Cell type-specific actions of Bcl11b in early T-lineage and group 2 innate lymphoid cells

Bcl11b binds to distinctive genomic regions with different partners and regulates completely different target genes in pro-T and ILC2 cells. Despite these divergences in Bcl11b function, a shared enhancer supports initial Bcl11b locus opening in both pro-T and ILC2 lineages.

The zinc finger transcription factor, Bcl11b, is expressed in T cells and group 2 innate lymphoid cells (ILC2s) among hematopoietic cells. In early T-lineage cells, Bcl11b directly binds and represses the gene encoding the E protein antagonist, Id2, preventing pro-T cells from adopting innate-like fates. In contrast, ILC2s co-express both Bcl11b and Id2. To address this contradiction, we have directly compared Bcl11b action mechanisms in pro-T cells and ILC2s. We found that Bcl11b binding to regions across the genome shows distinct cell type–specific motif preferences. Bcl11b occupies functionally different sites in lineage-specific patterns and controls totally different sets of target genes in these cell types. In addition, Bcl11b bears cell type–specific post-translational modifications and organizes different cell type–specific protein complexes. However, both cell types use the same distal enhancer region to control timing of Bcl11b activation. Therefore, although pro-T cells and ILC2s both need Bcl11b for optimal development and function, Bcl11b works substantially differently in these two cell types.

Runx3 prevents spontaneous colitis by directing the differentiation of anti-inflammatory mononuclear phagocytes

Mice deficient in the transcription factor Runx3 develop a multitude of immune system defects, including early onset colitis. This paper demonstrates that Runx3 is expressed in colonic mononuclear phagocytes (MNP), including resident macrophages (RM) and dendritic cell subsets (cDC2). Runx3 deletion in MNP causes early onset colitis due to their impaired maturation. Mechanistically, the resulting MNP subset imbalance leads to up-regulation of pro-inflammatory genes as occurs in IL10R-deficient RM. In addition, RM and cDC2 display a marked decrease in expression of anti-inflammatory/TGF β-regulated genes and β-catenin signaling associated genes, respectively. MNP transcriptome and ChIP-seq data analysis suggest that a significant fraction of genes affected by Runx3 loss are direct Runx3 targets. Collectively, Runx3 imposes intestinal immune tolerance by regulating maturation of colonic anti-inflammatory MNP, befitting the identification of RUNX3 as a genome-wide associated risk gene for various immune-related diseases in humans, including gastrointestinal tract diseases such as Crohn’s disease and celiac.

RUNX represses Pmp22 to drive neurofibromagenesis

Patients with neurofibromatosis type 1 (NF1) are predisposed to develop neurofibromas, but the underlying molecular mechanisms of neurofibromagenesis are not fully understood. We showed dual genetic deletion of Runx1 and Runx3 in Schwann cells (SCs) and SC precursors delayed neurofibromagenesis and prolonged mouse survival. We identified peripheral myelin protein 22 (Pmp22/Gas3) related to neurofibroma initiation. Knockdown of Pmp22 with short hairpin RNAs increased Runx1^fl/fl;Runx3^fl/fl;Nf1^fl/fl;DhhCre tumor-derived sphere numbers and enabled significantly more neurofibroma-like microlesions on transplantation. Conversely, overexpression of Pmp22 in mouse neurofibroma SCs decreased cell proliferation. Mechanistically, RUNX1/3 regulated alternative promoter usage and induced levels of protein expression of Pmp22 to control SC growth. Last, pharmacological inhibition of RUNX/core-binding factor β (CBFB) activity significantly reduced neurofibroma volume in vivo. Thus, we identified a signaling pathway involving RUNX1/3 suppression of Pmp22 in neurofibroma initiation and/or maintenance. Targeting disruption of RUNX/CBFB interaction might provide a novel therapy for patients with neurofibroma.

Attenuating the rate of total body fat accumulation and alleviating liver damage by oral administration of vitamin D-enriched edible mushrooms in a diet-induced obesity murine model is mediated by an anti-inflammatory paradigm shift

Background

Hypovitaminosis D is associated with many features of the metabolic syndrome, including non-alcoholic fatty liver disease. Vitamin D-enriched mushrooms extracts exert a synergistic anti-inflammatory effect. The aim of the present study is to determine the immunomodulatory effect of oral administration of vitamin D-enriched mushrooms extracts on high-fat diet (HFD) animal model of non-alcoholic steatohepatitis (NASH).

Methods

C57BL/6 mice on HFD were orally administered with vitamin D supplement, Lentinula edodes (LE) mushrooms extract, or vitamin D-enriched mushrooms extract for 25 weeks. Mice were studied for the effect of the treatment on the immune system, liver functions and histology, insulin resistance and lipid profile.

Results

Treatment with vitamin D-enriched LE extracts was associated with significant attenuation of the rate of total body fat accumulation, along with a decrease in hepatic fat content as measured by an EchoMRI. Significant alleviation of liver damage manifested by a marked decrease in ALT, and AST serum levels (from 900 and 1021 U/L in the control group to 313 and 340; 294 and 292; and 366 and 321 U/L for ALT and AST, in Vit D, LE and LE + Vit D treated groups, respectively). A corresponding effect on hepatocyte ballooning were also noted. A significant decrease in serum triglycerides (from 103 to 75, 69 and 72 mg/dL), total cholesterol (from 267 to 160, 157 and 184 mg/dL), and LDL cholesterol (from 193 mg/dL to 133, 115 and 124 mg/dL) along with an increase in the HDL/LDL ratio, and improved glucose levels were documented. These beneficial effects were associated with a systemic immunomodulatory effect associated with an increased CD4/CD8 lymphocyte ratio (from 1.38 in the control group to 1.69, 1.71 and 1.63), and a pro- to an anti-inflammatory cytokine shift.

Conclusions

Oral administration of vitamin-D enriched mushrooms extracts exerts an immune modulatory hepato-protective effect in NASH model.

An ensemble of regulatory elements controls Runx3 spatiotemporal expression in subsets of dorsal root ganglia proprioceptive neurons

Appel et al. defined the genomic transcription unit encompassing regulatory elements (REs) that mediate the tissue-specific expression of Runx3. Then, using transgenic mice expressing BAC reporters spanning the Runx3 locus, they discovered three REs that cross-talk with promoter-2 (P2) to drive TrkC neuron-specific Runx3 transcription.

