-Cre;Fam20C fl/fl mice had severe enamel and ameloblast defects, while their dentin and alveolar bone were not significantly affected. Accordingly, serum biochemistry of the K14-Cre;Fam20C fl/fl mice showed normal phosphate and FGF23 levels in the circulation. Analysis of these data indicates that, while FAM20C is a molecule essential to amelogenesis, its inactivation in the dental epithelium does not significantly affect dentinogenesis. Hypophosphatemia makes no significant contribution to the enamel defects in the mice with the ubiquitous deletion of Fam20C. A supplemental appendix to this article is published electronically only at http://jdr.sagepub.com/supplemental.

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“…The hunt for the kinase that phosphorylates SIBLINGs has continued for several decades. Family with sequence similarity member 20C (FAM20C), was found to be an evolutionarily conserved molecule expressed in various tissues, including bone and dentin (21)(22)(23). Loss-offunction mutations in the human FAM20C gene caused Raine syndrome, an osteosclerotic bone dysplasia (24), whereas Fam20C-knockout (KO) mice developed severe hypophosphatemic rickets due to renal phosphate wasting that was likely attributable to an increase in circulating fibroblast growth factor (FGF)-23 (25).…”

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confidence: 99%

Family with sequence similarity member 20C is the primary but not the only kinase for the small‐integrin‐binding ligand N‐linked glycoproteins in bone

et al. 2015

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Recent studies have identified family with sequence similarity member 20C (FAM20C) as a kinase that phosphorylates the Ser in Ser-X-Glu/phospho-Ser (pSer) motifs in the small-integrin-binding ligand N-linked glycoproteins (SIBLINGs). There is no in vivo evidence that validates this finding, and it is unclear whether FAM20C is the only kinase for SIBLINGs. We extracted bone noncollagenous proteins (NCPs) from Fam20C-knockout (KO) mice and analyzed the phosphorylation levels. The total NCPs were separated into osteopontin-, bone sialoprotein-, and dentin matrix protein-1-enriched fractions by anion-exchange chromatography and analyzed by SDS-PAGE, native PAGE, and Western immunoblot analysis. The NCP phosphorylation level in the KO mice was lower than that in the wild-type (WT). On the native gel, the SIBLINGs from KO mice showed a lower migration rate (M r ) than those from the WT. Calf intestine phosphatase treatment shifted SIBLINGs from the WT mice to the level adjacent to the KO, but failed to shift the latter, suggesting a phosphorylation loss of SIBLINGs in the KO mice. Mass spectrometry identified less pSers in the SIBLINGs from the KO mice [including the region of the acidic Ser-and aspartate-rich motif (ASARM) peptides]. In an intriguing finding, several pSers in the Ser-X-Glu motifs in the KO mice maintained their phosphorylation, whereas several others in non-Ser-X-Glu motifs did not. Phospho-Tyrs and phospho-Thrs in the SIBLINGs did not appear to be associated with FAM20C. Our results indicate that FAM20C is the primary, but not the only, kinase for the SIBLINGs.-Yang, X., Yan, W., Tian, Y., Ma, P., Opperman, L. A., Wang, X. Family with sequence similarity member 20C is the primary but not the only kinase for the small-integrin-binding ligand N-linked glycoproteins in bone. FASEB J. 30, 121-128 (2016 The organic phase of the extracellular matrix (ECM) in the bone is mainly composed of type I collagen and noncollagenous proteins (NCPs) synthesized and secreted by osteoblasts. A prominent category of NCPs in bone ECM is termed the small-integrin-binding ligand N-linked glycoprotein (SIBLING) family, which includes osteopontin (OPN), bone sialoprotein (BSP), and dentin matrix protein (DMP)-1. These polyanionic proteins play pivotal roles in osteogenesis and biomineralization, and their biologic functions are closely related to posttranslational modifications, such as phosphorylation (1-7).OPN is commonly recognized as an effective inhibitor of hydroxyapatite formation and growth (8). Rat bone OPN contains 12 phospho-Sers (pSers) and 1 phospho-Thr, and has considerable heterogeneity in degree of phosphorylation (9). In contrast, bovine milk OPN has 27 pSers and 1 phospho-Thr and appears to be maximally phosphorylated (10). The extent of phosphorylation of OPN, as well as of the specific sites, may play an important role in its physiologic function. The activity of OPN in regulating biomineralization is lost after the removal of the phosphates (2, 11). BSP in bone has been reported to have 11 phosp...

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FAM20C Plays an Essential Role in the Formation of Murine Teeth

Cited by 61 publications

References 36 publications

Crystal structure of the Golgi casein kinase

Crystal structure of the Golgi casein kinase

The Specific Role of FAM20C in Amelogenesis

Family with sequence similarity member 20C is the primary but not the only kinase for the small‐integrin‐binding ligand N‐linked glycoproteins in bone

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