Press release

Press release (In Japanese only)

Many organisms including insects, amphibians and yeasts use sex pheromones for attracting individuals of the opposite sex, but what happens to sex pheromones as new species emerge? Our research group studies sex pheromones in the fission yeast Schizosaccharomyces pombe, revealing an “asymmetric” pheromone recognition system (Figure) in which one pheromone operates extremely stringently whereas the other pheromone is free to undergo a certain degree of diversification, perhaps leading to a first step towards speciation. Our findings contribute new insights into the evolutionary mechanisms underlying the diversification of pheromones. Organisms might have such systems for creating new versions of pheromones, allowing them to persist enough long in a population to evolve adaptations of receptors. Before a mutant is completely lost, a second suppressor mutation may occur to recover the first defect. Thus, the coevolution of pheromones/receptors can proceed step-by-step.

Figure: An asymmetric system of pheromone recognition in fission yeast
The specificity of M-pheromone is extremely stringent, whereas that of the P-pheromone is relatively relaxed; therefore, the diversity of the two sex pheromones might facilitate asymmetrically in nature, perhaps as a first step toward speciation in S. pombe.

Mammalian Development/ Development of genetic-engineered mouse resource To analyze the function of genes in specific stage/tissue, Cre-loxp system is widely used in mouse. Cre-loxp system requires floxed genes and Cre recombinase which excise the flanked gene. To obtain such mouse, we need to cross the mouse for several times in a classical way. Here, we developed a new method to analyze the gene function in stage/tissue specific manner using chimera mouse. We established ES cells which contained germ cell specific inducible Cre and the reporter. Using this ES cells, we generated floxed-Ddx6 which is the important gene for RNA regulation. During male germ cell development, NANOS2 dependent RNA regulation is critical. Therefore, we asked whether DDX6 is required for the NANOS2 function using this developed chimera analysis. As a result, germ cell-specific Ddx6-KO resulted in the similar phenotype to NANOS2-KO mouse. This research enabled us to conduct the stage/tissue specific gene KO quickly and demonstrated the importance of cytosolic RNP granule in male germ cell development.

This research is partly supported by Grant-in-Aid for Scientific Research on Innovative Areas ”Epigenome dynamics and regulation in germ cells” and “Platform for Advanced Genome Science” to YS. Ryuki Shimada, the first author of this paper is a SOKENDAI student.

Figure: (a) Method for chimera- mediated cKO. (b) An example of chimera. Cre recombinase is activated by Tamoxifen injection only in germ cells (GFP-positive). (c) A model how NANOS2 regulate RNA metabolism. NANOS2-complex binds target RNA and may degrade RNA in P-bodies. DDX6 is required for P-body formation.