Jewels That May Help Explain Behavioral Disorders Found Among "Junk" DNA sciencedaily.com
The existence of smnRNAs has been known for some time. Until recently, they have been generally dismissed as unimportant. New studies are finding that they are actually quite abundant and involved in a wide variety of biological processes. As a result, some scientists are beginning to speculate that they may represent an entirely new class of gene and type of gene activity.
McInnes cited the theoretical work of John Mattick and Michael Gagen at the University of Queensland in Brisbane. Last year they published a lengthy paper in Molecular Biology and Evolution in which they argued that, rather than being useless, smnRNAs and introns – the sequences in the genome between genes that code for proteins that have been called junk DNA – form a powerful network that can turn ordinary genes on and off at the proper times.
"It appears that smnRNA may be especially relevant for understanding behavioral differences," McInnes said, "because they appear to be particularly enriched in the brain. They represent a swift and energy efficient means of regulating gene expression and may be especially important for rapid regulatory events."
Lack of expression of an smnRNA has already been strongly associated with one neuropsychiatric disorder, Prader Willi syndrome, McInnes reported. Prader-Willi syndrome is characterized by abnormally poor muscle tone and feeding difficulties in early infancy, followed by excessive eating and gradual development of morbid obesity. It is also accompanied by cognitive impairment.
In the initial trial of their new screen, the Mt. Sinai researchers identified a possible smnRNA molecule produced by an intron of the human corticotrophin-releasing hormone gene. Corticotrophin releasing hormone (CRH) plays a key role in the response of humans and other mammals to external threats. It acts at a number of sites in the nervous system to control automatic, behavioral and immunological responses of stress. Alterations in CRH neural activity appear to contribute to a number of mental illnesses including depression, anxiety disorders and anorexia nervosa. In addition, the CRH smnRNA appears to form a complimentary match with a sequence in an untranslated region associated with a receptor, called the NMDA-glutamate receptor, which is widely implicated in schizophrenia and other degenerative neurological disorders. |
