Crisp proteins and sperm chemotaxis: discovery in amphibians and explorations in mammals

Abstract

Crisp proteins appear to play multiple roles in the life history of sperm. One of these roles is to act as a sperm chemoattractant. Allurin, a 21 kDa Crisp protein rapidly released from the egg jelly of at least two frogs, X. laevis and X. tropicalis, elicits directed motility in both homospecific and heterospecific sperm. In X. tropicalis, allurin is coded for by the newly documented Crisp A gene. Recently, the observation that allurin can also elicit chemotaxis in mouse sperm raises the question of whether allurin-like proteins might act as sperm chemoattractants in mammals. Although an allurin gene has yet to be documented in mammals, Crisp proteins truncated post-translationally appear to exist in both the male and female reproductive tract of mammals.

In silico identification of the genes for sperm-egg interaction in the internal fertilization of the newt Cynops pyrrhogaster

“…CRISP proteins are reported to be expressed in the male reproductive tract of mammals and to modulate sperm maturation in the epididymis, as well as capacitation and fusion with the egg plasma membrane in the oviduct, at fertilization (Cohen et al, 2000;Roberts et al, 2003;Gibbs et al, 2006;Busso et al, 2007a;2007b;Burnett et al, 2008a;Cohen et al, 2008). In amphibians, allurin, a member of the CRISP family proteins, is expressed in the oviduct (Al-Anzi and Chandler, 1998;Olson et al, 2001;Xiang et al, 2004).…”

Allurin: Exploring the Activity of a Frog Sperm Chemoattractant in Mammals

“…In mammals, full-length Crisp proteins are associated with sperm production in the testis, sperm maturation in the epididymis, and sperm capacitation and oocyte binding in the female reproductive tract (Gibbs et al 2008 ;Burnett et al 2008a ). One might speculate that the ICR domain of these proteins may be modifying the behavior of ion channels in sperm.…”

“…Some of these ligands are diffusible in nature and emanate from extracellular coatings surrounding the egg whereas other ligands form a more stable part of the extracellular coat structure and act only on sperm in contact with these matrices. Diffusible ligands include peptides, steroids, amino acids, and even proteins (Burnett et al 2008a ).…”

“…One class of protein ligands that have received increasing interest are the cysteine-rich secretory (Crisp) proteins whose members include snake venom toxins, sperm chemoattractants, sperm decapacitation factors, sperm self-identifi cation markers, and sperm ion channel modulators (Burnett et al 2008a ;Gibbs et al 2008 ;Kratzschmar et al 1996 ;Koppers et al 2011 ). Full-length Crisp proteins contain three domains, as indicated in Fig.…”

“…4.1 , truncated members typically contain the PR and Hinge domains along with amino-acid sequences at the C-terminal that vary in length from a few residues to several hundred. Members of this class include allurin, the frog sperm chemoattractant whose characteristics are described in the current chapter, insect venom and hookworm antigen proteins (Burnett et al 2008a ), the protease inhibitor-like proteins P115 and P116 (Gibbs et al 2008 ), Ciona intestinalis (Ci) Urabin and Halocynthia roretzi (Hr) Urabin, recently discovered self-identity ligands on ascidian sperm (Urayama et al 2008 ;Yamaguchi et al 2011 ), and the glioma pathogenesis related-like proteins, whose functions are currently unknown, but which include members that are expressed in a testis-specifi c manner (Gibbs et al 2010b ).…”