Natural killer cells defend against malignancies and viral infections through a tightly controlled program of differentiation and maturation. However, the transcriptional mechanisms guiding this process remain incompletely defined. Using paired single-cell multiomic profiling, we identify GFI1 as an epigenetic regulator of NK cell differentiation, coordinating EOMES and T-BET transcriptional balance to promote NK cell proliferation and the transition from immature to terminally differentiated NK cell states. GFI1 represses FOXO1 chromatin accessibility in mature NK cells, which normally limits NK cell proliferation and maturation. Co-deletion of both GFI1 and FOXO1 largely rescues NK cell differentiation, identifying a critical GFI1-FOXO1 axis required for protection against tumour metastasis. These findings position GFI1 as a key transcriptional node integrating NK cell differentiation, activation and effector programs.

Heterozygous variants in the KAT6A gene encoding the histone lysine acetyltransferase KAT6A (MOZ, MYST3) cause Arboleda-Tham syndrome, a cognitive impairment syndrome. Histone acetylation is generally associated with active gene transcription. Genetic deletion of both alleles of the Kat6a gene in mice causes developmental defects including anterior homeotic transformation, cleft palate, interrupted aortic arch and cardiac septal defects. Loss of KAT6A impairs expression of HOX, DLX and TBX genes, which are essential for body segment identity specification, palate, heart and aortic arch development. However, the effects of loss of KAT6A on chromatin modifications and gene expression in neural cells, which are relevant to normal brain development and function, is still poorly understood. In this study, we used an automated high-throughput chromatin profiling method and RNA sequencing in mouse neural system and progenitor cells to assess the effects of loss of one or two alleles of Kat6a on gene expression, histone acetylation and methylation. We also assessed occupancy by a trithorax group protein and RNA polymerase II. Our data suggests two modes of action for KAT6A: (1) acetylation of histone H3 on lysine 23 at promoters and enhancers and (2) recruitment of the trithorax group protein MLL1 (KMT2A) to promote the expression of developmental genes, including SOX and homeodomain genes. Together, these two functions appear to be required for normal gene expression in neural progenitors and essential for proliferation and neuronal differentiation.

Pathogenic variants in one allele of the KAT6A gene encoding the histone acetyltransferase KAT6A (MOZ, MYST3) cause Arboleda-Tham syndrome (ARTHS), characterised by developmental delay, cognitive impairment, and autism-like behaviours. As histone acetylation is reversible, and brain development continues after birth, treatments that address deficits in histone acetylation may ameliorate the condition. Here, we examined the effects of ARTHS mutations on histone acetylation in human cells and the effects of heterozygous loss of Kat6a in mice (Kat6a+/-) on learning, memory, activity, and sociability. We found that KAT6A was required for normal levels of histone H3 lysine 23 acetylation (H3K23ac) in human cells and mouse brain. Kat6a+/- mice displayed hyperactivity and learning, memory, and sociability deficits compared with WT mice. Treatment with the acetyl-donor, acetyl-L-carnitine (ALCAR) resulted in the rescue of H3K23ac levels in mouse brain and amelioration of the hyperactivity and learning impairments. Our results suggest that some individuals with ARTHS might benefit from ALCAR treatment. However, the suitability of ALCAR treatment would depend on the specific KAT6A variant and should be discussed with health professionals.

Abstract PU.1 is an ETS-domain transcription factor that has critical roles in many aspects of hematopoiesis and immune cell fate and function. In addition, aberrant PU.1 expression has been implicated in the development of acute myeloid leukemia (AML). Loss of PU.1 during adult murine hematopoiesis results in the expansion of immature granulocytes suggesting that PU.1 plays an important role in granulocyte maturation. To understand the molecular underpinnings of this process, we combined gene expression, transcription factor binding and 3D genome analyses with conditional deletion of PU.1 in vivo. We find that in contrast to normal granulocytes, PU.1-deficient cells possessed a transcriptome of immature granulocytes, in line with their cellular phenotype. Furthermore PU.1-deficient granulocytes display altered 3D genome architecture with a significant loss of interactivity in regions bound by PU.1 in control cells. Overall, this study implicates PU.1 as a key regulator of granulocyte maturation and lineage commitment through control of transcriptional programs and 3D chromatin architecture.

