Evolution: moles strange heterosexuality (Introduction)

by David Turell , Thursday, October 08, 2020, 19:53 (1506 days ago) @ David Turell

The females make lots of testosterone:

https://phys.org/news/2020-10-duplications-inversions-dna-segments-masculinization.html

"Moles roam in an extreme habitat. As mammals that burrow deep into the earth, they have forepaws with an extra finger and exceptionally strong muscles. What's more, female moles are intersexual while retaining their fertility. Typical for mammals, they are equipped with two X chromosomes, but they simultaneously develop functional ovarian and testicular tissues. In female moles, both tissue types are united in one organ, the ovotestis—a feature unique among mammals.

"The testicular tissue of the female mole does not produce sperm, but large amounts of the sex hormone testosterone, meaning the females have similarly high levels as the males. Presumably, this natural "doping" makes the female moles aggressive and muscular, an advantage for life underground, where they have to dig burrows and fight for resources.

***

"According to the study, it is primarily changes in the structure of the genome that lead to altered control of genetic activity. In addition to the genetic program for testicular development, this also stimulates enzymes for male hormone production in the females.

***

"'We hypothesized that in moles, there are not only changes in the genes themselves, but particularly in the regulatory regions belonging to these genes," says Mundlos.

"In the course of the moles' evolution, then not only would individual letters of the DNA have changed, also larger pieces of the genome would have shifted, says the researcher. If segments of DNA move from one location to another, completely new or reorganized regulatory domains can emerge and thus activate new genes and enhance or attenuate their expression.

***

"...when comparing the genome to that of other animals and humans, the team discovered an inversion—i.e., an inverted genomic segment—in a region known to be involved in testicular development. The inversion causes additional DNA segments to get included in the regulatory domain of the gene FGF9, which reorganizes the control and regulation of the gene. "This change is associated with the development of testicular tissue in addition to ovarian tissue in female moles," explains Dr. Francisca Martinez Real, lead author of the study and scientist at the MPIMG as well as the Institute for Medical Genetics and Human Genetics at Charité.

"The team also discovered a triplication of a genomic region responsible for the production of male sex hormones (androgens), more specifically the androgen production gene CYP17A1. "The triplication appends additional regulatory sequences to the gene—which ultimately leads to an increased production of male sex hormones in the ovotestes of female moles, especially more testosterone," says Real.

***

"'Our findings are a good example of how important the three-dimensional organization of the genome is for evolution," says Lupiáñez. "Nature makes use of the existing toolbox of developmental genes and merely rearranges them to create a characteristic such as intersexuality. In the process, other organ systems and development are not affected.'"

Comment: This shows how God might dabble a genome. We do not know how is is driven naturally.