<Emphasis Type="Italic">Coprinus cinereus</Emphasis> Mer3 is required for synaptonemal complex formation during meiosis

Mer3 is an evolutionarily conserved DNA helicase that has crucial roles in meiotic recombination and crossover formation. We have identified the MER3 homolog in Coprinus cinereus (Ccmer3) and show that it is expressed in zygotene and pachytene meiocytes. Immunostaining analysis indicated that CcMer3 was localized on chromosomes at zygotene and pachytene and CcMer3 foci were more frequent on paired than unpaired chromosomes. We generated a C. cinereus mer3 mutant (#1) and found that it showed abnormal meiosis progression and underwent apoptosis after prophase I. Basidiospore production in #1 was reduced to 0.8% of the wild-type level; the spores showed slower germination at 25°C but were similar to the wild type at 37°C. Electron microscopic analysis of chromosome spreads revealed that axial elements were formed in the mutant but that synapsis was defective, resulting in a reduction in spore production. Our results demonstrate that CcMer3 is required for synaptonemal complex formation after axial elements align and is thus essential for homologous synapsis.     

Fatigue-induced changes in synergistic muscle force do not match tendon elongation

This study aimed to investigate whether fatigue-induced changes in synergistic muscle forces match their tendon elongation. The medial gastrocnemius muscle (MG) was fatigued by repeated electrical stimulation (1 min×5 times: interval 30 s, intensity: 20–30% of maximal voluntary plantar flexion torque) applied at the muscle belly under a partial occlusion of blood vessels. Before and after the MG fatigue task, ramp isometric contractions were performed voluntarily, during which tendon elongations were determined by ultrasonography, along with recordings of the surface EMG activities of MG, the soleus (SOL) and the lateral gastrocnemius (LG) muscles. The tendon elongation of MG and SOL in post-fatigue ramp was similar, although evoked MG forces dropped nearly to zero. In addition, for a given torque output, the tendon elongation of SOL significantly decreased while that of LG did not, although the activation levels of both muscles had increased. Results suggest that the fatigue-induced changes in force of the triceps surae muscles do not match their tendon elongation. These results imply that the tendons of the triceps surae muscles are mechanically coupled even after selective fatigue of a single muscle.     

New filarial nematode from Japanese serows (Naemorhedus crispus: Bovidae) close to parasites from elephants

A new onchocercid species, Loxodontofilaria caprini n. sp. (Filarioidea: Nematoda), found in subcutaneous tissues of 37 (33%) of 112 serows (Noemorhedus crispus) examined in Japan, is described. The female worm had the characteristics of Loxodontofilaria, e.g., the large body size, well-developed esophagus with a shallow buccal cavity, and the long tail with three caudal lappets. The male worm of the new species, which was first described in the genus, had unequal length of spicules, 10 pairs of pre- and post-caudal papillae, and three terminal caudal lappets. Deirids were present in both sexes. Among four species of the genus loxodontofiloria: one from the hippopotamus and three from the Elepantidae, L. caprini n. sp. appears close to L. asiatica Bain, Baker & Chabaud, 1982, a subcutaneous parasite of Elephas indicus in Myanmar (Burma). However, L. caprini n. sp. is distinct from L. asiatica in that the Japanese female worm has an esophagus half as long and the microfilariae also half as long with a coiled posterior. The microfilariae were found in the skin of serows. The new parasite appears to clearly illustrate a major event in the evolution of onchocercids: the host-switching. This might have occurred on the Eurasian continent, where elephantids and the lineage of rupicaprines diversified during the Pliocene-Pleistocene, or in Japan, into which some of these hosts migrated.     

Genetic relatedness among species in Aspergillus section Clavati as measured by electrophoretic comparison of enzymes,DNA base composition,and DNA-DNA hybridization

Aspergillus subgenus Clavati has four recognized species: A. clavatus (the type species), A. clavatonanicus, A. giganteus, and A. longivesica. These species are strictly anamorphic (mitotic) and defined by the morphological species concept. However, their genealogical relationships remain uncertain. In this study, we examined the genetic relatedness among the four species in this section, using electrophoretic comparison of enzymes, DNA base composition, and DNA-DNA hybridization. In a dendrogram based on the calculated similarity values of four enzymes, 10 strains in section Clavati, 3 strains in the xerophilic species, a strain in section Ornati, and a strain in section Cremei were separated into nine major clusters at a 60% similarity level. A. longivesica JCM 10186(T) had Q-10 in our analysis, but Kuraishi et al. (1990) reported A. longivesica JCM 1720(T) had Q-9 (49%) and Q-10 (46%). The G+C contents of the four species of section Clavati ranged from 48 to 50 mol%. The degree of the intraspecific reassociation among the DNAs from the strains of these species ranged from 77 to 99%, whereas the degrees of interspecific relative binding among strains of the four species ranged from 30 to 59%. Our data from enzyme patterns and DNA relatedness support the validity of the three species in section Clavati, except for A. longivesica.     

