Mechanism of the dependence of hepatitis B virus genotype G on co-infection with other genotypes for viral replication

Hepatitis B virus (HBV) is classified into several genotypes. Genotype G (HBV/G) is characterised by worldwide dispersion, low intragenotypic diversity and a peculiar sequence of the precore and core region (stop codon and 36-nucleotide insertion). As a rule, HBV/G is detected in co-infection with another genotype, most frequently HBV/A2. In a previous in vivo study, viral replication of HBV/G was significantly enhanced by co-infection with HBV/A2. However, the mechanism by which co-infection with HBV/A2 enhances HBV/G replication is not fully understood. In this study, we employed 1.24-fold HBV/A2 clones that selectively expressed each viral protein and revealed that the core protein expressing construct significantly enhanced the replication of HBV/G in Huh7 cells. The introduction of the HBV/A2 core promoter or core protein or both genomic regions into the HBV/G genome showed that both the core promoter and core protein are required for efficient HBV/G replication. The effect of genotype on the interaction between foreign core protein and HBV/G showed that HBV/A2 was the strongest enhancer of HBV/G replication. Furthermore, Western blot analysis of Dane particles isolated from cultures of Huh7 cells co-transfected by HBV/G and a cytomegalovirus (CMV) promoter-driven HBV/A2 core protein expression construct indicated that HBV/G employed HBV/A2 core protein during particle assembly. In conclusion, HBV/G could take advantage of core proteins from other genotypes during co-infection to replicate efficiently and to effectively package HBV DNA into virions.

Functional analysis of recombinant Bbeta15C and Bbeta15A fibrinogens demonstrates that Bbeta15G residue plays important roles in FPB release and in lateral aggregation of protofibrils

BACKGROUND AND OBJECTIVES

Analysis of dysfibrinogens has improved our understanding of molecular defects and their effects on the function of intact fibrinogen. To eliminate the influence of plasma heterozygous molecules, we synthesized and analyzed recombinant-variant fibrinogens.

METHODS

We synthesized two recombinant-variant fibrinogens with a single amino acid substitution at the 15Gly residue in the Bbeta-chain: namely, Bbeta15Cys and Bbeta15Ala.

RESULTS

Western blotting analysis of purified fibrinogen revealed the existence of a small amount of a dimeric form only for Bbeta15Cys fibrinogen. For Bbeta15Cys fibrinogen, functional analysis indicated (a) no thrombin-catalyzed fibrinopeptide B (FPB) release and (b) markedly impaired lateral aggregation in thrombin- and reptilase-catalyzed fibrin polymerizations. For Bbeta15Ala fibrinogen, such analysis indicated slight impairments of both thrombin-catalyzed FPB release and lateral aggregation in thrombin-catalyzed fibrin polymerization, but nearly normal lateral aggregation in reptilase-catalyzed fibrin polymerization. These impaired lateral aggregations were accompanied by thinner fibrin fiber diameters (determined by scanning electron microscopy of the corresponding fibrin clots).

CONCLUSION

We conclude that a region adjacent to Bbeta15Gly plays important roles in lateral aggregation not only in desA fibrin polymerization, but also in desAB fibrin polymerization, and we speculate that the marked functional differences between Bbeta15A and Bbeta15C fibrinogens in FPB release and fibrin polymerization might not only be due to the presence of a substituted cysteine residue in Bbeta15C fibrinogen, but also to the existence of disulfide-bonded forms. Finally, our data indicate that the Bbeta15Gly residue plays important roles in FPB release and lateral aggregation of protofibrils.

Loss of mRor1 enhances the heart and skeletal abnormalities in mRor2-deficient mice: redundant and pleiotropic functions of mRor1 and mRor2 receptor tyrosine kinases

The mammalian Ror family of receptor tyrosine kinases consists of two structurally related proteins, Ror1 and Ror2. We have shown that mRor2-deficient mice exhibit widespread skeletal abnormalities, ventricular septal defects in the heart, and respiratory dysfunction, leading to neonatal lethality (S. Takeuchi, K. Takeda, I. Oishi, M. Nomi, M. Ikeya, K. Itoh, S. Tamura, T. Ueda, T. Hatta, H. Otani, T. Terashima, S. Takada, H. Yamamura, S. Akira, and Y. Minami, Genes Cells 5:71-78, 2000). Here we show that mRor1-deficient mice have no apparent skeletal or cardiac abnormalities, yet they also die soon after birth due to respiratory dysfunction. Interestingly, mRor1/mRor2 double mutant mice show markedly enhanced skeletal abnormalities compared with mRor2 mutant mice. Furthermore, double mutant mice also exhibit defects not observed in mRor2 mutant mice, including a sternal defect, dysplasia of the symphysis of the pubic bone, and complete transposition of the great arteries. These results indicate that mRor1 and mRor2 interact genetically in skeletal and cardiac development.

