Do Pigs Get Autism?

What happens to a pig if it has a gene for autism?

There has been lots of research on mice who carry the same genes associated with autism in humans. Rats and recently monkeys have been studied as well. But the possibility of autistic pigs has been strangely neglected by science.

A new paper might just change that: Characterization of porcine autism susceptibility candidate 2 as a candidate gene for the number of corpora lutea in pigs. The authors found that, in female pigs, variation in a certain gene affects the function of the ovaries.

The corpus luteum is a little yellow blob (technically speaking) in the ovary. Its job is to secrete progesterone. Women's ovaries grow a new one during every menstrual cycle, and it normally breaks down and disappears before the period. However, if you get pregnant, the corpus luteum sticks around and continues producing that hormone.

Pigs, like many animals, can have more than one of these per ovary and it turns out that one of the genes controlling the number is a homolog of the human gene AUTS2. AUTS2 mutations are linked to autism (hence the name), smoking and mental retardation. The authors of this paper found several variants in this gene in domestic pig populations, and they show that it's expressed in the pig ovary.

It's quite a long leap from porcine lady bits to autism, I would say, but this actually does make sense, if you accept the Extreme Male Brain theory of autism. Boys are at least four times more likely to have autism than girls, and some say that masculinizing hormone testosterone may be the reason. This study fits with that, given that progesterone is a female hormone. Maybe mutations in AUTS2 gene alter sex hormone production?

On the other hand, it might be a coincidence. AUTS2 is strongly expressed in the brain, as well as the ovaries. Maybe it's just required for cell function, and if it's mutated, cells stop working normally: whether they be in the brain, or the corpus luteum.

Either way, it would be interesting to see whether AUTS2 affects pig behaviour... but I'm not sure what an autistic pig would look like.

Sato S, Hayashi T, & Kobayashi E (2011). Characterization of porcine autism susceptibility candidate 2 as a candidate gene for the number of corpora lutea in pigs. Animal reproduction science PMID: 21641132