In an advance, online publication of Science this week, two reports highlight the role of miR-33 in human cholesterol homeostasis. Katey Rayner and her colleagues at the New York University School of Medicine show that miR-33 "modulates the expression of genes involved in cellular cholesterol transport," adding that silencing miR-33 in vivo increases plasma HDL levels. "miR-33 appears to regulate HDL biogenesis in the liver and cellular cholesterol efflux," Rayner et al. conclude. Meanwhile, S. Hani Najafi-Shoushtari at the Massachusetts General Hospital Cancer Center and collaborators report that miR-33 acts alongside sterol regulatory element-binding protein host genes to control cholesterol homeostasis, and suggest that "miR-33 may represent a therapeutic target for ameliorating cardiometabolic diseases."
Also published online in advance in Science this week, a report from an international research team highlights the "genetic evidence for high-altitude adaptation" among Tibetans. In performing genome-wide scans, the team found that "positively selected haplotypes of EGLN1 and PPARA were significantly associated with the decreased hemoglobin phenotype that is unique to this highland population," adding that their analysis also "illuminates the complexity of hypoxia response pathways in humans."
In a perspectives piece this week, Rob Martienssen at Cold Spring Harbor Laboratory discusses two papers in the issue (published online in April), which highlight the mobile activity of small interfering RNA and microRNAs in Arabidopsis thaliana. While "mobile 24-nt siRNA may account for some curious properties of transposon silencing during plant development," the author suggests, "it remains to be seen if mobile small RNA will live up to that extraordinary vision."
Researchers in Australia demonstrate that partially recessive mutations act to maintain additive genetic variation in outbred populations of the weevil Callosobruchus maculatus. "Inbreeding depression was negatively genetically correlated with breeding values for traits under natural and sexual selection" in the weevil, the authors write, adding that their study reveals "the nature of good genes under sexual selection, and show how sexual selection can offset the cost of sex."
[UPDATE, Sept. 1, 2011: This paper has been retracted by its authors.]