Eutherian placenta, an organ that emerged in the course of mammalian evolution, provides essential architecture, the so-called feto-maternal interface, for fetal development by exchanging nutrition, gas and waste between fetal and maternal blood. Functional defects of the placenta cause several developmental disorders, such as intrauterine growth retardation in humans and mice. A series of new inventions and/or adaptations must have been necessary to form and maintain eutherian chorioallantoic placenta, which consists of capillary endothelial cells and a surrounding trophoblast cell layer(s). Although many placental genes have been identified, it remains unknown how the feto-maternal interface is formed and maintained during development, and how this novel design evolved. Here we demonstrate that retrotransposon-derived Rtl1 (retrotransposon-like 1), also known as Peg11 (paternally expressed 11), is essential for maintenance of the fetal capillaries, and that both its loss and its overproduction cause late-fetal and/or neonatal lethality in mice.

Nucleotides released from food sources into environmental water are supposed to act as feeding cues for many fish species. However, it remains unknown how fish can sensitively detect those nucleotides. Here we discover a novel olfactory mechanism for ATP sensing in zebrafish. Upon entering into the nostril, ATP is efficiently converted into adenosine through enzymatic reactions of two ecto-nucleotidases expressed in the olfactory epithelium. Adenosine subsequently activates a small population of olfactory sensory neurons expressing a novel adenosine receptor A2c that is unique to fishes and amphibians. The information is then transmitted to a single glomerulus in the olfactory bulb and further to four regions in higher olfactory centers. These results provide conclusive evidence for a sophisticated enzyme-linked receptor mechanism underlying detection of ATP as a food-derived attractive odorant linking to foraging behavior that is crucial and common to aquatic lower vertebrates.

Chemotopic odour representations in the olfactory bulb are transferred to multiple forebrain areas and translated into appropriate output responses. However, a comprehensive projection map of bulbar output neurons at single-axon resolution is lacking in vertebrates. Here we unravel a projectome of the zebrafish olfactory bulb through genetic single-neuron tracing and image registration. We show that five major target regions receive distinct modes of projections from olfactory bulb glomeruli. The central portion of posterior telencephalon receives non-selective, interspersed inputs from all glomeruli, whereas the ventral telencephalon is diffusely innervated by axons from particular glomerular clusters. The right habenula and posterior tuberculum (diencephalic nuclei) receive convergent inputs from restricted and all glomerular clusters, respectively. The bulbar recurrent projections are coarsely topographic. Thus, the primary chemotopic organization is transformed into distinct sensory representations in higher olfactory centres. These findings provide a framework to understand general principles as well as species-specific features in decoding of odour information.

Pheromones play vital roles for survival and reproduction in various organisms. In many fishes, prostaglandin F2α acts not only as a female reproductive hormone, facilitating ovulation and spawning, but also as a sex pheromone inducing male reproductive behaviors. Here, we unravel the molecular and neural circuit mechanisms underlying the pheromonal action of prostaglandin F2α in zebrafish. Prostaglandin F2α specifically activates two olfactory receptors with different sensitivities and expression in distinct populations of ciliated olfactory sensory neurons. Pheromone information is then transmitted to two ventromedial glomeruli in the olfactory bulb and further to four regions in higher olfactory centers. Mutant male zebrafish deficient in the high-affinity receptor exhibit loss of attractive response to prostaglandin F2α and impairment of courtship behaviors toward female fish. These findings demonstrate the functional significance and activation of selective neural circuitry for the sex pheromone prostaglandin F2α and its cognate olfactory receptor in fish reproductive behavior.

High doses of vitamin C inhibit the growth of H. pylori in vitro as well as in vivo.

Although embryonic stem (ES) cell lines derived from mice and primates are used extensively, the development of such lines from other mammals is extremely difficult because of their rapid decline in proliferation potential and pluripotency after several passages. This study describes the establishment of rabbit ES cell lines with indefinite proliferation potential. It was found that the feeder cell density determines the fate of rabbit ES cells, and that maximum proliferation potential was obtained when they were cultured on a feeder cell density of one-sixth of the density at confluency. Higher and lower densities of feeder cells induced ES cell differentiation or division arrest. Under optimized conditions, rabbit ES cells were passaged 50 times, after which they still possessed high telomerase activity. This culture system enabled efficient gene transduction and clonal expansion from single cells. During culture, rabbit ES cells exhibited flattened monolayer cell colonies, as reported for monkey and human ES cells, and expressed pluripotency markers. Embryoid bodies and teratomas formed readily in vitro and in vivo respectively. These ES cell lines can be safely cryopreserved for later use. Thus, rabbit ES cells can be added to the list of stable mammalian ES cells, enabling the rabbit to be used as a small animal model for the study of human cell transplantation therapy.

Because mouse embryonic stem cells (mESCs) do not contribute to the formation of extraembryonic placenta when they are injected into blastocysts, it is believed that mESCs do not differentiate into trophoblast whereas human embryonic stem cells (hESCs) can express trophoblast markers when exposed to bone morphogenetic protein 4 (BMP4) in vitro. To test whether mESCs have the potential to differentiate into trophoblast, we assessed the effect of BMP4 on mESCs in a defined monolayer culture condition. The expression of trophoblast-specific transcription factors such as Cdx2, Dlx3, Esx1, Gata3, Hand1, Mash2, and Plx1 was specifically upregulated in the BMP4-treated differentiated cells, and these cells expressed trophoblast markers. These results suggest that BMP4 treatment in defined culture conditions enabled mESCs to differentiate into trophoblast. This differentiation was inhibited by serum or leukemia inhibitory factor, which are generally used for mESC culture. In addition, we studied the mechanism underlying BMP4-directed mESC differentiation into trophoblast. Our results showed that BMP4 activates the Smad pathway in mESCs inducing Cdx2 expression, which plays a crucial role in trophoblast differentiation, through the binding of Smad protein to the Cdx2 genomic enhancer sequence. Our findings imply that there is a common molecular mechanism underlying hESC and mESC differentiation into trophoblast.

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