Structure, Evolutionary Significance, and Developmental Expression of the Sea Urchin Bindin Gene

紫球海胆和法国海胆之间的受精是由精子顶体蛋白Bindin与其受体的特异性相互作用控制的。这种相互作用目前负责维持这两个物种之间的物种隔离屏障，这两个物种的地理范围和繁殖季节重叠。对紫毛链霉菌和法国链霉菌克隆的完整蛋白质序列进行比较，以确定这两个物种之间发生了变化的蛋白质序列，因此可能是物种特异性结合的原因。覆盖这些区域的合成肽将被用于体外结合分析，并作为受精的竞争对手，以确定哪些改变的序列对结合活性的变化负责。对这两个物种的基因组克隆进行分析，并与第三个物种Lytechinus varegatus进行比较，将揭示这些重要序列的变化机制和方向。Bindin基因克隆也被用作幼年海胆睾丸发育的标记。将通过比较它们的启动子序列和确定它们共享启动子DNA结合蛋白的程度来研究Bindin和另一种睾丸特异基因-睾丸特异性精子组蛋白H2B的协调控制。由于物种间的不育性，自然物种中的%保持不变。戴维森博士已经证明，精子蛋白是造成两种共享栖息地的海胆之间存在这种障碍的原因。由于精子不能使其他物种的卵子受精，它们不能进行杂交，而这种能力是由于一种特定的精子蛋白造成的。戴维森博士建议对这两个物种的这种蛋白质进行分子研究，以准确地确定是什么导致了不相容。这两个物种是近亲，这种蛋白质在进化过程中明显出现了分化。对分子缺陷的研究将提供有助于了解精子-卵子黏附的正常过程的信息，这是所有物种受精的关键事件。

The species specificity of fertilization between the sea urchins Strongylocentrotus purpuratus and S. franciscanus is controlled by the specific interaction of a sperm acrosomal protein, bindin, with its receptor. This interaction is currently responsible for maintaining the species-isolating barrier between these two species, whose geographic ranges and reproductive seasons overlap. Comparisons of complete protein sequences from cDNA clones for S. purpuratus and S. franciscanus are being used to define protein sequences that have changed between the two species and may therefore be responsible for the species-specific binding. Synthetic peptides covering these regions will be used in in vitro binding assays and as competitors in fertilization in order to determine which altered sequences are responsible for the change in binding activity. Analysis of genomic clones from these two species and comparison to a third species, Lytechinus variegatus, will show the mechanism and direction of change for the important sequences. The bindin cDNA clones are also being used as a marker for testis development in juvenile sea urchins. The coordinate control of bindin and another testis specific gene, testis-specific sperm histone H2B, will be studied by comparing their promoter sequences and by determining the extent to which they share promoter DNA binding proteins. %%% In nature species are maintained due to infertility across species. Dr. Davidson has shown that the sperm protein is responsible for this barrier between two species of sea urchins who share a habitat. They can not interbreed due to the inability of the sperm to fertilize the egg of the other species and this inability is due to a species specific sperm protein. Dr. Davidson proposes a molecular investigation of this protein from the two species to determine precisely what is responsible for the incompatibility. The two species are close relatives and this protein has apparently diverged during evolution. The study of the molecular defect here will provide information that will lead to knowledge of the normal process of sperm-egg adhesion, a key event in fertilization in all species.