The guanine nucleotide exchange factor RapGEF2 is required for ERK-dependent immediate-early gene (Egr1) activation during fear memory formation.

The MAP kinase ERK is important for neuronal plasticity underlying associative learning, yet specific molecular pathways for neuronal ERK activation are undetermined. RapGEF2 is a neuron-specific cAMP sensor that mediates ERK activation. We investigated whether it is required for cAMP-dependent ERK activation leading to other downstream neuronal signaling events occurring during associative learning, and if RapGEF2-dependent signaling impairments affect learned behavior. Camk2α-cre+/-::RapGEF2fl/fl mice with depletion of RapGEF2 in hippocampus and amygdala exhibit impairments in context- and cue-dependent fear conditioning linked to corresponding impairment in Egr1 induction in these two brain regions. Camk2α-cre+/-::RapGEF2fl/fl mice show decreased RapGEF2 expression in CA1 and dentate gyrus associated with abolition of pERK and Egr1, but not of c-Fos induction, following fear conditioning, impaired freezing to context after fear conditioning, and impaired cAMP-dependent long-term potentiation at perforant pathway and Schaffer collateral synapses in hippocampal slices ex vivo. RapGEF2 expression is largely eliminated in basolateral amygdala, also involved in fear memory, in Camk2α-cre+/-::RapGEF2fl/fl mice. Neither Egr1 nor c-fos induction in BLA after fear conditioning, nor cue-dependent fear learning, are affected by ablation of RapGEF2 in BLA. However, Egr1 induction (but not that of c-fos) in BLA is reduced after restraint stress-augmented fear conditioning, as is freezing to cue after restraint stress-augmented fear conditioning, in Camk2α-cre+/-::RapGEF2fl/fl mice. Cyclic AMP-dependent GEFs have been genetically associated as risk factors for schizophrenia, a disorder associated with cognitive deficits. Here we show a functional link between one of them, RapGEF2, and cognitive processes involved in associative learning in amygdala and hippocampus.

Chronic social defeat alters brain vascular-associated cell gene expression patterns leading to vascular dysfunction and immune system activation.

Brain vascular integrity is critical for brain health, and its disruption is implicated in many brain pathologies, including psychiatric disorders. Brain-vascular barriers are a complex cellular landscape composed of endothelial, glial, mural, and immune cells. Yet currently, little is known about these brain vascular-associated cells (BVACs) in health and disease. Previously, we demonstrated that 14 days of chronic social defeat (CSD), a mouse paradigm that produces anxiety and depressive-like behaviors, causes cerebrovascular damage in the form of scattered microbleeds. Here, we developed a technique to isolate barrier-related cells from the mouse brain and subjected the isolated cells to single-cell RNA sequencing. Using this isolation technique, we found an enrichment in BVAC populations, including distinct subsets of endothelial and microglial cells. In CSD compared to non-stress, home-cage control, differential gene expression patterns disclosed biological pathways involving vascular dysfunction, vascular healing, and immune system activation. Overall, our work demonstrates a unique technique to study BVAC populations from fresh brain tissue and suggests that neurovascular dysfunction is a key driver of psychosocial stress-induced brain pathology.

Antibody Response to HML-2 May Be Protective in Amyotrophic Lateral Sclerosis.