The Runx3 transcription factor is essential for development and diversification of the dorsal root ganglia (DRGs) TrkC sensory neurons. In Runx3-deficient mice, developing TrkC neurons fail to extend central and peripheral afferents, leading to cell death and disruption of the stretch reflex circuit, resulting in severe limb ataxia. Despite its central role, the mechanisms underlying the spatiotemporal expression specificities of Runx3 in TrkC neurons were largely unknown. Here we first defined the genomic transcription unit encompassing regulatory elements (REs) that mediate the tissue-specific expression of Runx3. Using transgenic mice expressing BAC reporters spanning the Runx3 locus, we discovered three REs—dubbed R1, R2, and R3—that cross-talk with promoter-2 (P2) to drive TrkC neuron-specific Runx3 transcription. Deletion of single or multiple elements either in the BAC transgenics or by CRISPR/Cas9-mediated endogenous ablation established the REs’ ability to promote and/or repress Runx3 expression in developing sensory neurons. Our analysis reveals that an intricate combinatorial interplay among the three REs governs Runx3 expression in distinct subtypes of TrkC neurons while concomitantly extinguishing its expression in non-TrkC neurons. These findings provide insights into the mechanism regulating cell type-specific expression and subtype diversification of TrkC neurons in developing DRGs.

Expression of Runx1, -2 and -3 during tooth, palate and craniofacial bone development

We describe the expression of three Runt-related RUNX genes (previously termed AML, Cbfa, or Pebp2alpha) Runx1 and Runx3 during the development of teeth and other craniofacial tissues and compare them to Runx2 expression reported earlier. All three genes were expressed in mesenchymal condensates. Runx1 was expressed in several cartilage primordia earlier than Runx3, and Runx2 was intense in all mesenchymal condensations of bones and teeth. Only Runx1 was expressed in epithelia, and in tooth germs transcripts were detected in outer dental epithelium. Runx1 was also intensely expressed in the midline epithelium of palatal shelves. In early tooth morphogenesis Runx3 was coexpressed with Runx2 in a thin layer of mesenchymal cells underlying dental epithelium. Unlike Runx2, Runx3 was expressed in odontoblasts. However, Runx3 mutant mice did not show obvious tooth phenotype or deviations of Runx1 and Runx2 expression patterns in the tooth.

Runx3 specifies lineage commitment of innate lymphoid cells

Subsets of innate lymphoid cells (ILCs) reside in the mucosa and regulate immune responses to external pathogens. While ILCs can be phenotypically classified into ILC1, ILC2 and ILC3 subsets, the transcriptional control of commitment to each ILC lineage is incompletely understood. Here we report that the transcription factor Runx3 was essential for the normal development of ILC1 and ILC3 cells but not of ILC2 cells. Runx3 controlled the survival of ILC1 cells but not of ILC3 cells. Runx3 was required for expression of the transcription factor RORγt and its downstream target, the transcription factor AHR, in ILC3 cells. The absence of Runx3 in ILCs exacerbated infection with Citrobacter rodentium. Therefore, our data establish Runx3 as a key transcription factor in the lineage-specific differentiation of ILC1 and ILC3 cells.

Runx3 at the interface of immunity, inflammation and cancer

Inactivation of tumor suppressor genes (TSG) in normal cells provides a viability/growth advantage that contributes cell-autonomously to cancer. More than a decade ago claims arose that the RUNX3 member of the RUNX transcription factor family is a major TSG inactivated in gastric cancer, a postulate extended later to other cancers. However, evidence that Runx3 is not expressed in normal gastric and other epithelia has challenged the RUNX3-TSG paradigm. Here we critically re-appraise this paradigm in light of recent high-throughput, quantitative genome-wide studies on thousands of human samples of various tumors and new investigations of the role of Runx3 in mouse cancer models. Collectively, these studies unequivocally demonstrate that RUNX3 is not a bona fide cell-autonomous TSG. Accordingly, RUNX3 is not recognized as a TSG and is not included among the 2000 cancer genes listed in the "Cancer Gene Census" or "Network for Cancer Genes" repositories. In contrast, RUNX3 does play important functions in immunity and inflammation and may thereby indirectly influence epithelial tumor development.

Runx3-mediated transcriptional program in cytotoxic lymphocytes

The transcription factor Runx3 is highly expressed in CD8⁺ T and NK cytotoxic lymphocytes and is required for their effective activation and proliferation but molecular insights into the transcription program regulated by Runx3 in these cells are still missing. Using Runx3-ChIP-seq and transcriptome analysis of wild type vs. Runx3^-/- primary cells we have now identified Runx3-regulated genes in the two cell types at both resting and IL-2-activated states. Runx3-bound genomic regions in both cell types were distantly located relative to gene transcription start sites and were enriched for RUNX and ETS motifs. Bound genomic regions significantly overlapped T-bet and p300-bound enhancer regions in Runx3-expressing Th1 helper cells. Compared to resting cells, IL-2-activated CD8⁺ T and NK cells contain three times more Runx3-regulated genes that are common to both cell types. Functional annotation of shared CD8⁺ T and NK Runx3-regulated genes revealed enrichment for immune-associated terms including lymphocyte activation, proliferation, cytotoxicity, migration and cytokine production, highlighting the role of Runx3 in CD8⁺ T and NK activated cells.

Positional differences of axon growth rates between sensory neurons encoded by Runx3

The formation of functional connectivity in the nervous system is governed by axon guidance that instructs nerve growth and branching during development, implying a similarity between neuronal subtypes in terms of nerve extension. We demonstrate the molecular mechanism of another layer of complexity in vertebrates by defining a transcriptional program underlying growth differences between positionally different neurons. The rate of axon extension of the early subset of embryonic dorsal root ganglion sensory neurons is encoded in neurons at different axial levels. This code is determined by a segmental pattern of axial levels of Runx family transcription factor Runx3. Runx3 in turn determines transcription levels of genes encoding cytoskeletal proteins involved in axon extension, including Rock1 and Rock2 which have ongoing activities determining axon growth in early sensory neurons and blocking Rock activity reverses axon extension deficits of Runx3(-/-) neurons. Thus, Runx3 acts to regulate positional differences in axon extension properties apparently without affecting nerve guidance and branching, a principle that could be relevant to other parts of the nervous system.

Absence of Runx3 expression in normal gastrointestinal epithelium calls into question its tumour suppressor function

The Runx3 transcription factor regulates cell fate decisions during embryonic development and in adults. It was previously reported that Runx3 is strongly expressed in embryonic and adult gastrointestinal tract (GIT) epithelium (Ep) and that its loss causes gastric cancer. More than 280 publications have based their research on these findings and concluded that Runx3 is indeed a tumour suppressor (TS). In stark contrast, using various measures, we found that Runx3 expression is undetectable in GIT Ep. Employing a variety of biochemical and genetic techniques, including analysis of Runx3-GFP and R26LacZ/Runx3^Cre or R26tdTomato/Runx3^Cre reporter strains, we readily detected Runx3 in GIT-embedded leukocytes, dorsal root ganglia, skeletal elements and hair follicles. However, none of these approaches revealed detectable Runx3 levels in GIT Ep. Moreover, our analysis of the original Runx3^LacZ/LacZ mice used in the previously reported study failed to reproduce the GIT expression of Runx3. The lack of evidence for Runx3 expression in normal GIT Ep creates a serious challenge to the published data and undermines the notion that Runx3 is a TS involved in cancer pathogenesis.

Isolation and Characterization of a Novel Atrazine Metabolite Produced by the Fungus Pleurotus pulmonarius, 2-Chloro-4-Ethylamino-6-(1-Hydroxyisopropyl)Amino-1,3,5-Triazine

The white rot fungus Pleurotus pulmonarius exhibited metabolism of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) in liquid culture, producing the dealkylated metabolites desethylatrazine, desisopropylatrazine, and desethyl-desisopropylatrazine. A fourth, unknown metabolite was also produced. It was isolated and was identified as 2-chloro-4-ethylamino-6-(1-hydroxyisopropyl)amino-1,3,5-triazine by gas chromatography-mass spectrometry, Fourier transformed infrared spectroscopy, and H nuclear magnetic resonance analysis. The structure of this metabolite was confirmed by chemical synthesis of the compound and comparison with the fungally produced metabolite.

Translation regulation of Runx3

Runx3 protein products that are translated from the distal (P1)- and proximal (P2)-promoter transcripts appear on Western blots as a 47-46kDa doublet corresponding to full-length proteins bearing the P1- and P2-N-termini respectively. An additional 44kDa protein band, the origin and nature of which was unclear, is also detected. Transfection of full-length Runx3 cDNA bearing the P2 N-terminus (P2-cDNA) into HEK293 cells resulted in expression of both 46 and 44kDa proteins. Sequence analysis of the P2-cDNA revealed an in-frame ATG 90bp downstream (+90ATG) of the proximal +1ATG. Insertion of an N-terminal HA-tag into P2-cDNA immediately downstream of the +1ATG produced HA-tagged 46kDa and untagged 44kDa proteins, consistent with the possibility that the latter was translated through initiation at the internal +90ATG site. Deleting or blocking the activity of the +1ATG, the natural cap-dependent translation initiation site in P2-cDNA, abrogated production of the 46kDa Runx3 protein while facilitating production of the 44kDa product. These findings supported the notion that Runx3 44kDa protein resulted from internal translation initiation at the +90ATG. Northern blot and RT-PCR analyses performed on RNA from P2-cDNA transfected cells showed a single transcript and product respectively, of the expected size, ruling out the possibility that the 44kDa protein was translated from transcripts originating at a cryptic promoter or produced by alternative splicing. Taken together, the data indicate that the 44kDa protein results from translation initiation at the internal ATG and that Runx3, like its family members Runx1 and Runx2, contains a mechanism for internal mRNA translation initiation.

Runx3 and T-box proteins cooperate to establish the transcriptional program of effector CTLs

Activation of naive CD8⁺ T cells with antigen induces their differentiation into effector cytolytic T lymphocytes (CTLs). CTLs lyse infected or aberrant target cells by exocytosis of lytic granules containing the pore-forming protein perforin and a family of proteases termed granzymes. We show that effector CTL differentiation occurs in two sequential phases in vitro, characterized by early induction of T-bet and late induction of Eomesodermin (Eomes), T-box transcription factors that regulate the early and late phases of interferon (IFN) γ expression, respectively. In addition, we demonstrate a critical role for the transcription factor Runx3 in CTL differentiation. Runx3 regulates Eomes expression as well as expression of three cardinal markers of the effector CTL program: IFN-γ, perforin, and granzyme B. Our data point to the existence of an elaborate transcriptional network in which Runx3 initially induces and then cooperates with T-box transcription factors to regulate gene transcription in differentiating CTLs.

The evolutionary origin of the Runx/CBFbeta transcription factors--studies of the most basal metazoans

Background

Members of the Runx family of transcriptional regulators, which bind DNA as heterodimers with CBFβ, are known to play critical roles in embryonic development in many triploblastic animals such as mammals and insects. They are known to regulate basic developmental processes such as cell fate determination and cellular potency in multiple stem-cell types, including the sensory nerve cell progenitors of ganglia in mammals.

Results

In this study, we detect and characterize the hitherto unexplored Runx/CBFβ genes of cnidarians and sponges, two basal animal lineages that are well known for their extensive regenerative capacity. Comparative structural modeling indicates that the Runx-CBFβ-DNA complex from most cnidarians and sponges is highly similar to that found in humans, with changes in the residues involved in Runx-CBFβ dimerization in either of the proteins mirrored by compensatory changes in the binding partner. In situ hybridization studies reveal that Nematostella Runx and CBFβ are expressed predominantly in small isolated foci at the base of the ectoderm of the tentacles in adult animals, possibly representing neurons or their progenitors.

Conclusion

These results reveal that Runx and CBFβ likely functioned together to regulate transcription in the common ancestor of all metazoans, and the structure of the Runx-CBFβ-DNA complex has remained extremely conserved since the human-sponge divergence. The expression data suggest a hypothesis that these genes may have played a role in nerve cell differentiation or maintenance in the common ancestor of cnidarians and bilaterians.

RUN-CBFβ Interaction inC. elegans: Computational Prediction and Experimental Verification

The Runt domain proteins are eukaryotic transcription factors that regulate major developmental pathways. All members of this family contain a highly-conserved sequence-specific DNA binding domain: the Runt domain (RD). Structural and biochemical studies have shown that the Runt domain undergoes a conformational transition upon binding to DNA and that this process is regulated by an unrelated partner protein CBFbeta that enhances the DNA binding affinity of RD. Most of the reported studies on the Runt domain transcription factors were performed on proteins from mammals and Drosophila whereas very little has been known about the C. elegans RD protein, RUN, which provides the simplest model system for understanding the function of this class of transcription factors. We performed computational studies on RD domains from various species including C. elegans, Drosophila, and human, using the atom-atom contact surface area scoring method. The scoring analysis indicates that the DNA binding regulation of the C. elegans RD protein (CeRD) occurs via its interaction with a CBFbeta-like partner, as found for the human proteins, whereas a different mode of regulation may occur in the Drosophila system. Sequence, secondary structure and fold analyses of a putative CBFbeta protein identified in the C. elegans genome, CeCBFbeta, sharing a 22% identity with the human protein, predict a similar structure of this protein to that of the human CBFbeta protein. We produced the C. elegans proteins CeRD and CeCBFbeta in bacteria and confirmed their physical interaction as well as cross interactions with the corresponding human proteins. We also confirmed the structural similarity of CBFbeta and CeCBFbeta by circular dichroism analysis. The combined results suggest that a similar mechanism of regulation operates for the human and the C. elegans RD proteins despite the low sequence identity between their CBFbeta proteins and the evolutionary distance between the two systems.

