While gene regulatory networks involved in cardiogenesis have been characterized, the role of bioenergetics remains less studied. Here we show that until midgestation, myocardial metabolism is compartmentalized, with a glycolytic signature restricted to compact myocardium contrasting with increased mitochondrial oxidative activity in the trabeculae. HIF1α regulation mirrors this pattern, with expression predominating in compact myocardium and scarce in trabeculae. By midgestation, the compact myocardium downregulates HIF1α and switches toward oxidative metabolism. Deletion of the E3 ubiquitin ligase Vhl results in HIF1α hyperactivation, blocking the midgestational metabolic shift and impairing cardiac maturation and function. Moreover, the altered glycolytic signature induced by HIF1 trabecular activation precludes regulation of genes essential for establishment of the cardiac conduction system. Our findings reveal VHL-HIF-mediated metabolic compartmentalization in the developing heart and the connection between metabolism and myocardial differentiation. These results highlight the importance of bioenergetics in ventricular myocardium specialization and its potential relevance to congenital heart disease.

Background Increasing the knowledge about heart failure (HF) costs and their determinants is important to ascertain how HF management can be optimized, leading to a significant decrease of HF costs. This study evaluated the cumulative costs and healthcare utilisation in HF patients in Spain. Methods Observational, retrospective, population-based study using BIG-PAC database, which included data from specialized and primary care of people ≥18 years, from seven autonomous communities in Spain, who received care for HF between 2015 and 2019. The healthcare and medication costs were summarized on a yearly basis starting from the index date (1st January 2015), and then cumulatively until 2019. Results We identified 17,163 patients with HF (year 2015: mean age 77.3 ± 11.8 years, 53.5% men, 51.7% systolic HF, 43.6% on NYHA functional class II). During the 2015–2019 period, total HF associated costs reached 15,373 Euros per person, being cardiovascular disease hospitalizations the most important determinant (75.8%), particularly HF hospitalizations (51.0%). Total medication cost accounted for 7.0% of the total cost. During this period, there was a progressive decrease of cardiovascular disease hospital costs per year (from 2834 Euros in 2015 to 2146 Euros in 2019, P < 0.001), as well as cardiovascular and diabetic medication costs. Conclusions During the 2015–2019 period, costs of HF patients in Spain were substantial, being HF hospitalizations the most important determinant. Medication costs represented only a small proportion of total costs. Improving HF management, particularly through the use of drugs that reduce HF hospitalization may be helpful to reduce HF burden.

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The molecular complexes involved in the nonhomologous end-joining process that resolves recombinationactivating gene (RAG)-induced double-strand breaks and results in V(D)J gene rearrangements vary during mammalian ontogeny. In the mouse, the first immunoglobulin gene rearrangements emerge during midgestation periods, but their repertoires have not been analyzed in detail. We decided to study the postgastrulation DJ H joints and compare them with those present in later life. The embryo DJ H joints differed from those observed in perinatal life by the presence of short stretches of nontemplated (N) nucleotides. Whereas most adult N nucleotides are introduced by terminal deoxynucleotidyl transferase (TdT), the embryo N nucleotides were due to the activity of the homologous DNA polymerase (Pol), which was widely expressed in the early ontogeny, as shown by analysis of Pol ؊/؊ embryos. Based on its DNA-dependent polymerization ability, which TdT lacks, Pol also filled in small sequence gaps at the coding ends and contributed to the ligation of highly processed ends, frequently found in the embryo, by pairing to internal microhomology sites. These findings show that Pol participates in the repair of early-embryo, RAG-induced double-strand breaks and subsequently may contribute to preserve the genomic stability and cellular homeostasis of lymphohematopoietic precursors during development.The adaptive immune system is characterized by the great diversity of its antigen receptors, which result from the activities of enzymatic complexes that cut and paste the genomic DNA of antigen receptor loci. The nonhomologous end-joining (NHEJ) machinery is then recruited to repair the doublestrand DNA breaks (DSBs) inflicted by the products of the recombination-activating genes (RAGs) (45,65). Within B cells, each immunoglobulin (Ig) receptor represents a singular shuffling of two heavy (H) and two light (L) chains, which are derived from the recombination of V, D, and J gene segments of the IgH locus and of V and J for IgL (71). Besides these combinatorial possibilities, most Ig variability derives from extensive processing of the coding ends, including exonucleolytic trimming of DNA ends, together with the addition of palindromic (P) nucleotides templated by the adjacent germ line sequence and of nontemplated (N) nucleotides secondary to the activity of the terminal deoxynucleotidyl transferase (TdT), a lymphoid-specific member of family X of DNA polymerases (reviewed in reference 56). During B-lineage differentiation, IgH rearrangements occur before those of the IgL locus, and D-to-J H rearrangements precede V-to-DJ H rearrangements (62). DJ H joints are formed in any of the three open reading frames (ORFs). ORF1 is predominantly used in mature Igs, ORF2 is transcribed as a D protein that provides negative signals to the B-cell precursors, and ORF3 frequently leads to stop codons (32,33,37). Germ line V, D, and J gene segments display short stretches of mutually homologous nucleotides (SSH), which are frequently used in gene rea...

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In the adult spleen, CD19+CD45R−/lo (19+45Rlo) lymphocytes of embryonic origin exist as a distinct population to that of the conventional B cell lineage. These cells display a plasmablast phenotype, and they spontaneously secrete IgG1 and IgA, whereas the bone marrow population of 19+45Rlo cells contains B1 progenitors. In this study, we show that 19+45Rlo cells are also present in Peyer’s patches and in the spleen throughout the life span of wild-type mice, beginning at postnatal day 7. Although this population is heterogeneous, the surface phenotype of most of these cells distinguishes them from follicular, transitional, marginal zone, and B1 cells. In CBA/CaHN mice, few 19+45Rlo cells were detected at postnatal day 7, and none was observed in the adult spleen. Splenic 19+45Rlo cells exhibited homeostatic BrdU uptake in vivo and actively transcribed cell cycle genes. When transferred to immunodeficient RAG2−/−γchain−/− recipient mice, 19+45Rlo cells survived and differentiated into IgG1– and IgA–plasma cells. Moreover, in vitro stimulation of splenic 19+45Rlo cells with LPS, CpG, BAFF/IL4, and CD40/IL4 induced cell proliferation, IgG1/IgA secretion and the release of IL-10, suggesting a potential immunoregulatory role for this subset of innate-like B cells.

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Summary HIF1-alpha expression defines metabolic compartments in the developing heart, promoting glycolytic program in the compact myocardium and mitochondrial enrichment in the trabeculae. Nonetheless, its role in cardiogenesis is debated. To assess the importance of HIF1-alpha during heart development and the influence of glycolysis in ventricular chamber formation, herein we generated conditional knockout models of Hif1a in Nkx2.5 cardiac progenitors and cardiomyocytes. Deletion of Hif1a impairs embryonic glycolysis without influencing cardiomyocyte proliferation and results in increased mitochondrial number and transient activation of amino acid catabolism together with HIF2α and ATF4 upregulation by E12.5. Hif1a mutants display normal fatty acid oxidation program and do not show cardiac dysfunction in the adulthood. Our results demonstrate that cardiac HIF1 signaling and glycolysis are dispensable for mouse heart development and reveal the metabolic flexibility of the embryonic myocardium to consume amino acids, raising the potential use of alternative metabolic substrates as therapeutic interventions during ischemic events.