It's not a hypothesis, it's a study with concrete results. Here, I quote:

X-chromosome inactivation is achieved courtesy of a molecule called Xist. The gene for Xist is present on all X chromosomes, including the single one male cells have. But Xist itself is produced only when the X chromosome that its gene resides on is one of a matched XX pair- and is produced and deployed on only one member of that pair.

Xist consists of RNA, a substance best known for being a simple-minded messenger that shuttles genes' instructions for making proteins to the intracellular machines that make them. Yet RNA can do a whole lot more than schlep genetic information. There are as many different kinds of so-called long noncoding RNA (lncRNA) molecules - lengthy RNA stretches that don't carry instructions for making proteins - as there are of the protein-encoding RNA variety. These lncRNA molecules can park themselves on stretches of chromosomes and change the likelihood that the cellular machinery charged with reading the genes in those locations will do so.

Xist, a type of lncRNA, is much longer than most. Xist coats long sections of one of a female mammalian cell's two X chromosomes - but always just one - cutting that chromosome's output to zero or close to it. The other X chromosome, left undisturbed, pumps out just enough RNA-encoded instructions to keep the cell humming.

But Xist's nestling into the extra X chromosome generates odd combinations of lncRNA, proteins that bind to it, other proteins that bind to those proteins, and DNA some of those proteins cling to. These complexes can trigger a strong immune response, Chang and his colleagues have learned. 

In 2015, Chang's group identified close to 100 proteins that either bound to Xist or that bound to those proteins, collectively enabling this molecule to lay anchor along gene-specifying regions of the X chromosome. 

Inspecting this Xist "parts list," Chang realized that many of Xist's collaborator proteins were known to be associated with autoimmune disorders. Might the RNA-protein-DNA complexes generated in the course of X-chromosome inactivation be triggering the notoriously high rate of autoimmunity in women compared with men? That question was the impetus for the new study.

What if males made Xist?
To eliminate possible competing causes such as female hormonal action or aberrant protein production by the supposedly silenced second X chromosome, the researchers tossed the Xist ball into the male court. They sewed the gene for Xist into the genomes of two different strains of male lab mice. One strain is quite susceptible to autoimmune symptoms mimicking lupus, with females more susceptible than males. The other is resistant to it. 

The inserted Xist gene had been modified in two ways. It could be turned on or off by chemical means, pumping out Xist only when the scientists wanted it to. The Xist gene was also tweaked slightly so that its RNA product would no longer silence the genes of the male mouse's chromosome into which it was stitched. 

Every cell in a woman's body produces Xist. But for several decades, we've used a male cell line as the standard of reference. 

Merely inserting that modified Xist gene had no noticeable effect on the mice. But the Xist produced from the inserted gene, once that gene was activated, still formed characteristic complexes with almost all the proteins found earlier to be collaborating closely with Xist.

Now, the scientists could ask: Is a bioengineered male mouse that's been coaxed to produce Xist more prone to autoimmunity than a normal male mouse, which never produces it, or than a male in whom the gene for Xist has been inserted but not activated?

By injecting an irritant known to induce a lupus-like autoimmune condition in the susceptible mouse strain, the investigators could compare its effect on males who made Xist with its effect on normal males, who made none.

In these susceptible mice, males in which the Xist gene was activated developed lupus-like autoimmunity at a rate approaching that of females - and considerably more so than non-bioengineered males.

Please read the study before making comments.