Epitope selection in major histocompatibility complex class I-mediated pathway is affected by the intracellular localization of an antigen

We analyzed the mode of antigen presentation of an endogenous antigen localized in the cytoplasm or in the mitochondria. Pseudomonas aeruginosa PAO leucine-, isoleucine-, valine-binding protein (LIVAT-BP) encoded by the braC gene was used as a model antigen. Using mouse BALB/3T3 cells, we established two LIVAT-BP transfectants by transfection of a plasmid harboring the intact braC or braC gene fused with the mitochondrial transport signal derived from the yeast COXIV gene. One of the resulting transfectants, BC-15, expressed LIVAT-BP in the cytoplasm, while YZ-710 cells expressed LIVAT-BP in the mitochondria. The splenic effector cells derived from BALB/c mice primed with BC-15 cells exhibited cytotoxic T lymphocyte (CTL) activity against BC-15 cells, but not against YZ-710 cells, whereas splenic effector cells primed with YZ-710 cells exhibited CTL activity against YZ-710 cells, but not against BC-15 cells. Neither group of splenic effector cells showed CTL activity against parental BALB/3T3 cells. These CTL belonged to the CD8+ alphabeta T cell subset. Furthermore, we observed that the CTL activity against t BC-15 cells or YZ-710 cells was blocked with anti-H2-K(d) mAb, but not with anti-H2-D(d) or H2-L(d) mAb. The CTL against BC-15 or YZ-710 cells could kill parental BALB/3T3 cells in the presence of peptides produced by alkali lysis of the LIVAT-BP, suggesting that these CTL indeed recognized the peptide(s) derived from LIVAT-BP. We determined that the epitope for the CTL against BC-15 cells was QYGEGIATEV, corresponding to residues 162-171, and that the epitope recognized by the CTL against YZ-710 cells was GYKLIFRTI, corresponding to residues 123-131 of LIVAT-BP, respectively. Thus, we show here that epitope selection for MHC class I expression is affected by the intracellular localization of the antigenic protein.

Inhibition of arachidonate lipoxygenase activities by 2-(3,4-dihydroxyphenyl)ethanol, a phenolic compound from olives

The effects of olive fruit extract on arachidonic acid lipoxygenase activities were investigated using rat platelets and rat polymorphonuclear leukocytes (PMNL). Olive extract strongly inhibited both 12-lipoxygenase (12-LO) and 5-lipoxygenase (5-LO) activities. One of the compounds responsible for this inhibition was purified and identified as 2-(3,4-dihydroxyphenyl)ethanol (DPE). DPE inhibited platelet 12-LO activity (IC50, 4.2 microM) and PMNL 5-LO activity (IC50, 13 microM) but not cyclooxygenase activity in cell-free conditions. It also inhibited 12-LO activity in intact platelets (IC50, 50 microM) and reduced leukotriene B4 production in intact PMNL stimulated by A23187 (IC50, 26 microM). The inhibition by DPE of both lipoxygenase activities was stronger than that by oleuropein, caffeic acid, or 7 other related phenolic compounds, especially in intact cells. These results suggest that DPE is a potent specific inhibitor of lipoxygenase activities.

Identification of catechin oligomers from apple (Malus pumila cv. Fuji) in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and fast-atom bombardment mass spectrometry

Molecular size information for polymerized catechin larger than the decamer in unripe apple was obtained by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and by fast-atom bombardment mass spectrometry. Matrix-assisted laser desorption/ionization time of flight mass spectrometry provided evidence for the pentadecamer using trans-3-indoleacrylic acid as the matrix in the presence of silver ion. Even in the absence of silver ion, the dodecamer and undecamer were observed in the positive- and negative-ion modes, respectively. Fast-atom bombardment mass spectrometry also afforded evidence for the undecamer in both positive- and negative-ion modes.