KAT6A (MOZ) and KAT6B (QKF/MORF) are related histone lysine acetyltransferases (KATs) that have a high degree of functional redundancy during development. In the absence of KAT6A, embryos undergo an anterior homeotic transformation of the axial skeleton, develop an interrupted aortic arch, have ventricular septal defects and fail to form definitive hematopoietic stem cells. KAT6B has roles in brain, skeletal and hematopoietic system development. Because loss of KAT6A leads to highly penetrant phenotypes, this allows us to determine whether the acetylation function is essential for all activities. We show that loss of acetyltransferase activity did not phenocopy the loss of the KAT6A protein in mice. Although mutation of the KAT domains of both KAT6A and KAT6B together increased the severity of phenotypes observed, these were milder than complete KAT6A loss of function. KAT domain mutants displayed ventricular septal defects and reduced (but not eliminated) hematopoietic stem cell activity. However, they did not display homeotic transformations or aortic arch defects, suggesting that, while acetylation is important for some functions, others can proceed without this activity. Accordingly, KAT6 proteins appear to have functions beyond acetylation.

Given that the SARS-CoV-2 virus, and the COVID-19 pandemic, constitutes a major environmental challenge faced by billions of people worldwide, we investigated whether paternal pre-conceptual SARS-CoV-2 infection has impacts on sperm RNA content, and intergenerational (F1) and transgenerational (F2) effects on offspring phenotypes. Using an established mouse-adapted SARS-CoV-2 (P21) preclinical model, we infected adult male mice with the virus, or performed a mock control infection, and bred them with naïve female mice four weeks later, when males were no longer infectious. Here we show that offspring of infected sires display increased anxiety-like behaviors. Additionally, the F1 offspring have significant transcriptomic changes in their hippocampus. Various sperm small noncoding RNAs, including PIWI-interacting RNAs, transfer-derived RNAs and microRNAs, are differentially altered by prior paternal SARS-CoV-2 infection. Microinjection of RNA from the sperm of SARS-CoV-2 infected males into fertilized oocytes leads to a phenotype resembling that of the naturally born F1 offspring, supporting the interpretation that sperm RNAs are contributing to the outcomes of our paternal SARS-CoV-2 model. Therefore, this study provides evidence that paternal SARS-CoV-2 infection impacts sperm and affects offspring phenotypes. These findings have public-health implications and inform further research in males affected by COVID-19, and their offspring.

DNMT3A mutations are prevalent in haematologic malignancies. In our mouse model the murine homologue (R878H) of the human 'hotspot' R882H mutation is introduced into the mouse Dnmt3a locus. This results in globally reduced DNA methylation in all tissues. Mice with heterozygous R878H DNMT3A mutations develop γ-radiation induced thymic lymphoma more rapidly than control mice, suggesting a vulnerability to stress stimuli in Dnmt3aR878H/+ cells. In competitive transplantations, Dnmt3aR878H/+ Lin-Sca-1+Kit+ (LSK) haematopoietic stem/progenitor cells (HSPCs) have a competitive advantage over WT HSPCs, indicating a self-renewal phenotype at the expense of differentiation. RNA sequencing of Dnmt3aR878H/+ LSKs exposed to low dose γ-radiation shows downregulation of the p53 pathway compared to γ-irradiated WT LSKs. Accordingly, reduced PUMA expression is observed by flow cytometry in the bone marrow of γ-irradiated Dnmt3aR878H/+ mice due to impaired p53 signalling. These findings provide new insights into how DNMT3A mutations cause subtle changes in the transcriptome of LSK cells which contribute to their increased self-renewal and propensity for malignant transformation.

Toxoplasma and other Apicomplexan parasites, switch between different developmental stages to persist in and transmit between hosts. Toxoplasma can alternate between systemic tachyzoites and encysted bradyzoite forms found in the CNS and muscle tissues. How parasites sense these tissue types and trigger differentiation remains largely unknown. We show that Toxoplasma differentiation is induced under glucose-limiting conditions and using a CRISPR screen identify parasite genes required for growth under these conditions. From ∼25 identified genes important for differentiation we show that lactate and glutamine metabolism is linked to differentiation and demonstrate the importance of an E3 ubiquitin ligase complex, orthologous to glucose induced degradation deficient (GID) complex in yeast and CTLH complex in humans. We show that TgGID likely regulates translational repression of a key transcription factor required for differentiation, BFD1, through its 3' utr. Overall, this work provides important new insight into how these divergent parasites sense different host cell niches and trigger stage conversion through a ubiquitination-dependent program.

