Partner selection ultimately happens in the woman's reproductive tract


Date:
August 19, 2020
Source:
University of Eastern Finland
Summary:
The female reproductive tract has the final say in human mate
choice, according to new research.



FULL STORY ==========================================================================
The female reproductive tract has the final say in human mate choice,
according to new research from the University of Eastern Finland.


========================================================================== Achieving pregnancy has been shown to be more likely between
partners who carry dissimilar human leucocyte antigen (HLA) immune
genes. Accordingly, humans are expected to choose HLA dissimilar
reproductive partners. Earlier studies have demonstrated that HLA
dissimilarity preferences are mediated either by body odours or
facial preferences. However, it has been unclear whether HLA-based
mating preferences could occur after sexual intercourse in the female reproductive tract. Researchers at the University of Eastern Finland have
now shown that the women's reproductive tract is capable of mediating post-mating sexual selection (known as the "cryptic female choice")
towards the sperm of HLA dissimilar men. This indicates that the ultimate mating bias towards genetically compatible partners occurs only after
mating, at the gamete level.

The researchers conducted two experiments, where they activated sperm
from multiple men with follicular fluid (the oocyte surrounding bioactive liquid) or cervical mucus from several different women. Then they examined sperm motility and other functionally important physiological changes
of sperm in all possible male-female combinations. All the participants
were also genotyped for their Human Leucocyte Antigen (HLA) class I and
II alleles.

In both studies, the results showed that the fertilisation capability
and viability of sperm are strongly dependent on the male-female
combination. In other words, women's reproductive secretions had a
stronger effect on the sperm performance of some males than others. Both datasets also showed that the sperm performance was better in HLA
dissimilar male-female combinations than in HLA similar males and females.

Together, the results indicate that the fertilisation capability of sperm
is dependent on the immunogenetic compatibility of the reproductive
partners and that the fusion of the gametes may be a highly selective
process.

"These findings can have important implications for a deeper understanding
of sexual selection and the fertilisation process in humans and other
mammals," Associate Professor Jukka Keka"la"inen from the University of
Eastern Finland says.

"Since the gametes of some partners may be immunologically more compatible
than others, our results may also open up novel possibilities for
the development of more accurate infertility diagnostics," Annalaura
Jokiniemi, MSc, adds.


========================================================================== Story Source: Materials provided by University_of_Eastern_Finland. Note: Content may be edited for style and length.


========================================================================== Journal References:
1. Annalaura Jokiniemi, Martina Magris, Jarmo Ritari, Liisa Kuusipalo,
Tuulia Lundgren, Jukka Partanen, Jukka Keka"la"inen. Post-copulatory
genetic matchmaking: HLA-dependent effects of cervical mucus on
human sperm function. Proceedings of the Royal Society B: Biological
Sciences, 2020; 287 (1933): 20201682 DOI: 10.1098/rspb.2020.1682
2. Annalaura Jokiniemi, Liisa Kuusipalo, Jarmo Ritari, Satu Koskela,
Jukka
Partanen, Jukka Keka"la"inen. Gamete-level immunogenetic
incompatibility in humans-towards deeper understanding
of fertilization and infertility? Heredity, 2020; DOI:
10.1038/s41437-020-0350-8 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200819094748.htm

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