An international team led by investigators at the Scripps Research Institute this week shows that the human-specific gene duplications SRGAP2B and SRGAP2C are both partial, and that both encode a truncated F-BAR domain. "Expression of SRGAP2C phenocopies SRGAP2 deficiency," the authors write in a paper published online in advance in Cell this week. "It underlies sustained radial migration and leads to the emergence of human-specific features, including neoteny during spine maturation and increased density of longer spines."
In a separate but related study published online in advance this week, the University of Washington School of Medicine's Evan Eichler and his colleagues show that SRGAP2 duplicated three times in the human lineage approximately 1 million to 3.4 million years ago. Eichler et al. report having identified these human-specific duplications by leveraging "a haploid hydatidiform mole to identify highly identical sequences missing from the reference genome." Daily Scan has more on this study here.
In Cell Reports this week, researchers at Tel-Aviv University in Israel show that differential exon-intron GC content regulates exon inclusion level in a group of homeothermic genomes that has "retained the overall low GC content as well as the differential exon-intron GC content, and is associated with longer introns," and in which disease-associated mutations often lead to exon-skipping. "Our results reveal that differential exon-intron GC content is a previously unidentified determinant of exon selection and argue that the two GC content architectures reflect the two mechanisms by which splicing signals are recognized: exon definition and intron definition," the Tel-Aviv team writes.
And over in Developmental Cell, the Technion Israel Institute of Technology's Itai Yanai and his colleagues report that "embryonic development in five Caenorhabditis species proceeds through two distinct milestones, in which the transcriptome is resistant to differences in species-specific developmental timings." Comparing the complete protein-coding transcriptomes of individually timed embryos across ten morphological markers, Yanai et al. found that these milestones "can be characterized by their expression dynamics and activation of key developmental regulators."