Rat Species Has No Y Chromosome!

Amami Spiny Rat

A team of researchers at Hokkaido University in Japan has figured out how a species of rat is able to survive and reproduce despite not having a Y chromosome. The rat species they studied was the Amami spiny rat (Tokudaia osimensis), a rodent native to the island of Amami Ōshima in southern Japan. The species, also called the Ryukyu spiny rat, is unique in that males do not have a Y chromosome and females only have one X chromosome as well. Previous attempts to study the rat have not been able to reveal how males are able to develop within the population with no Y chromosome. Typically in mammals, a gene on the Y chromosome called SRY tells the organism's body to express male genes like the SOX9 gene for testes. Not having the Y chromosome scientists were stumped at how males could develop. Lead researcher, Asato Kuroiwa, and her colleagues at Hokkaido have now discovered the answer! The secret was looking at the autosomes, non-sex chromosomes, in the rat. On chromosome 3 they found that one copy had a duplicated region next to the SOX9 gene. The duplication increases the activity of the SOX9 gene and it is able to code for testes. This duplicated region effectively replaces the SRY gene on the Y chromosome and explains how males of this species are formed. If a rat has the duplication region it acts as a proto-Y and the rat will be a male, and if the duplication region is absent, it acts as a proto-X and the rat will be a female. Further work to explore this is limited as the rat is an endangered species but the research so far has shown an amazing trait inherited by this rat population. The researchers predict the trait appeared about 2 million years ago when the Amami spiny rats diverged from their ancestors with a Y chromosome. Kuroiwa believes that a mixed population existed initially on the island but then a natural disaster like flooding or rising seas left mostly rats without the Y chromosome and over time the rats reproduced and evolved into a new species with this trait. 

Personally, this was my favorite article to read so far about genetics. I find it incredible that a species can exist without a Y chromosome and that another chromosome was able to replace its function to make males. This is a really interesting example of population evolution, genetic drift, and speciation. I hope that these rats can be studied more to learn about this unique and interesting trait. 

Male Mice With No Y Chromosome

A new experiment suggests that a Y chromosome is no longer to needed to make a male. Scientists have taken mice and begun to "play" around with the chromosomes, making it possible that any detection of the Y chromosome simply does not exist. Some researchers believe that later in evolution  the Y chromosome will no longer be needed, other scientists disagree and so do I. The researchers found that the male mice that were made without the Y chromosome, could not produce sperm or had immature sperm. I think that without a Y chromosome, reproduction is not an option. Experimenters used the Sox9 gene usually turned on in females, was expressed, developing the male. These were the males that did not make sperm. For mice to make sperm they must have the Eif2s3y gene, therefore, if there was no Y chromosome, this gene is not there.

I find this article weird. Why would we try to find males without the Y chromosome? There is the X and Y chromosome which determines the sex, why are we looking for more options? I understand there are chromosome mutations such as Kleinfelter's Disease (XXY), but no Y at all, makes you a female. It is really an interesting topic, but very weird. It's hard to tell what scientists are trying to get from this type of study. 

Scientists Pinpoint Molecule That Controls Stem Cell Plasticity by Boosting Gene Expression

A team of researchers from the Rockefeller University has identified a protein, Sox9, which can control stem cell plasticity by boosting gene expression in the hair follicles. Sox9 makes the genes needed by stems cell to become active and later recruit other proteins to give the genes a boost. Also, a less common, yet more powerful version, the super-enhancer was identified by scientists. Super-enhancers contain a large number of transcription factors, histones, DNA packaging proteins, and epigenetic marks. Scientists found 377 super-enhancers in the hair follicle stem cells and many of them were bound by five transcription factors, usually to Sox9.

During the research, scientists took an epicenter from the super-enhancer and linked it to a gene, which would glow green when transcription factors were present. They found that in living mice, all of the hair follicle stem cells glowed green, but did not when the cells were removed from the follicle and placed in culture. Also, scientists found that some of the stem cells glowed green during a wound-repair when culture. The scientists concluded that Sox9 was the only transcription factor expressed in culture and living tissue and it is needed to prevent the death of the stem cells.

The study shows how stem cells response to different environments (culture or repairing wounds) as it maintains plasticity. Researchers studying Sox9 can use it to further the study of male pattern baldness. It could also aid in hair growth methods people who are balding. 

Original link: http://www.newswise.com/articles/scientists-pinpoint-molecule-that-controls-stem-cell-plasticity-by-boosting-gene-expression2
Related Link: http://link.springer.com/referenceworkentry/10.1007%2F978-3-642-16483-5_5492