Time to add another disease to the list of problems associated with wayward ERV expression:
Repeat after me everyone:
ERVs are junk DNA. We WANT them to be junk DNA. Yes, very rarely an ERV is domesticated for Good, but almost universally, ERV expression is BAD.
While the main idea of this paper is neat, the experimental biology in this paper isnt very satisfying at all. There is no firm, obvious experimentally derived connection between ERV protein expression and disease, here.
For instance, the protein in question is a dUTPase, coded from a particular HERV K, in a particular region of your genome (chromosome 6). So, they looked for antibodies to that particular dUTPase in psoriasis patients, and healthy controls. Neat finding: On average, the psoriasis patients had more antibodies to this ERV dUTPase than the controls! Maybe antibodies to dUTPase are causing psoriasis!!!
Not so fast. They only looked for antibodies in 23 patients, and 16 controls. And, some psoriasis patients had the same levels of dUTPase antibodies as healthy people, and some healthy people had the same levels of dUTPase antibodies as the psoriasis patients. This is not a nice, obvious indicator.
So, they looked at cytotoxic T-cell responses to this ERV dUTPase in patients and controls. Neat finding: The psoriasis patients had CTL responses to dUTPase, while the healthy controls did not. Maybe its not antibodies, but cellular immune responses to an ERV protein that are causing psoriasis!!!
Not so fast. They only looked for CTL responses in 13 patients and 11 controls. And while 5 of the patients did have a CTL response to dUTPase, 8 didnt. Again, not a nice, obvious indicator or connection between wayward ERV expression and the disease.
The ‘answer’ to psoriasis isnt easy, and we shouldnt expect it to be, and thats not the authors fault.
What is nice about this paper is the genetics. Neat finding: After looking at the HERV K dUTPase gene in 708 patients and 349 controls, there were 14 single nucleotide polymorphisms (tiny changes) is psoriasis patients and not the controls. Five of those changes were statistically associated with psoriasis.
That is neat. Teeny tiny changes in an endogenous retrovirus are associated with psoriasis.
But the problem inherent in most research involving ERVs and diseases is still up in the air: