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Background & Aims Environmental enteric dysfunction (EED) limits the Sustainable Development Goals of improved childhood growth and survival. We applied mucosal genomics to advance our understanding of EED. Methods The Study of Environmental Enteropathy and Malnutrition (SEEM) followed 416 children from birth to 24 months in a rural district in Pakistan. Biomarkers were measured at 9 months and tested for association with growth at 24 months. The duodenal methylome and transcriptome were determined in 52 undernourished SEEM participants and 42 North American controls and patients with celiac disease. Results After accounting for growth at study entry, circulating insulin-like growth factor-1 (IGF-1) and ferritin predicted linear growth, whereas leptin correlated with future weight gain. The EED transcriptome exhibited suppression of antioxidant, detoxification, and lipid metabolism genes, and induction of anti-microbial response, interferon, and lymphocyte activation genes. Relative to celiac disease, suppression of antioxidant and detoxification genes and induction of antimicrobial response genes were EED-specific. At the epigenetic level, EED showed hyper-methylation of epithelial metabolism and barrier function genes, and hypo-methylation of immune response and cell proliferation genes. Duodenal coexpression modules showed association between lymphocyte proliferation and epithelial metabolic genes and histologic severity, fecal energy loss, and wasting (weight-for-length/height Z < -2.0). Leptin was associated with expression of epithelial carbohydrate metabolism and stem cell renewal genes. Immune response genes were attenuated by giardia colonization. Conclusions Children with reduced circulating IGF-1 are more likely to experience stunting. Leptin and a gene signature for lymphocyte activation and dysregulated lipid metabolism are implicated in wasting, suggesting new approaches for EED refractory to nutritional intervention. ClinicalTrials.gov, Number: NCT03588013. (https://clinicaltrials.gov/ct2/show/NCT03588013), Graphical abstract

Molecular mechanisms driving disease course and response to therapy in ulcerative colitis (UC) are not well understood. Here, we use RNAseq to define pre-treatment rectal gene expression, and fecal microbiota profiles, in 206 pediatric UC patients receiving standardised therapy. We validate our key findings in adult and paediatric UC cohorts of 408 participants. We observe a marked suppression of mitochondrial genes and function across cohorts in active UC, and that increasing disease severity is notable for enrichment of adenoma/adenocarcinoma and innate immune genes. A subset of severity genes improves prediction of corticosteroid-induced remission in the discovery cohort; this gene signature is also associated with response to anti-TNFα and anti-α4β7 integrin in adults. The severity and therapeutic response gene signatures were in turn associated with shifts in microbes previously implicated in mucosal homeostasis. Our data provide insights into UC pathogenesis, and may prioritise future therapies for nonresponders to current approaches., The severity of ulcerative colitis, and response to treatment, is highly variable. Here, the authors examine rectal gene expression signatures and faecal microbiomes of children and adults with the disease and provide new insights in to pathogenesis.

Strong viral enhancers in gammaretrovirus vectors have caused cellular proto-oncogene activation and leukemia, necessitating the use of cellular promoters in “enhancerless” self-inactivating integrating vectors. However, cellular promoters result in relatively low transgene expression, often leading to inadequate disease phenotype correction. Vectors derived from foamy virus, a nonpathogenic retrovirus, show higher preference for nongenic integrations than gammaretroviruses/lentiviruses and preferential integration near transcriptional start sites, like gammaretroviruses. We found that strong viral enhancers/promoters placed in foamy viral vectors caused extremely low immortalization of primary mouse hematopoietic stem/progenitor cells compared to analogous gammaretrovirus/lentivirus vectors carrying the same enhancers/promoters, an effect not explained solely by foamy virus' modest insertional site preference for nongenic regions compared to gammaretrovirus/lentivirus vectors. Using CRISPR/Cas9-mediated targeted insertion of analogous proviral sequences into the LMO2 gene and then measuring LMO2 expression, we demonstrate a sequence-specific effect of foamy virus, independent of insertional bias, contributing to reduced genotoxicity. We show that this effect is mediated by a 36-bp insulator located in the foamy virus long terminal repeat (LTR) that has high-affinity binding to the CCCTC-binding factor. Using our LMO2 activation assay, LMO2 expression was significantly increased when this insulator was removed from foamy virus and significantly reduced when the insulator was inserted into the lentiviral LTR. Our results elucidate a mechanism underlying the low genotoxicity of foamy virus, identify a novel insulator, and support the use of foamy virus as a vector for gene therapy, especially when strong enhancers/promoters are required. IMPORTANCE Understanding the genotoxic potential of viral vectors is important in designing safe and efficacious vectors for gene therapy. Self-inactivating vectors devoid of viral long-terminal-repeat enhancers have proven safe; however, transgene expression from cellular promoters is often insufficient for full phenotypic correction. Foamy virus is an attractive vector for gene therapy. We found foamy virus vectors to be remarkably less genotoxic, well below what was expected from their integration site preferences. We demonstrate that the foamy virus long terminal repeats contain an insulator element that binds CCCTC-binding factor and reduces its insertional genotoxicity. Our study elucidates a mechanism behind the low genotoxic potential of foamy virus, identifies a unique insulator, and supports the use of foamy virus as a vector for gene therapy.