Transcription factors T-bet and Runx3 cooperate to activate Ifng and silence Il4 in T helper type 1 cells

Cell differentiation involves activation and silencing of lineage-specific genes. Here we show that the transcription factor Runx3 is induced in T helper type 1 (T(H)1) cells in a T-bet-dependent manner, and that both transcription factors T-bet and Runx3 are required for maximal production of interferon-gamma (IFN-gamma) and silencing of the gene encoding interleukin 4 (Il4) in T(H)1 cells. T-bet does not repress Il4 in Runx3-deficient T(H)2 cells, but coexpression of Runx3 and T-bet induces potent repression in those cells. Both T-bet and Runx3 bind to the Ifng promoter and the Il4 silencer, and deletion of the silencer decreases the sensitivity of Il4 to repression by either factor. Our data indicate that cytokine gene expression in T(H)1 cells may be controlled by a feed-forward regulatory circuit in which T-bet induces Runx3 and then 'partners' with Runx3 to direct lineage-specific gene activation and silencing.

Runx3 regulates dendritic epidermal T cell development

The Runx3 transcription factor regulates development of T cells during thymopoiesis and TrkC sensory neurons during dorsal root ganglia neurogenesis. It also mediates transforming growth factor-beta signaling in dendritic cells and is essential for development of skin Langerhans cells. Here, we report that Runx3 is involved in the development of skin dendritic epidermal T cells (DETCs); an important component of tissue immunoregulation. In developing DETCs, Runx3 regulates expression of the alphaEbeta7 integrin CD103, known to affect migration and epithelial retention of DETCs. It also regulates expression of IL-2 receptor beta (IL-2Rbeta) that mediates cell proliferation in response to IL-2 or IL-15. In the absence of Runx3, the reduction in CD103 and IL-2Rbeta expression on Runx3(-/-) DETC precursors resulted in impaired cell proliferation and maturation, leading to complete lack of skin DETCs in Runx3(-/-) mice. The data demonstrate the requirement of Runx3 for DETCs development and underscore the importance of CD103 and IL-2Rbeta in this process. Of note, while Runx3(-/-) mice lack both DETCs and Langerhans cells, the two most important components of skin immune surveillance, the mice did not develop skin lesions under pathogen-free (SPF) conditions.

Dynamic expression of Runx1 in skin affects hair structure

The three mammalian Runx transcription factors, some of which are known to be involved in human genetic diseases and cancer, are pivotal players in embryo development and function as key regulators of cell fate determination and organogenesis. Here, we report the expression of Runx1 during the development of hair and other skin appendages in the mouse and describe the effect of Runx1 on the structural hair output. In hair follicles, where the three Runx proteins are expressed, Runx1 expression is most prominent in both mesenchymal and epithelial compartments. The epithelial expression includes the hair keratin forming layers of the hair shaft and the bulge, where interestingly, Runx1 is co-expressed with keratin 15, a putative hair follicle stem cell marker. In the hair mesenchyme, during early stages of hair morphogenesis, Runx1 is expressed in a discrete dermal sub-epithelial layer, while at later stages it is found in a hair cycle dependent pattern in the dermal papilla. To elucidate the function of Runx1 in the hair follicle we have generated a Runx1 epidermal conditional knockout and found that the mutant mice display a remarkable structural deformation of the zigzag hair type. The data delineate Runx1 as a novel specific marker of several hair follicle cell types and sheds light on its role in hair morphogenesis and differentiation.

Groucho/transducin-like Enhancer-of-split (TLE)-dependent and -independent transcriptional regulation by Runx3

Regulation of gene expression by tissue-specific transcription factors involves both turning on and turning off transcription of target genes. Runx3, a runt-domain transcription factor, regulates cell-intrinsic functions by activating and repressing gene expression in sensory neurons, dendritic cells (DC), and T cells. To investigate the mechanism of Runx3-mediated repression in an in vivo context, we generated mice expressing a mutant Runx3 lacking the C-terminal VWRPY, a motif required for Runx3 interaction with the corepressor Groucho/transducin-like Enhancer-of-split (TLE). In contrast with Runx3(-/-) mice, which displayed ataxia due to the death of dorsal root ganglia TrkC neurons, Runx3(VWRPY-/-) mice were not ataxic and had intact dorsal root ganglia neurons, indicating that ability of Runx3 to tether Groucho/TLE is not essential for neurogenesis. In the DC compartment, the mutant protein Runx3(VWRPY-) promoted normally developed skin Langerhans cells but failed to restrain DC spontaneous maturation, indicating that this latter process involves Runx3-mediated repression through recruitment of Groucho/TLE. Moreover, in CD8(+) thymocytes, Runx3(VWRPY-) up-regulated alphaE/CD103-like WT Runx3, whereas unlike wild type, it failed to repress alphaE/CD103 in CD8(+) splenocytes. Thus, in CD8-lineage T cells, Runx3 regulates alphaE/CD103 in opposing regulatory modes and recruits Groucho/TLE to facilitate the transition from activation to repression. Runx3(VWRPY-) also failed to mediate the epigenetic silencing of CD4 gene in CD8(+) T cells, but normally regulated other pan-CD8(+) T cell genes. These data provide evidence for the requirement of Groucho/TLE for Runx3-mediated epigenetic silencing of CD4 and pertain to the mechanism through which other Runx3-regulated genes are epigenetically silenced.

Runx2 (Cbfa1) inhibits Shh signaling in the lower but not upper molars of mouse embryos and prevents the budding of putative successional teeth

Heterozygous mutations in the RUNX2 (CBFA1) gene cause cleidocranial dysplasia, characterized by multiple supernumerary teeth. This suggests that Runx2 inhibits successional tooth formation. However, in Runx2 knockout mice, molar development arrests at the late bud stage, and lower molars are more severely affected than upper ones. We have proposed that compensation by Runx3 may be involved. We compared the molar phenotypes of Runx2/Runx3 double-knockouts with those of Runx2 knockouts, but found no indication of such compensation. Shh and its mediators Ptc1, Ptc2, and Gli1 were down-regulated only in the lower but not the upper molars of Runx2 and Runx2/Runx3 knockouts. Interestingly, in front of the mutant upper molar, a prominent epithelial bud protruded lingually with active Shh signaling. Similar buds were also present in Runx2 heterozygotes, and they may represent the extension of dental lamina for successional teeth. The results suggest that Runx2 prevents the formation of Shh-expressing buds for successional teeth.

