Takahiko Shiosaka

Mutations in the envelope protein of Japanese encephalitis virus affect entry into cultured cells and virulence in mice

The nucleotide sequences of the envelope protein of the Kamiyama 1 strain of Japanese encephalitis (JE) virus and a passaged mutant (Kamiyama 2 strain) were determined. Two amino acid differences, Ser-Phe at residue 364 and Asn-Ile at residue 367, distinguished Kamiyama 2 from Kamiyama 1. Six neutralization-resistant variants were selected from these two strains using a JE species-specific monoclonal antibody with neutralization and hemagglutination-inhibition reactivities. All variants had a single amino acid substitution at residue 52 and significantly reduced reactivity with other JE species-specific monoclonal antibodies. The variants derived from Kamiyama 2 strain showed reduced virulence in 3-week-old mice after peripheral inoculation but were as virulent as the parent virus when inoculated intracranially. These variants also showed altered early virus-cell interaction but not replication and reproduction in Vero cells. These findings indicate that the mutations at residues 52, 364, and 367 affect early virus-cell interaction in Vero cells and virulence in mice.

Phenotypic and genotypic analysis of chronic myelogenous leukaemia with T lymphoblastic and megakaryoblastic mixed crisis

A case of blast crisis in chronic myelogeneous leukaemia (CML) in which two distinct cell lineages were involved is presented. The phenotype of blasts in lymph nodes was T11 (CD2)+, Ia+, TdT+, suggesting T cell lineage. On the other hand, blasts in bone marrow and peripheral blood expressed platelet glycoprotein IIb/IIIa complex on their surface, suggesting megakaryocyte lineage. Cytogenetic analysis of lymph node and bone marrow cells revealed the abnormalities. inv(7) (p15q34) and t(1;3) (q23;q21), respectively, as well as the presence of the Ph1 chromosome in both cell types. Rearrangement of the T cell receptor β‐chain gene was detected in lymph node blasts, although blast cells in peripheral blood showed a germ line configuration. The involvement of T cell and megakaryocyte lineages in the blast crisis phase of CML was confirmed in our phenotypic and genotypic analysis, and the pathogenic association between blast crisis lineages and the additional chromosome abnormalities present is discussed.

MOLECULAR CLONING OF THE CDNA ENCODING A + U-RICH ELEMENT RNA BINDING FACTOR

Using the differential display method, a new cDNA clone, termed laAUF1, encoding the human A + U-rich RNA-binding motif was isolated and sequenced. Analysis of the protein sequence of laAUF1 indicates 73% homology between the deduced polypeptide sequences of laAUF1 and AUF1 in the region encoding a consensus motif for two non-identical RNA recognition motifs (RRMs) and Gln-rich motif. We suggest that the similar affinities of laAUF1 and AUF1 for particular A + U-rich elements (ARE) sequences are related to their potencies as mRNA destabilizers.

Preferentially expressed genes in stomach adenocarcinoma cells

cDNA clones complementary to mRNA of neoplastic cells of human stomach tissue were used to examine quantitative changes in the mRNA levels of specific genes in neoplastic cells. Poly(A)+ RNA from poorly differentiated adenocarcinoma cells of a female patient with stomach cancer was used for construction of a complementary DNA (cDNA) library. Screening of the 18,000 colonies utilizing 32P-cDNAs derived from normal human tissue and stomach carcinoma tissue samples was used to select clones likely to represent sequences preferentially expressed in stomach carcinoma cells. Twenty-six recombinants were initially selected and further analysis of these clones indicated that eight (4-3D, 9-2D, 9-4G, 29-1G, 29-6F, 37-1B, 115-5A and 52-5F) contain sequences preferentially expressed in stomach carcinoma cells. We have identified the 9-4G, 29-1A, and 29-6F genes which are differentially expressed in human neoplasia.