OBJECTIVES: Reactivation of HERV-K(HML-2) has been found in subsets of individuals with amyotrophic lateral sclerosis (ALS). This study examines the antibody response against HML-2 in ALS and analyzes its clinical relevance. METHODS: Antibodies to HML-2 envelope (env) were analyzed using a peptide array for epitope mapping and by a peptide enzyme-linked immunosorbent assay (ELISA) in 242 healthy donors, and 243 ALS and 85 multiple sclerosis (MS) individuals. Extracellular levels of HML-2 were analyzed by digital polymerase chain reaction (PCR). RESULTS: Antibodies in the sera of ALS individuals recognized more HML-2 env peptides compared to healthy controls (p < 0.0001). ALS individuals had higher levels of HML-2 than healthy donors (p = 0.02) and higher antibody levels against a select HML-2 env peptide compared to healthy donors or individuals with multiple sclerosis (p < 0.0001). 55.14% of ALS compared to 21.16% of healthy donors and 13.10% of MS individuals had antibodies against the HML-2 peptide (AUC = 0.769, p < 0.0001). Levels of extracellular HML-2 DNA in serum (p = 0.02) and the number of HML-2 env peptides recognized by ALS sera (p = 0.02) correlated with disease duration. Among ALS individuals, lower levels of HML-2 antibodies were associated with a definite diagnosis per EL Escorial criteria (p = 0.03), and with a lower predicted (p = 0.02) and observed survival (p = 0.03). INTERPRETATION: There is a differential antibody response against specific epitopes of HML-2 env in ALS and controls, suggesting epitope spreading, likely due to persistent antigenic exposure following reactivation of the viral genes. Low levels of antibodies to HML-2 env in ALS are associated with poor prognosis and decreased survival probability. ANN NEUROL 2022;92:782-792.

The vitamin B12 processing enzyme, mmachc, is essential for zebrafish survival, growth and retinal morphology.

Cobalamin C (cblC) deficiency, the most common inborn error of intracellular cobalamin metabolism, is caused by mutations in MMACHC, a gene responsible for the processing and intracellular trafficking of vitamin B12. This recessive disorder is characterized by a failure to metabolize cobalamin into adenosyl- and methylcobalamin, which results in the biochemical perturbations of methylmalonic acidemia, hyperhomocysteinemia and hypomethioninemia caused by the impaired activity of the downstream enzymes, methylmalonyl-CoA mutase and methionine synthase. Cobalamin C deficiency can be accompanied by a wide spectrum of clinical manifestations, including progressive blindness, and, in mice, manifests with very early embryonic lethality. Because zebrafish harbor a full complement of cobalamin metabolic enzymes, we used genome editing to study the loss of mmachc function and to develop the first viable animal model of cblC deficiency. mmachc mutants survived the embryonic period but perished in early juvenile life. The mutants displayed the metabolic and clinical features of cblC deficiency including methylmalonic acidemia, severe growth retardation and lethality. Morphologic and metabolic parameters improved when the mutants were raised in water supplemented with small molecules used to treat patients, including hydroxocobalamin, methylcobalamin, methionine and betaine. Furthermore, mmachc mutants bred to express rod and/or cone fluorescent reporters, manifested a retinopathy and thin optic nerves (ON). Expression analysis using whole eye mRNA revealed the dysregulation of genes involved in phototransduction and cholesterol metabolism. Zebrafish with mmachc deficiency recapitulate the several of the phenotypic and biochemical features of the human disorder, including ocular pathology, and show a response to established treatments.

Zrsr2 Is Essential for the Embryonic Development and Splicing of Minor Introns in RNA and Protein Processing Genes in Zebrafish.

ZRSR2 (zinc finger CCCH-type, RNA binding motif and serine/arginine rich 2) is an essential splicing factor involved in 3' splice-site recognition as a component of both the major and minor spliceosomes that mediate the splicing of U2-type (major) and U12-type (minor) introns, respectively. Studies of ZRSR2-depleted cell lines and ZRSR2-mutated patient samples revealed its essential role in the U12-dependent minor spliceosome. However, the role of ZRSR2 during embryonic development is not clear, as its function is compensated for by Zrsr1 in mice. Here, we utilized the zebrafish model to investigate the role of zrsr2 during embryonic development. Using CRISPR/Cas9 technology, we generated a zrsr2-knockout zebrafish line, termed zrsr2hg129/hg129 (p.Trp167Argfs*9) and examined embryo development in the homozygous mutant embryos. zrsr2hg129/hg129 embryos displayed multiple developmental defects starting at 4 days post fertilization (dpf) and died after 8 dpf, suggesting that proper Zrsr2 function is required during embryonic development. The global transcriptome analysis of 3 dpf zrsr2hg129/hg129 embryos revealed that the loss of Zrsr2 results in the downregulation of essential metabolic pathways and the aberrant retention of minor introns in about one-third of all minor intron-containing genes in zebrafish. Overall, our study has demonstrated that the role of Zrsr2 as a component of the minor spliceosome is conserved and critical for proper embryonic development in zebrafish.

