An international team led by investigators at the Salk Institute for Biological Studies in La Jolla, Calif., shows that Imp — IGF-II messenger RNA binding protein — counteracts endogenous small interfering RNAs to stabilize self-renewal factor upd RNA in Drosophila testis. "However, similar to upd, Imp expression decreases in the hub cells of older males, which is due to the targeting of Imp by the heterochronic microRNA let-7," the team writes. "In the absence of Imp, upd mRNA therefore becomes unprotected and susceptible to degradation." Overall, the authors suggest that their study deepens understanding of "the mechanistic basis for aging-related changes in stem-cell behavior," as they write in Nature this week.
In another paper published online in advance this week, researchers in Italy and Germany show in humans, mice, and zebrafish "that Dicer and Drosha, but not downstream elements of the RNAi pathway, are necessary to activate the DDR [DNA damage response] upon exogenous DNA damage and oncogene-induced genotoxic stress." Further, the researchers show that DNA damage response is sensitive to RNase A treatment, such that "Dicer- and Drosha-dependent RNA products are required to restore DDR foci in RNase-A-treated cells."
Extremely low-coverage sequencing — from 0.1 to 0.5x — "captures almost as much of the common and low-frequency variation across the genome as SNP arrays," reports an international team led by researchers at Harvard School of Public Health in Nature Genetics. Using both simulated and real exome-sequencing datasets, the team shows "that association statistics obtained using extremely low-coverage sequencing data attain similar P values at known associated variants as data from genotyping arrays, without an excess of false positives."
Elsewhere in Nature Genetics, investigators at the University of California, Los Angeles, present spatial ancestry analysis — a model-based approach to depict the spatial distribution of human SNPs "by assigning an allele frequency as a continuous function in geographic space." Lead author Wen-Yun Yang and colleagues say that their method allows for the modeling of genotypes in 2D or 3D space.