Eosinophilic esophagitis (EoE) is an allergic inflammatory disorder of the esophagus that is compounded by genetic predisposition and hypersensitivity to environmental antigens. Using high-density oligonucleotide expression chips, a disease-specific esophageal transcript signature was identified and was shown to be largely reversible with therapy. In an effort to expand the molecular signature of EoE, we performed RNA sequencing on esophageal biopsies from healthy controls and patients with active EoE and identified a total of 1607 significantly dysregulated transcripts (1096 upregulated, 511 downregulated). When clustered by raw expression levels, an abundance of immune cell-specific transcripts are highly induced in EoE but expressed at low (or undetectable) levels in healthy controls. Moreover, 66% of the gene signature identified by RNA sequencing was previously unrecognized in the EoE transcript signature by microarray-based expression profiling and included several long non-coding RNAs (lncRNA), an emerging class of transcriptional regulators. The lncRNA BRAF-activated non-protein coding RNA (BANCR) was upregulated in EoE and induced in interleukin-13 (IL-13)-treated primary esophageal epithelial cells. Repression of BANCR significantly altered the expression of IL-13-induced proinflammatory genes. Together, these data comprise new potential biomarkers of EoE and demonstrate a novel role for lncRNAs in EoE and IL-13-associated responses.

Background The goal of this study was to identify transcriptomic signatures (RNA-Seq) in human peripheral blood mononuclear cells (PBMCs) and breast milk lymphocyte cells (BMLCs) in response to trivalent inactivated influenza vaccine (TIV) or live attenuated influenza vaccine (LAIV). Methods We performed a randomized, double-blind study in breastfeeding women who received either LAIV and intramuscular placebo, or TIV and intranasal placebo. A subset of subjects with available samples (LAIV, n = 10 and TIV, n = 6) was used for this study. Human milk was collected on days 0, 2, 8, and 28, and blood samples were collected on days 0 and 28. PBMC and BMLC RNA was extracted for RNA-Seq and differentially expressed (DE) gene analysis. Results We identified a total of 382 DE BMLC genes in the LAIV group, most of which were up-regulated at day 28. DE genes were preferentially involved in innate immune signaling pathways including cytokine-cytokine receptor interaction, TNF signaling, and NF-kappa B signaling. For TIV, 3 DE genes were identified of which 2 (IL1A and IL1B) overlapped with LAIV. Response time trends for co-expressed gene clusters by vaccine group showed that LAIV generally induced an early (day 2) up-regulation of innate immune signaling pathway genes, while TIV induced peak innate immune signaling gene responses ahead of LAIV (day 8 vs. day 28). A group of known interferon-alpha/β-inducible genes (IFIT3, OAS3, IFI44L, MX1, OAS2, IFIT1, IFI6) showed higher responses at day 2 for TIV but stronger peak levels by day 28 for the LAIV group (Fig 1). While no such innate immune signaling responses were observed in PBMCs at day 28, we identified an up-regulation of IgG gene (IGHG1 and IGHG3) expression in the TIV group (Fig 2). Conclusion We observed increased innate immune signaling responses in BMLC but not in PBMC at day 28 for the LAIV group. We hypothesize that breastfeeding extends the innate response to LAIV via mucosal immunity. Gene cluster time trends indicated an earlier innate immune signaling response for TIV. The day 28 increase in IGHG3 gene expression levels in TIV group PBMCs was correlated with corresponding increases in serum ELISA IgG titers for the influenza B antigen (Fig 3). Additional studies are required to investigate the differences in innate response signaling seen for BMLC and PBMC in this study. Disclosures All authors: No reported disclosures.