Bi-allelic TMEM94 Truncating Variants Are Associated with Neurodevelopmental Delay, Congenital Heart Defects, and Distinct Facial Dysmorphism.

Neurodevelopmental disorders (NDD) are genetically and phenotypically heterogeneous conditions due to defects in genes involved in development and function of the nervous system. Individuals with NDD, in addition to their primary neurodevelopmental phenotype, may also have accompanying syndromic features that can be very helpful diagnostically especially those with recognizable facial appearance. In this study, we describe ten similarly affected individuals from six unrelated families of different ethnic origins having bi-allelic truncating variants in TMEM94, which encodes for an uncharacterized transmembrane nuclear protein that is highly conserved across mammals. The affected individuals manifested with global developmental delay/intellectual disability, and dysmorphic facial features including triangular face, deep set eyes, broad nasal root and tip and anteverted nostrils, thick arched eye brows, hypertrichosis, pointed chin, and hypertelorism. Birthweight in the upper normal range was observed in most, and all but one had congenital heart defects (CHD). Gene expression analysis in available cells from affected individuals showed reduced expression of TMEM94. Global transcriptome profiling using microarray and RNA sequencing revealed several dysregulated genes essential for cell growth, proliferation and survival that are predicted to have an impact on cardiotoxicity hematological system and neurodevelopment. Loss of Tmem94 in mouse model generated by CRISPR/Cas9 was embryonic lethal and led to craniofacial and cardiac abnormalities and abnormal neuronal migration pattern, suggesting that this gene is important in craniofacial, cardiovascular, and nervous system development. Our study suggests the genetic etiology of a recognizable dysmorphic syndrome with NDD and CHD and highlights the role of TMEM94 in early development.

Compound heterozygous KCTD7 variants in progressive myoclonus epilepsy.

KCTD7 is a member of the potassium channel tetramerization domain-containing protein family and has been associated with progressive myoclonic epilepsy (PME), characterized by myoclonus, epilepsy, and neurological deterioration. Here we report four affected individuals from two unrelated families in which we identified KCTD7 compound heterozygous single nucleotide variants through exome sequencing. RNAseq was used to detect a non-annotated splicing junction created by a synonymous variant in the second family. Whole-cell patch-clamp analysis of neuroblastoma cells overexpressing the patients' variant alleles demonstrated aberrant potassium regulation. While all four patients experienced many of the common clinical features of PME, they also showed variable phenotypes not previously reported, including dysautonomia, brain pathology findings including a significantly reduced thalamus, and the lack of myoclonic seizures. To gain further insight into the pathogenesis of the disorder, zinc finger nucleases were used to generate kctd7 knockout zebrafish. Kctd7 homozygous mutants showed global dysregulation of gene expression and increased transcription of c-fos, which has previously been correlated with seizure activity in animal models. Together these findings expand the known phenotypic spectrum of KCTD7-associated PME, report a new animal model for future studies, and contribute valuable insights into the disease.

B-cells are abnormal in psychosocial stress and regulate meningeal myeloid cell activation.

There is increasing interest in how immune cells, including those within the meninges at the blood-brain interface, influence brain function and mood disorders, but little data on humoral immunity in this context. Here, we show that in mice exposed to psychosocial stress, there is increased splenic B cell activation and secretion of the immunoregulatory cytokine interleukin (IL)-10. Meningeal B cells were prevalent in homeostasis but substantially decreased following stress, whereas Ly6Chi monocytes increased, and meningeal myeloid cells showed augmented expression of activation markers. Single-cell RNA sequencing of meningeal B cells demonstrated the induction of innate immune transcriptional programmes following stress, including genes encoding antimicrobial peptides that are known to alter myeloid cell activation. Cd19-/- mice, that have reduced B cells, showed baseline meningeal myeloid cell activation and decreased exploratory behaviour. Together, these data suggest that B cells may influence behaviour by regulating meningeal myeloid cell activation.

Recurrent microdeletions at chromosome 2p11.2 are associated with thymic hypoplasia and features resembling DiGeorge syndrome.