Development of mouse submandibular gland studied by field emission scanning electron microscopy

The ultrastructural organization of mouse submandibular gland from 15 days gestation to 180 days of age was studied by field emission scanning electron microscopy. At 15 days of gestation several groups of acini, intercalated and striated ducts were present. They consisted of numerous pyramidal and/or polyhedral cells with spherical or elongated nuclei and short microvilli. At 3 days after birth different shapes of acinar structures covered by a network of fine collagen bundles were observed. The acinar portions corresponded to the terminal tubules and showed the acinar cells containing immature secretory granules. Fractured specimens of ducts revealed a flat surface with large central nuclei. At 14 days after birth acinar terminal portions possessed a round shape; branches of either intercalated and striated ducts were also observed. Gap junctions and interdigitations were numerous at the base of acinar cells. At 30 days after birth the acinar terminal portions and striated ducts revealed a large number of secretory granules. Acinar cells showed a pyramidal shape and basal nuclei. Freeze-cracked surfaces of the striated ductal cells evidenced also a pyramidal shape. Secretory granules ranged from 0.3 to 1.2 microns in size and were clearly observed by infoldings of the basement membranes. At 90 days after birth the ultrastructural features were more differentiated when compared with the previous ages. The freeze-cracked specimens showed very numerous secretory granules in all acinar and striated ductal cells. The granules occupied almost all the apical region of the cells. The outer surface of the basement membrane of acinar and myoepithelial cells was constituted by a spongy-like material covered by fine collagen fibrils. At 180 days after birth numerous secretory granules were seen either in acinar and ductal cells. A morphofunctional polarization of the cell was finally clearly observed in that the cytoplasmic organelles were concentrated in the basal portion whereas the secretory granules were located in the apical region of the cells.

Elevated L-kynurenine level and its normalization by prednisolone in a patient with eosinophilia-myalgia syndrome

We report a L-tryptophan-induced case of eosinophilia-myalgia syndrome in a Japanese woman and describe the time course of changes in tryptophan metabolism observed during steroid therapy. She had taken 1.0 g of the implicated L-tryptophan daily. When admitted due to painful swelling of her extremities, eosinophil count was 22.3 x 10(9)/L. Before prednisolone treatment, her serum L-kynurenine level was 10.2 mumol/L, a level about three-fold higher than the normal value, while serum tryptophan level was abnormally low (23.1 mumol/L). On the 14th day of prednisolone treatment (40 mg daily), L-kynurenine was declined to 8.1 mumol/L and, concomitantly, L-tryptophan level increased to the normal range (51.0 mumol/L). Subsequently, on the 42nd day of therapy, serum L-kynurenine was normalized. In contrast, serum serotonin level was unchanged throughout the course of this therapy. Prednisolone dramatically reduced the elevated serum L-kynurenine with a reciprocal increase in serum L-tryptophan indicates that abnormal tryptophan metabolism, may play a role in the pathogenesis of eosinophilia myalgia syndrome, and that the observed effect of steroid treatment was due to suppression of elevated activity of indoleamine 2, 3-dioxygenase, a first rate-limiting enzyme of the kynurenine pathway.

Immunohistochemical studies of vascular volume and proliferative activity in squamous cell carcinoma of the esophagus

For immunohistochemical investigation and clarification of the relationship between the vascular volume in esophageal carcinoma and the proliferative activity of its tumor cells, we examined surgical specimens of squamous cell carcinoma (SCC) of the esophagus from 15 patients. The vascular volume was evaluated by immunostaining for platelet-endothelial cell adhesion molecule-1 with monoclonal antibody JC70, and the proliferative activity of the carcinoma cells was evaluated by immunostaining for proliferating cell nuclear antigen (PCNA) with antibody 19A2. The ratio of the vascular area to the tumor area and the labeling index (LI) for PCNA in the carcinoma cells was then calculated. The antibody JC70 was useful for immunohistochemically detecting blood microvessels in esophageal carcinoma. The vascular volume, expressed as the ratio mentioned above, was higher in well- and moderately differentiated SCCs than in poorly differentiated SCC (P < 0.01), and the PCNA LI did not depend on the degree of differentiation. However, there was a significantly inverse relationship between the ratio of the vascular area to that of carcinoma and the PCNA LI of the carcinoma cells (P < 0.01). These findings show that angiogenesis is greater in esophageal carcinomas with little proliferative activity.

