User:Iamwillthinnes/Bio460Sandbox

=Tsix Practice Edits=

Tsix is a gene that functions as the antisense to the Xist gene during X chromosome inactivation. Tsix controls X chromosome inactivation by preventing the accumulation of Xist on one female X chromosome to maintain the active euchromatic state of the chosen chromosome.

Differences by species
This gene is only active in mice, although both bovine and humans have an inactive version of this gene. The deletion of a CpG island in the human Tsix gene prevents Tsix from imprinting on the X chromosomes. Instead, the human Tsix chromosome is coexpressed with the human Xist gene on the inactivated X chromosome. Random X inactivation in human cells indicates that Tsix is not an essential part of the process in humans.

Dosage Compensation
Tsix regulates X chromosome dosage compensation in female mice to prevent early embryonic mortality by a dual dose of X-linked genes. Tsix allows for equal dosage of X-linked genes for both males and females by inactivating the extra X chromosome in the females. The mutation of genes on maternal Tsix can cause over accumulation of Xist on both X chromosomes and cause early lethality of embryo as the two X chromosomes in females and the single X chromosome in male becomes inadvertently inactivated. However, if the paternal Tsix allele is active, it can rescue female embryos from the over-accumulation of Xist.

Thoughts on Tsix page improvements
We both are working together to write this section currently as we are together in person in the library. Overall edits that we have discussed include editing the page format and providing scope and additional insight into its function.

A main idea we could add is more on the scope of Tsix, and possibly include some negative phenotypes that occur when Tsix is mutated. Many of these happen to be lethal, because no X-chromosome genes are active when Xist is allowed to attack both chromosomes.

The Tsix page could be broken up into different categories, as we did above. We could also add that Tsix is the reverse of Xist, a fun fact, as Tsix functions as an antisense RNA to Xist.

We could talk about the function of an RNA gene and how it functions. We could talk about how transcription Tsix is regulated by a DXpas34 tandem repeat, as we found there is some information on in the article by Vigneau, seen on the talk page. The article states that this contributes to random inactivation in females and prevents X chromosome inactivation in males. These two ideas could go into the same header or be split up into different.

Another idea that we had would be to add information on what an X-inactivation center is, because the article does not go in depth on it.

We also added a link to Tsix on the X-inactivation page.

Active Resources
The paper DNA hypomethylation can activate Xist expression and silence X-linked genes discusses the effects of an induced mutation in DNA methyltransferase that causes hypomethylation. When this hypomethylation occurs, the Xist RNA can be affected. The study showed that at times an abnormal Xist was activated, causing inactivation of the incorrect X chromosome (in females) and the cell could have induced apoptosis as a result of this. The mutation can cause early termination of cells during development.

The article "Tsix, the gene antisense to Xist at the X-inactivation centre," discusses an RNA gene found to regulate Xist. Xist is expressed solely on the inactive gene, and is regulated by Tsix. Tsix is expressed in both X chromosomes (in females) and is turned off in one, which allows Xist to become active and inactive a chosen X-chromosome.