BioEssays

Invertebrate models of spinal muscular atrophy (SMA). On pages 956-965 Stuart Grice et al. highlight insights made into SMA using Drosophila melanogaster and Caenorhabditis elegans. With their tractable nervous systems, genetic amenability, and large reproductive capacities, the invertebrate models have provided a valuable contribution to understanding the cellular function of the survival motor neuron (SMN) protein, to unravelling the underlying genetic pathways pertinent to SMA, and to identifying potential therapeutics. The cover image shows a Drosophila larval brain lobe stained for SMN (green) with enrichments in the post embryonic neuroblasts (red; top left), a Drosophila larva expressing red fl uorescent protein in the nervous system (middle), and an adult C. elegans smn-1 point mutant expressing green fl uorescent protein within the nervous system (bottom right).

Cover by S. J. Grice and J. N. Sleigh

The Hox gene fushi tarazu (ftz) functions as a pair-rule segmentation gene in Drosophila. In contrast, Ftz protein from a beetle (Tc-Ftz) retains homeotic potential, indicated by its ability to transform antenna (upper left) to leg (lower right) and to repress Homothorax expression (red) when expressed in Drosophila, observed as loss of overlap between GFP, which marks Tc-Ftz expression, and Homothorax expression (upper right). Heffer et al. review the evidence that ftz evolved from a traditional Hox gene with homeotic potential to a gene with exclusive pair-rule segmentation function in Drosophila. The authors correlate Ftz functional evolution with the presence and absence of distinct co-factor interaction domains, necessary for either homeotic or segmentation function.

Backcover by A. Heffer, U. Löhr and L. Pick

The Ftz protein sequence changed over evolution, changing its function from homeotic to segmentation.

Studying the mixed mode of reproduction (sexual/asexual) in social insects such as ants and termites may provide insights into many basic evolutionary questions including the maintenance of sex, the expression of sexual conflict and kin conflict, and the evolution of cheating in asexual lineages.

In many species the mutation rate is higher in males that in females. The availability of whole genome sequences allows us to study factors — both sequence-specific and those acting on the genome globally — that affect these differences in mutation rates between males and females.

Drosophila melanogaster and Caenorhabditis elegans can be used as convenient model organisms to study the cellular and molecular mechanisms underlying the function of the SMN gene.