Sexing bovine embryos with monoclonal antibodies against the H-Y antigen

Engineering the male-specificity of Fab against SDM antigen by chain shuffling

High-titer serologically detected male (SDM) antibody fragments are essential for specific binding to the SDM antigen and promoting its application. The A8 clone previously obtained from an original phage antibody library was further affinity-matured by light- and high-chain shuffling respectively, to generate the end product B9 clone. The binding capacity of B9 phage Fabs to male splenocytes doubled the value of its parental A8 clone (determined using ELISA). Based on immunofluorescent staining, B9-Fabs mainly bound to the surface antigen of male splenocytes and recognized testicular cells. The resulting B9-Fabs detected a single protein (approximately 40 kDa determined using Western blot analysis of male splenocytes and testis); its high SDM antigen binding ability might have been because of mutation sites and varied lengths of the amino acid sequences in the complementarity determining regions-3 of the κ and Fd chains. The new recombinant clones of Fab that were phage-enhanced using chain shuffling were candidate molecules for investigating molecular mechanisms of SDM antigens specific binding and applications.

Sexing of murine and bovine embryos by developmental arrest induced by high-titer H-Y antisera

Murine and bovine embryos at the late morula stage were cultured in medium containing high-titer rat H-Y antisera. After 12h of incubation, embryos blocked at the late morulae stage were classified as males and those at the blastocyst stage were classified as females. Sexing of murine embryos by PCR and cytogenetics revealed that 83% of the embryos classified as males and 82% of those classified as females had their sex correctly predicted (P < 0.05). Bovine embryos were transferred to recipient females. Pregnancy rates were 71.4% (10/14) for embryos classified as males and 68.8% (11/16) for embryos classified as females. The sex was correctly predicted for 80% (8/10) of the embryos classified as males and for 81.8% (9/11) of those classified as females (overall accuracy, 80.9%, P < 0.05). Therefore, the induction of developmental arrest by high-titer male-specific antisera was an efficient strategy for non-invasive embryo sexing. The procedure was straightforward and has considerable commercial potential for sexing bovine embryos.

Sexing in vitro produced bovine embryos, at different stages of development, using rat H-Y antiserum

The male-specific H-Y antigen is present on mammalian cell membranes and has been identified by various methods, including antiserum cytotoxicity. The objective of the present study was to determine the sex of in vitro produced (IVP) bovine embryos, at varying stages of development, by culturing in the presence of rat monoclonal H-Y antibodies. Embryos derived from IVM/IVF were classified according to the interval after IVF (48, 96 or 120 h) as Category 1, 2 or 3 if they had 4 to 8, <32, and >32 cells, respectively. Embryos of each category were cultured for 24h in TCM-199 supplemented with bovine oviductal epithelial cells, fetal calf serum (FCS), and antibiotics (Control group), to which the following had been added: guinea pig serum (GPS; C' group); H-Y antiserum (HY group); or GPS and H-Y antiserum (C' + HY group). After culture, embryos were designated as "affected" when development was arrested or one or more blastomeres was degenerate; embryos lacking these changes were designated "unaffected." The sex of each embryo was subsequently determined by chromosome analysis. After 48h of IVF (Category 1), within each of the four treatments, the proportion of unaffected embryos was higher than the proportion of unaffected embryos (81% versus 19%, P < 0.05). Similarly, the Control, C' and HY groups of Categories 2 and 3 embryos had different proportions of unaffected versus affected embryos (75% versus 25%, P < 0.05). In all these groups, the male:female ratio did not significantly differ from 1:1. In contrast, in the C' + HY group of Categories 2 and 3 embryos, the ratio of unaffected versus affected embryos was 41% versus 59% (P < 0.05) and the male:female ratio differed (P < 0.05) from the expected 1:1 ratio (approximately 0.3:1 and 4.5:1 for unaffected versus affected, respectively). In conclusion, when bovine embryos were cultured in the presence of rat monoclonal H-Y antibodies and compliment, alterations occurred in embryos that were beyond the 8-cell stage; we inferred that the antibodies cross-reacted with H-Y antigens.

Do X and Y spermatozoa differ in proteins?

