Hot off the presses! Jun 01 Trends Genet

The Jun 01 issue of the Trends Genet is now up on Pubget (About Trends Genet): if you're at a subscribing institution, just click the link in the latest link at the home page. (Note you'll only be able to get all the PDFs in the issue if your institution subscribes to Pubget.)

Latest Articles Include:

• Editorial Board
  - Trends Genet 25(6):i (2009)
  
• Scaling laws in functional genome content across prokaryotic clades and lifestyles
  - Trends Genet 25(6):243-247 (2009)
  For high-level functional categories that are represented in almost all prokaryotic genomes, the numbers of genes in these categories scale as power-laws in the total number of genes. We present a comprehensive analysis of the variation in these scaling laws across prokaryotic clades and lifestyles. For the large majority of functional categories, including transcription regulators, the inferred scaling laws are statistically indistinguishable across clades and lifestyles, supporting the simple hypothesis that these scaling laws are universally shared by all prokaryotes.
• Evolutionary history of the Snail/Scratch superfamily
  - Trends Genet 25(6):248-252 (2009)
  The Snail transcription factors have crucial roles in metazoan development and disease. A phylogenetic analysis from placozoans to humans confirms that, along with the Scratch genes, Snail genes constitute a subgroup of the C2H2 zinc-finger transcription factors, within which neither the SNAG domain nor the number of fingers define group identities. Independent duplications in the different metazoan groups gave rise to the current complement of Snail genes, and the origin of the Snail/Scratch family can be traced back to a protosnail gene that underwent tandem duplication in the last common ancestor of Diploblasts and Bilateria.
• Do organellar genomes function as long-term redox damage sensors?
  - Trends Genet 25(6):253-261 (2009)
  A small group of proteins that form core components of electron transfer complexes are consistently encoded by organellar genomes in multicellular organisms, suggesting functional constraint. These genomes are costly to maintain and vulnerable to mutation. We propose that they provide cell lineages with sensors of long-term redox damage, and of bioenergetic and genomic competence. This proposed adaptive function sets tonic retrograde signalling to the nucleus and anterograde responses influencing protective and cell death pathways. The nature of the proposed gain-of-function signalling mechanisms is unclear but could involve defective complex assembly. Organellar proteomes therefore provide cumulative feedback on bioenergetic and genomic status within cell lineages, selection of the energetically 'fittest' cells and a means of removing cells that compromise survival of the organism.
• Understanding the neurogenetics of sleep: progress from Drosophila
  - Trends Genet 25(6):262-269 (2009)
  Most behaviors manifest themselves through interactions with environments. Sleep, however, is characterized by immobility and reduced responsiveness. Although nearly all animals sleep, the purpose of sleep remains an enduring puzzle. Drosophila melanogaster exhibits all the behavioral characteristics of mammalian sleep, enabling the use of powerful genetic approaches to dissect conserved fundamental neurogenetic aspects of sleep. Drosophila studies over the past four years have identified novel genes and pathways modulating sleep, such as Shaker and sleepless, and candidate brain regions known to function in circadian regulation and learning and memory. Advances in systems genetics coupled with the ability to target specific brain regions enable the characterization of transcriptional networks and neural circuits contributing to phenotypic variation in sleep.
• Origin and evolution of Y chromosomes: Drosophila tales
  - Trends Genet 25(6):270-277 (2009)
  Classically, Y chromosomes are thought to originate from X chromosomes through a process of degeneration and gene loss. Now, the availability of 12 Drosophila genomes provides an opportunity to study the origin and evolution of Y chromosomes in an informative phylogenetic context. Surprisingly, the majority of Drosophila Y-linked genes are recent acquisitions from autosomes and Y chromosome gene gains are more frequent than gene losses. Moreover, the Drosophila pseudoobscura Y chromosome lacks homology with the Y of most Drosophila species. Thus, the Drosophila Y has a different evolutionary history from canonical Y chromosomes (such as the mammalian Y) and it also might have a different origin.
• The different levels of genetic diversity in sex chromosomes and autosomes
  - Trends Genet 25(6):278-284 (2009)
  Sex chromosomes and autosomes differ in their effective population size, mutation and demography, all of which affect the relative level of genetic diversity within the genome. Moreover, natural selection acts differentially on the two chromosomal categories, for example, because recessive mutations are directly exposed to selection on the single X chromosome of males. Recent genome analyses reveal a heterogeneous picture of the sex-chromosome-to-autosome diversity ratio in different organisms. Reduced X chromosome diversity has been interpreted to reflect demographic features such as bottlenecks and male-biased dispersal, whereas more equal diversity in sex chromosomes and autosomes has been explained by polygynous mating systems.