Expression of the receptor tyrosine kinase genes, Ror1 and Ror2, during mouse development

In mammals, the Ror-family receptor tyrosine kinases consist of two structurally related proteins, Ror1 and Ror2, characterized by the extracellular Frizzled-like cysteine-rich domain and membrane proximal kringle domains. As an attempt to gain insights into their roles in mouse development, expression patterns of Ror1 and Ror2 during early embryogenesis were examined and compared. Interestingly, at early stages, Ror1 and Ror2 exhibit similar expression patterns in the developing face, including the frontonasal process and pharyngeal arches, which are derived from cephalic neural crest cells. On the other hand, they exhibit different expression patterns in the developing limbs and brain, where the expression of Ror2 was detected broadly compared with that of Ror1. At a later stage, both genes are expressed in a similar fashion in the developing heart and lung, yet in a distinct manner in the brain and eye.

Activity of the medaka translation elongation factor 1alpha-A promoter examined using the GFP gene as a reporter

The translation elongation factor 1alpha (EF-1alpha) is known to have several isoforms, which are expressed in a tissue- and stage-specific manner. Two genes encoding EF-1alpha exist per haploid genome in the medaka. In the present study, the promoter activity of the 5'-flanking region of the medaka EF-1alpha-A gene, an isoform of EF-1alpha, was characterized using transgenic techniques. First, using CAT gene as a reporter, it was revealed that about 1.8 kbp 5'-flanking sequence from the transcription initiation site of EF-1alpha-A was sufficient for high-level promoter activity. Second, the green fluorescent protein (GFP) gene fused to this region was introduced into medaka eggs using the microinjection method. Three germline transgenic individuals (one male and two female) were mated with non-transgenic medaka to obtain F1 offspring. In the case of embryonic and adult F1 transgenic individuals, GFP fluorescence was observed in almost all the tissues examined (e.g. kidney, liver, heart, gill, ovary, and testis), except for the skeletal muscle. In the case of F2 transgenic embryos derived from F1 transgenic males and non-transgenic females, the fluorescence was observed from the early gastrula stage. On the other hand, in the case of F2 transgenic embryos derived from F1 transgenic females and non-transgenic males, the fluorescence was observed even at the 1-cell stage, suggesting that this region is transcriptionally active during oogenesis. The usefulness of the EF-1alpha-A promoter as a tool for introducing foreign proteins into oocytes is discussed.

Cloning and characterization of rat casein kinase 1epsilon

Genes differentially expressed in the subjective day and night in the rat suprachiasmatic nucleus (SCN) were surveyed by differential display. A gene homologous to human casein kinase 1epsilon (CK1epsilon) was isolated, which initially appeared to be expressed in the suprachiasmatic nucleus (SCN) in a circadian manner. We here describe the cDNA cloning of the rat CK1epsilon and characterization of the protein products. The rCK1epsilon is predominantly expressed in the brain including the SCN, binds and phosphorylates mPer1, mPer2, and mPer3 in vitro, and translocates mPer1 and mPer3, but not mPer2, to the cell nucleus depending on its kinase activity when coexpressed with these Per proteins in COS-7 cells.

Expression of GFP in Nuclear Transplants Generated by Transplantation of Embryonic Cell Nuclei from GFP-Transgenic Fish into Nonenucleated Eggs of Medaka,Oryzias latipes

In order to investigate whether foreign genes can be used as genetic markers of donor nuclei in fish nuclear transplantation, expression of the GFP gene derived from donor nuclei was examined in nuclear transplants in medaka (Oryzias latipes). Embryonic nuclei were obtained from blastula embryos produced by crossing of transgenic fish of the wild-type strain heterozygous for the GFP gene with nontransgenic ones or by mutual crossing between transgenic fish. The GFP gene was driven by the promoter of the medaka elongation factor gene, EF-1alpha-A, which is known to induce GFP expression in many tissues except for the muscle in the transgenic fish. The nuclei were transplanted into nonenucleated unfertilized eggs of the orange-red strain. Adult nuclear transplants were successfully obtained at the rate of about 2% of the operated eggs. They were triploid and had no reproductive potential. The GFP gene was expressed in embryos, fry, and adults of nuclear transplants in a pattern similar to that in the transgenic fish. These results indicate that GFP is useful as a foreign genetic marker of donor nuclei in fish nuclear transplantation.

