Satoshi D. Ohdachi

Molecular phylogeny of a newfound hantavirus in the Japanese shrew mole (Urotrichus talpoides)

Recent molecular evidence of genetically distinct hantaviruses in shrews, captured in widely separated geographical regions, corroborates decades-old reports of hantavirus antigens in shrew tissues. Apart from challenging the conventional view that rodents are the principal reservoir hosts, the recently identified soricid-borne hantaviruses raise the possibility that other soricomorphs, notably talpids, similarly harbor hantaviruses. In analyzing RNA extracts from lung tissues of the Japanese shrew mole (Urotrichus talpoides), captured in Japan between February and April 2008, a hantavirus genome, designated Asama virus (ASAV), was detected by RT-PCR. Pairwise alignment and comparison of the S-, M-, and L-segment nucleotide and amino acid sequences indicated that ASAV was genetically more similar to hantaviruses harbored by shrews than by rodents. However, the predicted secondary structure of the ASAV nucleocapsid protein was similar to that of rodent- and shrew-borne hantaviruses, exhibiting the same coiled-coil helix at the amino terminus. Phylogenetic analyses, using the maximum-likelihood method and other algorithms, consistently placed ASAV with recently identified soricine shrew-borne hantaviruses, suggesting a possible host-switching event in the distant past. The discovery of a mole-borne hantavirus enlarges our concepts about the complex evolutionary history of hantaviruses.

Intraspecific phylogeny and geographical variation of six species of northeastern Asiatic Sorex shrews based on the mitochondrial cytochrome b sequences

Intraspecific phylogeny and genetic variation were investigated based on nucleotide sequences of the mitochondrial cytochrome b gene in six soricine shrew species, Sorex unguiculatus, S. caecutiens, S. shinto, S. gracillimus, S. minutissimus and S. hosonoi, collected primarily from northeastern Asia. Maximum likelihood trees and a phylogenetic network were generated to estimate intraspecific phylogenies. S. minutissimus showed high congruence between phylogenetic position and geographical origin and S. gracillimus showed low congruence. In contrast, there was no congruence between phylogeny and geography in S. unguiculatus and the S. caecutiens from Sakhalin‐Eurasia. Positive correlation between genetic and geographical distances was found in S. minutissimus and S. gracillimus, but not in the other species (or regional populations). The results of the phylogenetic and genetic analyses suggest that S. minutissimus and S. gracillimus have occupied their present ranges for a longer time than the other species if we assume a stepping‐stone model of population structure. In addition, there was no contradiction between the present investigations and the hypotheses of multiple immigration by S. gracillimus and a single immigration by S. unguiculatus into Hokkaido Island. It is proposed that these six northeastern Asian species experienced different historical processes of range expansion and dispersal despite the fact that some of them currently show similar patterns of distribution.

Mammalian skull heterochrony reveals modular evolution and a link between cranial development and brain size

The multiple skeletal components of the skull originate asynchronously and their developmental schedule varies across amniotes. Here we present the embryonic ossification sequence of 134 species, covering all major groups of mammals and their close relatives. This comprehensive data set allows reconstruction of the heterochronic and modular evolution of the skull and the condition of the last common ancestor of mammals. We show that the mode of ossification (dermal or endochondral) unites bones into integrated evolutionary modules of heterochronic changes and imposes evolutionary constraints on cranial heterochrony. However, some skull-roof bones, such as the supraoccipital, exhibit evolutionary degrees of freedom in these constraints. Ossification timing of the neurocranium was considerably accelerated during the origin of mammals. Furthermore, association between developmental timing of the supraoccipital and brain size was identified among amniotes. We argue that cranial heterochrony in mammals has occurred in concert with encephalization but within a conserved modular organization.

