Cyritestin is a membrane-anchored sperm protein belonging to the ADAM (f1.gif" BORDER="0"> f2.gif" BORDER="0">isintegrin and f1.gif" BORDER="0"> f3.gif" BORDER="0">etalloprotease) family of proteins, which are proposed to be involved in cell-cell adhesion through binding to integrin receptors. Several lines of evidence support a role of cyritestin and other members of this protein family in the fusion of sperm and the egg plasma membrane. In an effort to elucidate the physiological function of cyritestin, we have disrupted its locus by homologous recombination. Male homozygous null mutants are infertile, even though spermatogenesis, mating, and migration of sperm from the uterus into the oviduct are normal. In vitro experiments showed that infertility is due to the inability of the cyritestin-deficient sperm to bind to the zona pellucida. However, after removal of the zona pellucida, sperm-egg membrane fusion monitored by the presence of pronuclei and generation of 2- and 4-cell embryos did not reveal any differences from the wild-type situation. These results demonstrate that cyritestin is crucial in the fertilization process at the level of the sperm-zona pellucida interaction.

To identify genes that are differentially expressed during self-repair processes in mouse brain, we screened a subtracted cDNA library enriched for brain-specific clones. One of these clones, H74, detected a 4.4-kb mRNA predominantly expressed in brain and dorsal root ganglia neurons. Expression increased continuously during the lifespan and the state of differentiation, but decreased after entorhinal-cortex lesion. A full-length cDNA clone was isolated from a cerebellum cDNA library and characterized. Sequence analysis and database search revealed high sequence similarity to FAP52, a protein expressed in focal-adhesion contacts, and uncharacterized Echinococcus and Caenorhabditis elegans gene products. Furthermore, peptide sequences derived from human cDNA fragments showed up to 65% sequence identity at the amino acid level. The presence of a C-terminal src homology 3 (SH3) domain and its phosphorylation by casein kinase 2 (CK2) and protein kinase C (PKC) imply a role in signaling. Here we demonstrate that the gene encodes a phosphoprotein, referred to as PACSIN, with a restricted spatial and temporal expression pattern.Keywords : signal transduction; neuron; SH3 domain; phosphorylation; brain protein.Partial deafferentation in selected areas of the adult rodent brain induces a sequence of compensatory events in both the remaining afferent fibers and the denervated dendrites, resulting in reorganization of the circuitry in the denervated area. The regeneration events include sprouting of the remaining afferent fibers, restoration of spine density and length, as well as replacement of vacated synaptic contacts [1]. One of the most carefully examined mammalian brain structures is the hippocampus, which is known for its role in learning and memory and which appears to maintain a high degree of anatomical plasticity even in adult animals. This phenomenon has been studied particularly for changes in the dentate gyrus in response to the loss of input after unilateral entorhinal cortex lesion (ECL).Relatively little is known regarding the molecular and biochemical events that underlie regeneration or self-repair proCorrespondence to M. Plomann,

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Synthetic peptides corresponding to specific regions of the mouse acrosomal transmembrane protein cyritestin have been used as competitors in in vitro fertilization experiments. One peptide representing a putative egg-receptor binding site within the disintegrin domain of cyritestin lowered the fertilization rate to 30% of the normal value.

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