RhoA GTPase has been shown in vitro in cell lines and in vivo in nonmammalian organisms to regulate cell division, particularly during cytokinesis and abscission, when 2 daughter cells partition through coordinated actomyosin and microtubule machineries. To investigate the role of this GTPase in the rapidly proliferating mammalian erythroid lineage, we developed a mouse model with erythroid-specific deletion of RhoA. This model was proved embryonic lethal as a result of severe anemia by embryonic day 16.5 (E16.5). The primitive red blood cells were enlarged, poikilocytic, and frequently multinucleated, but were able to sustain life despite experiencing cytokinesis failure. In contrast, definitive erythropoiesis failed and the mice died by E16.5, with profound reduction of maturing erythroblast populations within the fetal liver. RhoA was required to activate myosin-regulatory light chain and localized at the site of the midbody formation in dividing wild-type erythroblasts. Cytokinesis failure caused by RhoA deficiency resulted in p53 activation and p21-transcriptional upregulation with associated cell-cycle arrest, increased DNA damage, and cell death. Our findings demonstrate the role of RhoA as a critical regulator for efficient erythroblast proliferation and the p53 pathway as a powerful quality control mechanism in erythropoiesis.

Interactions between the host and gut microbial community likely contribute to Crohn disease (CD) pathogenesis; however, direct evidence for these interactions at the onset of disease is lacking. Here, we characterized the global pattern of ileal gene expression and the ileal microbial community in 359 treatment-naive pediatric patients with CD, patients with ulcerative colitis (UC), and control individuals. We identified core gene expression profiles and microbial communities in the affected CD ilea that are preserved in the unaffected ilea of patients with colon-only CD but not present in those with UC or control individuals; therefore, this signature is specific to CD and independent of clinical inflammation. An abnormal increase of antimicrobial dual oxidase (DUOX2) expression was detected in association with an expansion of Proteobacteria in both UC and CD, while expression of lipoprotein APOA1 gene was downregulated and associated with CD-specific alterations in Firmicutes. The increased DUOX2 and decreased APOA1 gene expression signature favored oxidative stress and Th1 polarization and was maximally altered in patients with more severe mucosal injury. A regression model that included APOA1 gene expression and microbial abundance more accurately predicted month 6 steroid-free remission than a model using clinical factors alone. These CD-specific host and microbe profiles identify the ileum as the primary inductive site for all forms of CD and may direct prognostic and therapeutic approaches.

Safely achieving long-term engraftment of genetically modified hematopoietic stem cells (HSCs) that maintain therapeutic transgene expression is the benchmark for successful application of gene therapy for hemoglobinopathies. We used the pigtailed macaque HSC transplantation model to ascertain the long-term safety and stability of a γ-globin lentivirus vector. We observed stable gene-modified cells and fetal hemoglobin expression for 3 years. Retrovirus integration site (RIS) analysis spanning 6 months to 3.1 years revealed vastly disparate integration profiles, and dynamic fluctuation of hematopoietic contribution from different gene-modified HSC clones without evidence for clonal dominance. There were no perturbations of the global gene-expression profile or expression of genes within a 300 kb region of RIS, including genes surrounding the most abundantly marked clones. Overall, a 3-year long follow-up revealed no evidence of genotoxicity of the γ-globin lentivirus vector with multilineage polyclonal hematopoiesis, and HSC clonal fluctuations that were not associated with transcriptome dysregulation.

In spite of tremendous advances in the analysis of hematopoietic progenitors and transcription factors that give rise to different lineages, molecular insight into the mechanisms that underlie cell fate choice at the level of individual cells is lacking. We utilized single-cell RNA sequencing of murine granulocyte-monocyte progenitors (GMPs) to analyze the molecular basis of cell fate choice. Over 200 libraries were generated with average read depths of 4 million per library and an expressed gene call of over 3,800 genes with FPKM >3. Our data reveal a varied but coherent spectrum of gene expression patterns in individual murine GMPs. The majority of cells could be clustered into ones expressing either granulocytic or monocytic genes, suggesting that they were primed for lineage determination. A minority of GMPs expressed a mixed-lineage pattern of genes. The single-cell data suggested an antagonistic transcription factor circuit involving Gfi1 and IRF8 that was validated with both loss- and gain-of-function experiments in GMPs. Our data highlight the utility of single cell RNA-Seq analysis to reveal molecular mechanisms controlling lineage fate decisions in hematopoiesis. Disclosures No relevant conflicts of interest to declare.

