Species-specific adhesion of sperm to the egg during sea urchin fertilization involves the interaction of the sperm adhesive protein, bindin, and a complementary receptor on the egg surface, and serves to restrict the gene pool to individuals of the same species. We used PCR representation difference analysis to clone the species-specific egg receptor for bindin, EBR1, from Strongylocentrotus franciscanus (Sf) and S. purpuratus (Sp). Sf-EBR1 contains a novel ADAMTS-like N-terminal domain followed by ∼19 tandem EBR repeats consisting of alternating CUB and thrombospondin type 1 (TSP-1) domains where the last 10 EBR repeats are species-specific and highly conserved. Recombinant protein corresponding to the species-specific EBR repeat displays species-specific sperm adhesion and bindin-binding activity. The Sp-EBR1 ortholog has the same ADAMTS (a disintegrin and metalloprotease with thrombospondin type-1 modules) core region followed by eight and one-half tandem egg bindin receptor (EBR) repeats that share 88% identity with the Sf-EBR1 repeats, but has an entirely different species-specific domain consisting of hyalin-like (HYR) repeats. Thus, the species-specific domains of egg bindin receptor 1 (EBR1) from both species function as the egg surface receptor to mediate species-specific sperm adhesion. Received July 14, 2003; revised version accepted August 25, 2003. Sperm-egg interaction typically exhibits species specificity in most animals. Several molecules from both sperm and eggs that are thought to mediate gamete interaction have been identified in many animals. In abalone, the acrosomal protein of sperm, lysin, interacts with the egg vitelline envelope receptor for lysin (VERL) and creates a hole on the extracellular matrix (ECM) of the egg with species selectivity (Swanson and Vacquier 1997). In mammals, numerous molecules, such as galactosyltransferase, ADAM (a disintegrin and metalloprotease), and Sp56, have been identified from sperm and are proposed to interact with such as egg zona pellucida proteins Zp2, Zp3, or Integrins on the egg. However, a clear understanding of the specificity of these interactions and the regulation of species specificity is not yet known (Primakoff and Myles 2002;He et al. 2003).Acrosome-reacted sea urchin sperm adhere to glycoprotein receptors that are components of the vitelline envelope (VE) known as the ECM of the egg. It has been known for several decades that the protein bindin on the acrosome-reacted sea urchin sperm head mediates the species-specific adhesion of sperm to the VE during fertilization (Summers and Hylander 1975;Glabe and Vacquier 1977b;Vacquier and Moy 1977;Glabe et al. 1982). The egg ECM also serves as a major barrier for interspecific fertilization in mammalian systems (Yanagimachi 1981(Yanagimachi , 1994. In sea urchins, the complementary receptor for bindin was shown to be an ∼350-kD protein on the VE of the egg (Glabe and Vacquier 1978;Carroll et al. 1986;Ohlendieck et al. 1993). However, the identity of this receptor has remained elusive, and att...

Fertilization is a programmed process that has many molecules and sequential events amenable to study. The biochemistry of fertilization has identified cellular and acellular components fundamental to the interactions between sperm and egg. Recent studies highlight the molecular details of the species-specificity of fertilization that involve protein-protein and protein-carbohydrate interactions. Although the diversity of structure and mechanism may imply rapid evolution of fertilization proteins, understanding the structure-function relationships has become important. Here, we introduce the molecules controlling the sperm AR, sperm attachment to, and penetration through, the egg investments.

SummaryMultipotent human central nervous system-derived neural stem cells transplanted at doses ranging from 10,000 (low) to 500,000 (very high) cells differentiated predominantly into the oligodendroglial lineage. However, while the number of engrafted cells increased linearly in relationship to increasing dose, the proportion of oligodendrocytic cells declined. Increasing dose resulted in a plateau of engraftment, enhanced neuronal differentiation, and increased distal migration caudal to the transplantation sites. Dose had no effect on terminal sensory recovery or open-field locomotor scores. However, total human cell number and decreased oligodendroglial proportion were correlated with hindlimb girdle coupling errors. Conversely, greater oligodendroglial proportion was correlated with increased Ab step pattern, decreased swing speed, and increased paw intensity, consistent with improved recovery. These data suggest that transplant dose, and/or target niche parameters can regulate donor cell engraftment, differentiation/maturation, and lineage-specific migration profiles.

Clinical immunosuppression protocols use calcineurin inhibitors, such as cyclosporine A (CsA) or tacrolimus (FK506), or mammalian target of rapamycin (mTOR) inhibitors, such as sirolimus (rapamycin). These compounds alter immunophilin ligand signaling pathways, which are known to interact downstream with mediators for human neural stem cell (hNSC) differentiation and proliferation, suggesting that immunosuppressants may directly alter hNSC properties. We investigated whether immunosuppressants can exert direct effects on the differentiation, proliferation, survival, and migration of human central nervous system-derived stem cells propagated as neurospheres (hCNSSCns) in vitro and in an in vivo model of spinal cord injury. We identified unique, immunosuppressant-dependent effects on hCNS-SCns differentiation and proliferation in vitro. All immunosuppressants tested increased neuronal differentiation, and CsA and rapamycin inhibited proliferation in vitro. No immunosuppressant-mediated effects on hCNS-SCns survival or migration in vitro were detected. These data suggested that immunosuppressant administration could alter hCNS-SCns properties in vivo. We tested this hypothesis by administering immunosuppressants to constitutively immunodeficient spinal cord injured mice and assessed survival, proliferation, differentiation, and migration of hCNS-SCns after 14 weeks. In parallel, we administered immunosuppressants to immunocompetent spinal cord injury (SCI) mice and also evaluated hCNS-SCns engraftment and fate. We identified no effect of immunosuppressants on the overall hCNS-SCns fate profile in either xenotransplantation model. Despite a lower level of human cell engraftment in immunocompetent SCI mice, functional locomotor recovery was observed in animals receiving hCNS-SCns transplantation with no evidence of allodynia. These data suggest that local cues in the microenvironment could exert a stronger influence on hCNS-SCns than circulating levels of immunosuppressants; however, differences between human and rodent metabolism/pharmokinetics and xenograft versus allograft paradigms could be determining factors. STEM CELLS TRANSLATIONAL MEDICINE 2013;2: 731-744

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