BACKGROUND: Thymic hypoplasia/aplasia occurs as a part of DiGeorge syndrome, which has several known genetic causes, and with loss-of-function mutations in forkhead box N1 (FOXN1). OBJECTIVE: We sought to determine the cause of selective T-cell lymphopenia with inverted kappa/lambda ratio in several kindreds. METHODS: Patients were identified through newborn screening for severe combined immunodeficiency using the T-cell receptor excision circle assay. Those found to have selective T-cell lymphopenia underwent testing with chromosomal microarray analysis. Three-week-old mice heterozygous for a loss-of-function mutation in forkhead box I3 (FOXI3), a candidate gene within the common deleted region found in patients, were compared with wild-type littermates. Assessments included body and organ weights, flow cytometric analysis of thymocytes and splenocytes, and histologic/transcriptomic analyses of thymic tissue. RESULTS: Five kindreds with similar immunophenotypes that included selective T-cell lymphopenia had overlapping microdeletions at chromosome 2p11.2 that spanned FOXI3 and, in most cases, the immunoglobulin kappa light chain locus. Studies in a mouse knockout strain for FOXI3 revealed smaller body weights and relatively lower thymus weights in heterozygous compared with wild-type animals. Histology and flow cytometry on spleens and thymi from 3-week-old pups for T- and B-cell subsets and epithelial cells did not show any significant qualitative or quantitative differences. Transcriptomic analysis of thymic RNA revealed divergence in global transcriptomic signatures, and Ingenuity Pathway Analysis revealed predicted dysfunction in epithelial adherens junctions. CONCLUSIONS: Microdeletions at chromosome 2p11.2 are associated with T-cell lymphopenia and probable thymic hypoplasia in human subjects, and haploinsufficiency for FOXI3, a candidate gene within the deleted region, is the likely underlying cause.

Analysis of cerebrovascular dysfunction caused by chronic social defeat in mice.

Psychological stress and affective disorders are clinically associated with hypertension and vascular disease, but the biological links between the conditions have not been fully explored. To examine this relationship, we used chronic social defeat (CSD) stress, which produces anxiety-like and depressive-like behavioral declines in susceptible mice. In such mice, CSD also produces cerebrovascular microbleeds in scattered locations. Here, we showed further evidence of vascular pathology and blood-brain barrier breakdown by visualizing plasma immunoglobulins and erythrocytes within the parenchyma and perivascular spaces of CSD brains. To further characterize the impact of stress on the cerebrovasculature, brain endothelial cells (bECs) were isolated, and global gene expression profiles were generated. Bioinformatic analysis of CSD-induced transcriptional changes in bECs showed enrichment in pathways that delineate the vascular response to injury. These pathways followed a temporal sequence of inflammation, oxidative stress, growth factor signaling, and wound healing (i.e., platelet aggregation, hemostasis, fibrinogen deposition, and angiogenesis). Immunohistochemical staining for markers of fibrinogen deposition and angiogenesis confirmed the existence of the markers at the sites of vascular disruptions. Recovery after CSD cessation was marked by recruitment of leukocytes perhaps participating in vascular repair. The data suggest that co-morbidity of affective disorders and vascular diseases may be attributed in part to a common link in altered endothelial cell function.

Functional and epigenetic studies reveal multistep differentiation and plasticity of in vitro-generated and in vivo-derived follicular T helper cells.

Follicular T helper (Tfh) cells provide critical help to B cells for germinal center (GC) formation. Mutations affecting SLAM-associated protein (SAP) prevent GC formation because of defective T cell-B cell interactions, yet effects on Tfh cell differentiation remain unclear. We describe the in vitro differentiation of functionally competent "Tfh-like" cells that expressed interleukin-21, Tfh cell markers, and Bcl6 and rescued GC formation in SAP-deficient hosts better than other T helper (Th) cells. SAP-deficient Tfh-like cells appeared virtually indistinguishable from wild-type, yet failed to support GCs in vivo. Interestingly, both Tfh-like and in vivo-derived Tfh cells could produce effector cytokines in response to polarizing conditions. Moreover, Th1, Th2, and Th17 cells could be reprogrammed to obtain Tfh cell characteristics. ChIP-Seq analyses revealed positive epigenetic markings on Tbx21, Gata3, and Rorc in Tfh-like and ex vivo Tfh cells and on Bcl6 in non-Tfh cells, supporting the concept of plasticity between Tfh and other Th cell populations.

