Secreted frizzled-related protein 4 is a negative regulator of peak BMD in SAMP6 mice
Secreted frizzled-related protein 4 is a negative regulator of peak BMD in SAMP6 mice
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DOI：
10.1359/jbmr.060719
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发表时间：
2006-11-01
影响因子：
6.2
通讯作者：
Nakamura, Takashi
中科院分区：
文献类型：
--
作者：
Nakanishi, Rika;Shimizu, Motoyuki;Nakamura, Takashi
我们通过产生加速衰老的小鼠SAMP6的同源亚系，分离了一个在Chr 13上的峰值BMD的QTL。Sfrp 4在该位点负责较低的BMD的SAMP6。介绍：我们的全基因组连锁研究使用SAMP6和SAMP2显示了显着的数量性状位点（QTL）的峰值BMD染色体（Chr）13。为了验证调节峰值BMD的基因，我们产生了一个同源株，P6.P2-Pbd 2（B），其携带一个15-cM的SAMP 2间隔在一个突变的SAMP 6背景，并表明该Pbd 2位点增加峰值BMD在SAMP 6中。材料和方法：为了缩小这个间隔，我们产生了一个新的同源亚系P6.12 - 13。我们研究了该位点对体内成骨细胞形态和组织形态学特征以及体外成骨细胞的影响。结果：新的同源株P6.P2 - 13在SAMP6背景下保留了2.4Mb的SAMP2区间，在此区间内存在11个基因。在形态计量学分析中，与SAMP6相比，P6. P2 - 13使股骨骨干皮质的骨面积分数（BA/TA）增加6.6%（p <0.001），使股骨远端干骺端的骨小梁体积（BV/TV）增加54.2%（p <0.05）。P6.P2 - 13组股骨皮质骨膜表面成骨率明显增加，这是由于P6.P2 - 13组成骨细胞增殖率高于SAMP6组所致。颅骨组织的定量RT-PCR分析显示，SAMP6中Sfrp4的表达水平比P6中高40倍。结合重组Sfrp4抑制成骨细胞增殖的结果，我们推测Sfrp4通过拮抗Writ信号通路抑制成骨细胞增殖。SAMP6来源的成骨细胞对Writ配体Wnt3A的反应性低于P6.P2 - 13来源的成骨细胞。结论：在SAMP6小鼠中，Sfrp4通过抑制Writ信号负性调节骨形成并降低BMD。
We segregated a QTL for peak BMD on Chr 13 by generating congenic sublines of the senescence-accelerated mouse SAMP6. Sfrp 4 within this locus was responsible for lower BMD of SAMP6.Introduction: Our genome-wide linkage study using SAMP6 and SAMP2 showed a significant quantitative trait locus (QTL) for peak BMD on chromosome (Chr) 13. To verify the gene that regulates peak BMD, we generated a congenic strain, P6.P2-Pbd2(b), which carried a 15-cM SAMP2 interval on an osteoporotic SAMP6 background, and showed that this Pbd2 locus increased peak BMD in SAMP6.Materials and Methods: To narrow down this interval, we generated a new congenic subline P6.12-13. We studied the effect of this locus on morphological and histomorphological features in vivo and on ostcoblasts in vitro. The levels of expression of all genes in the segregated interval were examined, and we clarified the effect of the candidate gene, secreted frizzled-related protein (Sfrp4), on osteoblasts in vitro.Results: The new congenic strain, P6.P2-13, retained the 2.4-Mb SAMP2 interval on the SAMP6 background, and 11 genes existed in this interval. In morphometrical analysis, P6.P2-13 increased the bone area fraction (BA/TA) by 6.6% at the diaphysial cortex (p < 0.001) and increased the trabecular bone volume (BV/TV) by 54.2% at the distal metaphysis (p < 0.05) in the femora compared with those of SAMP6. The bone formation rate of P6.P2-13 was markedly increased at the periosteal surface of femoral cortex and that was caused by a higher proliferation rate of osteoblasts in P6.P2-13 compared with those in SAMP6. Quantitative RT-PCR analysis of calvaria tissue showed similar to 40-fold higher levels of expression of Sfrp4 in SAMP6 than in P6.P2-13. Taken together with the result that recombinant Sfrp4 suppressed the proliferation of osteoblasts, we hypothesized that Sfrp4 inhibited the proliferation of osteoblasts through its antagonistic effect on Writ signaling. TCF/beta-catenin-dependent reporter activity in osteoblasts derived from SAMP6 showed lower responsiveness for the Writ ligand, Wnt3A, than that in osteoblasts from P6.P2-13.Conclusions: In SAMP6 mice, Sfrp4 negatively regulates bone formation and decreases BMD through the inhibition of Writ signaling.