This article reviews the current knowledge about X- and Y-chromosomal gene expression during spermatogenesis and possible differences between X- and Y-chromosome-bearing spermatozoa (X and Y sperm) in relation to whether an immunological method of separation of X and Y spermatozoa might some day be feasible. Recent studies demonstrated that X- and Y-chromosome-bearing spermatids do express X- and Y-chromosomal genes that might theoretically result in protein differences between X and Y sperm. Most, if not all, of these gene products, however, are expected to be shared among X and Y spermatids via intercellular bridges. Studies on aberrant mouse strains indicate that complete sharing might not occur for all gene products. This keeps open the possibility that X and Y sperm may differ in proteins, but until now, this has not been confirmed by comparative studies between flow-cytometrically sorted X and Y sperm for H-Y antigen or other membrane proteins.

Cloning and molecular characterization of cDNA encoding a mouse male-enhanced antigen-2 (Mea-2): a putative family of the Golgi autoantigen

The male-enhanced antigen-2 (Mea-2) gene was originally identified with a monoclonal histocompatibility Y (H-Y) antibody (mAb4VII). There is no report of the full length cDNA encode for Mea-2 product until this report. In this study, we isolated the full length mouse Mea-2 cDNA by screening a testis cDNA library with a PCR-amplified Mea-2 product, and direct PCR amplification of its upstream sequences from the cDNA library. The primary structure of the Mea-2 peptide, deduced from this nucleotide sequence, shows that it encode a 150 kDa protein, of 1325 amino acid residues, which contained five putative N-glycosylation sites and four leucine zipper motifs. A data bank search indicated that it has high homology with a human Golgi autoantigen (golgin-160) both in its nucleotides (78%) and amino acids sequence (83%). This suggests that Mea-2 gene product may encode a golgi structural protein. In situ hybridization analysis suggested that the Mea-2 gene is expressed in spermatids during spermatogenesis as already shown by Mea-1, suggesting that Mea-2 gene product as well as Mea-1 have also some role for spermatogenesis.

Sex selection in mammals: A review

New methods for sperm separation and embryo sexing provide the opportunity to select the gender of the offspring of domestic mammals. We review here procedures currently available for pre- and post-fertilization sex determination, including flow cytometric selection of X- and Y-chromosome bearing spermatozoa and the application of the polymerase chain reaction to biopsied embryos. Modern techniques are considered in the context of the development of the field and parallel innovations in human medicine are briefly considered.

The production of anti-H-Y monoclonal antibodies: their potential use in a sex test for bovine embryos

In an attempt to improve the accuracy of sexing bovine embryos, new anti-H-Y monoclonal antibodies were produced and selected, using an extended screening procedure. In addition to the commonly used screening of soluble H-Y antigen sources, such as testis supernatant and Daudi supernatant, the binding specificity to cell surface H-Y antigen was tested also. A radioimmunoassay (RIA) employing male and, as a control, female bovine lymphocytes, and enzyme-linked immunosorbent assays (ELISAs) on solubilized membrane fractions resulted in the selection of a number of clones producing monoclonal antibody (mAb) with male-enhanced binding. Four of the anti-H-Y mAb were assessed for binding to Day 7 or 8 bovine embryos. The accuracy of sexing bovine embryos ranged from 58% to 71%. Two of the four antibodies did not react with presumed soluble H-Y antigen-containing sources in an ELISA. These results raise doubts about the suitability of the presumed soluble H-Y antigen sources, Daudi, TM4 and testis supernatant, to be used in screening tests for anti-H-Y antibodies.

Generation and applications of monoclonal antibodies for livestock production

Monoclonal antibodies (MCAs) have found widespread applications in livestock production. Although the generation of murine MCAs is at present a routine, the production of homologous MCAs, especially important for in vivo applications, is still hampered by the lack of efficient homologous fusion partners for immortalization of antibody producing lymphocytes of livestock species. At present, MCAs are used in immunodiagnostic tests e.g. to monitor livestock reproduction and quality of livestock products. In the future MCAs will also be used in immunosensors for real-time and on-site applications in the same areas. The commercial application of MCAs for the immunomodulation of (pharmacologically induced) physiological processes underlying important (re)production traits is at present limited to the use of anti-PMSG MCAs in PMSG-induced superovulation. However, many potentially interesting applications are under investigation (e.g. immunopotentiation of growth hormone to enhance growth; immunocytolysis of adipocytes to increase lean meat production; immunoneutralization of GnRH for immunocastration; immunoimitation of hormone activity with anti-idiotype antibodies). Attempts to use specific MCAs for the sexing of embryos have been disappointing, mainly because of the relatively low accuracy. In the future, MCAs against membrane proteins which are specific for X- or Y-chromosome bearing spermatozoa might be used for bulk separation of livestock sperm. In general, it is expected that engineered (homologous) recombinant MCAs will largely contribute to the development of a new generation of rapid immunodiagnostic tests and effective immunomodulation applications. They will further increase the use of MCAs in livestock production.

