Phytohaemagglutinin as a molecular probe to study the membrane constituents of human X- and Y-bearing spermatozoa

Differential but beneficial effect of phytohemagglutinin on efficiency of in vitro porcine embryo production by somatic cell nuclear transfer or in vitro fertilization

In vitro production of porcine embryos has become routine in most laboratories but the yield and quality of the resultant blastocysts remains sub-optimal. Phytohemagglutinin (PHA) is an N-acetylgalactosamine/galactose sugar-specific lectin with a wide variety of biological activities including mitogenesis, mediation of cell recognition and agglutination of cells. This study was therefore, designed to investigate the effect of PHA on the preimplantation development and quality of parthenogenetic, somatic cell nuclear transferred (SCNT) and in vitro fertilized (IVF) porcine embryos cultured in the absence or presence of PHA. Analysis showed that, supplementation of PHA significantly improved the blastocyst rate of parthenogenetic (70.6 +/- 0.2 vs. 51.4 +/- 0.6%) and SCNT (27.7 +/- 1.7 vs. 12.5 +/- 0.3%) embryos but not IVF embryos (25.0 +/- 14.3 vs. 20.1 +/- 12.7%). Nonetheless, PHA-treated blastocysts had higher hatching ability and contained higher cell number than control blastocysts in all the groups (P < 0.05). TUNEL labeling revealed that blastocysts cultured in the presence of PHA were less predisposed to biochemical apoptosis and showed lower indices of TUNEL, fragmentation and total apoptosis than those cultured in the absence of PHA (P < 0.05). Real time qRT-PCR analysis of parthenogenetic blastocysts revealed that PHA decreased the expression ratio of BAX:BCL-xL transcripts. Therefore, our study suggests that PHA improves the blastocyst yield and quality by enhancing blastocyst expansion, hatching and total cell number and decreasing the apoptosis. However, PHA has a differential effect on development rate of IVF derived embryos. These results may represent an approach towards achieving better preimplantation development of porcine embryos in vitro.

Enrichment of bovine X- and Y-chromosome-bearing sperm with monoclonal H-Y antibody-fluorescence-activated cell sorter

Bovine spermatozoa were assessed indirectly for the presence of a Y chromosome by monitoring expression of the H-Y antigen. Spermatozoa labeled with a monoclonal H-Y antibody (MoAb) and fluorescein-conjugated goat antibody to mouse F(ab)2 were counted with both a fluorescent microscope and a fluorescence-activated cell sorter (FACS). Of ejaculated spermatozoa, 40% to 60% fluoresced by this procedure compared to 1% to 15% of sperm reacted with nonimmune serum. Semen from three bulls was exposed to nonimmune serum (control) or MoAb, sorted by FACS, and analyzed for DNA content with a scanning microdensitometer. Control samples showed two distinct peaks with a mean difference in DNA content of 3.95%; these peaks were assumed to represent Y- and X-chromosome-bearing spermatozoa populations, respectively. DNA analyses of the MoAb-treated sperm of three bulls that sorted positively for H-Y antigen (fluorescent sperm) yielded ratios of Y- to X-chromosome-bearing spermatozoa of 76 : 24, 88 : 12, and 77 : 23, and those sorted negatively for H-Y antigen (nonfluorescent sperm) yielded ratios of 26 : 74, 35 : 65, and 23 : 77. The proportions of Y- and X-chromosome-bearing spermatozoa in nonsorted samples were not different from 50 : 50. Suitable MoAbs can be used in conjunction with FACS to enrich the proportion of Y- or X-chromosome-bearing spermatozoa in bovine semen.

Immunological sexing of mammalian semen: current status and future options

Although numerous schemes have been devised and promoted for the putative separation of X- and Y-chromosome-bearing spermatozoa, none has gained widespread acceptance. We have reexamined the possibility that Y-chromosome-bearing spermatozoa express a male-specific antigen on their plasma membrane, but that the same antigen is absent from X-chromosome-bearing spermatozoa. Immunohistochemical studies with high titer serologically detectable, male-specific antiserum revealed that serologically detectable, male-specific antigen is present on approximately 50% of spermatozoa and is located on both the postacrosomal region of the head and the midpiece of the flagellum. Similar results have also been described by other investigators working with bull spermatozoa. These data renew the question of whether the expression of serologically detectable, male-specific antigen on spermatozoa is a result of Y-chromosome-specific haploid gene expression. If so, then serologically detectable, male-specific antigen could possibly be targeted as a means of immunologically separating X- and Y-chromosome-bearing spermatozoa.

Human X- and Y-bearing sperm differ in cell surface sialic acid content

Analysis of cell surface charge of human sperm by means of free-flow electrophoresis revealed that the electrophoretic mobility of X-bearing sperm was faster than that of Y-bearing sperm, indicating that X-bearing sperm have a higher net negative charge on the cell surface than do Y-bearing sperm. Sialidase treatment of X- and Y-bearing sperm caused an obvious and progressive reduction in the electrophoretic mobilities of the two types of cells, until they finally merged into a single peak. This observation suggests that the difference in net negative charge between X- and Y-bearing sperm is due mainly to sialic acid content on the cell surface.

Is Haploid gene expression possible for sperm antigens?

The development of spermatozoon (sperm) from a spermatid involves a complex process of differentiation during which a variety of new gene products appear. It has been generally assumed that no genetic transcription occurs after meiosis and, if this were so, that all the new sperm proteins would have to to be transcribed from stored messenger RNA. However, the biochemical evidence suggests that there is no abrupt change in the rate of RNA synthesis during meiosis and that qualitative changes in RNA synthesis, to the extent that they are known, favor the likelihood of continuing messenger RNA synthesis. Experimental analyses of distorted transmission ratios of t-alleles and unbalanced chromosomal states in makes also suggest that genes are expressed in haploid nuclei after meiosis. It is probable that spermatozoa are functionally equivalent in most respects because of intercellular bridges that create a continuous cytoplasm between developing spermatozoa, facilitating an exchange of most postmeiotic gene products. Plasma membrane proteins which are potential antigens might not be shared across the intercellular bridges but the evidence to date for haploid expression of sperm antigens is poor.