X chromosome-wide analyses of genomic DNA methylation states and gene expression in male and female neutrophils.

The DNA methylation status of human X chromosomes from male and female neutrophils was identified by high-throughput sequencing of HpaII and MspI digested fragments. In the intergenic and intragenic regions on the X chromosome, the sites outside CpG islands were heavily hypermethylated to the same degree in both genders. Nearly half of X chromosome promoters were either hypomethylated or hypermethylated in both females and males. Nearly one third of X chromosome promoters were a mixture of hypomethylated and heterogeneously methylated sites in females and were hypomethylated in males. Thus, a large fraction of genes that are silenced on the inactive X chromosome are hypomethylated in their promoter regions. These genes frequently belong to the evolutionarily younger strata of the X chromosome. The promoters that were hypomethylated at more than two sites contained most of the genes that escaped silencing on the inactive X chromosome. The overall levels of expression of X-linked genes were indistinguishable in females and males, regardless of the methylation state of the inactive X chromosome. Thus, in addition to DNA methylation, other factors are involved in the fine tuning of gene dosage compensation in neutrophils.

A myelopoiesis-associated regulatory intergenic noncoding RNA transcript within the human HOXA cluster.

We have identified an intergenic transcriptional activity that is located between the human HOXA1 and HOXA2 genes, shows myeloid-specific expression, and is up-regulated during granulocytic differentiation. The novel gene, termed HOTAIRM1 (HOX antisense intergenic RNA myeloid 1), is transcribed antisense to the HOXA genes and originates from the same CpG island that embeds the start site of HOXA1. The transcript appears to be a noncoding RNA containing no long open-reading frame; sucrose gradient analysis shows no association with polyribosomal fractions. HOTAIRM1 is the most prominent intergenic transcript expressed and up-regulated during induced granulocytic differentiation of NB4 promyelocytic leukemia and normal human hematopoietic cells; its expression is specific to the myeloid lineage. Its induction during retinoic acid (RA)-driven granulocytic differentiation is through RA receptor and may depend on the expression of myeloid cell development factors targeted by RA signaling. Knockdown of HOTAIRM1 quantitatively blunted RA-induced expression of HOXA1 and HOXA4 during the myeloid differentiation of NB4 cells, and selectively attenuated induction of transcripts for the myeloid differentiation genes CD11b and CD18, but did not noticeably impact the more distal HOXA genes. These findings suggest that HOTAIRM1 plays a role in the myelopoiesis through modulation of gene expression in the HOXA cluster.

Toll-like receptor-mediated activation of neutrophils by influenza A virus.

Influenza virus infection of the respiratory tract is characterized by a neutrophil infiltrate accompanied by inflammatory cytokine and chemokine production. We and others have reported that Toll-like receptor (TLR) proteins are present on human neutrophils and that granulocyte-macrophage colony-stimulating factor (GM-CSF) treatment enhances IL-8 (CXCL8) secretion in response to stimulation with TLR ligands. We demonstrate that influenza virus can induce IL-8 and other inflammatory cytokines from GM-CSF-primed human neutrophils. Using heat inactivation of influenza virus, we show that viral entry but not replication is required for cytokine induction. Furthermore, endosomal acidification and viral uncoating are necessary. Finally, using single-cell analysis of intracellular cytokine accumulation in neutrophils from knockout mice, we prove that TLR7 is essential for influenza viral recognition and inflammatory cytokine production by murine neutrophils. These studies demonstrate neutrophil activation by influenza virus and highlight the importance of TLR7 and TLR8 in that response.

Essential role of nuclear factor-kappaB for NADPH oxidase activity in normal and anhidrotic ectodermal dysplasia leukocytes.

This work investigated the functional role of nuclear factor-kappaB (NF-kappaB) in respiratory burst activity and in expression of the human phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase genes CYBB, CYBA, NCF1, and NCF2. U937 cells with a stably transfected repressor of NF-kappaB (IkappaBalpha-S32A/S36A) demonstrated significantly lower superoxide release and lower CYBB and NCF1 gene expression compared with control U937 cells. We further tested Epstein-Barr virus (EBV)-transformed B cells from patients with anhidrotic ectodermal dysplasia with immunodeficiency (EDA-ID), an inherited disorder of NF-kappaB function. Superoxide release and CYBB gene expression by EDA-ID cells were significantly decreased compared with healthy cells and similar to cells from patients with X-linked chronic granulomatous disease (X91(0) CGD). NCF1 gene expression in EDA-ID S32I cells was decreased compared with healthy control cells and similar to that in autosomal recessive (A47(0)) CGD cells. Gel shift assays demonstrated loss of recombinant human p50 binding to a NF-kappaB site 5' to the CYBB gene in U937 cells treated with NF-kappaB inhibitors, repressor-transfected U937 cells, and EDA-ID patients' cells. Zymosan phagocytosis was not affected by transfection of U937 cells with the NF-kappaB repressor. These studies show that NF-kappaB is necessary for CYBB and NCF1 gene expression and activation of the phagocyte NADPH oxidase in this model system.

Nuclease sensitive element binding protein 1 gene disruption results in early embryonic lethality.

Nuclease sensitive element binding protein 1 (NSEP1) is a member of the EFIA/NSEP1/YB-1 family of DNA-binding proteins whose members share a cold shock domain; it has also been termed DNA-binding protein B and Y box binding protein-1 because of its recognition of transcriptional regulatory elements. In addition, NSEP1 functions in the translational regulation of renin, ferritin, and interleukin 2 transcripts, and our laboratory has reported that it plays a role in the biosynthesis of selenium-containing proteins. To test the functional importance of NSEP1 in murine embryonic development, we have utilized a clone of ES cells in which the NSEP1 gene had been disrupted by integration of a plasmid gene-trapping vector into the seventh exon. Injection of these cells into C57BL/6 blastocysts resulted in 11 high percentage chimeric mice; crosses to wild type C57BL/6 mice generated 82 F1 agouti mice, indicating germ line transmission of the ES cell clone, but genotyping showed no evidence of the disrupted allele in any of these agouti offspring even though spermatozoa from four of five tested mice contained the targeted allele. Embryos harvested after timed matings of chimeric male mice demonstrated only the wildtype allele in 27 embryos tested at E7.5, E12.5, and E18.5. These results suggest that gene targeting of NSEP1 induces a lethal phenotype in early embryos, due to either haploinsufficiency of NSEP1 or formation of a dominant negative form of the protein. In either case, these data indicate the functional importance of the NSEP1 gene in murine early embryonic development.