Induction of recombination activating gene expression in a human lymphoid progenitor cell line: requirement of two separate signals from stromal cells and cytokines

The activation and expression of recombination activating genes (RAGs) plays critical roles in V(D)J gene recombination machinery and lymphocyte development. We showed that RAG gene expression was induced in freshly isolated human bone marrow cells and a human lymphoid progenitor cell line, FL8.2.4.4, by coculture on a monolayer of a murine bone marrow-derived stromal cell line, PA6, in the presence of a mixture of recombinant cytokines. The RAG transcripts were detected 12 hours after initiation of culture, and the increased level was sustained at 24 hours. Among recombinant cytokines, interleukin-3 (IL-3), IL-6, and IL-7, but not IL-2, IL-4, stem cell factor (SCF), and granulocyte-macrophage colony-stimulating factor (GM-CSF) could induce RAG-1 activation in FL8.2.4.4 cells, and a significant synergistic effect between IL-3, IL-6, and IL-7 was observed. Using a double chamber culture technique, it was shown that a cognate interaction between FL8.2.4.4 cells and PA6 stromal cells was a prerequisite for RAG-1 activation. Furthermore, RAG-1 transcripts were induced in FL8.2.4.4 cells when they were cocultured on paraformaldehyde-fixed PA6 stromal cells in the presence of cytokines. These results suggest that two separate signals are both required for induction of RAG-1 activation in lymphoid progenitors; one from the cell surface molecule(s) on stromal cells, and the other from the recombinant cytokine(s). Finally, we showed that expression of RAG mRNA in FL8.2.4.4 cells was concomitant with induction of recombinase activity. This system may provide useful means for further understanding the mechanisms controlling RAG activation and lymphocyte development in the human system.

Married patients with eating disorders in Japan

A total of 40 married and 22 unmarried female patients with eating disorders were studied in order to investigate the relationship between eating disorders and marriage. Eating disorders developed in 14 patients before marriage (premarital onset) and in 26 patients at the time of or after marriage (postmarital onset). The postmarital-onset group was characterized by a significantly higher age at onset, but was similar in age and duration of illness to the group of 22 unmarried patients. However, the various clinical features of the three groups did not differ. For premarital-onset patients showed exaggerated clinical features after marriage, but the other patients showed no change in clinical features after marriage. In the postmarital-onset group, eating disorders were triggered in 18 patients (69%) by marital problems, separation or divorce. In contrast, eating disorders were triggered by dieting in order to lose weight in 8 patients (57%) in the premarital-onset group and 12 patients (55%) in the unmarried group. These results suggest that marital conflict plays an important role in the development and continuation of eating disorders in married women.

Outbreak of multi-drug resistant Staphylococcus aureus: a cluster analysis

BACKGROUND

Outbreaks of multi-drug resistant Staphylococcus aureus over eight years were investigated to prevent future endemic.

METHODS

Isolates of multiresistant S. aureus underwent a cluster analysis combined with canonical discriminant analysis using bacteriologic biotyping and sensitivity to 21 drugs.

RESULTS

Of a total of 786 strains recovered from 155 in-patients, the specialty surgical ward (SW) exhibited 470 isolates (59.8%) and the general SW 214 (27.2%). Among six clusters formed, four clusters were predominant in the general SW. An ordination diagram from the canonical discriminant analysis revealed a distribution in which clusters were localized temporally (year) and spatially (ward). A yearly shift of clusters indicated emergence of a new phenotype of multiresistant S. aureus.

CONCLUSIONS

The cluster analysis of isolates of multiresistant S. aureus using biotyping and sensitivity may supplement the classical method of tracing the spreading patterns of this microbe.