Molecular convergence in ex vivo models of Diamond-Blackfan anemia.

Diamond-Blackfan anemia (DBA) is a congenital bone marrow failure syndrome characterized by erythroid hypoplasia, usually without perturbation of other hematopoietic lineages. Approximately 65% of DBA patients with autosomal dominant inheritance have heterozygous mutations or deletions in ribosomal protein (RP) genes while <1% of patients with X-linked inheritance have been identified with mutations in the transcription factor GATA1 Erythroid cells from patients with DBA have not been well characterized, and the mechanisms underlying the erythroid specific effects of either RP or GATA1 associated DBA remain unclear. We have developed an ex vivo culture system to expand peripheral blood CD34+ progenitor cells from patients with DBA and differentiate them into erythroid cells. Cells from patients with RP or GATA1 mutations showed decreased proliferation and delayed erythroid differentiation in comparison with controls. RNA transcript analyses of erythroid cells from controls and patients with RP or GATA1 mutations showed distinctive differences, with upregulation of heme biosynthesis genes prominently in RP-mediated DBA and failure to upregulate components of the translational apparatus in GATA1-mediated DBA. Our data show that dysregulation of translation is a common feature of DBA caused by both RP and GATA1 mutations. This trial was registered at www.clinicaltrials.gov as #NCT00106015.

Dopamine is Required for Activity-Dependent Amplification of Arc mRNA in Developing Postnatal Frontal Cortex.

The activity-regulated gene Arc/Arg3.1 encodes a postsynaptic protein crucially involved in glutamatergic synaptic plasticity. Genetic mutations in Arc pathway and altered Arc expression in human frontal cortex have been associated with schizophrenia. Although Arc expression has been reported to vary with age, what mechanisms regulate Arc mRNA levels in frontal cortex during postnatal development remains unclear. Using quantitative mRNA analysis of mouse frontal cortical tissues, we mapped the developmental profiles of Arc expression and found that its mRNA levels are sharply amplified near the end of the second postnatal week, when mouse pups open their eyes for the first time after birth. Surprisingly, electrical stimulation of the frontal cortex before eye-opening is not sufficient to drive the amplification of Arc mRNA. Instead, this amplification needs both electrical stimulation and dopamine D1-type receptor (D1R) activation. Furthermore, visual stimuli-driven amplification of Arc mRNA is also dependent on D1R activation and dopamine neurons located in the ventral midbrain. These results indicate that dopamine is required to drive activity-dependent amplification of Arc mRNA in the developing postnatal frontal cortex and suggest that joint electrical and dopaminergic activation is essential to establish the normal expression pattern of a schizophrenia-associated gene during frontal cortical development.

Overexpression and knockout of miR-126 both promote leukemogenesis.

It is generally assumed that gain- and loss-of-function manipulations of a functionally important gene should lead to the opposite phenotypes. We show in this study that both overexpression and knockout of microRNA (miR)-126 surprisingly result in enhanced leukemogenesis in cooperation with the t(8;21) fusion genes AML1-ETO/RUNX1-RUNX1T1 and AML1-ETO9a (a potent oncogenic isoform of AML1-ETO). In accordance with our observation that increased expression of miR-126 is associated with unfavorable survival in patients with t(8;21) acute myeloid leukemia (AML), we show that miR-126 overexpression exhibits a stronger effect on long-term survival and progression of AML1-ETO9a-mediated leukemia stem cells/leukemia initiating cells (LSCs/LICs) in mice than does miR-126 knockout. Furthermore, miR-126 knockout substantially enhances responsiveness of leukemia cells to standard chemotherapy. Mechanistically, miR-126 overexpression activates genes that are highly expressed in LSCs/LICs and/or primitive hematopoietic stem/progenitor cells, likely through targeting ERRFI1 and SPRED1, whereas miR-126 knockout activates genes that are highly expressed in committed, more differentiated hematopoietic progenitor cells, presumably through inducing FZD7 expression. Our data demonstrate that miR-126 plays a critical but 2-faceted role in leukemia and thereby uncover a new layer of miRNA regulation in cancer. Moreover, because miR-126 depletion can sensitize AML cells to standard chemotherapy, our data also suggest that miR-126 represents a promising therapeutic target.

