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Studying the genetic code allows researchers to know whether some patients with neuropsychiatric disorders either have extra copies of the CHRNA7 gene or are missing copies. Pluripotent stem cell technology helps better understand neuropsychiatric disorders. Taking skin biopsies from patients with these conditions, grow the cells in culture in the lab and reprogram them to become brain cells. Using this approach, researchers gained insights into the mechanisms of disease at the neuronal level.
The CHRNA7 gene is translated into CHRNA7 proteins that form a channel on the cell membrane that allows calcium to enter the cells. By regulating calcium levels, the CHRNA7 gene plays an important role on how neurons communicate and function with each other. The researchers found that neurons with fewer copies of the gene show a reduction in calcium flux, almost half of what they see in control samples, which they expect will have functional consequences on neuronal functioning in those patients.
These results provide insights into why the patients with fewer copies of the gene share clinical characteristics with the patients with extra copies of the gene, despite having opposite underlying genetic makeup. In both cases, the result of the genetic imbalance is a decrease in calcium flux in the neurons. Clinically, while the patients with fewer copies present with moderate to severe cognitive impairment, high prevalence of autism and other neuropsychiatric problems, those with extra copies present with similar but less severe characteristics.
Opposite genetic imbalance results in similar biological effect mediated by different mechanisms. In the case of neurons with fewer copies of the gene, and therefore fewer CHRNA7 proteins to form calcium channels, the researchers proposed that the reduction in calcium flux in the cells results from having fewer calcium channels.For the neurons with extra copies of the gene, we found that having extra copies of the gene results in more CHRNA7 proteins, which overwhelms the process that assembles them together, causes cellular stress and disturbs the formation of calcium channels.
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