Runx3 is involved in hair shape determination

Transcriptional regulators of the Runx family play critical roles in normal organ development and, when mutated, lead to genetic diseases and cancer. Runx3 functions during cell lineage decisions in thymopoiesis and neurogenesis and mediates transforming growth factor-beta signaling in dendritic cells. Here, we study the function of Runx3 in the skin and its appendages, primarily the hair follicle, during mouse development. Runx3 is expressed predominantly in the dermal compartment of the hair follicles as they form and during the hair cycle, as well as in the nail and sweat gland skin appendages. Distinct expression is also detected periodically in isolated cells of the epidermis and in melanocytes, populating the hair bulb. Runx3-deficient mice display a perturbation of the normal hair coat, which we show to be due to hair type and hair shape changes. Thus, one of the functions of Runx3 in skin may be to regulate the formation of the epithelial derived structural hair by affecting dermal to epidermal interactions.

Inhibitory effects of stress on postprandial gastric myoelectrical activity and vagal tone in healthy subjects

The aim was to investigate gastric myoelectrical activity (GMA) and vagal activity in response to stress. The study was performed in 10 healthy subjects in three sessions (control, relaxation and stress). The control session was composed of 30-min recordings before and 30-min recordings after a test meal. The protocol of two other sessions was similar except that the fasting recording was extended to 60 min and the subjects were continuously watching a horror movie (stress) or guided meditation tape (relaxation) after the 30-min baseline. GMA was recorded using electrogastrography and heart rate variability (HRV) was derived from the electrocardiogram. Meal resulted in a postprandial increase in the dominant frequency (2.91 cpm vs 3.17 cpm, P < 0.007), dominant power (30.0 dB vs 32.5 dB, P < 0.05), and percentage of normal slow waves (79.8%vs 87.4%, P = 0.09). Similar responses were found in the relaxation session. Stress inhibited all these normal postprandial response and reduced the regularity of gastric slow waves (82.0%vs 66.0%, P < 0.01). In addition, spectral analysis of the HRV demonstrated an inhibition of postprandial vagal activity and an increase of postprandial sympathetic activity with stress. Stress has an inhibitory effect on postprandial GMA and this may involve both vagal and sympathetic pathway.

Loss of Runx3 function in leukocytes is associated with spontaneously developed colitis and gastric mucosal hyperplasia

RUNX transcription factors are key regulators of lineage-specific gene expression and might be involved in autoimmune diseases. Runx3 plays a role during the development of sensory neurons and T cells and regulates transforming growth factor beta (TGF-beta) signaling in dendritic cells. Here, we report that at 4 weeks of age, Runx3 knockout (KO) mice spontaneously develop inflammatory bowel disease (IBD) characterized by leukocyte infiltration, mucosal hyperplasia, formation of lymphoid clusters, and increased production of IgA. Additionally, at a considerably older age (8 months), the KO mice also develop progressive hyperplasia of the gastric mucosa associated with disturbed epithelial differentiation and cellular hyaline degeneration. Analysis of cytokines in the colonic mucosa of Runx3 KO mice revealed a mixed T helper 1/T helper 2 response. By using immunohistochemistry and RNA in situ hybridization, Runx3 expression in the gastrointestinal tract is detected in lymphoid and myeloid populations but not in the epithelium. The data indicate that loss of leukocytic cell-autonomous function of Runx3 results in IBD and gastric lesion in the KO mice. IBD in humans is viewed as a complex genetic disorder. Several susceptibility loci were identified on different human chromosomes including the chromosomal region 1p36 where RUNX3 resides. It is thus tempting to speculate that mutations in RUNX3 may constitute an IBD risk factor in humans.

Structure and regulated expression of mammalian RUNX genes

The RUNX are key regulators of lineage-specific gene expression in major developmental pathways. The expression of RUNX genes is tightly regulated, leading to a highly specific spatio/temporal expression pattern and to distinct phenotypes of gene knockouts. This review highlights the extensive structural similarities between the three mammalian RUNX genes and delineates how regulation of their expression at the levels of transcription and translation are orchestrated into the unique RUNX expression pattern.

Runx3 regulates mouse TGF-beta-mediated dendritic cell function and its absence results in airway inflammation

Runx3 transcription factor regulates cell lineage decisions in thymopoiesis and neurogenesis. Here we report that Runx3 knockout (KO) mice develop spontaneous eosinophilic lung inflammation associated with airway remodeling and mucus hypersecretion. Runx3 is specifically expressed in mature dendritic cells (DC) and mediates their response to TGF-beta. In the absence of Runx3, DC become insensitive to TGF-beta-induced maturation inhibition, and TGF-beta-dependent Langerhans cell development is impaired. Maturation of Runx3 KO DC is accelerated and accompanied by increased efficacy to stimulate T cells and aberrant expression of beta2-integrins. Lung alveoli of Runx3 KO mice accumulate DC characteristic of allergic airway inflammation. Taken together, abnormalities in DC function and subset distribution may constitute the primary immune system defect, which leads to the eosinophilic lung inflammation in Runx3 KO mice. These data may help elucidate the molecular mechanisms underlying the pathogenesis of allergic airway inflammation in humans.

[Mouse whole mount RNA in situ hybridization: an effective technique for analyzing gene expression]

OBJECTIVE

To set up a method of analyzing gene expression profile from mouse whole embryos.

METHODS

Mouse whole mount RNA in situ hybridization(WM-ISH) of E10.5-E14 embryos was carried out by using digoxigenin-labeled Runx1 and Runx3 RNA probes and their expression profile was observed by detecting the existence and status of corresponding mRNAs in the embryonic tissues.

RESULTS

Clear hybridization signals were observed in different tissues and organs hybridized by Runx1 or Runx3 RNA probe. Different probes and ages of embryos had need of their own optimal proteinase K treatment conditions.

CONCLUSION

Mouse whole mount RNA in situ hybridization is an effective method of analyzing gene expression. It is useful for revealing whole gene expression profile and has a great potentiality in the era of functional genomics. It provides an alternative method of studies on gene expression which is at least as good as LacZ staining and immunohistochemistry. The key factor of the success to mouse whole mount RNA in situ hybridization is whether the proteinase K treatment conditions are optimal or not.

