We have previously reported that leukemic dendritic cells (DC) can be generated ex vivo from myelomonocytic precursors in chronic myelogenous leukemia. In this study we report the generation of DC from acute myelogenous leukemia (AML) cells and their potent ability to stimulate leukemia-specific cytolytic activity in autologous lymphocytes. DC were generated in vitro using granulocyte-macrophage colony-stimulating factor +interleukin-4 in combination with either tumor necrosis factor- or CD40 ligand (CD40L). Cells from 19 AML patients with a variety of chromosomal abnormalities were studied for their ability to generate DC. In all but 1 case, cells with the morphology, phenotypic characteristics, and T-cell stimulatory properties of DC could be generated. These cells expressed high levels of major histocompatibility complex class I and class II antigens as well as the costimulatory molecules B7-2 and ICAM-1. In three cases these cells were determined to be of leukemic origin by fluorescence in situ hybridization for chromosomal abnormalities or Western blotting for the inv(16) fusion gene product. Autologous lymphocytes cocultured with AML-derived DC (DC-AL) were able to lyse autologous leukemia targets, whereas little cytotoxicity was noted against autologous, normal cells obtained from the patients during remission. We conclude that leukemia derived DC may be useful for immunotherapy of many AML patients.

The microbiome plays an important role in shaping plant growth and immunity, but few plant genes and pathways impacting plant microbiome composition have been reported. In Arabidopsis thaliana, the phosphate starvation response (PSR) was recently found to modulate the root microbiome upon phosphate (Pi) starvation through the transcriptional regulator PHR1. Here, we report that A. thaliana PHR1 directly binds to the promoters of rapid alkalinization factor (RALF) genes, and activates their expression under phosphate‐starvation conditions. RALFs in turn suppress complex formation of pathogen‐associated molecular pattern (PAMP)‐triggered immunity (PTI) receptor through FERONIA, a previously‐identified PTI modulator that increases resistance to certain detrimental microorganisms. Suppression of immunity via the PHR1‐RALF‐FERONIA axis allows colonization by specialized root microbiota that help to alleviate phosphate starvation by upregulating the expression of PSR genes. These findings provide a new paradigm for coordination of host‐microbe homeostasis through modulating plant innate immunity after environmental perturbations.

Neural tube defects (NTDs) are serious congenital malformations. Excessive maternal homocysteine (Hcy) increases the risk of NTDs, while its mechanism remains elusive. Here we report the role of histone homocysteinylation in neural tube closure (NTC). A total of 39 histone homocysteinylation sites are identified in samples from human embryonic brain tissue using mass spectrometry. Elevated levels of histone KHcy and H3K79Hcy are detected at increased cellular Hcy levels in human fetal brains. Using ChIP-seq and RNA-seq assays, we demonstrate that an increase in H3K79Hcy level down-regulates the expression of selected NTC-related genes including Cecr2, Smarca4, and Dnmt3b. In human NTDs brain tissues, decrease in expression of CECR2, SMARCA4, and DNMT3B is also detected along with high levels of Hcy and H3K79Hcy. Our results suggest that higher levels of Hcy contribute to the onset of NTDs through up-regulation of histone H3K79Hcy, leading to abnormal expressions of selected NTC-related genes.

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Impaired folate metabolism is considered a risk factor for neural tube defects (NTDs). However, the relationship between folate deficiency and the risk of NTDs remains unclear, because experimentally induced dietary folate deficiency is insufficient to cause NTDs in non-mutant mice. Methotrexate (MTX) is a specific folate antagonist that competitively inhibits dihydrofolate reductase (DHFR) activity. The objective of this study was to develop a folate dysmetabolism murine model, and study the development of NTDs and its mechanism. Pregnant mice were injected with different doses of MTX [0, 0.5, 1.0, 3.0, 4.5 and 6.0 mg kg(-1) body weight (b/w) intraperitoneally (i.p.)] on gestational day 7.5 and sacrificed on gestational day 11.5. DHFR activity in embryonic tissues was detected, and folate concentrations were analyzed using LC/MS/MS. Copy number variations (CNVs) in neural tube tissues were detected using array comparative genomic hybridization (aCGH). A dose of MTX 4.5 mg kg(-1) b/w, resulted in the highest incidence of NTDs (31.4%) compared with the other groups, and DHFR activities, 5-MeTHF and 5-FoTHF concentrations in embryonic tissues decreased significantly after MTX injection. Furthermore, we found three high-confidence CNVs on chromosome X using aCGH, which was confirmed by RT-PCR and MassARRAY. These results indicate that MTX could cause a folate-associated dysmetabolism, which is similar to that of dietary folate deficiency in mice. The presence of CNVs in neural tube tissues was associated with the development of NTDs.

The biogenesis of ribosomes in vivo is an essential process for cellular functions. Transcription of ribosomal RNA (rRNA) genes is the rate-limiting step in ribosome biogenesis controlled by environmental conditions. Here, we investigated the role of folate antagonist on changes of DNA double-strand breaks (DSBs) landscape in mouse embryonic stem cells. A significant DSB enhancement was detected in the genome of these cells and a large majority of these DSBs were found in rRNA genes. Furthermore, spontaneous DSBs in cells under folate deficiency conditions were located exclusively within the rRNA gene units, representing a H3K4me1 hallmark. Enrichment H3K4me1 at the hot spots of DSB regions enhanced the recruitment of upstream binding factor (UBF) to rRNA genes, resulting in the increment of rRNA genes transcription. Supplement of folate resulted in a restored UBF binding across DNA breakage sites of rRNA genes, and normal rRNA gene transcription. In samples from neural tube defects (NTDs) with low folate level, up-regulation of rRNA gene transcription was observed, along with aberrant UBF level. Our results present a new view by which alterations in folate levels affects DNA breakage through epigenetic control leading to the regulation of rRNA gene transcription during the early stage of development.

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