Possible roles for products of polymorphic MHC and linked olfactory receptor genes during selection processes in reproduction.
OBJECTIVE
Polymorphic genes of the human major histocompatibility complex [MHC; human leukocyte antigen (HLA)] are probably important in determining resistance to parasites and avoidance of inbreeding. We investigated whether HLA-associated sexual selection could also involve HLA-linked olfactory receptor (OR) genes, which might not only participate in olfaction-guided mate choice, but also in selection processes within the testis.


METHODS
The testicular expression status of HLA class I molecules (by immunohistology) and HLA-linked OR genes (by transcriptional analysis) was determined.


RESULTS
Various HLA class I heavy chains, but not beta2-microglobulin (beta2m), were expressed, mainly at the spermatocyte I stage. Of 17 HLA-linked OR genes analyzed, eight were found to be transcribed in the testis. They exhibited varying numbers of 5'- or 3'-non-coding exons as well as differential splicing.


CONCLUSIONS
We suggest that testis-expressed polymorphic HLA and OR proteins are functionally connected and serve the selection of spermatozoa, enabling them to distinguish 'self from 'non-self [the sperm-receptor-selection (SRS) hypothesis].
D004848:Epithelium / Q000378:metabolism; D006801:Humans; D008285:Major Histocompatibility Complex / Q000235:genetics* / Q000502:physiology; D008297:Male; D018035:Receptors, Odorant / Q000235:genetics* / Q000378:metabolism; D012098:Reproduction / Q000235:genetics*; D012708:Sertoli Cells / Q000378:metabolism; D013094:Spermatozoa / Q000378:metabolism; D013737:Testis / Q000378:metabolism
D018035:Receptors, Odorant