The Xist Gene

The Xist Gene

In our today's efficiency-oriented society one of the greatest fears of parents is the diagnosis of their offspring with a genetic disorder. It is driven by the concern of ones child not being able to fit into our society due to mental or physical developmental disabilities which are often caused by the presence of an additional chromosome in the child's genome.
Lately scientists have achieved a milestone in the research about such trisomy disorders. The idea of being able to eliminate the affects of the genetic disorder all orbits around the discovery of the so called Xist gene.
Researchers have found this gene in the investigation of the natural process of silencing one of the two x chromosomes in female mammals. The presence of this x inactivation gene in the x chromosome helps to prevent the gene expression the particular chromosome. When activated, the Xist gene covers the the chromosome like a blanket.
Now researchers are trying to adapt this method to other chromosomes and hope, one day to be able to silece additional chromosomes in humans and thereby prevent the gene expression causing developmental issues in humans affected by trisomy dissorders.

http://www.nature.com/news/researchers-turn-off-down-s-syndrome-genes-1.13406

Xist (Gene)

Chromosome disorders are diseases which occur to people due to an abnormality within the individuals chromosomes. One example of an chromosome disorder would be down syndrome, this chromosome disorder is caused when a person is born with an extra copy of the chromosome 21. Similarly to this there is a gene known as the Xist which is likely to effect a persons X chromosome changing the developmental process within females. There are teams around the world that are researching into the Xist gene seeing if they could use it in order to treat, or cure chromosome disorders such as down syndrome. The Xist gene is an RNA gene that acts in the early process of mammalian females/placental mammals development and causes a major effect on the X inactivation process.  During the development of the being the Xist gene transcriptionally silences one of the two pairs of X chromosomes, thus providing and equivalence between that particular female and other males, due to the shortage of an X chromosome. It's full name is X-inactive specific transcription. When a person has a disease such as down syndrome it means that they have copy of already existing chromosome so in order to treat it or "cure it" scientist are using the Xist gene to get ride/silence one of the two existing pairs of 21 chromosomes. Using genome editing with zinc finger nucleus's, scientist insert a large portion of the Xist gene into the locus of the chromosome 21, in down's syndrome stem cells. The Xist coats chromosomes 21 and triggers stable 'hetero-chromatin modification, supposedly silencing DNA to form a chromosome 21 barr body.' Treating the down syndrome patient.

Xist Gene

The Xist gene is used by the body to silence one X chromosome, in a pair of homologous X chromosomes. Xist is a RNA gene, which comes from the splicing of non-coding RNA (which don’t code for proteins).The Xist gene will silence an X chromosome in female mammals so that the dosage between males and females are equal. The process of gene inactivation begins at the X inactivation center, where the Xist gene is located.

Down syndrome is caused by an extra 21 chromosome in the body, also known as trisomy 21. Due to the accumulated information about the Xist gene, and its effects, scientists believe they could silence the extra chromosome with the Xist gene. An experiment performed by Jeanne Lawrence showed that the Xist gene could be used to silence the extra 21 chromosome (Chr21).

Xist Gene

Xist gene (X-inactive specific transcript) is an RNA gene, and is affiliated with the non-coding RNA class. Diseases associated with Xist gene are x-inactivation, familial skewed or craniofrontnasal dysplasia. The Xist RNA is expressed on the inactive chromosome rather than the active one. It is formed in a way resembling the mRNAs. X chromosomes without the Xist gene will not be inactivated, however duplication of it on another chromosome results in inactivation of that chromosome. 

Function:

X inactivation is developed early in mammalian females that transcriptionally silence one of the X chromosomes, which results in dosage equivalence in males and females. The process depends on multiple factors, such as the region of chromosome X which is also called the X inactivation centre (XIC). The XIC compromises sever non coding and protein-coding genes .Xis gene was the first gene to be identified with the X inactivation Centre. This gene is expressed solely from the XIC of the inactive X chromosome, and is needed for the spread of the X-inactivation. 

Xist gene and it's relation to chromosome disorders

Do you have a problem with your chromosomes and you don't know how to fix it? Do you need some things sliced and diced? Well we have the solution for you, introducing the new and improved Xist gene who can solve all of your problems!!!

What is it and how can it help

Xist stands for X inactive specific transcript, this gene is found in the early developmental process of mammalian females. The genes job is to slice one of the pairs of X chromosomes. Scientists believe that they can use this gene to fix the chromosome disorders, for example down syndrome. When the Xist gene is activated a RNA molecule is produced and it coats the surface of the chromosome and it blocks other genes form being expressed. 

The Xist gene slicing for down syndrome.

Scientists have found a way to slice chromosome 21 when down syndrome is present.

Xist (gene) - Yoonsik Park

XIST (X-Inactive Specific Transcript)

Yoonsik Park

What is it?

