Deletions or duplications of chromosomal segment 16p11.2 — previously reported as a key autism region — are seen in people with developmental delays and speech and behavioral problems, but not necessarily autism. That’s the finding from two large studies published last week of people carrying these rare genetic variations.

Deleting MeCP2, the gene that’s mutated in Rett syndrome, alters both the size and function of neurons in the mouse brain — at least in one brain region, the locus ceruleus — according to a 30 September report in the Journal of Neuroscience.

A report in the October issue of Nature Neuroscience says the amygdala — the brain region that controls emotions, as well as the way individuals interpret and respond to social situations and recognize possible threats — governs the preference for personal space.

Genetic analysis of one Belgian family with a history of autism has pinpointed a piece of DNA on chromosome 16, within a segment thought to be missing in about one percent of all cases of autism. The unpublished data was presented on Saturday at the World Congress of Psychiatric Genetics in San Diego.

The Psychiatric GWAS Consortium has released its first batch of analyses, identifying several significant common variations associated with schizophrenia. The results were presented Sunday at the World Congress of Psychiatric Genetics in San Diego.

Scientists have identified several autism-specific variants in a gene that lies within a chromosomal region linked to the disorder, according to a poster presented at the World Congress of Psychiatric Genetics in San Diego.

Variations linked to autism and schizophrenia crop up in people with a large variety of conditions, including bipolar disorder, seizures and obsessive-compulsive disorder, as well as in healthy people. This notion gained new support from unpublished data presented at the World Congress for Psychiatric Genetics in San Diego.

A new mutation in the neuroligin-4 (NLGN4) gene, one of the few genes convincingly tied to autism, has been found in two brothers with autism, further implicating the gene in the disorder, scientists reported in the Journal of Neuroscience.

Although the head overall is bigger in some children with autism, researchers have found more informative differences in size — some smaller, some larger — across regions of the brain.

Small duplications in chromosomal region 16p11.2 increase the risk of schizophrenia about 14-fold, confirming the mutation’s importance in the disorder, according to a study published online 25 October in Nature Genetics.