Runx3 and Runx1 are required for CD8 T cell development during thymopoiesis

The RUNX transcription factors are important regulators of lineage-specific gene expression. RUNX are bifunctional, acting both as activators and repressors of tissue-specific target genes. Recently, we have demonstrated that Runx3 is a neurogenic transcription factor, which regulates development and survival of proprioceptive neurons in dorsal root ganglia. Here we report that Runx3 and Runx1 are highly expressed in thymic medulla and cortex, respectively, and function in development of CD8 T cells during thymopoiesis. Runx3-deficient (Runx3 KO) mice display abnormalities in CD4 expression during lineage decisions and impairment of CD8 T cell maturation in the thymus. A large proportion of Runx3 KO peripheral CD8 T cells also expressed CD4, and in contrast to wild-type, their proliferation ability was largely reduced. In addition, the in vitro cytotoxic activity of alloimmunized peritoneal exudate lymphocytes was significantly lower in Runx3 KO compared with WT mice. In a compound mutant mouse, null for Runx3 and heterozygous for Runx1 (Runx3-/-;Runx1+/-), all peripheral CD8 T cells also expressed CD4, resulting in a complete lack of single-positive CD8+ T cells in the spleen. The results provide information on the role of Runx3 and Runx1 in thymopoiesis and suggest that both act as transcriptional repressors of CD4 expression during T cell lineage decisions.

Runx3 knockouts and stomach cancer

Gene targeting often results in knockout mice that show several phenotypes, some of which may not directly relate to the intrinsic function of the disrupted gene. Hence, to study the biological function of genes using knockout mice, one must identify the defects that are directly due to the loss of the targeted gene. Runx3 is a transcription factor that regulates lineage-specific gene expression in developmental processes. Recently, two groups produced Runx3 knockout mice. Two comparable defects were identified in both knockout strains, one involved neurogenesis and the other thymopoiesis. In addition, a stomach defect pertaining to gastric cancer was observed in one of the mutant strains, but not in the other. Here, we assess the differences between the two Runx3 mutant strains and discuss further studies that could reconcile these discrepancies. This article highlights the difficulties of inferring gene function through the interpretation of knockout phenotypes.

Phylogenesis and regulated expression of the RUNT domain transcription factors RUNX1 and RUNX3

The RUNX transcription factors are key regulators of lineage specific gene expression in developmental pathways. The mammalian RUNX genes arose early in evolution and maintained extensive structural similarities. Sequence analysis suggested that RUNX3 is the most ancient of the three mammalian genes, consistent with its role in neurogenesis of the monosynaptic reflex arc, the simplest neuronal response circuit, found in Cnidarians, the most primitive animals. All RUNX proteins bind to the same DNA motif and act as activators or repressors of transcription through recruitment of common transcriptional modulators. Nevertheless, analysis of Runx1 and Runx3 expression during embryogenesis revealed that their function is not redundant. In adults both Runx1 and Runx3 are highly expressed in the hematopoietic system. At early embryonic stages we found strong Runx3 expression in dorsal root ganglia neurons, confined to TrkC sensory neurons. In the absence of Runx3, knockout mice develop severe ataxia due to the early death of the TrkC neurons. Other phenotypic defects of Runx3 KO mice including abnormalities in thymopoiesis are also being investigated.

Expression of Runx1, -2 and -3 during tooth, palate and craniofacial bone development

We describe the expression of three Runt-related RUNX genes (previously termed AML, Cbfa, or Pebp2alpha) Runx1 and Runx3 during the development of teeth and other craniofacial tissues and compare them to Runx2 expression reported earlier. All three genes were expressed in mesenchymal condensates. Runx1 was expressed in several cartilage primordia earlier than Runx3, and Runx2 was intense in all mesenchymal condensations of bones and teeth. Only Runx1 was expressed in epithelia, and in tooth germs transcripts were detected in outer dental epithelium. Runx1 was also intensely expressed in the midline epithelium of palatal shelves. In early tooth morphogenesis Runx3 was coexpressed with Runx2 in a thin layer of mesenchymal cells underlying dental epithelium. Unlike Runx2, Runx3 was expressed in odontoblasts. However, Runx3 mutant mice did not show obvious tooth phenotype or deviations of Runx1 and Runx2 expression patterns in the tooth.

Inhibitory effect of white wine on gastric myoelectrical activity and the role of vagal tone

Although extensively investigated throughout the gastrointestinal tract, the influence of alcohol on gastric motility is still unclear. Our aim was to investigate the effect of wine on gastric myoelectrical activity and vagal activity. Ten healthy subjects were studied in two sessions with the electrogastrogram (EGG) for 30 min at baseline, 30 min after ingesting the test liquid [white wine (12.5% alcohol) or matched juice], and 60 min after a standard test meal. Spectral analysis was performed to compute EGG parameters and their postprandial changes. The vagal activity was assessed based on spectral analysis of the heart rate variability (HRV) signal derived from the ECG recording. White wine preload significantly diminished the postprandial increase in EGG dominant power compared to juice preload (1.16 +/- 1.57 vs 5.48 +/- 1.01 dB, P < 0.001). A significant decrease in vagal activity was observed after wine (23.40 +/- 4.30 vs 17.43 +/- 3.40%, P < 0.005), which remained unchanged after the test meal (23.40 +/- 4.30 vs 16.77 +/- 4.40%, P < 0.05). This decrease was not noted in the juice session. A correlation was established between changes after wine consumption in EGG dominant power and in the percentage of the vagal activity (r = 0.89, P < 0.05). In conclusion, white wine preload inhibits the postprandial EGG dominant power, suggesting a possible inhibition of postprandial gastric contractions. This effect may be associated with diminished vagal activity.

DNA recognition by the RUNX1 transcription factor is mediated by an allosteric transition in the RUNT domain and by DNA bending

The Runt domain proteins are transcription regulators of major developmental pathways. Here we present the crystal structures of the Runt domain (RD) of the human protein RUNX1 and its DNA binding site in their free states and compare them with the published crystal structures of RD bound to DNA and to the partner protein CBFbeta. We demonstrate that (1) RD undergoes an allosteric transition upon DNA binding, which is further stabilized by CBFbeta, and that (2) the free DNA target adopts a bent-helical conformation compatible with that of the complex. These findings elucidate the mechanism by which CBFbeta enhances RD binding to DNA as well as the role of the intrinsic conformation of the DNA target in the recognition process.

