Genetics and mental illness

I recently read a Cell paper from Duan et al at JHU on the role of disc1, a particular gene, on the ways neurons grow.

DISC stands for Disrupted In SChizophrenia, and that's pretty much all that's known about the gene: it was identified by looking comparing the genome of a family with a very high incidence of the disease to the 'standard' human genome. The function of this gene was studied by treating some adult mice with an engineered virus that interfered with the normal function of the gene. Adult nerve growth was in those mice was compared to that in an untreated group.

The nerves that were studied were ordinary adult-growth nerves in the hippocampus. (Yes, new nerves are growing in our brains all the time, even as adults.) In short, reducing DISC1 caused adult neurogenesis to occur more rapidly after injury, and the new neurons conducted signals more efficiently, grew more quickly and formed more synapses with existing neurons in the brain. This suggests that in people with the genetic mutation that disrupts disc1 (who are also shown to have a higher-than-average incidence of bipolar disease and depression), a similar thing happens. As other investigators have suggested that many mental disorders are developmental in nature, which could be related to unusual nerve integration, the role of disc1 in increasing the tempo of adult nerve growth and integration may indeed be related.