Functional Analysis of NHA-oc/NHA2 in vivo

描述（由申请人提供）：破骨细胞对骨的破坏是正常骨发育所必需的。破骨细胞缺乏导致骨质疏松症，其特征是骨量增加，并可能导致骨畸形，严重时甚至导致死亡。另一方面，破骨细胞数量和活性的增加导致骨吸收增加，并可能导致骨质疏松症和其他溶骨疾病。更好地了解破骨细胞形成、活性和存活的分子调控将为控制这些疾病的治疗干预提供新的靶点。最近，我们发现了一个基因，nha-oc/NHA2，在体外和体内rankl诱导的破骨细胞分化过程中被强烈上调。nha-oc/NHA2编码一种在破骨细胞中选择性表达的新型阳离子/质子反转运蛋白（CPA）。NHA-oc/NHA2蛋白定位于线粒体，介导Na+依赖性线粒体肿胀。因此，NHA-oc/NHA2是第一个被鉴定的哺乳动物线粒体CPA2。RNA沉默nha-oc/nha2可减少破骨细胞分化和骨吸收，强烈表明nha-oc/nha2在这些过程中发挥作用。在Aim 1中，我们将通过在NHA-oc/NHA2位点携带诱变逆转录病毒插入的敲除小鼠模型来表征NHA-oc/NHA2在体内骨稳态中的作用。在Aim 2中，我们将描述NHA-oc/NHA2在体内病理性骨质流失中的作用。为此，我们将比较野生型和纯合子突变小鼠卵巢切除术引起的骨质流失。nha-oc/NHA2对体内破骨细胞形成和骨吸收的影响将通过各种骨分析方法来确定。我们的目标是确定NHA-oc/NHA2在破骨细胞分化和功能中的作用，并最终在体内调节骨量。这些研究可能会发现一个新的参与人类骨质疏松症发展的候选基因，并为抗骨吸收治疗提供一个重要的新靶点。

DESCRIPTION (provided by applicant): Bone destruction by osteoclasts is essential for normal bone development. Osteoclast deficiency leads to osteopetrosis, which is characterized by increased bone mass and may lead to bone deformities or in severe cases, to death. Increased numbers and activity of osteoclasts, on the other hand, cause increased bone resorption, and may lead to osteoporosis and other osteolytic diseases. A better understanding of the molecular regulation of osteoclast formation, activity, and survival will provide novel targets for therapeutic intervention in the control of these diseases. Recently, we identified a gene, nha-oc/NHA2, which is strongly up-regulated during RANKL-induced osteoclast differentiation in vitro and in vivo. nha-oc/NHA2 encodes a novel cation/proton antiporter (CPA) that is selectively expressed in osteoclasts. NHA-oc/NHA2 protein localizes to the mitochondria, where it mediates Na+dependent mitochondrial swelling. NHA-oc/NHA2 is therefore the first characterized mammalian mitochondrial CPA2. RNA silencing of nha-oc/nha2 reduces osteoclast differentiation and bone resorption, strongly indicating a role for NHA-oc/NHA2 in these processes. In Aim 1, we will characterize the role of NHA-oc/NHA2 in bone homeostasis in vivo by using a knockout mouse model carrying a mutagenic retroviral insertion in the nha-oc/NHA2 locus. In Aim 2, we will characterize the role of NHA-oc/NHA2 on pathological bone loss in vivo. For that, we will compare bone loss induced by ovariectomy in wild type and homozygous mutant mice. The effects of nha-oc/NHA2 on osteoclast formation and bone resorption in vivo will be determined using a variety of analytic approaches for bone. Our goal is to establish the role that NHA-oc/NHA2 plays in osteoclast differentiation and function, and ultimately in regulating bone mass in vivo. These studies may identify a new candidate gene involved in the development of human osteopetrosis as well as provide an important new target for anti-resorptive therapies. PUBLIC HEALTH RELEVANCE: Osteoclasts are cells that are responsible for bone removal ('resorption') during normal bone development and maintenance. In contrast, abnormal osteoclast numbers and/or activity cause a spectrum of diseases ranging from osteopetrosis to osteoporosis. This project seeks to determine the role of a novel gene that we have discovered in osteoclasts, termed 'NHA-oc/NHA2', in osteoclast formation, function and ultimately in regulating bone mass in vivo. This work will aid us in the design of appropriate new therapies based on drugs that interfere with NHA-oc/NHA2 activity for the prevention of pathological bone loss.