matched controls without IBD. Information including diagnosis, IBD type, IBD activity, IBD medications, proton pump inhibitor (PPI) use, hospitalizations and antibiotic use was recorded. Patients were followed with repeat fecal and serum samples obtained. Cytotoxic culture for CD along with PCR to detect the toxin B gene was conducted on stool. Pulsed field gel electrophoresis (PFGE) was performed to determine strain type. Enzyme-linked Immunosorbent Assay (ELISA) was used to determine immunoglobulin G, A andM responses to CD toxin A and B from serum. Results: The prevalence of CD carriage was significantly greater in patients with IBD (17%) compared with controls (3%) (p=0.012). PCR to detect the toxin B gene compared to the gold standard of cytotoxic culture had a sensitivity of 92% and specificity of 100%. No patients showed clinical evidence of active CD infection. Among patients with IBD, IBD type, disease activity, IBD therapy, antibiotic use and hospitalizations were not found to be associated with CD carriage. PPI use was significantly more frequent in patients with CD carriage (54% vs. 25%, p,0.05). PFGE identified 6 different North American Pulsed Field Type (NAP) strains that then varied over time. There was a significantly greater proportion of patients with a positive antibody response to toxin A with IBD (69%) vs. controls (53%) (p,0.05), with a parallel trend of increased IgG and IgA responses against both toxin A and toxin B in those with IBD. Conclusions: Our findings show that asymptomatic toxigenic CD carriage, likely acquired in the community, is increased in pediatric IBD outpatients compared with controls. A variety of NAP strains were identified and these changed over time in CD colonized patients. PPI use was associated with an increased risk of carriage. Antibody responses of patients with IBD to CD toxins were increased, potentially promoting asymptomatic colonization. Future studies are needed to identify risk factors for symptomatic CD in pediatric IBD.

Abstract 976 Introduction: Erythrocyte cytoskeleton disorders, a common cause of hereditary hemolytic anemia, consist of a genetically and phenotypically variable group of diseases that include hereditary spherocytosis (HS), elliptocytosis (HE), pyropoikilocytosis (HPP), and stomatocytosis (HSt) syndromes. The diagnosis is most commonly based on the morphology of the red blood cells (RBCs) on the blood smear and on ektacytometry and osmotic fragility studies. However, in infants and children with transfusion-dependent hemolytic anemia these studies are challenging to obtain since the patient has mostly transfused RBCs. Molecular diagnosis has not been easily attainable so far due to the number and large size of the genes involved in pathogenesis and due to the fact that each kindred has frequently a private mutation in the responsible gene(s) (Gallagher, Hematology, 2005). Methods and Results: We have developed a high-throughput assay for the diagnosis of known and discovery of new genetic mutations causing erythrocyte cytoskeleton disorders. The complete exon sequences of 24 genes encoding cytoskeleton proteins (spectrin a-chain (SPTA1), spectrin b-chain (SPTB), ankyrin 1 (ANK1), band 3 (SLC4A1), protein 4.1 (EPB41), protein 4.2 (EPB42), adducins (ADD), dematin (EPB49), tropomyosins (TPM), tropomodulins (TMOD), Rh-associated glycoprotein (RhAG), erythrocyte protein p55 (MPP1), stomatin (EPB72), Glut1-glucose transporter (SLC2A1), and K-Cl-cotransporter (SLC12A4, SLC12A6, SLC12A7) were determined using a Next Generation Sequencing technology. Analysis was performed on eleven patients diagnosed with erythrocyte cytoskeleton disorder along with a negative control. Informed consent was obtained from all subjects under an Institutional Review Board-approved protocol. The RainDance Technologies RDT1000 instrument was used for target enrichment covering the exons, 20 bases of exon/intron junctions, and 500 bases up and downstream of the 24 genes of interest. The products were then sequenced on an Illumina HiSeq2000 system. Bioinformatic analysis was performed in a blinded fashion as to the disease characteristics and inheritance mode of the patient using the GATK software package from the Broad Institute (DePristo et al, Nature Genetics, 2011). Mutations predicted to have significant impact to the corresponding protein structure and therefore likely to cause disease were identified in 9 out of the 11 patients ( Table 1 ). Shared pathogenic mutation(s) were identified blindly in family members, e.g. siblings HS-S1 and HS-S2, or parents sHS-M, sHS-F with child sHS. Two EPB49 mutations predicted to impair gene function were identified in an infant with clinical picture of HPP, implicating dematin in HPP pathogenesis. Immunoblotting of RBC membranes from this patient demonstrated decreased dematin. Conclusions: Next generation sequencing for the genetically variable erythrocyte cytoskeleton disorders can provide a cost-effective and faster patient diagnosis compared with a gene-by-gene approach and it is a feasible diagnostic method in a transfusion-dependent child. Moreover, a precise genetic diagnosis can facilitate natural history studies to understand genotype-phenotype correlations in the erythrocyte cytoskeleton disorders and offer valuable insights into the structure-function relationship of the erythrocyte cytoskeleton proteins. Table 1 . Characteristics of patients with erythrocyte cytoskeleton disorder tested and corresponding gene mutation(s) identified. # Subject Phenotype Gene Mutation Comment 1 HS-S1 Mild HS SPTB Q1946* Sibling of HS-S2 2 HS-S2 Mild HS SPTB Q1946* 3 sHS Severe HS SPTA1 SPTB I2262T R1972Q 4 sHS-M Asymptomatic SPTA1 I2262T Mother of sHS 5 s-HS-F Asymptomatic SPTB R1972Q Father of sHS 6 TDHA Transfusion-dependent hemolytic anemia SPTA1 SPTA1 L1432* A970D No family history 7 HS-3 Mild HS SLC4A1 E473Gfs*38 Father with HS 8 HS-4 Moderate HS SPTA1 c.1351-1G>T Father with HS 9 HPP Neonate with HPP, transfusion requirement resolved after 4 months of age EPB49 R19Q and K170R No family history 10 HS-5 Moderate chronic hemolysis None found No family history 11 HE-1 Severe hemolytic anemia, compensated after 18 months of age None found Mother with mild HE Disclosures: No relevant conflicts of interest to declare.

