International Mammalian Genome Society

The 14th International Mouse Genome Conference (2000)

B19. Some Spermatogenic Proteins are Serologically Detectable Male Antigens (SDM) as Revealed by Male-Enhanced Antigen-1 (Mea1) and -2 (Mea2) Identified with Polyclonal and Monoclonal Anti-H-Y Antibodies, Respectively

Shizuyo Sutou1, Shoichi Matsukuma2, Masaaki Kondo3, Yasuhide Ohinata1, and Youji Mitsui1
1National Institute of Bioscience and Human-Technology, 1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan;
Kanagawa Cancer Center Research Institute, Nakao 1-1-2, Asahi-ku, Tokohama, 241-0815, Japan;
Central Research Institute, Itoham Foods Inc., 1-2 Kubogaoka, Moriya, Kitasoma, Ibaraki 302-0104, Japan

Of four combinations of skin grafts between genotypically identical males and females, only grafts from males to females were rejected (Eichwald and Silmser, 1955), suggesting the existence of at least one male-specific transplantation antigen, the H-Y antigen (H-Y). After H-Y was proposed as the sex-determining factor (Tdy, testis-determining gene on Y) in 1975 (Wachtel et al.) mainly on the basis of a finding that only heterogamates presented serological H-Y on the cell surface, a wide variety of research into H-Y was conducted. Scrutinizing accumulated, controversial data on H-Y, Silvers and Gasser (1982) put forward an idea that serologically detectable male antigens (SDM) must be different from H-Y detected by cytotoxicity or skin-graft tests. The H-Y gene assigned to the Y chromosome was not Tdy (McLaren et al., 1984), which was later identified as Sry (sex-determining region Y, Gubbay et al., 1990). What are then H-Y and SDM?

Elusive H-Y was identified as Smcy (selected mouse cDNA on Y, Scott et al., 1995) 40 years after its discovery. Smcy encodes two H-Y peptide epitopes H-YKk and H-YDk that are presented on the cell surface with the H-2Kk and H-2Dk major histocompatibility complex (MHC) molecules, respectively. Another epitope H-YDb is encoded by Uty (ubiquitously transcribed tetratricopeptide repeat gene on the Y chromosome, Greenfield et al., 1996). Thus, H-Y is the product of more than one gene on the Y chromosome.

Lau et al. (1989) identified male-enhanced antigen-1 (Mea1) by screening an expression cDNA library of the mouse testis with polyclonal anti-H-Y antibody. Su et al. (1992) also indicated the existence of male-enhanced antigen-2 (Mea2) using monoclonal anti-H-Y antibody. We cloned mouse and bovine cDNA and genomic DNA of Mea1/MEA1 (Kondo et al., 1996). Mea1/MEA1 consisted of three exons with multiple transcription initiation sites and encoded 174 aa.Mea1 is transcribed mainly in spermatocytes and translated in spermatids. Mea1 is located on the chromosome 17 in mice. We also cloned 4.5 kb cDNA of mouse Mea2 (Kondo et al., 1997). A transgenic mouse strain T604 had a reciprocal translocation between chromosome 5 and 19. Male homozygotes were deficient in spermatogenesis, while female homozygotes seemed normal. Comparison of cDNA and genomic DNA indicated that Mea2, which consists of 23 exons, encodes 1448 aa and is located on the chromosome 5, was the exact translocation breakage site in T604 mice (Matsukuma et al., 1999). The Mea2 gene product (Golgin-160) is a member of the Golgi apparatus and located mainly in the Golgi of spermatocytes. Truncated Mea2 made up of exons 8-23 produced morphologically abnormal sperm.

Mea1 and Mea2 are quite different genes. These were cloned using anti-H-Y antibodies and therefore comprise SDM. Both are autosomal genes and involved in spermatogenesis. SDM is expressed on the surface of sperm. Apoptosis occurs frequently in the testis; some fragments of spermatogenic proteins may not be antigenic to males, but be to females. We propose here that SDM consists of several or more antigens and spermatogenic proteins are the main source of SDM.

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