Identification of vegetable species in gastric contents using HPLC

Identification of 16 vegetables, focusing on the influence of digestion in the stomach, was carried out on the basis of the types of flavonoids detected on chromatograms using HPLC. Among the 12 vegetables for which flavonoids were detected, the chromatographic patterns of the flavonoids in digested vegetables were the same as those of the corresponding raw vegetables, making it possible to identify the species of vegetables even after digestion. In our analysis, 5 mg of a freeze-dried sample was found be an adequate quantity to enable the detection of flavonoids. Brief practical cases are also described.

IFN-gamma induces expression of MHC class I molecules in adult mouse dorsal root ganglion neurones

The expression of major histocompatibility complex (MHC) class I molecules on adult mouse DRG neurones was analysed using immunofluorescence and reverse transcription-polymerase chain reaction (RT-PCR). MHC class I molecules were not expressed in untreated dorsal root ganglion (DRG) neurones. The molecules, however, were detected on the surface of neurones following IFN-gamma treatment. In addition, expression of the MHC class I beta 2-microglobulin and genes was induced in neurones following IFN-gamma treatment. Expression of Tap-1 and Lmp-2 genes, which are involved in antigen processing and presentation, was also induced by IFN-gamma treatment. These results indicated that DRG neurones are able to express MHC class I molecules following IFN-gamma treatment and suggest that DRG neurones themselves are susceptible to recognition by cytotoxic T cells.

Chromatin structure and transcriptional regulation of human RAG-1 gene

The recombination activating genes (RAGs) play a critical role in V(D)J recombination machinery and lymphocyte development. Their expression is strictly regulated during lymphocyte ontogeny, with expression being rapidly lost as the lymphoid precursors differentiate into their progeny. To elucidate molecular mechanisms of regulation of human RAG-1 gene expression, we examined a chromatin structure of a approximately 24-kb DNA segment adjacent to a human RAG-1 promoter region in various cell lines by analyzing DNase I hypersensitive (DNase I HS) sites. In a RAG-1-expressing human pre-B-cell line, at least four DNase I HS sites (HS1, HS2, HS3, and HS4) were identified. Among these HS sites, one HS site (HS1) was ubiquitously detected in all cell lines examined, but the other three HS sites (HS2, HS3, and HS4) were associated only with RAG-1-expressing lymphoid cell lines. Using transient expression assays, we showed that the 5' upstream region of the major transcription start site showed low but significant promoter activity and that a DNA segment within HS3 located in the promoter region was indispensable to its basal promoter activity. Importantly, this promoter region was shown to be active in both RAG-1-expressing and RAG-1-nonexpressing cell lines. These results suggest that alteration of chromatin structure in the promoter region, in addition to other control elements outside of the promoter region, is one of the mechanisms regulating tissue- and stage-specific expression of human RAG-1 gene.

Ubiquitin-like polypeptide inhibits the IgE response of lipopolysaccharide-activated B cells

Monoclonal non-specific suppressor factor (MNSF), a lymphokine produced by a murine hybridoma, was originally found to inhibit the generation of lipopolysaccharide (LPS)-induced Ig-secreting cells. Most recently, we demonstrated the recombinant form of the ubiquitin-like segment (rUbi-L) or MNSF beta, an isoform of MNSF, has a MNSF activity. To investigate the possible role of rUbi-L, a 8.5 kDa ubiquitin-like polypeptide, in the regulation of Ig isotype secretion, rUbi-L was added to purified B cell cultures stimulated with LPS plus IL-4. rUbi-L notable suppressed the IgE and IgG1 responses when added at culture initiation. In addition, rUbi-L had a strong effect on IgG3 production and a little effect on IgM production by LPS-stimulated B cells, whereas the level of other isotypes (IgG2a, IgG2b and IgA) was not affected. These findings demonstrate the isotype-specific suppression, but not pan-suppression, of Ubi-L. IFN-alpha and IFN-gamma, which are also known to inhibit the IgE response, showed a synergistic effect with Ubi-L, albeit the effects of IFN-alpha were smaller. The action was reversed by the addition of neutralizing antibodies of these cytokines. Therefore, Ubi-L, a ubiquitin-like protein, may have an important immunoregulatory role on the IgE response.