Closely related genes typically display common essential functions but also functional diversification, ensuring retention of both genes throughout evolution. The histone lysine acetyltransferases KAT6A (MOZ) and KAT6B (QKF/MORF), sharing identical protein domain structure, are mutually exclusive catalytic subunits of a multiprotein complex. Mutations in either KAT6A or KAT6B result in congenital intellectual disability disorders in human patients. In mice, loss of function of either gene results in distinct, severe phenotypic consequences. Here we show that, surprisingly, 4-fold overexpression of Kat6b rescues all previously described developmental defects in Kat6a mutant mice, including rescuing the absence of hematopoietic stem cells. Kat6b restores acetylation at histone H3 lysines 9 and 23 and reverses critical gene expression anomalies in Kat6a mutant mice. Our data suggest that the target gene specificity of KAT6A can be substituted by the related paralogue KAT6B, despite differences in amino acid sequence, if KAT6B is expressed at sufficiently high levels.

Loss of the gene encoding the histone acetyltransferase KAT6B (MYST4/MORF/QKF) causes developmental brain abnormalities as well as behavioral and cognitive defects in mice. In humans, heterozygous variants in the KAT6B gene cause two cognitive disorders, Say-Barber-Biesecker-Young-Simpson syndrome (SBBYSS; OMIM:603736) and genitopatellar syndrome (GTPTS; OMIM:606170). Although the effects of KAT6B homozygous and heterozygous mutations have been documented in humans and mice, KAT6B gain-of-function effects have not been reported. Here, we show that overexpression of the Kat6b gene in mice caused aggression, anxiety, and spontaneous epilepsy. Kat6b overexpression led to an increase in histone H3 lysine 9 acetylation and upregulation of genes driving nervous system development and neuronal differentiation. Kat6b overexpression additionally promoted neural stem cell proliferation and favored neuronal over astrocyte differentiation in vivo and in vitro. Our results suggest that, in addition to loss-of-function alleles, gain-of-function KAT6B alleles may be detrimental for brain development.

The MYST family histone acetyltransferase gene, KAT6B (MYST4, MORF, QKF) is mutated in two distinct human congenital disorders characterised by intellectual disability, facial dysmorphogenesis and skeletal abnormalities; the Say-Barber-Biesecker-Young-Simpson variant of Ohdo syndrome and Genitopatellar syndrome. Despite its requirement in normal skeletal development, the cellular and transcriptional effects of KAT6B in skeletogenesis have not been thoroughly studied. Here, we show that germline deletion of the Kat6b gene in mice causes premature ossification in vivo, resulting in shortened craniofacial elements and increased bone density, as well as shortened tibias with an expanded pre-hypertrophic layer, as compared to wild type controls. Mechanistically, we show that the loss of KAT6B in mesenchymal progenitor cells promotes transition towards an osteoblast-progenitor state with upregulation of gene targets of RUNX2, a master regulator of osteoblast development and concomitant downregulation of SOX9, a critical gene in chondrocyte development. Moreover, we find that compound heterozygosity at Kat6b and Runx2 loci partially rescues the reduction in ossification of Runx2 heterozygous, but not homozygous mice, suggesting that KAT6B may limit the action of RUNX2, possibly through a role in maintaining progenitors in an undifferentiated state. Moreover, our results show that KAT6B has essential roles in regulating the expression of a large number of genes involved in skeletogenesis and bone development.

Interferon-gamma (IFNγ) is critical for immunity against intra-macrophagic pathogens, signaling through the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway to induce a tyrosine-phosphorylation cascade that ensures a potent immune response. Excessive JAK-STAT signaling can drive hyperinflammation and autoimmunity; thus, signaling is tightly and selectively regulated by the IFNγ-inducible protein, suppressor of cytokine signaling 1 (SOCS1). SOCS1 inhibits signaling by directly blocking JAK kinase activity. Here, we identified a SOCS1-interacting partner, ankyrin repeat and pleckstrin homology domain 2 (ARAP2), that fine-tunes SOCS1 function. We report that tyrosine 415 in ARAP2 binds the SOCS1-Src homology 2 (SH2) domain and limits the ability of SOCS1 to inhibit IFNγ signaling. Our findings show that ARAP2 promotes the IFNγ response through a phosphorylation-dependent interaction with the negative regulator SOCS1, and this exacerbates inflammation in a mouse model of influenza virus infection.

