RESUMEN
Mutations in GATA6 are associated with congenital heart disease, most notably conotruncal structural defects. However, how GATA6 regulates cardiac morphology during embryogenesis is undefined. We used knockout and conditional mutant zebrafish alleles to investigate the spatiotemporal role of gata6 during cardiogenesis. Loss of gata6 specifically impacts atrioventricular valve formation and recruitment of epicardium, with a prominent loss of arterial pole cardiac cells, including those of the ventricle and outflow tract. However, there are no obvious defects in cardiac progenitor cell specification, proliferation or death. Conditional loss of gata6 starting at 24â h is sufficient to disrupt the addition of late differentiating cardiomyocytes at the arterial pole, with decreased expression levels of anterior secondary heart field (SHF) markers spry4 and mef2cb. Conditional loss of gata6 in the endoderm is sufficient to phenocopy the straight knockout, resulting in a significant loss of ventricular and outflow tract tissue. Exposure to a Dusp6 inhibitor largely rescues the loss of ventricular cells in gata6-/- larvae. Thus, gata6 functions in endoderm are mediated by FGF signaling to regulate the addition of anterior SHF progenitor derivatives during heart formation.
Asunto(s)
Diferenciación Celular , Endodermo , Factor de Transcripción GATA6 , Corazón , Proteínas de Pez Cebra , Pez Cebra , Animales , Pez Cebra/embriología , Pez Cebra/genética , Factor de Transcripción GATA6/metabolismo , Factor de Transcripción GATA6/genética , Proteínas de Pez Cebra/genética , Proteínas de Pez Cebra/metabolismo , Endodermo/metabolismo , Endodermo/embriología , Endodermo/citología , Diferenciación Celular/genética , Corazón/embriología , Organogénesis/genética , Regulación del Desarrollo de la Expresión Génica , Miocitos Cardíacos/metabolismo , Miocitos Cardíacos/citología , Transducción de Señal , Factores de Crecimiento de Fibroblastos/metabolismo , Factores de Crecimiento de Fibroblastos/genética , Fosfatasa 6 de Especificidad Dual/metabolismo , Fosfatasa 6 de Especificidad Dual/genética , Factores de Transcripción GATARESUMEN
The pollination services provided by the honey bee are critical in both natural and agricultural ecosystems. Honey bee colonies in the United States have suffered from an increased rate of die-off in recent years, stemming from a complex set of interacting stresses that remain poorly described. Defining specific common cellular processes and cellular stress responses impacted by multiple stressors represent a key step in understanding these synergies. Proteotoxic stresses negatively impact protein synthesis, folding, and degradation. Diverse proteotoxic stresses induce expression of genes encoding small heat shock proteins (sHSP) of the expanded lethal (2) essential for life (l(2)efl) gene family. In addition to upregulation by the Integrated Stress Response (ISR), the Heat Shock Response (HSR), and the Oxidative Stress Response (OSR), our data provide first evidence that sHSP genes are upregulated by the Unfolded Protein Response (UPR). As these genes appear to be part of a core stress response that could serve as a useful biomarker for cellular stress in honey bees, we designed and tested an RT-LAMP assay to detect increased l(2)efl gene expression in response to heat-stress. While this assay provides a powerful proof of principle, further work will be necessary to link changes in sHSP gene expression to colony-level outcomes, to adapt our preliminary assay into a Point of Care Testing (POCT) assay appropriate for use as a diagnostic tool for use in the field, and to couple assay results to management recommendations.
Asunto(s)
Abejas/genética , Proteínas de Choque Térmico/genética , Respuesta al Choque Térmico , Proteínas de Insectos/genética , Animales , Abejas/fisiología , Proteostasis , Respuesta de Proteína Desplegada , Regulación hacia ArribaRESUMEN
The mitochondrial unfolded protein response (UPRmt) is an organellar stress signaling pathway that functions to detect and restore disruption of mitochondrial proteostasis. The UPRmt is involved in a wide range of physiological and disease conditions, including aging, stem cell maintenance, innate immunity, neurodegeneration, and cancer. Here we report that the UPRmt is integral to zebrafish fin regeneration. Taking advantage of a novel zebrafish UPRmt reporter, we observed that UPRmt activation occurs in regenerating fin tissue shortly after injury. Through chemical and genetic approaches, we discovered that the Sirt1-UPRmt pathway, best known for its role in promoting lifespan extension, is crucial for fin regeneration. The metabolism of NAD+ is an important contributor to Sirt1 activity in this context. We propose that Sirt1 activation induces mitochondrial biogenesis in injured fin tissue, which leads to UPRmt activation and promotes tissue regeneration.
RESUMEN
Adult neural stem cells (NSC) serve as a reservoir for brain plasticity and origin for certain gliomas. Lineage tracing and genomic approaches have portrayed complex underlying heterogeneity within the major anatomical location for NSC, the subventricular zone (SVZ). To gain a comprehensive profile of NSC heterogeneity, we utilized a well-validated stem/progenitor-specific reporter transgene in concert with single-cell RNA sequencing to achieve unbiased analysis of SVZ cells from infancy to advanced age. The magnitude and high specificity of the resulting transcriptional datasets allow precise identification of the varied cell types embedded in the SVZ including specialized parenchymal cells (neurons, glia, microglia) and noncentral nervous system cells (endothelial, immune). Initial mining of the data delineates four quiescent NSC and three progenitor-cell subpopulations formed in a linear progression. Further evidence indicates that distinct stem and progenitor populations reside in different regions of the SVZ. As stem/progenitor populations progress from neonatal to advanced age, they acquire a deficiency in transition from quiescence to proliferation. Further data mining identifies stage-specific biological processes, transcription factor networks, and cell-surface markers for investigation of cellular identities, lineage relationships, and key regulatory pathways in adult NSC maintenance and neurogenesis.
