STRUCTURE AND FUNCTION OF FRIZZLED-LIKE PROTEINS IN SKELETAL DEVELOPMENT

Frzb是一种分泌蛋白，最初从纯化的软骨提取物中分离，其与Wnt受体的卷曲家族的富含半胱氨酸的结构域（CRD）具有同源性。Wnt蛋白是分泌的信号分子，具有许多发育功能，包括骨骼发育以及肿瘤发生中的功能障碍。已经表明，Frzb可以结合并抑制Wnt活性，导致对其的推测在修饰Wnt诱导的发育和致癌事件中的潜在治疗用途。我们已经证明，Frzb的时间和空间表达在骨骼和颅面发育。为了了解Frzb在发育中的作用，我们正在使用Cre-LoxP重组系统进行条件性基因敲除。我们首先通过同源重组产生了floxed小鼠，其中Frzb基因两侧是LoxP位点。随后将这些小鼠与在普遍存在的启动子控制下表达Cre重组酶的转基因小鼠系杂交，以在发育早期删除Frzb。无效表型似乎是致死性的，我们目前正在确定致死性发生在哪个阶段。因此，为了观察Frzb缺失在面部发育过程中的影响，我们正在产生转基因小鼠品系以在面部间充质中特异性表达Cre重组酶。这些小鼠在Msx-1启动子的控制下表达Cre，目前正在测试Cre重组酶活性的特异性。- 发育，wnt受体，信号传导

Frzb is a secreted protein, initially isolated from purified cartilage extracts, which shares homology to the cysteine rich domain (CRD) of the frizzled family of Wnt receptors. The Wnt proteins are secreted signaling molecules having numerous developmental functions, including skeletal development, as well as dysfunction in oncogenesis. It has been shown that Frzb can bind to and inactivate Wnt activity, leading to speculation for its potential therapeutic use in modifying Wnt induced developmental and oncogenic events. We have demonstrated that Frzb is temporally and spatially expressed during skeletal and craniofacial development. In an attempt to understand the role of Frzb in development we are conducting a conditional gene knockout, using the Cre-LoxP recombination system. We first generated floxed mice, in which the Frzb gene is flanked by LoxP sites, by homologous recombination. These mice were subsequently crossed to a transgenic mouse line expressing Cre recombinase under the control of a ubiquitous promoter to delete Frzb early in development. The null phenotype appears to be lethal and we are currently determining at what stage the lethality occurs. Consequently, in order to observe the effect that loss of Frzb has during face development we are generating a transgenic mouse line to express Cre recombinase specifically in facial mesenchyme. These mice, which express Cre under the control of the Msx-1 promoter, are currently being tested for the specificity of the Cre recombinase activity. - development, wnt receptors, signaling