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。以前的研究表明骨细胞可能参与机械感受和Ca^2+代谢。然而，骨的内部是一个由众多骨细胞组成的网络，其具体功能至今仍是一个谜。DMP 1在骨细胞中高度表达，因此是骨细胞谱系的良好标志物，并且在骨基质内的骨细胞小管中沿着特异性表达。假设是DMP 1基因的顺式调控区包含一个骨细胞特异性控制模块，该模块将激活内源性DMP 1基因。因此，我们确定了12 Kbp的顺式调控区，其中包含骨细胞特异性控制模块。我们构建了DMP 1-GFP的顺式调控区，构建了在骨细胞中特异表达GFP的转基因小鼠，最近的研究表明，DMP 1基因缺失导致骨细胞成熟缺陷和FGF 23表达增加，导致肾性磷酸盐消耗相关的低磷酸盐血症。基于这一结果，我们假设DMP 1过表达将导致FGF 23表达降低，导致高磷血症。然后，我们评估了磷酸盐稳态和血清FGF-23在DMP 1过表达的转基因小鼠（DMP 1-Tg）。DMP 1-Tg小鼠的TmP/GFR和血清FGF 23值与野生型小鼠无显著性差异。我们的研究结果表明，DMP 1并不直接诱导FGF-23在骨组织中的表达，并且DMP 1诱导的骨软化症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.