Asunto(s)
Envejecimiento/genética , Linaje de la Célula , Ventrículos Laterales/anatomía & histología , Ventrículos Laterales/citología , Nicho de Células Madre/genética , Transcriptoma/genética , Células Madre Adultas/citología , Células Madre Adultas/metabolismo , Animales , Biomarcadores/metabolismo , Linaje de la Célula/genética , Proteínas Fluorescentes Verdes/metabolismo , Humanos , Ratones , Células-Madre Neurales/citología , Células-Madre Neurales/metabolismo , TransgenesRESUMEN
The Gata4/5/6 sub-family of zinc finger transcription factors regulate many aspects of cardiogenesis. However, critical roles in extra-embryonic endoderm also challenge comprehensive analysis during early mouse cardiogenesis, while zebrafish models have previously relied on knockdown assays. We generated targeted deletions to disrupt each gata4/5/6 gene in zebrafish and analyzed cardiac phenotypes in single, double and triple mutants. The analysis confirmed that loss of gata5 causes cardia bifida and validated functional redundancies for gata5/6 in cardiac precursor specification. Surprisingly, we discovered that gata4 is dispensable for early zebrafish development, while loss of one gata4 allele can suppress the bifid phenotype of the gata5 mutant. The gata4 mutants eventually develop an age-dependent cardiomyopathy. By combining combinations of mutant alleles, we show that cardiac specification depends primarily on an overall dosage of gata4/5/6 alleles rather than a specific gene. We also identify a specific role for gata6 in controlling ventricle morphogenesis through regulation of both the first and second heart field, while loss of both gata4/6 eliminates the ventricle. Thus, different developmental programs are dependent on total dosage, certain pairs, or specific gata4/5/6 genes during embryonic cardiogenesis.This article has an associated First Person interview with the first author of the paper.
Asunto(s)
Factor de Transcripción GATA4/genética , Factor de Transcripción GATA5/genética , Factor de Transcripción GATA6/genética , Regulación del Desarrollo de la Expresión Génica , Corazón/embriología , Organogénesis/genética , Pez Cebra/embriología , Alelos , Animales , Factor de Transcripción GATA4/metabolismo , Factor de Transcripción GATA5/metabolismo , Factor de Transcripción GATA6/metabolismo , Dosificación de Gen , Marcación de Gen , Genotipo , Morfogénesis/genética , Mutación , FenotipoRESUMEN
Ten-eleven translocation (Tet) enzymes (Tet1/2/3) mediate 5-methylcytosine (5mC) hydroxylation, which can facilitate DNA demethylation and thereby impact gene expression. Studied mostly for how mutant isoforms impact cancer, the normal roles for Tet enzymes during organogenesis are largely unknown. By analyzing compound mutant zebrafish, we discovered a requirement for Tet2/3 activity in the embryonic heart for recruitment of epicardial progenitors, associated with development of the atrial-ventricular canal (AVC). Through a combination of methylation, hydroxymethylation, and transcript profiling, the genes encoding the activin A subunit Inhbaa (in endocardium) and Sox9b (in myocardium) were implicated as demethylation targets of Tet2/3 and critical for organization of AVC-localized extracellular matrix (ECM), facilitating migration of epicardial progenitors onto the developing heart tube. This study elucidates essential DNA demethylation modifications that govern gene expression changes during cardiac development with striking temporal and lineage specificities, highlighting complex interactions in multiple cell populations during development of the vertebrate heart.
Asunto(s)
Dioxigenasas/genética , Matriz Extracelular/metabolismo , Corazón/fisiopatología , Organogénesis/genética , Proteínas de Pez Cebra/genética , Animales , Movimiento Celular , Pez CebraRESUMEN
Bacterial infection often leads to suppression of mRNA translation, but hosts are nonetheless able to express immune response genes through as yet unknown mechanisms. Here, we use a Drosophila model to demonstrate that antimicrobial peptide (AMP) production during infection is paradoxically stimulated by the inhibitor of cap-dependent translation, 4E-BP (eIF4E-binding protein; encoded by the Thor gene). We found that 4E-BP is induced upon infection with pathogenic bacteria by the stress-response transcription factor ATF4 and its upstream kinase, GCN2. Loss of gcn2, atf4, or 4e-bp compromised immunity. While AMP transcription is unaffected in 4e-bp mutants, AMP protein levels are substantially reduced. The 5' UTRs of AMPs score positive in cap-independent translation assays, and this cap-independent activity is enhanced by 4E-BP. These results are corroborated in vivo using transgenic 5' UTR reporters. These observations indicate that ATF4-induced 4e-bp contributes to innate immunity by biasing mRNA translation toward cap-independent mechanisms, thus enhancing AMP synthesis.