Prolonged exposure to a high-fat diet (HFD) exacerbates intestinal disease pathology, yet the early events preceding the development of gut inflammation remain poorly understood. Here, we show that within 48 h, HFD impairs intestinal group 3 innate lymphoid cells (ILC3s) and their capacity to produce interleukin-22 (IL-22), critical for maintaining gut homeostasis. This loss of function was associated with rapid dysbiosis, increased gut permeability, and reduced production of antimicrobial peptides, mucus, and tight-junction proteins. While saturated fatty acids metabolized through oxidation impaired ILC3 function, unsaturated fatty acids sustained IL-22 secretion by ILC3s through the formation of lipid droplets using diacylglycerol O-acyltransferase (DGAT) enzymes. Upon inflammation, saturated fatty acids impaired IL-22 production by ILC3s and increased the susceptibility of the gut to injury. Our findings reveal the differential acute impact of saturated and unsaturated fatty acids on gut homeostasis through distinct metabolic pathways in ILC3s.

Fibrosis is driven by the emergence of myofibroblasts, which are the primary producers of the extracellular matrix proteins that form fibrotic lesions. Despite this critical role, detecting myofibroblasts remains challenging due to the paucity of selective markers. We therefore screened for novel myofibroblast-specific markers, discovering that the expression of the close homolog of L1 (ChL-1) and embigin (Emb) distinguish activated myofibroblasts from their quiescent precursors. We report that ChL-1+/Emb+ fibroblasts: (1) emerge during cardiac inflammation, (2) have elevated expression of collagens and inflammatory factors and (3) localise to fibrotic zones - consistent with activated myofibroblasts. Mechanistically, Chl1+/Emb+ myofibroblasts differentiate from resident fibroblasts which upregulate these markers in response to proinflammatory cytokines, such as IL-1 and IL-17. Moreover, we show that embigin could be exploited to target antibody-based therapies to myofibroblasts and confirm this protein as a conserved marker of activated fibroblasts in multiple tissues and settings. Collectively, these findings identify ChL-1 and embigin as novel myofibroblast surface-markers that could be used to identify, enumerate and target this pathogenic population. ### Competing Interest Statement The authors have declared no competing interest.

Although asymptomatic malaria was historically perceived as innocuous, emerging evidence revealed an immunosuppressive signature induced by asymptomatic Plasmodium falciparum infections. To examine if a similar process occurs in Plasmodium vivax malaria, we pursued a systems approach, integrating transcriptional profiling together with previously reported and novel mass cytometry phenotypes from individuals with symptomatic and asymptomatic P. vivax malaria. Symptomatic P. vivax malaria featured upregulation of anti-inflammatory pathways and checkpoint receptors. A profound downregulation of transcripts with roles in monocyte function was observed in symptomatic P. vivax malaria. This reduction in monocyte transcriptional activity was accompanied by a significant depletion of CCR2+CXCR4+ classical monocytes in symptomatic individuals. Despite allowing transcriptional profiles supporting T-cell differentiation, dysregulation of genes associated with monocyte activation and the inflammasome was also evident in individuals carrying P. vivax asymptomatic infections. Our results identify monocyte dysregulation as a key feature of the response to P. vivax malaria and support the concept that asymptomatic infection is not innocuous and might not support all immune processes required to eliminate parasitemia or efficiently respond to vaccination.

Abstract Minor splicing is an under-appreciated splicing system required for the correct expression of ~700 genes in the human genome. This small subset of genes (0.35%) harbours introns containing non-canonical splicing sequences that are recognised uniquely by the minor spliceosome and cannot be processed by the major spliceosome. Using in vivo zebrafish and mouse cancer models, we show that heterozygous expression of Rnpc3, encoding a unique protein component of the minor spliceosome, restricts the growth and survival of liver, lung and gastric tumours without impacting healthy cells. RNPC3 knockdown in human lung cancer-derived A549 cells also impairs cell proliferation and RNA-seq analysis reveals a robust and selective disruption to minor intron splicing and transcription-wide effects on gene expression. We further demonstrate that these perturbations are accompanied by DNA replication stress, DNA damage, accumulation of TP53 protein and activation of a Tp53-dependent transcriptional program that induces cell cycle arrest and apoptosis. Together our data reveal a vulnerability of cancer cells to minor splicing inhibition that restricts tumour growth.