Induction of hydroxyapatite resorptive activity in bone marrow cell populations resistant to bafilomycin A1 by a factor with restricted expression to bone and brain, neurochondrin

Bone, one of the favored sites for tumor metastasis, is a dynamic organ undergoing formation and resorption. We found bone metastasis with osteolytic lesion in the bone marrow of the femur by injecting BW5147 T-lymphoma cells into the tail vein of AKR mice. To understand this bone destruction, we constructed a cDNA library from BW5147 with a cloning vector that allowed in vitro synthesis of mRNAs, and then identified a particular cDNA clone by adding the conditioned medium from Xenopus oocytes following injection of the mRNA synthesized in vitro to primary bone marrow heterogeneous cell populations on hydroxyapatite thin films. By means of this method, we isolated a factor with 16% leucine residues, termed neurochondrin, that induces hydroxyapatite resorptive activity in bone marrow cells resistant to bafilomycin A1, an inhibitor of macrophage- and osteoclast-mediated resorption. Expression of the gene was localized to chondrocyte, osteoblast, and osteocyte in the bone and to the hippocampus and Purkinje cell layer of cerebellum in the brain. This may provide insights into the molecular mechanisms underlying bone resorption with potential implications for the activation of cells other than macrophages and osteoclasts in bone marrow cells.     

Genome structure and differential expression of two isoforms of a novel PDZ-containing myosin (MysPDZ) (Myo18A)

We previously cloned a gene for a novel myosin (called MysPDZ) containing a PDZ-domain from bone marrow stromal cells. This new myosin is found in humans and classified as one of the class XVIII myosins (Myo18A). Here, we report the hematopoietic cell-specific splicing isoform (MysPDZbeta) in addition to the previously reported isoform (MysPDZalpha). Combined with mouse genome sequence data, the overall genome structure and generation of the two spliced isoforms are deduced. The MysPDZbeta protein lacks a PDZ-domain in the N-terminal region. Studies of the subcellular localization of the two spliced isoforms indicated that MysPDZalpha containing the PDZ domain co-localizes with the ER-Golgi complex, while MysPDZbeta, which lacks the PDZ domain, localizes diffusely in the cytoplasm. These results suggest that the isoforms differ in their subcellular localization and may have different functions in membrane ruffling and membrane traffic pathways. The PDZ-containing spliced isoform (MysPDZalpha) is not expressed in bone marrow hematopoietic cells, whereas MysPDZbeta lacking the PDZ is specifically expressed in most hematopoietic cells. It is noted that neither isoform is expressed in red blood cells. Interestingly, MysPDZalpha was detected in mature but not in immature macrophages, and its level increased after the induction of differentiation of M1 cells, suggesting a functional role of PDZ-containing myosin in macrophages.     

Gene expression profiling during thymus ontogeny and its association with TCRVβ8.1-Dβ2.1 rearrangements of inbred mouse strains

The V(D)J recombination of TCR and in early developing T-cells is a highly modulated phenomenon initiated and completed by recombinase complex (RAG-1 and RAG-2), and regulated by other gene products such as interleukins. To further evaluate the association of several other gene products with the evolution of TCRV8.1 V(D)J rearrangements in vivo, the mRNA expression levels of seven interleukins, three cytokines, receptors TCRV8.1 and IL-2R, MHC-I/MHC-II, RAG-1/RAG-2 and retroviral superantigen MMTV(SW) were measured by RT-PCR during the fetal development of the thymus of three inbred mouse strains (Balb-c, C57Bl/6 and CBA/J). Clustering using the Tree View software, was used to organize these genes based on similarity of expression patterns. Each strain displayed a different expression profile during thymus ontogeny.During the late developmental stage the most evident association was the kinetics of MMTV(SW) retrovirus, IL-2R and IL-7 overexpression with reduction of TCRV8.1-D2.1 rearrangement in the thymus of CBA/J mice. These data suggest a susceptibility of this strain to expression of MMTV(SW) upon reduction of the rearranged TCRV8.1-D2.1 segment in developing thymocytes, with parallel IL-7 overexpression.