A homologue of cysteine-rich secretory proteins induces premature degradation of vitelline envelopes and hatching of Xenopus laevis embryos. 
We cloned Xenopus laevis CRISP, XCRISP, a homologue of the mammalian family of cysteine-rich secretory proteins (CRISPs), which has been previously identified as a Wnt3a/noggin responsive gene in an expression screen [Mech.  Dev.  87 (1999) 21].  We detected XCRISP expression exclusively in the hatching gland.  XCRISP enters the secretory pathway and accumulates on the surface of presumptive hatching gland cells.  Overexpression studies of XCRISP and XCRISP-mutants show that XCRISP induces premature hatching of embryos preceded by degradation of the vitelline envelope.  A deletion mutant that lacks a 35 amino acid domain even accelerates hatching, while further deletion of the carboxy-terminus reverses these effects.  From our studies, we conclude that XCRISP is sufficient to induce degradation of vitelline envelopes and that this activity maps to the most C-terminal amino acids, while the adjacent domain regulates XCRISP activity.