Abstract 111 Growth Factor Independence 1 (Gfi1) is a regulator of HSC maintenance, and lack of Gfi1 leads to myeloid progenitor accumulation and neutropenia. The Gfi1 transcription factor contains both a SNAG repressor domain, and a zinc-finger DNA-binding domain. A proline to alanine substitution at position 2 in the SNAG domain (P2A) blocks RCoR/Lysine Specific Demethylase 1 (LSD1) interaction and abrogates Gfi1-mediated repression. Mouse models have been developed which either delete Gfi1 exons 2–3 (Gfi1Δex2-3) or knock in the P2A mutation (GfiP2A). Both models are neutropenic, and demonstrate an accumulation of arrested myeloid progenitors. Transgenic shRNA knockdown of Lsd1 in the hematopoietic system results in the accumulation of myeloid progenitors and inhibits terminal granulocytic differentiation; however, the role of Lsd1/Gfi1 in this process has not been established. To characterize the global role of Gfi1 dependent transcriptional regulation in progenitor maintenance and lineage determination, we utilized a Next Generation Sequencing (NGS) approach to profile Gfi1Δex2-3and GfiP2A lineage negative bone marrow cells. Using gene-level analyses, a representative group of 1,019 genes were identified that exhibited more than 1.5 fold deregulation (by FPKM) and differential gene expression relative to WT sample profiles in at least one model. Interestingly, some of the Gfi1-dependent genes encode putative lncRNAs, which were validated independently. Using an shRNA mediated approach, we identified one lncRNA whose expression (like Gfi1) affects the granulo- monocytic balance of differentiating myeloid progenitors. Bioinformatic interrogation revealed that genes regulated by Gfi1 are mainly involved in normal and aberrant progenitor regulation, with processes such as immunology, signal transduction, and myelopoiesis modestly represented. Given the phenotype of Lsd1 knockdown in hematopoietic cells, we hypothesized that loss of Gfi1 (and/or SNAG) activity would disrupt Lsd1 activity at Gfi1-target genes, resulting in the accumulation of histone 3 lysine 4 dimethyl (H3K4me2) marks. For the subset of genes deregulated in both Gfi1Δex2-3and GfiP2A models, chromatin immunoprecipitation revealed direct Gfi1 DNA binding and increased H3K4me2 marks in a majority of the significantly deregulated genes. We previously showed that accumulation of Gfi1 null myeloid progenitors was dose dependent upon the Gfi1 target gene HoxA9. In our current experiments, HoxA9 was deregulated in both Gfi1 null and Lsd1 knockdown, bound by Gfi1 in ChIP, and showed increased H3K4me2 peaks upon Gfi1 loss; providing a mechanistic explanation for the common phenotypes of Gfi1 null and Lsd1 knockdown in hematopoietic progenitors. Our results collectively reveal multiple transcriptional circuits controlled by the Gfi1/Lsd1 complex underlying normal progenitor maintenance and differentiation. Disclosures: No relevant conflicts of interest to declare.

