Xist ribonucleoproteins promote female sex-biased autoimmunity | Hacker News Reader

Xist ribonucleoproteins promote female sex-biased autoimmunity

cell.com

31 pointsPaulHoule5 comments

Females are XX and double dosage of the X chromosome genes is fatal. One of the copies must be deactivated.

Double dosage of any chromosome in humans is typically not compatible with life or will cause severe mental and developmental dysfunction. The body and its development are fine tuned for the gene doses it receives.

In order for females to be healthy, the double X system evolved to self-deactivate the second X chromosome so a double dosage does not occur. The resulting inactive X chromosome is termed a barr body. You can also see this effect in female calico cats - the fur patterns are the result of some cells having one X active and other cells having the other one.

This paper states that the gene regulatory mechanisms that shut down the second X chromosome are the causal agent for this differential sex determined auto-immunity. Though the X deactivation mechanisms play a critical role, they can accidentally trigger the immune system to attack self.

This behavior is also a cause of tetrachromacy in females: A mutation in a color receptor gene in one X chromosome only ends up affecting roughly half of the receptors of that type.

The population of that receptor is then split between mutated and non-mutated, making the person sensitive to both the original wavelength (but less so) and a new wavelength, giving them four primaries and enhanced color separation - tetrachromacy.

Even if the mutation is broken, they retain trichomacy - just with reduced light sensitivity. This is why women color blindness is rare, while men has no such backup.

Notably, one of the few non-serious duplication types is 47,XYY

[https://medlineplus.gov/genetics/condition/47xyy-syndrome/#:....]

It tends to just make folks a little taller than they otherwise would (plus a small additional chance of ADHD/ASD).

Weird eh?

Turner syndrome happens when one of the X chromosomes is missing. The result in humans is a short female who may have some heart issues and may be sterile. At least according to the woman I know who has it.

As in men, the single X-chromosome doesn't deactivate.

I'm curious how single-X manifests in other mammals. And if Turner has autoimmune implications.

https://www.mayoclinic.org/diseases-conditions/turner-syndro...

Based on your comment, it appears to me that there may be a correlation between the number of X or Y chromosomes and an individual's height. Typically, individuals possess either XX or XY chromosomes. However, variations such as XXY (Klinefelter syndrome) or XYY syndrome do exist and are associated with increased stature. The question of whether this correlation is scientifically substantiated and the mechanisms behind these phenotypic expressions are intriguing and worth exploring further.

Reply on news.ycombinator.com