The body's tendency to silence the expression of one parental allele in favor of the other -- a practice known as genomic imprinting -- is much more widespread than scientists have believed, according to a new genome-wide study in mice, published online this week in Science.
The study found that the number of genes in mouse brains with a bias toward either the maternal or paternal allele is thirteen times higher than previously thought.
"Overall, the results tell us that imprinting is a major mode of epigenetic regulation," said study author Catherine Dulac at Harvard University. In addition, she and her colleagues argue that understanding imprinting in the brain may shed light on sex-specific brain diseases.
Genomic imprinting is a type of epigenetic regulation, in which chemical reactions cause changes in gene expression without altering the underlying DNA. Over the last ten years, many researchers have tried brute-force methods like microarrays to determine the number of imprinted genes, said Michael O'Neill, a molecular biologist at the University of Connecticut who was not involved in the research. "This is the best, most comprehensive study I've seen thus far," he said. "They can see very subtle parental biases, which you can't typically see with other methods."
Prior to this study, only around 100 imprinted genes had been identified -- most either stumbled over or found on a case-by-case basis. Of those 100 genes, the majority are involved in embryonic development, but the second most frequent phenotype is brain function.
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