PDF(Pubmed)
Abstract：
Metazoan eggs have a specialized coat of extracellular matrix that aids in sperm-egg recognition. The coat is rapidly remodeled after fertilization to prevent polyspermy and establish a more permanent barrier to protect the developing embryo. In nematodes, this coat is called the vitelline layer, which is remodeled into the outermost layer of a rigid and impermeable eggshell. We have identified three key components of the vitelline layer structural scaffold - PERM-2, PERM-4 and CBD-1, the first such proteins to be described in the nematode C. elegans. CBD-1 tethered PERM-2 and PERM-4 to the nascent vitelline layer via two N-terminal chitin-binding domains. After fertilization, all three proteins redistributed from the zygote surface to the outer eggshell. Depletion of PERM-2 and PERM-4 from the scaffold led to a porous vitelline layer that permitted soluble factors to leak through the eggshell and resulted in embryonic death. In addition to its role in vitelline layer assembly, CBD-1 is also known to anchor a protein complex required for fertilization and egg activation (EGG-1-5/CHS-1/MBK-2). We found the PERM complex and EGG complex to be functionally independent, and structurally organized through distinct domains of CBD-1. CBD-1 is thus a multifaceted regulator that promotes distinct aspects of vitelline layer assembly and egg activation. In sum, our findings characterize the first vitelline layer components in nematodes, and provide a foundation through which to explore both conserved and species-specific strategies used by animals to build protective barriers following fertilization.
摘要：
后生卵具有特殊的细胞外基质涂层，有助于精卵识别。受精后，外套迅速重塑，以防止多精子症，并建立更永久的屏障来保护发育中的胚胎。在线虫中，这种外套叫做卵黄层，它被重塑成刚性和不可渗透的蛋壳的最外层。我们已经确定了卵黄层结构支架的三个关键成分-PERM-2，PERM-4和CBD-1，这是线虫C.elegans中描述的第一个此类蛋白质。CBD-1通过两个N端几丁质结合域将PERM-2和PERM-4束缚到新生卵黄层上。受精后,所有三种蛋白质都从受精卵表面重新分布到外蛋壳。从支架中耗尽PERM-2和PERM-4导致多孔卵黄层，使可溶性因子泄漏通过蛋壳并导致胚胎死亡。除了在卵黄层组装中的作用外，还已知CBD-1锚定受精和卵活化所需的蛋白质复合物(EGG-1-5/CHS-1/MBK-2)。我们发现PERM复合物和EGG复合物在功能上是独立的，并通过CBD-1的不同域进行结构组织。因此,CBD-1是促进卵黄层组装和卵活化的不同方面的多方面调节剂。总之,我们的发现描述了线虫中第一个卵黄层的成分，并提供了一个基础，通过它来探索动物使用的保守和物种特异性策略，以建立受精后的保护性屏障。