Purification and characterisation of blarinasin, a new tissue kallikrein-like protease from the short-tailed shrew Blarina brevicauda: comparative studies with blarina toxin

Abstract A new tissue kallikrein-like protease, blarinasin, has been purified from the salivary glands of the short-tailed shrew Blarina brevicauda. Blarinasin is a 32-kDa N-glycosylated protease with isoelectric values ranging between 5.3 and 5.7, and an optimum pH of 8.5 for enzyme activity. The cloned blarinasin cDNA coded for a pre-pro-sequence and a mature peptide of 252 amino acids with a catalytic triad typical for serine proteases and 43.7–54.0% identity to other mammalian tissue kallikreins. Blarinasin preferentially hydrolysed Pro-Phe-Arg-4-methylcoumaryl-7-amide (MCA) and N-tert-butyloxycarbonyl-Val-Leu-Lys-MCA, and preferentially converted human high-molecular-weight kininogen (HK) to bradykinin. The activity of blarinasin was prominently inhibited by aprotinin (K i=3.4 nM). A similar kallikrein-like protease, the lethal venom blarina toxin, has previously been purified from the salivary glands of the shrew Blarina and shows 67.9% identity to blarinasin. However, blarinasin was not toxic in mice. Blarinasin is a very abundant kallikrein-like protease and represents 70–75% of kallikrein-like enzymes in the salivary gland of B. brevicauda.

Phylogenetical Positions of Sorex sp. (Insectivora, Mammalia) from Cheju Island and S. caecutiens from the Korean Peninsula, Inferred from Mitochondrial Cytochrome b Gene Sequences

Abstract Phylogenetical positions of Sorex specimens unassigned to species from Cheju Island, Korea, and S. caecutiens from southern Korean Peninsula were investigated based on full nucleotide sequences (1,140 bp) of the mitochondrial cytochrome b gene, comparing specimens of the S. caecutiens/shinto group from locations throughout its range. In the phylogenetic tree obtained, S. caecutiens were separated into two main groups: Hokkaido and Continent-Sakhalin-Cheju clusters. Shrews from Cheju and Korean Peninsula were included in the latter cluster. Thus, we suggest that the shrew on Cheju Island should be ranked as S. caecutiens, although taxonomic description of the shrew has to be conducted elsewhere. The Cheju shrews formed a single sub-cluster while the peninsular shrews were not included in a single sub-cluster. The clustering of individuals in Continent-Sakhalin-Cheju cluster did not always reflect the geographical proximity of their capture locations. We interpret these findings as indicating ancestral isolation of a Hokkaido population and recent rapid range expansion of the modern population in Eurasian Continent-Sakhalin-Cheju.

Molecular phylogeny of Crocidura shrews in northeastern Asia: A special reference to specimens on Cheju Island, South Korea

Molecular phylogeny of crocidurine shrews (Insectivora, Soricidae) in northeastern Asia was investigated to confirm the taxonomic status of unidentified specimens ofCrocidura from Cheju Island, South Korea. Phylogenetic trees were constructed by neighbor-joining (NJ) and maximum likelihood (ML) methods, based on mitochondrial cytochromeb gene sequences (402 base pairs) of 37 individuals of seven crocidurine species and three unidentified specimens from 31 localities mainly in northeastern Asia. Phylogenetic position of the three unidentified specimens from Cheju Island were compared with those of Suncus murinus,C. attenuata, C. dsinezumi, C. lasiura, C. sibirica, C. suaveolens, andC. watasei. Both in NJ and ML trees, the three unidentified specimens were included in the cluster ofC. dsinezumi and were obviously different fromC. suaveolens on Cheju Island. Thus, the present investigation demonstrated that bothC. suaveolens andC. dsinezumi exist on Cheju Island.

Biogeographical history of northeastern Asiatic soricine shrews (insectivora, mammalia)

A hypothetical biogeographical history of northeastern Asiatic soricine shrews in the late Quaternary was developed by integrating their present distributions, fossil records, a hypothetical phylogeny, and geological investigations. First, a biological area cladogram of the northeastern Asiatic region was constructed by applying the vicariance hypothesis to the phylogeny of thecaecutiens/shinto group, a monophyletic group proposed by Ohdachi et al. (1997). Comparing the biological area cladogram with a geological hypothesis by Ohshima (1990,1991,1992), we hypothesized a geographical history of northeastern Asia. Species were then located on the dendrogram of the geographical history, referring to the present distributions, fossil records, and phylogeny of shrews. According to our hypothesis, higher species diversity of the northern region of northeastern Asia (Hokkaido, Sakhalin, and Eastern Siberia) was achieved by several series of colonizations and habitat expansion. On the other hand, the shrew communities of the southern region (Honshu, Sado, Shikoku, and Kyushu) were created by extinction and isolation followed by speciation.