Heterozygous mutations in the histone lysine acetyltransferase gene KAT6B (MYST4/MORF/QKF) underlie neurodevelopmental disorders, but the mechanistic roles of KAT6B remain poorly understood. Here, we show that loss of KAT6B in embryonic neural stem and progenitor cells (NSPCs) impaired cell proliferation, neuronal differentiation, and neurite outgrowth. Mechanistically, loss of KAT6B resulted in reduced acetylation at histone H3 lysine 9 and reduced expression of key nervous system development genes in NSPCs and the developing cortex, including the SOX gene family, in particular Sox2, which is a key driver of neural progenitor proliferation, multipotency and brain development. In the fetal cortex, KAT6B occupied the Sox2 locus. Loss of KAT6B caused a reduction in Sox2 promoter activity in NSPCs. Sox2 overexpression partially rescued the proliferative defect of Kat6b-/- NSPCs. Collectively, these results elucidate molecular requirements for KAT6B in brain development and identify key KAT6B targets in neural precursor cells and the developing brain.

Supplementary Figure S18 showing that removal of mutant TP53 in SUM159 human breast cancer cells does not impair metastasis in vivo

The histone lysine acetyltransferase KAT6B (MYST4, MORF, QKF) is the target of recurrent chromosomal translocations causing hematological malignancies with poor prognosis. Using Kat6b germline deletion and overexpression in mice, we determined the role of KAT6B in the hematopoietic system. We found that KAT6B sustained the fetal hematopoietic stem cell pool but did not affect viability or differentiation. KAT6B was essential for normal levels of histone H3 lysine 9 (H3K9) acetylation but not for a previously proposed target, H3K23. Compound heterozygosity of Kat6b and the closely related gene, Kat6a, abolished hematopoietic reconstitution after transplantation. KAT6B and KAT6A cooperatively promoted transcription of genes regulating hematopoiesis, including the Hoxa cluster, Pbx1, Meis1, Gata family, Erg, and Flt3. In conclusion, we identified the hematopoietic processes requiring Kat6b and showed that KAT6B and KAT6A synergistically promoted HSC development, function, and transcription. Our findings are pertinent to current clinical trials testing KAT6A/B inhibitors as cancer therapeutics.

Paternal pre-conceptual environmental experiences, such as stress and diet, can affect offspring brain and behavioral phenotypes via epigenetic modifications in sperm. Furthermore, maternal immune activation due to infection during gestation can reprogram offspring behavior and brain functioning in adulthood. However, the effects of paternal pre-conceptual exposure to immune activation on the behavior and physiology of offspring (F1) and grand-offspring (F2) are not currently known. We explored effects of paternal pre-conceptual exposure to viral-like immune activation on F1 and F2 behavioral and physiological phenotypes using a C57BL/6J mouse model. Males were treated with a single injection (intraperitoneal) of the viral mimetic polyinosinic:polycytidylic acid (Poly I:C: 12 mg/kg) then bred with naive female mice four weeks after the Poly I:C (or 0.9% saline control) injection. The F1 offspring of Poly I:C treated fathers displayed increased depression-like behavior in the Porsolt swim test, an altered stress response in the novelty-suppressed feeding test, and significant transcriptomic changes in their hippocampus. Additionally, the F1 male offspring of Poly I:C treated F0 males showed significantly increased immune responsivity after a Poly I:C immune challenge (12 mg/kg). Furthermore, the F2 male grand-offspring took longer to enter and travelled significantly shorter distances in the light zone of the light/ dark box. An analysis of the small noncoding RNA profiles in sperm from Poly I:C treated males and their male offspring revealed significant effects of Poly I:C on the sperm microRNA content at the time of conception and on the sperm PIWI-interacting RNA content of the male offspring. Notably, eight miRNAs with an FDR < 0.05 (miR141-3p, miR-126b-5p, miR-669o-5p, miR-10b-3p, miR-471-5p, miR-463-5p, miR-148b-3p, and miR-181c-5p) were found to be significantly downregulated in the sperm of Poly I:C treated males. Collectively, we demonstrate that paternal pre-conceptual exposure to a viral immune challenge results in both intergenerational and transgenerational effects on brain and behavior that may be mediated by alterations in the sperm small noncoding RNA content.