Biased genes

A genome-wide analysis in mice has added complexity to scientists' understanding of gene expression in the brains of developing and adult mice. For more than 1,300 of the 20,000 genes known to be active in the mouse brain, there is significant bias as to whether the active copy is maternally or paternally inherited, researchers report.

Imprinting, a process through which chemical marks are placed on one copy of a gene, leads to the dominant expression of either the maternal or paternal copy of this gene. A team led by Catherine Dulac and Christopher Gregg of Harvard University (Cambridge, MA) decided to explore how much gene imprinting affects mouse behavior.

To evaluate this parental bias in mice, they compared the sequences of the RNA products of all the active genes they could find in the brains of embryonic mice and in two regions of adult mouse brains (Science doi:10.1126/science.1190830 and doi:10.1126/science.1190831; published online 8 July 2010). Interestingly, about 60% of the imprinted genes in the mouse embryonic brain were maternal, while 70% of the imprinted genes in the adult brain were paternal. Furthermore, 347 genes were imprinted in either adult females or males but not both. A better understanding of genomic imprinting in mice could help elucidate diseases, such as multiple sclerosis, that are linked to imprinting.

The basics of being animal

The oldest surviving multicellular animals (or metazoans)—sponges—are simple organisms. Though they lack organs and muscles, they possess valuable genetic information that explains how cells first came to cooperate and behave as a collective. Understanding the mechanisms underlying the development of multicellularity can help us to define what it really means to be an animal. As dysfunctions in these same cell development and communication mechanisms frequently give rise to cancer and autoimmune disorders, this knowledge may also lead to a better understanding of these diseases.

The genome of a sponge from the Great Barrier Reef, Amphimedon queenslandica, was recently sequenced by a team of researchers led by Daniel Rokhsar (University of California, Berkeley, and Joint Genome Institute, Walnut Creek, CA). The group identified more than 18,000 genes involved in key processes, such as cell division and growth, programmed cell death, cell adhesion, developmental signaling, immunity and cell differentiation, that characterize all animals (Nature doi:10.1038/nature09201; published online 5 August 2010). The results suggest that these hallmarks of modern animals originated much earlier than previously recognized and that their genetic underpinnings were likely present in a surprisingly complex common animal ancestor.

Guidelines ARRIVE

PLoS Biology and five other journals recently published new guidelines, called ARRIVE (Animal Research: Reporting In Vivo Experiments), aimed at improving the reporting of animal research experiments (PLoS Biol. 8, e1000412; 2010). The UK-based National Centre for the Replacement of Animals in Research (NC3Rs), in consultation with the scientific community, developed these guidelines.

In a New Scientist opinion piece about ARRIVE, Vicky Robinson, chief executive of the NC3Rs, noted that a recent NC3Rs study “found that key information was missing from many of the 300 or so publications that we analysed that described publicly funded experiments on rodents and monkeys in the UK and US.” This same study found that most of these studies did not report using randomization or blinding (PLoS One 4, e7824; 2009).

The ARRIVE guidelines, which were developed using the CONSORT Statement recommendations for reporting randomized control trials as a foundation, identify 20 items that should be included in scientific publications reporting animal research. These items include a statement of the ethical review and licenses necessary for the research; a clear statement of the study design; details of all procedures carried out, animals used, animal housing and husbandry; and a statement on the possibility of translating the results to other species, including humans.