Spata4 promotes osteoblast differentiation through Erk-activated Runx2 pathway

Protein Science Key Laboratory of Ministry of Education, State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Medicine, Tsinghua University, Beijing, People's Republic of China.
Journal of bone and mineral research: the official journal of the American Society for Bone and Mineral Research (Impact Factor: 6.83). 08/2011; 26(8):1964-73. DOI: 10.1002/jbmr.394
Source: PubMed


The spermatogenesis associated 4 gene (Spata4, previously named TSARG2) was demonstrated to participate in spermatogenesis. Here we report that Spata4 is expressed in osteoblasts and that overexpression of Spata4 accelerates osteoblast differentiation and mineralization in MC3T3-E1 cells. We found that Spata4 interacts with p-Erk1/2 in the cytoplasm and that overexpression of Spata4 enhances the phosphorylation of Erk1/2. Intriguingly, we observed that Spata4 increases the transcriptional activity of Runx2, a critical transcription factor regulating osteoblast differentiation. We showed that Spata4-activated Runx2 is through the activation of Erk1/2. Consistent with this observation, we found that overexpression of Spata4 increases the expression of osteoblastic marker genes, including osteocalcin (Ocn), Bmp2, osteopontin (Opn), type 1 collagen, osterix (Osx), and Runx2. We concluded that Spata4 promotes osteoblast differentiation and mineralization through the Erk-activated Runx2 pathway. Our findings provided new evidence that Spata4 plays a role in regulation of osteoblast differentiation.

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    • "Therefore, it was proposed that Spata4 participates in the spermatogenesis process [1], and may function during adolescence and maintain spermatogenesis ability, as transcript expression profiles indicated [1], [6]. In addition, recent studies indicate that Spata4 modulates cell growth, proliferation and differentiation in various cell types [1], [7], [8]. Sertoli cells produce essential factors for germ cell development and modulate male fertility [9]. "
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    ABSTRACT: Spermatogenesis associated 4 (Spata4), a testis-specific and CpG island associated gene, is involved in regulating cell proliferation, differentiation and apoptosis. To obtain insight into the role of Spata4 in cell cycling control, we characterized the promoter region of Spata4 and investigated its transcriptional regulation mechanism. The Spata4 promoter is unidirectional transcribed and possesses multiple transcription start sites. Moreover, we present evidence that regulatory factor X1 (RFX1) could bind the typical 14-bp cis-elements of Spata4 promoter, modulate transcriptional activity and endogenous expression of Spata4, and further regulate the proliferation of Sertoli cells. Overexpression of RFX1 was shown to down-regulate both the promoter activity and mRNA expression of Spata4, whereas knockdown of RFX1 demonstrated the opposite effects. Our studies provide insight into Spata4 gene regulation and imply the potential role of RFX1 in growth of Sertoli cells. RFX1 may have negative effect on cell proliferation of Sertoli cells via modulating Spata4 expression levels by binding the conserved 14-bp cis-elements of Spata4 promoter.
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    • "After prolonged incubation, these differences were eventually less apparent because of cell confluence (Fig. 3B). Human MSC behavior (cell adhesion and collective organization) on large nano-depth surfaces resulted in a preferential differentiation into an osteogenic lineage, which was confirmed by immunoblotting and immunofluorescence staining of three common protein osteogenic markers: Runx2 (an essential transcription factor in osteoblast differentiation), Osterix (Osx, a transcriptional factor induced by Runx2, which is required for the differentiation of osteoprogenitor cells into functional osteoblasts) (Wang et al., 2011; Zhang et al., 2008), and osteopontin (OPN). This analysis for the detection of osteogenic protein expression of hMSCs was conducted on cells cultured for 1 week for Runx2 and Osx, and 3 weeks for OPN. "
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    • "Alternatively, the interaction in vivo is more stable than that in vitro. A recent study suggests that SPATA4 is localized to the cytosol in the osteoblast cell line MC3T3-E1 where it interacts with and promotes the phosphorylation of the kinase ERK1 [23]. An earlier study reported the localization of GFP-SPATA4 to the nucleus [18]. "
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    ABSTRACT: The TRAPP vesicle-tethering complex consists of more than 10 distinct polypeptides and is involved in protein transport. Using the C2 subunit as bait we identified SPATA4, a spermatocyte-specific protein of unknown function, as an interacting partner in a yeast two hybrid screen. Further studies indicate SPATA4 interacts with the C2 portion of the TRAPP complex. SPATA4 fractionates with both cytosolic and nuclear fractions suggesting it may have several distinct functions. SPATA4 is one of only three human proteins that contain a DUF1042 domain and we show that C2 does not interact with another one of the DUF1042 domain-containing proteins. Our results suggest a role for SPATA4 in membrane traffic and a specialized function for TRAPP in spermatocytes.
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