Medical scientists from Columbia University, Cold Spring Harbor Laboratory and the University of British Columbia discovered the new alteration in the production of microRNAs in mice bred to have the same chromosome deletions found in some humans with schizophrenia. MicroRNAs are molecules that regulate the expression of genes.

Individuals with those deletions "are at high risk of developing schizophrenia," said Dr. Maria Karayiorgou of Columbia, one of the study's authors. "By digging further into this chromosome, we have been able to see at the gene expression level that abnormalities in microRNAs can be linked to the behavioral and cognitive deficits associated with the disease," she added.

The investigators produced a mouse deficient for just one of the affected genes and observed its performance on a variety of cognitive, behavioral and neuroanatomical tests. They observed the same deficits often observed in people with schizophrenia.

The investigators say their findings bring them a step closer to understanding the biological mechanisms of schizophrenia.

The study appears in the journal Nature Genetics.