Abstract 13 Mutations in ELANE, GFI1, G6PC3, and HAX1 account for the genetic defects in many patients with severe congenital neutropenia (SCN). Here we utilized next generation sequencing technology to characterize genome-wide transcriptome activity and chromatin structure states associated with normal and SCN–affected hematopoietic precursor cells. We profiled cells from Gfi1−/−, Gfi1P2A, LysM-Cre Mcl1flox and wild type mice. Growth factor independent-1 (Gfi1) is a zinc finger transcription repressor required for murine and human granulopoiesis. In Gfi1−/− bone marrow cells, the genetic lack of Gfi1 protein blocks granulopoietic programming. In Gfi1P2A knockin mice the Gfi1 protein is made, but the substitution of alanine for proline (P2A) inhibits the function of the SNAG transcriptional repressor domain; resulting in neutropenia. Mcl1 is a Bcl2 family member required for the survival of multiple hematopoietic lineage cells. LysM-Cre Mcl1flox mice are neutropenic due to myeloid-lineage-specific Cre-mediated deletion of Mcl1 and subsequent apoptosis of neutrophil progenitors after the metamyelocyte stage. Other hematopoietic lineages in LysM-Cre-Mcl1flox mice are normal. Thus, all three models are neutropenic; two lack a functional lineage specifying transcription factor while one lacks a survival factor. Bone marrow cells from each of these mouse models were processed through Miltenyi AutoMacs lineage-depletion. Total RNA was extracted and subjected to paired-end deep RNA-sequencing using Illumina Truseq library preparation methods. Reads were aligned to the reference mouse mm9 genome and Refseq and ENSEMBL gene transcript models using Tophat, Bowtie, and Cufflinks analysis suite. Both gene and transcript model specific gene expression level were estimated using the fragments per kilobase of exon model per million mapped reads (FKPM) approach. Using gene-level analyses, a representative group of 2,186 genes were identified that exhibited relatively high level expression (>50th %ile by FPKM in at least one sample type) and differential gene expression relative to WT sample profiles in at least one model. First, our data indicate that the SNAG domain is critical for most Gfi1 associated functions. The SNAG domain associates with the Lysine specific demethylase-1 (Lsd1), an enzyme which removes histone 3 lysine 4 dimethyl (H3K4me2) marks. Chromatin immunoprecipitation revealed increased H3K4me2 marks in many genes deregulated in Gfi1−/− and Gfi1P2A Lin- bone marrow cells. Moreover, the group of genes overexpressed in Gfi1−/− and Gfi1P2A Lin- bone marrow cells was functionally associated with a variety of signal transduction and transcriptional control programs responsible for the development and differentiation of myeloid and lymphoid lineages, whereas genes that were commonly downregulated were associated with erythroid development. Many of the overexpressed immune myeloid genes were the targets of the ETS family of transcription factors and included a rich overrepresentation of genes associated with vesicle/lysosome/ and granule formation. Furthermore, using statistical and clustering-based analyses, approximately 70% of the dysregulated genes exhibited similar over-expression and under-expression in all three models. The large scale similarity of these patterns and the disparate genetic and biological mechanism of neutropenia in the three models suggests an underlying signature of the bone marrow progenitor activation in response to neutropenia. To confirm these findings in a different setting, we next examined the gene expression of human CD34+ cells from several ELANE mutant SCN patients and a single GFI1N382S patient, compared to normal CD34+ cells. Notably, all patients received G-CSF. In fact, a significant number of genes differentially expressed between ELANE and normal CD34+ cells were commonly deregulated in the GFI1 patient sample. Thus, human samples also demonstrate a signature associated with bone marrow progenitor activation in response to neutropenia. Our results reveal not only the transcriptional circuits controlled by Gfi1, but also cell autonomous transcriptional circuits underlying neutropenia. Disclosures: No relevant conflicts of interest to declare.