Molecular phylogenetic analysis of nuclear genes suggests a Cenozoic over-water dispersal origin for the Cuban solenodon

The Cuban solenodon (Solenodon cubanus) is one of the most enigmatic mammals and is an extremely rare species with a distribution limited to a small part of the island of Cuba. Despite its rarity, in 2012 seven individuals of S. cubanus were captured and sampled successfully for DNA analysis, providing new insights into the evolutionary origin of this species and into the origins of the Caribbean fauna, which remain controversial. We conducted molecular phylogenetic analyses of five nuclear genes (Apob, Atp7a, Bdnf, Brca1 and Rag1; total, 4,602 bp) from 35 species of the mammalian order Eulipotyphla. Based on Bayesian relaxed molecular clock analyses, the family Solenodontidae diverged from other eulipotyphlan in the Paleocene, after the bolide impact on the Yucatan Peninsula, and S. cubanus diverged from the Hispaniolan solenodon (S. paradoxus) in the Early Pliocene. The strikingly recent divergence time estimates suggest that S. cubanus and its ancestral lineage originated via over-water dispersal rather than vicariance events, as had previously been hypothesised.

Genetic Diversity of Artybash Virus in the Laxmann's Shrew (Sorex caecutiens)

Although based on very limited M and L segment sequences, Artybash virus (ARTV) was proposed previously as a unique hantavirus harbored by the Laxmanns shrew (Sorex caecutiens). To verify this conjecture, lung tissues from 68 Laxmanns shrews, captured during 2006 to 2014 in eastern Siberia, Russia, and Hokkaido, Japan, were analyzed for ARTV RNA using reverse transcription polymerase chain reaction (RT-PCR). ARTV RNA was detected in six Laxmanns shrews. Pairwise alignment and comparison of partial- and full-length S, M, and L segment sequences from these Laxmanns shrews, as well as phylogenetic analyses, using maximum likelihood and Bayesian methods indicated that ARTV was distinct from other soricine shrew-borne hantaviruses and representative hantaviruses harbored by rodents, moles, and bats. Taxonomic identity of the ARTV-infected Laxmanns shrews was confirmed by full-length cytochrome b mitochondrial DNA sequence analysis. Our data indicate that the hantavirus previously known as Amga virus (MGAV) represents genetic variants of ARTV. Thus, the previously proposed designation of ARTV/MGAV should be replaced by ARTV.

Intraspecific Phylogeny and Nucleotide Diversity of the Least Shrews, the Sorex minutissimus-S. yukonicus Complex, Based on Nucleotide Sequences of the Mitochondrial Cytochrome b Gene and the Control Region

Abstract. Phylogenetic analysis was conducted for various populations of the Sorex minutissimus-S. yukonicus complex based on mitochondrial gene (cytochrome b and/or the control region) sequences. Sorex minutissimus was divided into some monophyletic groups in Eurasia; it was divided into 2 main groups, eastern and western Eurasian clades, based on combined data of the cytochrome b and the control region. Monophyly of shrews from Hokkaido-Sakhalin, Primorye, Mongolia-Transbaikalia, southeastern Finland was strongly supported respectively in most analyses. Sorex yukonicus was phylogenetically close to S. minutissimus in eastern Siberia. Some shrews from western and central Siberia were included in the clade of southeastern Finland. Also, most shrews from central-northern Finland and Norway made a clade close to but different from the southeastern Finland clade. This finding suggests that Fennoscandian shrews might consist of individuals which were recolonised from various refugia after the Last Glacial Maximum. Nucleotide diversity of shrews from Hokkaido and Alaska was low. Three regional groups in Kamchatka-Sakha, Sakhalin, and Mongolia-Transbaikalia tended to have medium nucleotide diversity. In contrast, shrews from Cisbaikalia-western Siberia and Fennoscandia had high nucleotide diversity. The S. minutissimus-S. hosonoi group appears to have experienceed a quit different biogeographic history from two shrews with similar ranges, the S. caecutiens-S. hosonoi group and S. tundrensis.