FATE SPECIFICATION ALONG THE SEA URCHIN EMBRYO A-V AXIS

VEB(极早期囊胚)基因是第一个严格合子基因 在海胆胚胎中被激活；它们在大约 80%的胚胎，但不在植物杆周围的区域。VEB 因此，消息分发提供了最早的分子之一 母体特定的动植物轴的适应症。几行 大量证据表明VEB基因活性的不对称性受 一个或多个母性因子，其活动类似地分布在 蛋和早期胚胎。此外，VEB基因SPAN编码一种天冬氨酸- 具有激活生长因子SpBMP4功能的家族蛋白酶 TGFb超家族的因子。因此，SPAN基因是一个强有力的候选基因 对于非常早期的开发中的转换点，它将预本地化 母体基因调控信息对空间调控生产的影响 一种可能在规范中具有重要早期作用的生长因子 沿动植物(AV)轴的细胞命运，这取决于细胞- 细胞间的相互作用。为了检验这一总体假设，我们正在(目标I)研究 SPAN和第二个VEB基因(SPHE)的空间调控，SPHE编码 孵化酶)，以努力了解 创建房室轴并(目标II)检查 SpN/SpBMP4作为形态发生因子。顺式作用元件和反式作用元件 调控SPAN和SPHE转录的因素正在由IN分析 海胆胚胎中启动子转基因构建的活体分析 蛋白质-DNA相互作用的体外检测。SPAN/SpBMP4在骨形态发生发展中的作用 将通过分离编码基因的cdna克隆来研究命运的指定。 SpBMP4受体(SpBMP4R)； 表达SpBMP4和SpBMP4R多肽；通过过表达， Span、SpBMP4和SpBMP4的错误表达和显性负干扰 SpBMP4R函数。(目标三)适当的产妇调节器候选人 我们鉴定了VEB基因，其功能在空间上是受限的 将进行类似的实验，以测试 扰乱了它们的功能。

The VEB (very early blastula) genes are the first strictly zygotic genes activated in the sea urchin embryo; they are transcribed in approximately 80% of the embryo, but not in a region around the vegetal pole. The VEB message distribution thus provides one of the earliest molecular indications of the maternally specified animal-vegetal axis. Several lines of evidence suggest that the asymmetry of VEB gene activity is regulated by one or more maternal factors whose activity is similarly disposed in the egg and early embryo. Furthermore, one VEB gene, SpAN, encodes an astacin- family protease with demonstrated function in activating SpBMP4, a growth factor of the TGFb superfamily. Thus, the SpAN gene is a strong candidate for a switch point in very early development which converts prelocalized maternal gene regulatory information to spatially regulated production of a growth factor likely to have an important early function in specification of cell fates along the animal-vegetal (AV) axis, which depends on cell- cell interactions. To test this overall hypothesis we are (Aim I) studying spatial regulation of SpAN and a second VEB gene (SpHE, which encodes the hatching enzyme) in an effort to understand the molecular mechanism that creates the AV axis and (Aim II) examining the potential role of SpAN/SpBMP4 as a morphogen. The cis-acting elements and trans-acting factors which regulate SpAN and SpHE transcription are being analyze by in vivo assays of promoter transgene constructs in sea urchin embryos and by in vitro assays of protein-DNA interaction. The role of SpAN/SpBMP4 in fate specification will be studied by isolating cDNA clones encoding the receptor for SpBMP4 (SpBMP4R); by characterizing the developmental expression of SpBMP4 and SpBMP4R peptides; and by overexpression, misexpression and dominant negative interference with SpAN, SpBMP4 and SpBMP4R function. (Aim III) if suitable candidate maternal regulators of the VEB genes are identified, whose functions are spatially restricted, we shall carry out similar experiments to test the developmental effects of perturbing their function.