The Runx3 transcription factor regulates development and survival of TrkC dorsal root ganglia neurons

The RUNX transcription factors are important regulators of linage-specific gene expression in major developmental pathways. Recently, we demonstrated that Runx3 is highly expressed in developing cranial and dorsal root ganglia (DRGs). Here we report that within the DRGs, Runx3 is specifically expressed in a subset of neurons, the tyrosine kinase receptor C (TrkC) proprioceptive neurons. We show that Runx3-deficient mice develop severe limb ataxia due to disruption of monosynaptic connectivity between intra spinal afferents and motoneurons. We demonstrate that the underlying cause of the defect is a loss of DRG proprioceptive neurons, reflected by a decreased number of TrkC-, parvalbumin- and beta-galactosidase-positive cells. Thus, Runx3 is a neurogenic TrkC neuron-specific transcription factor. In its absence, TrkC neurons in the DRG do not survive long enough to extend their axons toward target cells, resulting in lack of connectivity and ataxia. The data provide new genetic insights into the neurogenesis of DRGs and may help elucidate the molecular mechanisms underlying somatosensory-related ataxia in humans.

Spatial and temporal expression pattern of Runx3 (Aml2) and Runx1 (Aml1) indicates non-redundant functions during mouse embryogenesis

The human RUNX3/AML2 gene belongs to the 'runt domain' family of transcription factors that act as gene expression regulators in major developmental pathways. Here, we describe the expression pattern of Runx3 during mouse embryogenesis compared to the expression pattern of Runx1. E10.5 and E14.5-E16.5 embryos were analyzed using both immunohistochemistry and beta-galactosidase activity of targeted Runx3 and Runx1 loci. We found that Runx3 expression overlapped with that of Runx1 in the hematopoietic system, whereas in sensory ganglia, epidermal appendages, and developing skeletal elements, their expression was confined to different compartments. These data provide new insights into the function of Runx3 and Runx1 in organogenesis and support the possibility that cross-regulation between them plays a role in embryogenesis.

The RUNX3 gene--sequence, structure and regulated expression

The RUNX3 gene belongs to the runt domain family of transcription factors that act as master regulators of gene expression in major developmental pathways. In mammals the family includes three genes, RUNX1, RUNX2 and RUNX3. Here, we describe a comparative analysis of the human chromosome 1p36.1 encoded RUNX3 and mouse chromosome 4 encoded Runx3 genomic regions. The analysis revealed high similarities between the two genes in the overall size and organization and showed that RUNX3/Runx3 is the smallest in the family, but nevertheless exhibits all the structural elements characterizing the RUNX family. It also revealed that RUNX3/Runx3 bears a high content of the ancient mammalian repeat MIR. Together, these data delineate RUNX3/Runx3 as the evolutionary founder of the mammalian RUNX family. Detailed sequence analysis placed the two genes at a GC-rich H3 isochore with a sharp transition of GC content between the gene sequence and the downstream intergenic region. Two large conserved CpG islands were found within both genes, one around exon 2 and the other at the beginning of exon 6. RUNX1, RUNX2 and RUNX3 gene products bind to the same DNA motif, hence their temporal and spatial expression during development should be tightly regulated. Structure/function analysis showed that two promoter regions, designated P1 and P2, regulate RUNX3 expression in a cell type-specific manner. Transfection experiments demonstrated that both promoters were highly active in the GM1500 B-cell line, which endogenously expresses RUNX3, but were inactive in the K562 myeloid cell line, which does not express RUNX3.

Architecture and anatomy of the genomic locus encoding the human leukemia-associated transcription factor RUNX1/AML1

The RUNX1 gene on human chromosome 21q22.12 belongs to the 'runt domain' gene family of transcription factors (also known as AML/CBFA/PEBP2alpha). RUNX1 is a key regulator of hematopoiesis and a frequent target of leukemia associated chromosomal translocations. Here we present a detailed analysis of the RUNX1 locus based on its complete genomic sequence. RUNX1 spans 260 kb and its expression is regulated through two distinct promoter regions, that are 160 kb apart. A very large CpG island complex marks the proximal promoter (promoter-2), and an additional CpG island is located at the 3' end of the gene. Hitherto, 12 different alternatively spliced RUNX1 cDNAs have been identified. Genomic sequence analysis of intron/exon boundaries of these cDNAs has shown that all consist of properly spliced authentic coding regions. This indicates that the large repertoire of RUNX1 proteins, ranging in size between 20-52 kDa, are generated through usage of alternatively spliced exons some of which contain in frame stop codons. The gene's introns are largely depleted of repetitive sequences, especially of the LINE1 family. The RUNX1 locus marks the transition from a ~1 Mb of gene-poor region containing only pseudogenes, to a gene-rich region containing several functional genes. A search for RUNX1 sequences that may be involved in the high frequency of chromosomal translocations revealed that a 555 bp long segment originating in chromosome 11 FLI1 gene was transposed into RUNX1 intron 4.1. This intron harbors the t(8;21) and t(3;21) chromosomal breakpoints involved in acute myeloid leukemia. Interestingly, the FLI1 homologous sequence contains a breakpoint of the t(11;22) translocation associated with Ewing's tumors, and may have a similar function in RUNX1.

Transcription-coupled translation control of AML1/RUNX1 is mediated by cap- and internal ribosome entry site-dependent mechanisms

AML1/RUNX1 belongs to the runt domain transcription factors that are important regulators of hematopoiesis and osteogenesis. Expression of AML1 is regulated at the level of transcription by two promoters, distal (D) and proximal (P), that give rise to mRNAs bearing two distinct 5' untranslated regions (5'UTRs) (D-UTR and P-UTR). Here we show that these 5'UTRs act as translation regulators in vivo. AML1 mRNAs bearing the uncommonly long (1,631-bp) P-UTR are poorly translated, whereas those with the shorter (452-bp) D-UTR are readily translated. The low translational efficiency of the P-UTR is attributed to its length and the cis-acting elements along it. Transfections and in vitro assays with bicistronic constructs demonstrate that the D-UTR mediates cap-dependent translation whereas the P-UTR mediates cap-independent translation and contains a functional internal ribosome entry site (IRES). The IRES-containing bicistronic constructs are more active in hematopoietic cell lines that normally express the P-UTR-containing mRNAs. Furthermore, we show that the IRES-dependent translation increases during megakaryocytic differentiation but not during erythroid differentiation, of K562 cells. These results strongly suggest that the function of the P-UTR IRES-dependent translation in vivo is to tightly regulate the translation of AML1 mRNAs. The data show that AML1 expression is regulated through usage of alternative promoters coupled with IRES-mediated translation control. This IRES-mediated translation regulation adds an important new dimension to the fine-tuned control of AML1 expression.

