In mammals,
the presence of the Y chromosome during embryonic development decides whether
its offspring will be male or female. Although that is usually the case in
mammals, The Amami spiny rat is something extraordinary for they lack Y
chromosomes and Sry genes. The Sry gene—Sex-determining Region Y—is located on
the short branch of the Y chromosome which initiates the embryonic development of
males. In male Amami spiny rats, they only have one X chromosome, while females
have both XX.
To understand the gene expression
differences in female and male, Cheryl Rosenfeld collaborated with Asato
Kuroiwa from Hokkaido University Takamichi Jogahara of the Frontier Science
Research Center in Japan, and Scott Givan, associate director of the MU
Informatics Research Core Facility to experiment on brain activity of Amami spiny rats. They collected brain samples were collected
and RNA was sequenced to compare. Male encoded for various zinc finger protein
genes which could be what balanced the loss of SRY genes. The gonad then progressed
as testes as a way to help program the brain to be a male. The absence of zinc
finger protein led to the development of female. By turning on all the zinc
finger proteins this stimulates the differentiation in the sexes.
Animals that are not mammals have different
sex-determination than humans. I think people are so focused and interested in
learning about the SRY genes that people tend to overlook that there are other
contributing factors in the determination of sexes. By researching more on unexplained
sexes with the absences of the Y chromosome, we can fully go in depth on how
gonadal and brain sexual differentiation works for different animals.
I think this is interesting as an article I did recently discussed who other creatures like Butterflies and birds have much more complicated sexual determination processes than most mammals do. So seeing that there is also a mammal that has a much different method of determining its sex is rather fascinating, and it's also interesting to see that this rats sexing process is also very different from other creatures abnormal sex determination processes.
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