Expansion of the silkworm GMC oxidoreductase genes is associated with immunity

The glucose-methanol-choline (GMC) oxidoreductases constitute a large gene family in insects. Some of these enzymes play roles in developmental or physiological process, such as ecdysteroid metabolism. However, little is known about the functional diversity of the insect GMC family. Here, we identified 43 GMC genes in the silkworm genome, the largest number of GMC genes among all the insect genomes sequenced to date. Similar to the other insects, there is a highly conserved GMC cluster within the second intron of the silkworm flotillin-2 (flo-2) gene. However, the silkworm GMC genes outside of the conserved GMC cluster have experienced a large expansion. Phylogenetic analysis suggested that the silkworm GMCβ subfamily contained 22 copies and made a major contribution to expansion of the silkworm GMC genes. Eighteen of the 22 members of the silkworm GMCβ subfamily are located outside of the conserved GMC cluster, and are known as silkworm expansion genes (SEs). Relative-rate tests showed that SEs evolved significantly faster than the GMCβ genes inside the conserved GMC cluster. Accordingly, the third position GC content (GC3s) and codon bias of SEs are significantly different from those of the GMCβ genes in the conserved GMC cluster. The elevated evolutionary rate of the silkworm GMCβ genes outside of the conserved GMC cluster may reflect the evolution of function diversity. At least 24 of the 43 silkworm GMC genes were differently transcribed and expressed in a tissue- or stage-specific manner during the larval stage. Strikingly, microarray data revealed that four different pathogens upregulated most of the silkworm GMCβ genes. Furthermore, RNA interference of representative upregulated GMCβ genes reduced the survival rate of the silkworm when infected by pathogens. Taken together, the results suggested that expansion of the silkworm GMC oxidoreductase genes is associated with immunity.     

The pattern of gene expression in mouse Gr-1(+) myeloid progenitor cells

To understand the pattern of gene expression in mouse myeloid progenitor cells, we carried out a genome-wide analysis of gene expression in mouse bone marrow Gr-1(+) cells using SAGE and GLGI techniques. We identified 22,033 unique SAGE tags with quantitative information from 73,869 collected SAGE tags. Among these unique tags, 64% match known sequences, including many genes important for myeloid differentiation, and 36% have no matches to known sequences and are likely to represent novel genes. We compared the expression of mouse Gr-1(+) and human CD15(+) myeloid progenitor cells and showed that the pattern of gene expression of these two cell populations had some similarities. We also compared the expression of mouse Gr-1(+) myeloid progenitor cells with that of mouse brain tissue and found a highly tissue-specific manner of gene expression in these two samples. Our data provide a basis for studying altered gene expression in myeloid disorders using mouse models.