X inactivation occurs in the early developmental stage of female mammals where one of the two X chromosomes are silenced during transcription. The Xist gene is the RNA responsible for this, according to http://www.ncbi.nlm.nih.gov/gene/7503. This process can be seen in the picture below.

http://mmg-233-2014-genetics-genomics.wikia.com/wiki/File:Expression-of-Xist.jpg

What is significant about this is the possibility to use it to shut down extra chromosomes that cause chromosomal disorders such as Trisomy-21 and Trisomy-18.

https://mydoctor.kaiserpermanente.org/ncal/Images/trisomy18_tcm63-951309.png

For example, Trisomy-21, or better known as Down Syndrome, is caused from an extra chromosome 21, causing other abnormal gene expressions. People with Down Syndrome will have abnormal physical characteristics such as short neck and short height and there is a high chance that they will have problems with learning.

http://www.nature.com/news/researchers-turn-off-down-s-syndrome-genes-1.13406
http://phenomena.nationalgeographic.com/2013/07/17/how-to-shut-down-the-extra-chromosome-in-downs-syndrome/

XIST

While treatment for genetic disorders seems improbable, as the therapy would have to affect each cell in the patient's body, there has been promising development in this field, as scientists have found a gene that could potentially remove, that is silence, extra chromosomes that arise in genetic disorders such as Down's Syndrome. 

This gene is called XIST, short for X-inactive specific transcript, and it is found on the X chromosomes of all female placental mammals. Because females have two X chromosomes, while males have only one, the greater amount of material produced by the two X chromosomes could be dangerous, so one of the X chromosomes is silenced, that is the chromosome is coated in heterochromatin, a substance which is created by the XIST gene, and does not allow most of the chromosome to undergo gene expression. 

Scientist are looking into using the gene to silence other chromosomes. The gene could potentially be used to treat patients with disorders with extra chromosomes. Researchers have successfully silenced an extra chromosome 21 in an artificially grown Down's syndrome cell.

There is much work to be done before this treatment can actually be used to help people, and there is much debate on whether it would work, because there is a chance that the gene would silence other chromosomes instead of the one that was targeted.

http://phenomena.nationalgeographic.com/2013/07/17/how-to-shut-down-the-extra-chromosome-in-downs-syndrome/

Xist gene

Xist gene and how it relates to chromosomal disorders?

Xist gene- X inactive specific transcript 

Xist is an RNA gene on the X chromosome of the placental mammals that acts as a major effector of the X inactivation process. It is a component of the Xic - X-chromosome inactivation centre - along with two other RNA genes (Jpx and Ftx) and two protein genes (Tsx andCnbp2). The Xist RNA, a large transcript, is on the inactive chromosome and not on the active one. However, it remains untranslated. It has been suggested that this RNA gene evolved at from a protein coding gene that became a pseudogene.

Some new studies have shown that it may help into chromosomal disorder treatment. 

XIST Gene

New studies all over the world have brought to light a newly discovered gene called the Xist gene. This gene is thought to be able to aid in the treatment of chromosomal disorder like trisomy 21; down syndrome. It would aid in the treatment as so far research has showed that the xist gene is able to silence a chromosome. With the help of this newfound ''cure'' researchers would be able to identify reasons behind chromosomal disorder and then develop treatments and ways of prevention.

What is the XIST gene?
The xist gene is an RNA gene found on one of the two X chromosomes in all mammalian females. During a female's development one of the two X chromosomes inside her is silenced by something called a heterochromatin formation; which is a tightly packed form of DNA. This is done in order to make sure that a process called X inactivation occurs. X inactivation is the process in which the heterochromatin formation ensures that equal levels of the X-linked gene are expressed in both,  XX females and XY males.

The Xist Gene and Down Syndrome

New studies have shown that the Xist gene could be used to treat chromosome disorders such as Down Syndrome by silencing a chromosome. The method could help researchers to identify the cellular pathways behind the disorder's symptoms, and to design targeted treatments.

What is the Xist gene?

Figure 1- The expression of the Xist gene on one of the X
chromosomes leads to the recruitment of protein to that
chromosome that are required to inactivate the chromosome. 

Xist, which stands for X-inactive specific transcript, is an RNA gene on the X chromosome in placental mammals which affects the X inactivation process. According to NCBI Gene, X inactivation is an early developmental process in mammalian females that transcriptionally silences one of the pair of X chromosomes. As seen in Figure 1, this is because when the Xist gene is activated, it produces an RNA molecule that coats the surface of a chromosome like a blanket, which blocks other genes from being expressed (Beth Mole, nature.com).

Xist gene and Down Syndrome

Figure 2- The Xist gene can be used to
treat Down Syndrome as it
silences the extra copy of
chromosome 21

According to a study conducted by Jiang et al, the Xist gene can be used to silence one of the two X chromosomes carried by all females mammals, which is beneficial for chromosome disorders such as Down Syndrome as it can silence the extra copy of chromosome 21.











Bibliography:

Mole, Beth. Nature.com. Nature Publishing Group, n.d. Web. 12 May 2016.

http://www.nature.com/news/researchers-turn-off-down-s-syndrome-genes-1.13406

"XIST." Genetics Home Reference. N.p., n.d. Web. 12 May 2016.

https://ghr.nlm.nih.gov/gene/XIST#location