Temporal dynamics and genetic control of transcription in the human prefrontal cortex.

Previous investigations have combined transcriptional and genetic analyses in human cell lines, but few have applied these techniques to human neural tissue. To gain a global molecular perspective on the role of the human genome in cortical development, function and ageing, we explore the temporal dynamics and genetic control of transcription in human prefrontal cortex in an extensive series of post-mortem brains from fetal development through ageing. We discover a wave of gene expression changes occurring during fetal development which are reversed in early postnatal life. One half-century later in life, this pattern of reversals is mirrored in ageing and in neurodegeneration. Although we identify thousands of robust associations of individual genetic polymorphisms with gene expression, we also demonstrate that there is no association between the total extent of genetic differences between subjects and the global similarity of their transcriptional profiles. Hence, the human genome produces a consistent molecular architecture in the prefrontal cortex, despite millions of genetic differences across individuals and races. To enable further discovery, this entire data set is freely available (from Gene Expression Omnibus: accession GSE30272; and dbGaP: accession phs000417.v1.p1) and can also be interrogated via a biologist-friendly stand-alone application (http://www.libd.org/braincloud).

A systems genetics approach identifies CXCL14, ITGAX, and LPCAT2 as novel aggressive prostate cancer susceptibility genes.

Although prostate cancer typically runs an indolent course, a subset of men develop aggressive, fatal forms of this disease. We hypothesize that germline variation modulates susceptibility to aggressive prostate cancer. The goal of this work is to identify susceptibility genes using the C57BL/6-Tg(TRAMP)8247Ng/J (TRAMP) mouse model of neuroendocrine prostate cancer. Quantitative trait locus (QTL) mapping was performed in transgene-positive (TRAMPxNOD/ShiLtJ) F2 intercross males (n = 228), which facilitated identification of 11 loci associated with aggressive disease development. Microarray data derived from 126 (TRAMPxNOD/ShiLtJ) F2 primary tumors were used to prioritize candidate genes within QTLs, with candidate genes deemed as being high priority when possessing both high levels of expression-trait correlation and a proximal expression QTL. This process enabled the identification of 35 aggressive prostate tumorigenesis candidate genes. The role of these genes in aggressive forms of human prostate cancer was investigated using two concurrent approaches. First, logistic regression analysis in two human prostate gene expression datasets revealed that expression levels of five genes (CXCL14, ITGAX, LPCAT2, RNASEH2A, and ZNF322) were positively correlated with aggressive prostate cancer and two genes (CCL19 and HIST1H1A) were protective for aggressive prostate cancer. Higher than average levels of expression of the five genes that were positively correlated with aggressive disease were consistently associated with patient outcome in both human prostate cancer tumor gene expression datasets. Second, three of these five genes (CXCL14, ITGAX, and LPCAT2) harbored polymorphisms associated with aggressive disease development in a human GWAS cohort consisting of 1,172 prostate cancer patients. This study is the first example of using a systems genetics approach to successfully identify novel susceptibility genes for aggressive prostate cancer. Such approaches will facilitate the identification of novel germline factors driving aggressive disease susceptibility and allow for new insights into these deadly forms of prostate cancer.

nlz1 is required for cilia formation in zebrafish embryogenesis.

