NEUROLOGY

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Rare Gene Glitch May Hold Clues For Schizophrenia

Schizophrenia is known to have a strong genetic component – having a parent or sibling with the disorder increases one’s risk tenfold. Previous studies suggested that schizophrenia, might, in many cases, be rooted in different genetic causes in each affected individual, complicating prospects for cures. Based on an article published online in Nature (23 February 2011), the scientific world is now eyeing a rare genetic glitch for clues to improved treatments for some people with schizophrenia, even though the mutation was found in only one third of 1% of patients. In the study, schizophrenia patients were 14 times more likely than controls to have multiple copies of a gene on Chromosome 7. The mutations were in the gene for VIPR2, the receptor for vasoactive intestinal peptide (VIP) – a chemical messenger known to play a role in brain development. As schizophrenia affects about 1% of adults, discovery of the same genetic abnormality in even a small group of patients provides hope for progress in a field humbled by daunting complexity in recent years.

The VIPR2 CNV is among the first to implicate a specific gene and neurobiological pathway in schizophrenia. CNVs previously identified, spanning dozens of genes, were too large to yield such clues. In the new genome-wide scan, the mutation was found in 29 of 8,290 patients (.35%) compared to only 2 of 7431 healthy controls. A few other schizophrenia-linked CNVs seen in previous studies were also detected. VIP and its receptor are known to play a role in regulating the growth of neurons and in learning and memory. They are also expressed in the immune and cardiovascular systems and in the gut – hence its name.

When VIP binds to the VIPR2 receptor on a neuron, it triggers a key relay chemical within the cell, called cyclic AMP. The study found that both VIP and cyclic AMP were overactive in blood cells of patients with the VIPR2 mutations.

Since the mutations lead to an overexpression of VIPR2, agents that block the receptor, which already exist, might hold potential for treatment development.

According to the authors, in addition to genetic screening of patients for such personalized medicine, there may be new opportunities for neuroimaging studies. Knowing where the VIPR2 gene is expressed in the human brain may point to specific regions where VIP activity levels may differ between people who carry this mutation and those who don’t.

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