Regulation of AML2/CBFA3 in hematopoietic cells through the retinoic acid receptor alpha-dependent signaling pathway

AML2 is a member of the acute myelogenous leukemia, AML family of transcription factors. The biologic functions of AML1 and AML3 have been well characterized; however, the functional role of AML2 remains unknown. In this study, we found that AML2 protein expressed predominantly in cells of hematopoietic origin is a nuclear serine phosphoprotein associated with the nuclear matrix, and its expression is not cell cycle-related. In HL-60 cells AML2 expression can be induced by all three natural retinoids, all-trans-retinoic acid (RA), 13-cis-RA, and 9-cis-RA in a dose-dependent manner. A synthetic retinoic acid derivative, 4HPR, which neither activates RA receptor (RAR) alpha nor retinoic X receptor alpha was unable to induce the expression of AML2. A RAR-selective activator, TTNPB, induced AML2 expression similar to RA. Our study further showed that AGN193109, a potent RARalpha antagonist, suppressed AML2 expression induced by RA and that a retinoic X receptor pan agonist AGN194204 had no effect on its expression. Taken together, these studies conclusively demonstrated that the expression of AML2 in HL-60 cells is regulated through the RARalpha-specific signaling pathway. Our study further showed that after all-trans-retinoic acid priming, AML2 expression could be augmented by vitamin D(3). Based on these studies we hypothesize that AML2 expression is normally regulated by retinoid/vitamin D nuclear receptors mainly through the RARalpha-dependent signaling pathway and that it may play a role in hematopoietic cell differentiation.

Tannic acid and thiocarbohydrazide as structural reinforcement agents in the preparation of rabbit knee articular cartilage for the scanning electron microscope

Samples from seven sectors of the rabbit knee articular cartilage were shaved and prepared for the scanning electron microscope using either tannic acid, thiocarbohydrazide or nothing (control). Surface morphology was found to be more typical to a given sector and less so to a specific preparation procedure. Rough areas were recorded from load-bearing sectors, while smooth areas appeared on load-free ones. However, fibrillations were discerned on control load-bearing sectors only, and pits and humps were never detected. Tannic acid and thiocarbohydrazide may have exerted their structural reinforcing effect on the tissue preservation by enhancing the binding of osmium tetroxide to it, possibly along with that of other soluble tissue constituents.

Regenerating synovial lining of the normal rabbit knee: a scanning electron microscopy study

Regeneration of the synovial lining in the synovectomized rabbit knee was studied using the scanning electron microscope. The resected synovia regenerated considerably 3 weeks after synovectomy. However, 44 weeks following excision, their surface morphology was still very different from that of the normal tissue of intact animals. The regenerated synovia were characterized by three main features: the large number of various patterns, the many fields harboring fibrillation and the almost total lack of a bubble layer (the latter was formerly shown to be predominant on normal, intact synovia). The surface morphology of the non-operated (contralateral) knee differed greatly from that of normal synovia. The surface of sham-operated synovia was totally covered by the bubble layer. The appearance of vast fields harboring fibrillations indicated deficient ultrastructural regeneration. The altered surface morphology of the contralateral synovia was a novel finding. We wonder whether it would be appropriate to propose that the systemic reaction induced by synovectomy of the experimental knee initiated the synovial appearances recorded on the contralateral knee. The data reported here rule out the possibility of using the contralateral leg as an intact control.

Transcriptional repression by AML1 and LEF-1 is mediated by the TLE/Groucho corepressors

The mammalian AML/CBFalpha runt domain (RD) transcription factors regulate hematopoiesis and osteoblast differentiation. Like their Drosophila counterparts, most mammalian RD proteins terminate in a common pentapeptide, VWRPY, which serves to recruit the corepressor Groucho (Gro). Using a yeast two-hybrid assay, in vitro association and pull-down experiments, we demonstrate that Gro and its mammalian homolog TLE1 specifically interact with AML1 and AML2. In addition to the VWRPY motif, other C-terminal sequences are required for these interactions with Gro/TLE1. TLE1 inhibits AML1-dependent transactivation of the T cell receptor (TCR) enhancers alpha and beta, which contain functional AML binding sites, in transfected Jurkat T cells. LEF-1 is an additional transcription factor that mediates transactivation of TCR enhancers. LEF-1 and its Drosophila homolog Pangolin (Pan) are involved in the Wnt/Wg signaling pathway through interactions with the coactivator beta-catenin and its highly conserved fly homolog Armadillo (Arm). We show that TLE/Gro interacts with LEF-1 and Pan, and inhibits LEF-1:beta-catenin-dependent transcription. These data indicate that, in addition to their activity as transcriptional activators, AML1 and LEF-1 can act, through recruitment of the corepressor TLE1, as transcriptional repressors in TCR regulation and Wnt/Wg signaling.

Expression of AML1-d, a short human AML1 isoform, in embryonic stem cells suppresses in vivo tumor growth and differentiation

The human AML1 gene encodes a heterodimeric transcription factor which plays an important role in mammalian hematopoiesis. Several alternatively spliced AML1 mRNA species were identified, some of which encode short protein products that lack the transactivation domain. When transfected into cells these short isoforms dominantly suppress transactivation mediated by the full length AML1 protein. However, their biological function remains obscure. To investigate the role of these short species in cell proliferation and differentiation we generated embryonic stem (ES) cells overexpressing one of the short isoforms, AML1-d, as well as cells expressing the full length isoforms AML1-b and AML2. The in vitro growth rate and differentiation of the transfected ES cells were unchanged. However, overexpression of AML1-d significantly affected the ES cells' ability to form teratocarcinomas in vivo in syngeneic mice, while a similar overexpression of AML1-b and AML2 had no effect on tumor formation. Histological analysis revealed that the AML1-d derived tumors were poorly differentiated and contained numerous apoptotic cells. These data highlight the pleiotropic effects of AML1 gene products and demonstrate for the first time an in vivo growth regulation function for the short isoform AML1-d.

Impaired postprandial gastric slow waves in patients with functional dyspepsia

The aim of this study was to investigate gastric myoelectrical activity in patients with functional dyspepsia. Thirteen healthy subjects and 14 patients with functional dyspepsia participated in the study. The electrogastrogram (EGG) recording was made in each subject for 30 min in the fasting state and 120 min after a standard test meal of 475 calories. Spectral analysis methods were applied to derive quantitative EGG parameters. There was no difference in the EGG between the patients and controls in the fasting state. However, abnormalities in the postprandial EGG were found in the patients. The percentage of 2-4 cpm waves was significantly lower (74.4+/-4.0% vs 85.7+/-1.6%, P < 0.03) and the postprandial increase in EGG dominant power was significantly less (-0.52+/-0.92 dB vs 2.24+/-0.88 dB, P < 0.03) in patients than in controls. It was also found that the percentage of postprandial 2-4 cpm waves could be used to differentiate the patients with functional dyspepsia from the healthy controls with a specificity of 100% and a sensitivity of 43%. It was concluded that a subset of patients with functional dyspepsia have impaired gastric myoelectrical activity in the fed state.