MAIA, Fc receptor-like 3, supersedes JUNO as IZUMO1 receptor during human fertilization.

Gamete fusion is a critical event of mammalian fertilization. A random one-bead one-compound combinatorial peptide library represented synthetic human egg mimics and identified a previously unidentified ligand as Fc receptor-like 3, named MAIA after the mythological goddess intertwined with JUNO. This immunoglobulin super family receptor was expressed on human oolemma and played a major role during sperm-egg adhesion and fusion. MAIA forms a highly stable interaction with the known IZUMO1/JUNO sperm-egg complex, permitting specific gamete fusion. The complexity of the MAIA isotype may offer a cryptic sexual selection mechanism to avoid genetic incompatibility and achieve favorable fitness outcomes.

Fine structure and morphology of sterlet (Acipenser ruthenus L. 1758) spermatozoa and acrosin localization.

Ultrastructure of sterlet Acipenser ruthenus L. 1758 sperm was examined by scanning and transmission electron microscopy, which allowed us to use various methods for visualizations of different parts of sterlet spermatozoa. Sperm cells possess a head with a distinct acrosome, a midpiece and a single flagellum surrounded by the flagellar plasma membrane. The average length of the head including the acrosome and the midpiece was estimated as 5.14+/-0.42 microm. Nine to 10 posterolateral projections were derived from the acrosome. Three inter-twining endonuclear canals bounded by membranes traversed the nucleus in its whole length from the acrosome to the implantation fossa. Acrosin was located in all the three parts (acrosome, endonuclear canals and implantation fossa). The proximal and distal centrioles located in the midpiece compacted of nine peripheral triplets of microtubules. One cut of the midpiece contained from two to six mitochondria with area of 215+/-85 nm(2) in average. The flagellum was 42.47+/-1.89 microm in length with typical eukaryotic organization of one central pair and nine peripheral pairs of microtubules. It passed through a cytoplasmic channel in the midpiece, which was formed by an invagination at the plasmalemma. The flagellum gradually developed two lateral extensions of its plasma membrane, so-called "fins". Detected morphological variation can be described by four principal component axes corresponding to groups of individual morphometric characters defined on the sperm structures. Correlations among the characters indicate that the sperms are variable in their shape rather than size. Significant variation among examined fish individuals was found only in flagellum and nucleus length. Comparison between the present and previous studies of morphology of sturgeon spermatozoa confirmed large inter- and/or intra-specific differences that could be of substantial taxonomic value.

Expression of beta-tubulin epitope in human sperm with pathological spermiogram.

OBJECTIVE: To determine the location of the corresponding epitope on the tubulin molecule and to find any differences in its exposition in human sperm with normal and pathological spermiograms. The mature spermatozoon exhibits extraordinary structural compartmentalization that is related to the presence of cytoskeletal proteins and has a functional role in connection with fertilization and motility. Previously, we have shown that anti-beta-tubulin antibody TU-12 provided an unexpectedly strong reaction in human and boar sperm head. DESIGN: A retrospective study. SETTING: Academic research laboratories and private IVF center. PATIENT(S): One hundred thirteen men participating in the IVF program. INTERVENTION(S): Sperm were divided into five categories: normozoospermia, oligozoospermia, asthenozoospermia, teratozoospermia, and asthenoteratozoospermia. Well-characterized monoclonal antibodies were applied for monitoring tubulin epitope distributions in pathological spermatozoa. MAIN OUTCOME MEASURE(S): Qualitative and quantitative detection of tubulin. RESULT(S): TU-12 epitope was located in the beta-tubulin region beta 426-435. Immunoblotting revealed differences in the amount of tubulin among men with normozoospermia and pathological spermiogram. Striking differences were observed in the exposition of TU-12 epitope in heads of normal and pathological spermatozoa. CONCLUSION(S): The results suggest that tubulin epitopes could be useful biomarkers of the pathological sperm state.