RESUMO
The extraembryonic yolk sac (YS) ensures delivery of nutritional support and oxygen to the developing embryo but remains ill-defined in humans. We therefore assembled a comprehensive multiomic reference of the human YS from 3 to 8 postconception weeks by integrating single-cell protein and gene expression data. Beyond its recognized role as a site of hematopoiesis, we highlight roles in metabolism, coagulation, vascular development, and hematopoietic regulation. We reconstructed the emergence and decline of YS hematopoietic stem and progenitor cells from hemogenic endothelium and revealed a YS-specific accelerated route to macrophage production that seeds developing organs. The multiorgan functions of the YS are superseded as intraembryonic organs develop, effecting a multifaceted relay of vital functions as pregnancy proceeds.
Assuntos
Desenvolvimento Embrionário , Saco Vitelino , Feminino , Humanos , Gravidez , Coagulação Sanguínea/genética , Macrófagos , Saco Vitelino/citologia , Saco Vitelino/metabolismo , Desenvolvimento Embrionário/genética , Atlas como Assunto , Expressão Gênica , Perfilação da Expressão Gênica , Hematopoese/genética , Fígado/embriologiaRESUMO
Haematopoiesis in the bone marrow (BM) maintains blood and immune cell production throughout postnatal life. Haematopoiesis first emerges in human BM at 11-12 weeks after conception1,2, yet almost nothing is known about how fetal BM (FBM) evolves to meet the highly specialized needs of the fetus and newborn. Here we detail the development of FBM, including stroma, using multi-omic assessment of mRNA and multiplexed protein epitope expression. We find that the full blood and immune cell repertoire is established in FBM in a short time window of 6-7 weeks early in the second trimester. FBM promotes rapid and extensive diversification of myeloid cells, with granulocytes, eosinophils and dendritic cell subsets emerging for the first time. The substantial expansion of B lymphocytes in FBM contrasts with fetal liver at the same gestational age. Haematopoietic progenitors from fetal liver, FBM and cord blood exhibit transcriptional and functional differences that contribute to tissue-specific identity and cellular diversification. Endothelial cell types form distinct vascular structures that we show are regionally compartmentalized within FBM. Finally, we reveal selective disruption of B lymphocyte, erythroid and myeloid development owing to a cell-intrinsic differentiation bias as well as extrinsic regulation through an altered microenvironment in Down syndrome (trisomy 21).
Assuntos
Células da Medula Óssea/citologia , Medula Óssea , Síndrome de Down/sangue , Síndrome de Down/imunologia , Feto/citologia , Hematopoese , Sistema Imunitário/citologia , Linfócitos B/citologia , Células Dendríticas/citologia , Síndrome de Down/metabolismo , Síndrome de Down/patologia , Células Endoteliais/patologia , Eosinófilos/citologia , Células Eritroides/citologia , Granulócitos/citologia , Humanos , Imunidade , Células Mieloides/citologia , Células Estromais/citologiaRESUMO
Molecular dissection of inborn errors of immunity can help to elucidate the nonredundant functions of individual genes. We studied 3 children with an immune dysregulation syndrome of susceptibility to infection, lymphadenopathy, hepatosplenomegaly, developmental delay, autoimmunity, and lymphoma of B-cell (n = 2) or T-cell (n = 1) origin. All 3 showed early autologous T-cell reconstitution following allogeneic hematopoietic stem cell transplantation. By whole-exome sequencing, we identified rare homozygous germline missense or nonsense variants in a known epigenetic regulator of gene expression: ten-eleven translocation methylcytosine dioxygenase 2 (TET2). Mutated TET2 protein was absent or enzymatically defective for 5-hydroxymethylating activity, resulting in whole-blood DNA hypermethylation. Circulating T cells showed an abnormal immunophenotype including expanded double-negative, but depleted follicular helper, T-cell compartments and impaired Fas-dependent apoptosis in 2 of 3 patients. Moreover, TET2-deficient B cells showed defective class-switch recombination. The hematopoietic potential of patient-derived induced pluripotent stem cells was skewed toward the myeloid lineage. These are the first reported cases of autosomal-recessive germline TET2 deficiency in humans, causing clinically significant immunodeficiency and an autoimmune lymphoproliferative syndrome with marked predisposition to lymphoma. This disease phenotype demonstrates the broad role of TET2 within the human immune system.
Assuntos
Proteínas de Ligação a DNA/deficiência , Mutação em Linhagem Germinativa , Mutação com Perda de Função , Transtornos Linfoproliferativos/genética , Proteínas Proto-Oncogênicas/deficiência , Imunodeficiência Combinada Severa/genética , Aloenxertos , Apoptose , Subpopulações de Linfócitos B/patologia , Técnicas de Reprogramação Celular , Códon sem Sentido , Metilação de DNA , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/fisiologia , Dioxigenases , Evolução Fatal , Feminino , Transplante de Células-Tronco Hematopoéticas , Humanos , Células-Tronco Pluripotentes Induzidas/patologia , Recém-Nascido , Linfoma Difuso de Grandes Células B/genética , Linfoma Difuso de Grandes Células B/patologia , Linfoma de Células T Periférico/genética , Linfoma de Células T Periférico/patologia , Masculino , Mutação de Sentido Incorreto , Neoplasias Primárias Múltiplas/genética , Linhagem , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas/fisiologia , Imunodeficiência Combinada Severa/patologia , Subpopulações de Linfócitos T/patologia , Sequenciamento do ExomaRESUMO
Interleukin-2, which conveys essential signals for immunity, operates through a heterotrimeric receptor. Here we identify human interleukin-2 receptor (IL-2R) ß chain (IL2RB) gene defects as a cause of life-threatening immune dysregulation. We report three homozygous mutations in the IL2RB gene of eight individuals from four consanguineous families that cause disease by distinct mechanisms. Nearly all patients presented with autoantibodies, hypergammaglobulinemia, bowel inflammation, dermatological abnormalities, lymphadenopathy, and cytomegalovirus disease. Patient T lymphocytes lacked surface expression of IL-2Rß and were unable to respond to IL-2 stimulation. By contrast, natural killer cells retained partial IL-2Rß expression and function. IL-2Rß loss of function was recapitulated in a recombinant system in which IL2RB mutations caused reduced surface expression and IL-2 binding. Stem cell transplant ameliorated clinical symptoms in one patient; forced expression of wild-type IL-2Rß also increased the IL-2 responsiveness of patient T lymphocytes in vitro. Insights from these patients can inform the development of IL-2-based therapeutics for immunological diseases and cancer.