A child case of CD34+, CD33-, HLA-DR-, CD7+, CD56+ stem cell leukemia with thymic involvement

It has been reported that the CD56+/CD7+/CD3- phenotype of natural killer (NK) cells develop from the CD34+/HLA-DR- bone marrow (BM) mononuclear cell population in long-term BM culture (LTBMC). An HLA-DR-/CD33+/CD56+/CD16- myeloid/natural killer cell acute leukemia has been described. We report here a 7-year-old boy who developed stem cell acute leukemia with superior vena cava syndrome secondary to thymic involvement. Surface marker analyses revealed that the leukemia cells showed CD34+/HLA-DR-/CD33-/CD7+/CD56+ phenotype. When stimulated with phorbol ester in vitro the leukemic cells morphologically differentiated to myeloid cells developing CD13, CD15 and CD56 antigens. Our results suggest that CD34+/HLA-DR-/CD7+/CD56+ stem cell leukemia may arise from transformation of a pluripotent precursor cell, which could differentiate to both myeloid and NK cell lineages.

[Indication for surgery of pediatric testicular and funicular hydroceles in view of natural course]

PURPOSE

The purpose of this study is to confirm the definite indication for surgery of pediatric testicular and funicular hydroceles in view of natural course.

METHODS

During the period from 1978 to 1994, we encountered 160 hydroceles in 149 pediatric patients. Patients ages ranged from 5 days after birth to 13 years and the mean follow-up periods was 4.7 years. We investigated the indication for surgery of pediatric hydroceles in six points of view: value of an aspiration of hydroceles, of what testicular or funicular or both, communication, size, age and testicular development.

RESULTS

Nevertheless, of 160 hydroceles, 66 (41%) were performed an aspiration of hydroceles, the aspiration of hydrocele was ineffective in the majority of patients. Common hydroceles in neonates and infants required no specific treatment, as the majority of hydrocele resolve spontaneously, however surgical treatment was required for a communicating large hydrocele that had been often attacked by aspiration and appeared at older age. Funicular hydroceles were more difficult to spontaneous healing. Ipsilateral testis manifests a well-developed comparing control material.

CONCLUSION

The indication for surgery of pediatric hydroceles were as follows: 1) hydroceles complicated by a inguinal hernia or cryptorchidism, 2) hydroceles appeared at older age and not resolved during 2-3 years over, 3) giant communicating funicular and testicular hydroceles present with an/hindrance for daily life.

Analysis of the promoter of the auxin-inducible gene, parC, of tobacco

The auxin-responsive region (AuxRR) in the promoter of the parC gene was analyzed in transgenic tobacco plants in which the 5' flanking region of the parC promoter was placed upstream of the gene for beta-glucuronidase (GUS). The AuxRR was located between nucleotides (nt) -226 and -54. Detailed dissection of this segment revealed that the presence of the non-contiguous sequences from nt -226 to -151 and from nt -84 to -54 was required for the expression of the auxin responsiveness of the parC promoter. The sequence from nt -226 to -151 was found to contain a sequence which resembles the as-1 element in the 35S promoter of cauliflower mosaic virus (CaMV). Although it has been reported that the as-1 element is involved in auxin responsiveness [Liu and Lam (1994) J. Biol. Chem. 269: 668], we showed that introduction of a point mutation into the as-1-like sequence completely eliminated auxin responsiveness, a result that suggests that the sequence is indispensable for auxin responsiveness. However, the presence of the as-1-like sequence alone was not sufficient for auxin responsiveness, since the segment (nt -226 to -84) that included the as-1-like sequence failed to confer auxin responsiveness on the core promoter. It is possible that the two separately located sequences play specific roles in interactions with trans-factors that are required for the expression of the auxin responsiveness of the parC promoter.

