Despite all the years of research that have gone into them, cognitive conditions like autism and schizophrenia are still largely a mystery. Here's one nice step toward figuring them out though: Researchers from UCLA have discovered a specific genetic trait in a small community in Finland that might have some clues.
There are communities in northern Finland that have been extremely isolated from the outside world for years. So many rare genes and genetic defects are more common in those populations. One in particular had a high rate of autism, schizophrenia, and other cognitive conditions. After examining data from 173 participants in that community compared to 1586 from the rest of Finland, it was found that a chromosome 22 deletion was present in 18 of the 173 compared to just one in the larger sample.
With a sample of 173 could the over representation of this deletion be an unrelated manifestation of such a small genetic pool? In other words are these just specific to the particular to the region? It's not likely actually. Chromosome 22 deletion affects the creation of an enzyme called TOP3β, which helps translate DNA into RNA. It's still up in the air exactly how this works to disrupt brain development, but there's a clear link between TOP3β and conditions like schizophrenia and fragile X.