Binding of anti-H-Y monoclonal antibodies to separated X and Y chromosome-bearing porcine and bovine sperm

Studies designed to answer the question whether or not H-Y antigen is preferentially expressed on Y chromosome bearing sperm have resulted in conflicting results. This is probably due to the absence of reliable methods for estimating the percentage of X and Y chromosome bearing sperm in fractions, enriched or depleted for H-Y antigen positive sperm. In recent years a reliable method for separating X and Y chromosome bearing sperm has been published. With this method, separation is achieved by using a flow cytometer/cell sorter, which detects differences in DNA content. This technique provided the first opportunity for testing anti-H-Y antibody binding to fractions enriched for X and Y chromosome bearing sperm, directly. A total of 7 anti-H-Y monoclonal antibodies were tested using sorted porcine sperm and in one experiment also sorted bovine sperm. All monoclonal antibodies bound only a fraction of the sperm (20 to 50%). However, no difference in binding to the X and Y sperm enriched fractions was found. Therefore, the present experiments do not yield evidence that H-Y antigen is preferentially expressed in Y chromosome bearing sperm.

Embryo sex selection by a rat male-specific antibody and the cytogenetic and developmental confirmation in cattle embryos

Embryos of mouse, rabbit, goat, sheep, and cattle were separated into 2 groups on the basis of their morphology when incubated with a male-specific antibody (qualified here as the H-Y antibody) prepared from newborn rat testis. When morula-stage embryos were cultured in the presence of this H-Y antibody, the development of roughly one half of the embryos was arrested at that stage, whereas the other half continued to develop to the blastocyst stage. The developmentally arrested group of embryos resumed their development into blastocysts when cultured in antibody-free medium. Eighty to 90% of cattle embryos whose development was unaffected by the antibody were shown to possess a female karyotype (XX), and close to 80% of those embryos whose development was arrested possessed a male karyotype (XY). Cattle embryos whose sex had been presumptively identified by development in the presence of the H-Y antibody were cryopreserved and transferred, and the sex of the calves was examined. The overt sex of the young born from sexed embryos was found to be the same as that determined by chromosomal analysis.

Isolation of a phylogenetically conserved and testis-specific gene using a monoclonal antibody against the serological H-Y antigen

Several cDNA clones of a gene termed male-enhanced antigen-2 (Mea-2), have been isolated from a mouse testicular expression cDNA library using a monoclonal histocompatability Y (H-Ys) antibody which detects specific protein(s) present in the mouse testis but not the ovary. The Mea-2 gene is phylogenetically conserved among various mammalian species examined, and is expressed at high levels in adult mouse testis. The expression pattern of Mea-2 is very similar to that of another gene, the male-enhanced antigen-1 (Mea-1), previously isolated using a polyclonal H-Ys antibody. Northern blotting and RT-PCR analyses demonstrated that Mea-2 is also expressed in other adult and fetal mouse organs at low levels. The testis-enhanced expression of this gene is associated with germ cell development at mid- to late-meiotic stages of spermatogenesis. Analysis of an intersubspecies mouse backcross has assigned this gene to chromosome 5, between the loci Gus and Hnf-1.

Production and characterization of monoclonal antibodies against the H-Y antigen

Monoclonal antibodies against the H-Y antigen were produced using spleen cells from female C57BL/6 mice hyperimmunized with cells from syngeneic males. Anti-H-Y positive clones were detected by enzyme immunoassays. Supernatant fluids from Daudi cell cultures and testicular cell preparations taken from mice, rabbits or calves served as presumptive sources of H-Y antigen. In addition, testis supernatant from genetically sterile mice was used. Male specificity was ascertained by the fact that the antibodies could be absorbed with spleen cells from male but not from female mice. Binding of the antibodies to H-Y antigen on the surface of male and female cells, obtained from a number of tissues and species, was confirmed by an indirect immunofluorescence assay. Several monoclonal antibodies appeared to be positive in all assays tested, suggesting that the molecule conferring the H-Y antigenicity lacks species-specificity and appears to be identical for soluble and membrane-bound H-Y antigen.