The formation of cilia is a fundamental developmental process affecting diverse functions such as cellular signaling, tissue morphogenesis and body patterning. However, the mechanisms of ciliogenesis during vertebrate development are not fully understood. In this report we describe a novel role of the Nlz1 protein in ciliogenesis. We demonstrate morpholino-mediated knockdown of nlz1 in zebrafish causes abnormal specification of the cells of Kupffer's vesicle (KV); a severe reduction of the number of cilia in KV, the pronephros, and the neural floorplate; and a spectrum of later phenotypes reminiscent of human ciliopathies. In vitro and in vivo data indicate that Nlz1 acts downstream of Foxj1a and Wnt8a/presumed canonical Wnt signaling. Furthermore, Nlz1 contributes to motile cilia formation by positively regulating Wnt11/presumed non-canonical Wnt signaling. Together, our data suggest a novel role of nlz1 in ciliogenesis and the morphogenesis of multiple tissues.

Targeted correction of RUNX1 mutation in FPD patient-specific induced pluripotent stem cells rescues megakaryopoietic defects.

Familial platelet disorder with predisposition to acute myeloid leukemia (FPD/AML) is an autosomal dominant disease of the hematopoietic system that is caused by heterozygous mutations in RUNX1. FPD/AML patients have a bleeding disorder characterized by thrombocytopenia with reduced platelet numbers and functions, and a tendency to develop AML. No suitable animal models exist for FPD/AML, as Runx11/2 mice and zebra fish do not develop bleeding disorders or leukemia. Here we derived induced pluripotent stem cells (iPSCs) from 2 patients in a family with FPD/AML, and found that the FPD iPSCs display defects in megakaryocytic differentiation in vitro. We corrected the RUNX1 mutation in 1 FPD iPSC line through gene targeting, which led to normalization of megakaryopoiesis of the iPSCs in culture. Our results demonstrate successful in vitro modeling of FPD with patient-specific iPSCs and confirm that RUNX1 mutations are responsible for megakaryopoietic defects in FPD patients.

Genome-wide SNP and haplotype analyses reveal a rich history underlying dog domestication.

Advances in genome technology have facilitated a new understanding of the historical and genetic processes crucial to rapid phenotypic evolution under domestication. To understand the process of dog diversification better, we conducted an extensive genome-wide survey of more than 48,000 single nucleotide polymorphisms in dogs and their wild progenitor, the grey wolf. Here we show that dog breeds share a higher proportion of multi-locus haplotypes unique to grey wolves from the Middle East, indicating that they are a dominant source of genetic diversity for dogs rather than wolves from east Asia, as suggested by mitochondrial DNA sequence data. Furthermore, we find a surprising correspondence between genetic and phenotypic/functional breed groupings but there are exceptions that suggest phenotypic diversification depended in part on the repeated crossing of individuals with novel phenotypes. Our results show that Middle Eastern wolves were a critical source of genome diversity, although interbreeding with local wolf populations clearly occurred elsewhere in the early history of specific lineages. More recently, the evolution of modern dog breeds seems to have been an iterative process that drew on a limited genetic toolkit to create remarkable phenotypic diversity.

TET1 plays an essential oncogenic role in MLL-rearranged leukemia.

The ten-eleven translocation 1 (TET1) gene is the founding member of the TET family of enzymes (TET1/2/3) that convert 5-methylcytosine to 5-hydroxymethylcytosine. Although TET1 was first identified as a fusion partner of the mixed lineage leukemia (MLL) gene in acute myeloid leukemia carrying t(10,11), its definitive role in leukemia is unclear. In contrast to the frequent down-regulation (or loss-of-function mutations) and critical tumor-suppressor roles of the three TET genes observed in various types of cancers, here we show that TET1 is a direct target of MLL-fusion proteins and is significantly up-regulated in MLL-rearranged leukemia, leading to a global increase of 5-hydroxymethylcytosine level. Furthermore, our both in vitro and in vivo functional studies demonstrate that Tet1 plays an indispensable oncogenic role in the development of MLL-rearranged leukemia, through coordination with MLL-fusion proteins in regulating their critical cotargets, including homeobox A9 (Hoxa9)/myeloid ecotropic viral integration 1 (Meis1)/pre-B-cell leukemia homeobox 3 (Pbx3) genes. Collectively, our data delineate an MLL-fusion/Tet1/Hoxa9/Meis1/Pbx3 signaling axis in MLL-rearranged leukemia and highlight TET1 as a potential therapeutic target in treating this presently therapy-resistant disease.