Expression of murine early embryonic antigens, SSEA-1 and antigenic determinant of EMA-1, in embryos and ovarian follicles of a teleost medaka (Oryzias latipes)

Stage-specific embryonic antigen-1 (SSEA-1) and the antigenic determinant of monoclonal antibody EMA-1 are expressed in a stage-specific manner in mouse early embryos. To study whether these antigens generally exist in fish, expression of the antigens was examined in embryos, ovarian follicles, and adult tissues of a teleost medaka (Oryzias latipes), using immunohistochemical techniques. In 1-cell-stage embryos, these carbohydrate antigens were found in numerous cytoplasmic granules in the blastodisc and the cortical cytoplasm. These granules gradually decreased in number as the embryos developed. In 4-cell-stage embryos, the antigens appeared on the cleavage planes and were located on the cleavage planes within the blastoderm in the following cleavage stages. In blastula-stage embryos, the expression was ubiquitously found on the cell surface of blastomeres. At the mid-gastrula stage, the antigens were restricted to the enveloping layer, yolk syncytial layer, and cortical cytoplasm, but were rarely found in deep cells that contribute to formation of the embryonic body. In later-stage embryos and adult fish, the antigens were located in various tissues. In ovarian follicles, the antigens were found in granules of oocytes and granulosa cells. These observations were basically consistent with those in mice; however, expression in 1-cell-stage embryos and ovarian follicles has not been observed in mice. This unexpected finding suggests that the antigens are produced in granulosa cells and transferred to 1-cell-stage embryos via oocytes, and that the antigens involved in the early developmental process are maternally prepared in teleosts.

Usefulness of the medaka beta-actin promoter investigated using a mutant GFP reporter gene in transgenic medaka (Oryzias latipes)

The activity of the medaka beta-actin promoter as a ubiquitous expression vector in transgenic medaka was examined using complementary DNA of the green fluorescent protein (GFP). Plasmid pOBA-GFP contained both the medaka beta-actin promoter and cDNA of the wild-type GFP, while pOBA-hGFP contained the medaka beta-actin promoter and cDNA of the mutant GFP in which serine was substituted for threonine at position 65 and codon usage was humanized to promote translation in vertebrate cells. The ApaI-SmaI fragment of both plasmids was microinjected into the nuclei of oocytes or the cytoplasm of embryos at the one-cell stage. The gene expression was detected, using a fluorescent stereomicroscope, from early stages of development to 1 week after hatching. The expression of the wild-type GFP was detected in early embryos, in the yolk sac and in small portions of the muscle and epidermis. This expression pattern was similar to that of the Escherichia coli beta-galactosidase reporter gene (lacZ), driven by the medaka beta-actin promoter, which was examined in our previous studies. The mutant GFP was expressed in early embryos and in many tissues such as the epidermis, blood vessels, muscle, notochord, fin ray, gut, eyes, and yolk sac, and the fluorescence was much stronger than that of the wild-type GFP. Thus, the usefulness of the medaka beta-actin promoter as a ubiquitous expression vector was confirmed using the mutant GFP as a reporter gene.

Auditory and colored visual P300 in patients with sequelae of subacute myelo-optico-neuropathy

To study the cognitive function in 13 patients with sequelae of subacute myelo-optico-neuropathy (SMON), event-related potentials (ERPs) were elicited with tones, clicks, and colored visual stimuli in different tasks. P300 latency was delayed, and P300 amplitude reduced or absent in 5 patients (38%), although neuropsychological assessment for dementia did not differ between patients and 21 age-matched normal controls. P300 and N200 latencies with the tone/tone auditory stimuli and N200 latency with the visual stimuli were significantly delayed, but the latencies of early components (N100 and P200) were not delayed. These findings suggest that SMON patients may have cognitive dysfunction to a slight degree.