Osteotropic factor-stimulated synthesis of thrombospondin in rat dental pulp cells

The amount of thrombospondin (TSP) mRNA in confluent clonal rat dental pulp cells was increased by transforming growth factor-beta (TGF-beta), 1 alpha-25-dihydroxyvitamin D3 (1,25(OH)2D3), and phorbol 12,13-didecanoate (PDD), with maximal levels 6, 36 and 2 h, respectively, after stimulation. These increases were accompanied by enhanced syntheses of TSP proteins which were found in the different forms in cell layer/matrix fraction (198 and 165 kDa TSP) and the culture medium (180 kDa TSP). These three factors also raised the mRNA level of osteopontin, which is thought to play an important role in mineralization in dentin and bone. The order of effectiveness of these factors was PDD > TGF-beta > 1,25(OH)2D3 for all the stimulations described above. These results suggest that the osteotropic factors enhance TSP synthesis at the pretranslational level and that TSP produced by dental pulp cells participates in formation of reparative dentin.

Isolation and characterization of a TATA-less promoter for the human RAG-1 gene

Human recombination activating gene-1 (RAG-1) genomic DNA clones containing the first exon coding for the 5' untranslated region and the second exon coding for the remaining 5' untranslated region, coding region, and 3' untranslated region were cloned. Primer extension analysis and RNase protection analysis demonstrated the multiple RAG-1 transcription start sites, clustered in a 31 nucleotide (nt) region. Sequence analysis showed that the RAG-1 promoter lacked a TATA box as well as an initiator sequence. Transient expression assays using a luciferase reporter gene with truncated promoter fragments and substitution mutants, showed that the 5' promoter region containing the CCAAT box between -110 and -86, is indispensable for its basal promoter activity in RAG-1 expressing Nalm 6 cell line. Comparative transient expression assays in various cell lines revealed that the 854 nt upstream promoter region was active, not only in RAG-1 expressing cell lines but also in RAG-1 non-expressing cell lines. These data indicate that the 854 nt upstream region of RAG-1 gene confer basal promoter activity, and that the tissue- and stage-specific expression of RAG-1 is controlled by elements present outside of the promoter region and/or differential chromatin structure(s) of the individual cells.

A multiple-stimuli-responsive as-1-related element of parA gene confers responsiveness to cadmium but not to copper

The expression of parA, an auxin-regulated gene expressed during the culture of tobacco (Nicotiana tabacum L.) mesophyll protoplasts, is induced by cadmium. To identify the cadmium-responsive element, we examined the parA promoter using the GUS reporter gene. Cadmium responsiveness was retained in a 5' deletion of the parA promoter to -78 bp, but it was nullified by further deletion to -49bp, which implies that the region -49 to -78 bp contained a cadmium-responsive element. This region contains a sequence similar to as-1, an enhancer sequence from the cauliflower mosaic virus 35S RNA promoter that binds the nuclear factor ASF-1. We named the sequence in the parA promoter pas. Gel-shift assays revealed that pas and as-1 compete for the same DNA-binding nuclear protein(s). Since pentamers of either pas and as-1 were able to confer cadmium responsiveness on a minimal promoter but mutant as-1 was not, we propose that pas and as-1 are involved in cadmium-responsive gene expression. Neither pas nor as-1 conferred responsiveness to copper. The specificity of this response, involving the function of as-1-related elements including pas, is discussed.

A light and electron microscopic radioautographic study on RNA synthesis in the retina of chick embryo

The incorporation of 3H-uridine into RNA of chick embryo retina was studied by light and electron microscopic radioautography. The numbers of silver grains were counted over the nucleus, nucleolus and cytoplasm of the cells in three different regions of the same retina of 2, 3, 4, and 7 day chick embryos. The results showed an increase of 3H-uridine incorporation from embryonic day 2 to 7. In every stage of development of the chick embryo retina, the number of silver grains was higher in the anterior than in the other two regions of the retina. In the three cell compartments of every embryo group, the number of silver grains was higher in the nucleus than in the nucleolus and cytoplasm. The results show further that the grains were less in the cytoplasm of the retinal cells of the day 2 embryo group and higher in the other groups especially in the day 7 embryos. Ultrastructural changes were also observed during the studied period of retina development.

