Developmental Delays Linked to Nicotine Gene?

Reported November 10, 2009

(Ivanhoe Newswire) – The loss of a gene that mediates response to nicotine is also associated with significant abnormalities in learning and behavior, and may offer a target for treatment using smoking cessation drugs.

The gene encodes a protein called an ion channel, which allows ions to flow in and out of neurons in the brain. Defects in ion channels have previously been associated with forms of epilepsy or seizure. "This gene encodes a subunit of a nicotinic receptor," Dr. Arthur L. Beaudet, chair of molecular and human genetics at Baylor College of Medicine (BCM), was quoted as saying. "It is a gene that mediates the response to nicotine via a receptor whose normal ligand is acetylcholine."

"If insufficient expression of the nicotinic receptor causes most or all of the problems associated with deletions in this particular area of chromosome 15, then it offers a target for drug treatment," Dr. Pawel Stankiewicz, assistant professor of molecular and human genetics at BCM, was quoted as saying. One such drug is Chantix, a medicine now used to help people quit smoking.

"This research goes about 95 percent of the way to pinning these problems in a specific group of individuals to this gene,” said Beaudet. The gene's role in schizophrenia has been under study for some time. Beaudet believes the deletion will be identified in other people with behavioral problems, developmental delay and epilepsy.

In this study, researchers identified 10 people from four unrelated families with the same deletion in the chromosome. Nine of the 10 subjects had developmental delay and/or mental retardation. Four of the 10 had seizure disorders or an abnormal electroencephalogram (EEG).

In two of the families, the patients had inherited the deletion from a parent. In one family, researchers found the same deletion in the patient's mother, two siblings, maternal aunt and maternal grandmother. Both the patient's mother and her sister had mental retardation and epilepsy. Both of the patient’s siblings had developmental delay. The patient had severe mental retardation and obesity and mild facial dysmorphism.

A second patient with impaired growth and severe developmental delay inherited her deletion from her mother, who had normal intelligence but had suffered from epilepsy from childhood.

SOURCE: Nature Genetics, November 8, 2009