Genetic Consequences of Reduced Sperm Competition in Polygynous Gorillas

Alapfogalmak

Reduced sperm competition in polygynous gorillas is associated with relaxed purifying selection on genes related to male reproductive function, leading to the accumulation of deleterious mutations and contributing to the low efficacy of gorilla spermatogenesis.

Kivonat

The study explores the genetic consequences of the polygynous social system in gorillas, which results in a dramatic reduction of sperm competition. The authors used a suite of evolutionary methods to analyze 13,310 orthologous protein-coding genes across 261 mammals and identified 578 genes that experienced relaxed purifying selection (K<1) in the gorilla lineage, compared to only 96 genes that were positively selected.
The genes under relaxed selection in gorillas have accumulated numerous deleterious amino acid substitutions, are preferentially expressed in male germ cells, and are enriched in functions related to meiosis and sperm biology. The authors used a Drosophila model system to functionally characterize 41 novel spermatogenesis genes among the gorilla relaxed genes, and found that the human orthologs of these genes are enriched for loss-of-function variants in infertile men.
These findings provide compelling evidence that the reduced sperm competition in gorillas is associated with relaxed purifying selection on genes related to male reproductive function. The accumulation of deleterious mutations in these genes likely contributes to the low efficacy of gorilla spermatogenesis and uncovers new candidate genes for human male infertility.

Statisztikák

Gorillas have relatively small testicles with few spermatogenic cells, low sperm counts, and a large proportion of morphologically abnormal and immotile sperm.
Gorillas have a small epididymis, lack of seminal vesicles, and a small prostate that appears to lack a distinct cranial lobe.
Gorilla sperm have a smaller midpiece and extremely low mitochondrial function, resulting in slow swimming speed and weak swimming force.

Idézetek

"The near absence of sperm competition in gorillas is associated with the degeneration of many male reproductive system traits associated with postcopulatory male-male and sperm competition."
"Genes under relaxed selection in gorillas have accumulated numerous deleterious amino acid substitutions, their expression is biased towards male germ cells, and are enriched in functions related to meiosis and sperm biology."
"The accumulation of deleterious mutations in these genes likely provides the mechanistic basis behind the low efficacy of gorilla spermatogenesis and uncovers new candidate genes for human male infertility."

Főbb Kivonatok

Pervasive relaxed selection on spermatogenesis genes coincident with the evolution of polygyny in gorillas

by Bowm... : www.biorxiv.org 10-27-2023

https://www.biorxiv.org/content/10.1101/2023.10.27.564379v2

Mélyebb kérdések

How do the genetic changes in gorilla spermatogenesis genes compare to other polygynous species, and what insights can this provide about the evolutionary trajectories of reproductive systems?

In gorillas, the genetic changes in spermatogenesis genes show a pattern of relaxed purifying selection, leading to the accumulation of deleterious mutations. This is in contrast to other polygynous species, where genes related to male reproductive function often experience positive selection to enhance sperm competition. The comparison highlights the unique evolutionary trajectory of gorilla reproductive systems, where reduced sperm competition has led to the erosion of male reproductive traits and the accumulation of deleterious mutations in spermatogenesis genes. This insight suggests that the mating system and level of sperm competition play a crucial role in shaping the genetic architecture of male reproductive systems across different species.

What are the potential physiological or behavioral adaptations in gorillas that may have compensated for the reduced sperm competition and the accumulation of deleterious mutations in spermatogenesis genes?

To compensate for the reduced sperm competition and the accumulation of deleterious mutations in spermatogenesis genes, gorillas may have undergone physiological and behavioral adaptations. Physiologically, gorillas may have evolved mechanisms to optimize the limited sperm production and quality, such as increasing the efficiency of sperm transport and fertilization. Behaviorally, gorillas may have developed strategies to enhance mating success and reproductive fitness, such as maintaining social structures that ensure dominant males have exclusive access to females. These adaptations could help offset the negative effects of reduced sperm competition and genetic changes in spermatogenesis genes, ultimately contributing to the reproductive success of gorillas in their polygynous social system.

Given the deep conservation of the genetic program responsible for male germ cell development, how can the insights from this study on gorilla relaxed genes be leveraged to develop new diagnostic tools or therapeutic approaches for human male infertility?

The insights from studying gorilla relaxed genes, particularly those related to male germ cell development, can provide valuable information for understanding human male infertility. By identifying genes with relaxed purifying selection in gorillas that are associated with male reproductive function, researchers can prioritize these genes as potential candidates for human male infertility studies. These genes may serve as novel targets for diagnostic tools to identify genetic causes of male infertility and as potential therapeutic targets for developing treatments to improve male reproductive health. Leveraging the deep conservation of the genetic program responsible for male germ cell development across species, including humans and gorillas, can lead to the discovery of new pathways and mechanisms involved in spermatogenesis, offering promising avenues for addressing male infertility issues.