Multicopy suppressors of the cold-sensitive phenotype of the pcsA68 (dinD68) mutation in Escherichia coli

The Escherichia coli strain cs2-68 is a cold-sensitive (c) mutant that forms a long filamentous cell at 20 degrees C with a large nucleoid mass in its central region. We have recently shown that the pcsA68 mutation causing the cs phenotype is a single-base substitution within the dinD gene, a DNA damage-inducible gene which maps at 82 min. Since null mutants of the pcsA (dinD) gene are viable, with no discernible defect in cell growth, the cs phenotype is attributed to a toxic effect by the mutant protein. In an attempt to identify a target(s) for the toxic pcsA68 mutant protein, we screened for chromosomal fragments on multicopy plasmids that could suppress the cs phenotype. Three different BamHI fragments were found to suppress cold sensitivity, and the lexA, dinG, and dinI genes were identified to be responsible for the suppression in each fragment. DinG shares multiple motifs with many DNA helicases. The complete sequence of dinI revealed that DinI is a small protein of 81 amino acids. It is similar in size and sequence to ImpC of the Salmonella typhimurium plasmid TP110 and to a protein (ORFfs) of the retronphage phi R67, both of which are also under the control of LexA.

Mouse-Musashi-1, a neural RNA-binding protein highly enriched in the mammalian CNS stem cell

There is increasing interest in the role of RNA-binding proteins during neural development. Drosophila Musashi is one of the neural RNA-binding proteins essential for neural development and required for asymmetric cell divisions in the Drosophila adult sensory organ development. Here, a novel mammalian neural RNA-binding protein, mouse-Musashi-1, was identified based on the homology to Drosophila Musashi and Xenopus NRP-1. In the developing CNS, mouse-Musashi-1 protein was highly enriched in the CNS stem cell. Single-cell culture experiments indicated that mouse-Musashi-1 expression is associated with neural precursor cells that are capable of generating neurons and glia. In contrast, in fully differentiated neuronal and glial cells mouse-Musashi-1 expression is lost. This expression pattern of mouse-Musashi-1 is complementary to that of another mammalian neural RNA-binding protein, Hu (a mammalian homologue of a Drosophila neuronal RNA-binding protein Elav), that is expressed in postmitotic neurons within the CNS. In vitro studies indicated that mouse-Musashi-1 possesses binding preferences on poly(G) RNA homopolymer, whereas Hu is known to preferentially bind to short A/U-rich regions in RNA. Based on their differential expression patterns and distinct preferential target RNA sequences, we believe that the mouse-Musashi-1 and Hu proteins may play distinct roles in neurogenesis, either through sequential regulatory mechanisms or differential sorting of mRNA populations during asymmetric division of neural precursor cells.

Developmental expression of the Bombyx Antennapedia homologue and homeotic changes in the Nc mutant

BACKGROUND

Abundant availability of homeotic mutants in Bombyx mori provides us with clues to study the body plan of the silkworm. Previous studies indicated that the ECa/ECa and EN/EN embryos, which reveal drastic morphological changes (Itikawa 1943, 1952) lack the homologue of abd-A and the homologues of abd-A and Ubx, respectively (Ueno et al. 1992). It will be interesting to characterize a mutant named Nc, the locus of which was mapped about 1.4 cm apart from the E loci (Itikawa 1944, 1952).

RESULTS

In the present study we cloned and identified the Bombyx Antennapedia cDNA from a library of larval middle silk gland. The developmental expression patterns of the Bombyx Antennapedia were analysed in embryos and larval middle silk glands. We found the Bombyx Antennapedia mRNA of the Nc mutant lacks the homeobox region and its downstream region. This defect comes from a corresponding deletion on the Nc chromosome. Development of the Nc/Nc embryos terminates at stage 26, revealing a transformation of the prothoracic legs into antennae, milder changes in the mesothoracic legs, compression between the prothoracic and mesothoracic segments as well as in the gnathocephalon region, and a severe growth suppression of the silk glands.

CONCLUSIONS

These results give a molecular basis and detailed morphological abnormalities of the Nc mutant known since 1944.