Produdion of transgenic mice and functional analysis ofosteaytesusingcis-regulatory regions

骨细胞是骨中最丰富的细胞。在成熟骨中，骨细胞的数量大约是成骨细胞的10倍。先前的研究表明骨细胞可能参与机械传感和Ca^<2+>代谢。然而，骨内部是一个由众多骨细胞组成的网络，其具体功能仍然是一个谜。DMP1在骨细胞中高度表达，因此是骨细胞谱系的良好标记，并在骨基质内的骨细胞小管中特异性表达。假设DMP1基因的顺式调控区域包含一个骨细胞特异性控制模块，该模块将激活内源性DMP1基因。因此，我们确定了12Kbp的顺式调控区域，其中包含骨细胞特异性控制模块。然后，构建DMP1-GFP顺式调控区，生成在骨细胞中特异性表达GFP的转基因小鼠。最近对DMP1缺失小鼠的研究表明，DMP1缺失导致骨细胞成熟缺陷和FGF23表达增加，导致肾磷消耗相关的低磷血症。基于这一结果，我们假设dmp1过表达会导致FGF23表达降低，导致高磷血症。然后我们评估了dmp1过表达转基因小鼠（DMP1-Tg）的磷酸盐稳态和血清FGF-23。DMP1-Tg与野生小鼠TmP/GFR及血清FGF23值差异无统计学意义。我们的研究结果表明，DMP1并不直接诱导骨组织中FGF-23的表达，DMP1诱导骨软化的缺失可能导致骨组织中FGF-23的增加。

Osteocytes are the most abundant cells in bone. There are approximately 10 times as many osteocytes as osteoblasts in mature bone. Previous studies suggested that osteocytes may be involved in mechanosensing and Ca^<2+> metabolism. However, inside of bone is a network of numerous osteocytes, whose specific function has remained an enigma. DMP1 is highly expressed in the osteocyte and therefore a good marker for the osteocyte lineage and is specifically expressed along and in the canaliculi of osteocytes within the bone matrix. The hypothesis is that the cis-regulatory region of the DMP1 gene contains an osteocyte-specific control module that will activate the endogenous DMP1 gene. Therefore, we identified the 12Kbp cis-regulatory region, which contained osteocyte-specific control module. Then, we made the constructs of cis-regulatory regions of DMP1-GFP, to generation of the transgenic mice that express GFP specifically in the osteocyte.Recent study using DMP1-null mice demonstrated that absence of DMP1 results in defective osteocyte maturation and increased FGF23 expression, leading to renal phosphate-wasting associated hypophosphatamia. Based on this result, we hypothesize that DMP1-overexpression will result in decreased FGF23 expression, leading to hyperphosphatemia. Then we evaluate the phosphate homeostasis and serum FGF-23 in DMP1-overexpressed transgenic mice (DMP1-Tg). There is no significance of TmP/GFR and serum FGF23 values between DMP1-Tg and wild mice. Our findings indicated that DMP1 did not directly induced FGF-23 expression in bony tissue and that loss of DMP1 inducing osteomalacia may lead to increased FGF-23 in bony tissue.