Biology and genome of a newly discovered sibling species of Caenorhabditis elegans.

A 'sibling' species of the model organism Caenorhabditis elegans has long been sought for use in comparative analyses that would enable deep evolutionary interpretations of biological phenomena. Here, we describe the first sibling species of C. elegans, C. inopinata n. sp., isolated from fig syconia in Okinawa, Japan. We investigate the morphology, developmental processes and behaviour of C. inopinata, which differ significantly from those of C. elegans. The 123-Mb C. inopinata genome was sequenced and assembled into six nuclear chromosomes, allowing delineation of Caenorhabditis genome evolution and revealing unique characteristics, such as highly expanded transposable elements that might have contributed to the genome evolution of C. inopinata. In addition, C. inopinata exhibits massive gene losses in chemoreceptor gene families, which could be correlated with its limited habitat area. We have developed genetic and molecular techniques for C. inopinata; thus C. inopinata provides an exciting new platform for comparative evolutionary studies.

Transgenesis by microparticle bombardment for live imaging of fluorescent proteins in Pristionchus pacificus germline and early embryos.

Pristionchus pacificus is a free-living nematode used as a model organism for evolutionary developmental and ecological biology. Although a transgenic technique to form complex arrays by microinjection has been established in P. pacificus, transgene expression from the array in the germline and early embryos tends to be silenced. Here, we established a method to integrate transgenes into the genome of P. pacificus using microparticle bombardment with hygromycin B selection. Additionally, we isolated a mutant exhibiting significantly lower autofluorescence in the germline and early embryos, facilitating visualization of transgene-derived fluorescent proteins for live imaging. Transgenic lines constructed using these tools successfully expressed GFP-tagged proteins in the germline and early embryos and enabled live imaging of chromosomes, microtubules, and centrosomes.

Caenorhabditis elegans Aurora A kinase is required for the formation of spindle microtubules in female meiosis.

In many animals, female meiotic spindles are assembled in the absence of centrosomes, the major microtubule (MT)-organizing centers. How MTs are formed and organized into meiotic spindles is poorly understood. Here we report that, in Caenorhabditis elegans, Aurora A kinase/AIR-1 is required for the formation of spindle microtubules during female meiosis. When AIR-1 was depleted or its kinase activity was inhibited in C. elegans oocytes, although MTs were formed around chromosomes at germinal vesicle breakdown (GVBD), they were decreased during meiotic prometaphase and failed to form a bipolar spindle, and chromosomes were not separated into two masses. Whereas AIR-1 protein was detected on and around meiotic spindles, its kinase-active form was concentrated on chromosomes at prometaphase and on interchromosomal MTs during late anaphase and telophase. We also found that AIR-1 is involved in the assembly of short, dynamic MTs in the meiotic cytoplasm, and these short MTs were actively incorporated into meiotic spindles. Collectively our results suggest that, after GVBD, the kinase activity of AIR-1 is continuously required for the assembly and/or stabilization of female meiotic spindle MTs.

Yersinia enterocolitica serovar O:8 infection in breeding monkeys in Japan.

In the period from December 2002 to January 2003, 5 of 50 squirrel monkeys (Saimiri sciureus) housed at a Zoological Garden in the Kanto region of Japan died following a few days' history of diarrhea. After this outbreak had ended in the squirrel monkeys, 1 of 2 dark-handed gibbons (Hylobates agilis) died in April of 2003, showing similar clinical signs. We examined the organs of 3 of the dead squirrel monkeys and of the dark-handed gibbon, and Yersinia enterocolitica serovar O:8, which is the most pathogenic serovar of Y. enterocolitica, was isolated. In order to determine the source and the transmission route of infection, 98 fecal samples (45 from squirrel monkeys, 20 from other monkeys of 18 different species, and 33 from black rats captured around the monkey houses) and 7 water samples were collected in the Zoological Garden, and were examined for the prevalence of Y. enterocolitica serovar O:8. Serovar O:8 was isolated from 21 of 65 monkeys (32.3%) and 5 of 33 (15.2%) black rats (Rattus rattus). Furthermore, we examined the 30 isolates using molecular typing methods, pulsed field gel electrophoresis (PFGE), ribotyping using the RiboPrinter system, and restriction endonuclease analysis of virulence plasmid DNA (REAP), and compared the isolates in this outbreak with Japanese O:8 isolates previously identified. Genotyping showed that almost all the isolates were identical, and the genotype of the isolates was highly similar to that from wild rodents captured in Niigata Prefecture. This is the first report of fatal cases of Y. enterocolitica serovar O:8 infection in monkeys anywhere in the world.