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Genomics In The Journals: Apr 28, 2011

By a GenomeWeb staff reporter

NEW YORK (GenomeWeb News) – In the early, online edition of the Proceedings of the National Academy of Sciences, researchers from the US, France, and UK explain how they used microarray analyses to find genes that are differentially expressed in North American house finches that are sensitive or resistant to infections by Mycoplasma galliseptum, a bacterial species that can cause respiratory infection and conjunctivitis in some birds. Two weeks after exposing finches from Arizona and Alabama to the bug, researchers found distinct gene expression patterns in the spleens of birds from the eastern population, which have been exposed to the M. galliseptum in the wild for about 12 years, compared to birds from the western population, which have not.

"These results support the hypothesis that resistance has evolved by natural selection in the exposed populations," senior author Scott Edwards, an organismic and evolutionary biology researcher at Harvard University, and co-authors wrote. "We hypothesize that host resistance arose and spread from standing genetic variation in the eastern US and highlight that natural selection can lead to rapid phenotypic evolution in populations when acting on such variation."

Mutations in a gene called NDE1 influence the size and shape of a brain structure known as the cerebral cortex, according to two studies in the American Journal of Human Genetics. A Saudi Arabian and American research team used genome-wide linkage analysis and targeted sequencing to track down NDE1-truncating mutations in two Saudi Arabian families in which one or more children had dramatically diminished brain size, known as microcephaly, and simplified cortical features. The team did not find NDE1 mutations when they screened hundreds more individuals who were neurologically normal or who had other sorts of disorders.

Meanwhile, in another AJHG study, researchers from the US, UK, Northern Ireland, and Turkey report that they also detected NDE1 mutations in three microcephaly-affected families — two from Pakistan and one from Turkey. From their findings in these families and follow-up functional experiments, that team concluded that NDE1 is important for neurogenesis and speculated that the gene may have played a part in the evolutionary events that shaped the human brain.

In PLoS ONE, researchers from George Washington University Medical Center and the National Institute of Mental Health describe genetic variants linked to different autism spectrum disorder subtypes and symptom severity. The team did quantitative trait association analyses followed by a case-control association study involving more than 2,400 unaffected controls and nearly 1,900 individuals from four ASD sub-groups defined by different language, social, and other symptom patterns. Together, the approach yielded 18 SNPs that were associated with at least one of the four ASD subtypes, including 10 linked to more than one of the subtypes.

"The goal of our research is to identify SNPs associated with a subtype of ASD that rise above the 'noise' of the hundreds of thousands of other SNPs when compared against controls," lead author Valerie Hu, a biochemistry and molecular biology researcher at George Washington University, said in a statement, "with the hope that we can identify genetic biomarkers for these disorders as well as clues to the biology of autism."

In Neuron, an international research group led by investigators at the Max Planck Institute of Psychiatry report that variants in the neuronal transporter gene SLC6A15 contribute to depression risk. The team found the link through a genome-wide association study involving hundreds of individuals from a German clinic who had been recruited through the Munich Antidepressant Response Signature study. After verifying the association in roughly 15,000 more individuals sampled through six published studies, the researchers did gene expression, imaging, and animal model experiments hinting that decreased SLC6A15 expression in the hippocampus ups stress susceptibility and depression risk.

"Because SLC6A15 appears amenable to drug targeting, our results may incite the discovery of a novel class of antidepressant drugs," co-corresponding author Elisabeth Binder, a psychiatry researcher affiliated with Max Planck and Emory University, said in a statement.

Genomics In The Journals is a weekly feature pointing readers to select, recently published articles involving genomics and related research.

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