ABSTRACT
The DEAH helicase RHAU (alias DHX36, G4R1) is the only helicase shown to have G-quadruplex (G4)-RNA resolvase activity and the major source of G4-DNA resolvase activity. Previous report showed RHAU mRNA expression to be elevated in human lymphoid and CD34(+) BM cells, suggesting a potential role in hematopoiesis. Here, we generated a conditional knockout of the RHAU gene in mice. Germ line deletion of RHAU led to embryonic lethality. We then targeted the RHAU gene specifically in the hematopoiesis system, using a Cre-inducible system in which an optimized variant of Cre recombinase was expressed under the control of the Vav1 promoter. RHAU deletion in hematopoietic system caused hemolytic anemia and differentiation defect at the proerythroblast stage. The partial differentiation block of proerythroblasts was because of a proliferation defect. Transcriptome analysis of RHAU knockout proerythroblasts showed that a statistically significant portion of the deregulated genes contain G4 motifs in their promoters. This suggests that RHAU may play a role in the regulation of gene expression that relies on its G4 resolvase activity.
Subject(s)
DEAD-box RNA Helicases/physiology , Hematopoiesis/genetics , Promoter Regions, Genetic/genetics , Anemia, Hemolytic, Congenital/genetics , Animals , Bone Marrow Transplantation , Cell Cycle , Crosses, Genetic , DEAD-box RNA Helicases/deficiency , DEAD-box RNA Helicases/genetics , Embryonic Development/genetics , Embryonic Development/physiology , Erythroblasts/pathology , Erythropoietin/blood , Genes, Lethal , Genes, Synthetic , Green Fluorescent Proteins/analysis , Green Fluorescent Proteins/genetics , Hematopoiesis/physiology , Leukopenia/congenital , Leukopenia/genetics , Mice , Mice, Inbred C57BL , Mice, Knockout , Protein Folding , Proto-Oncogene Proteins c-vav/genetics , Radiation Chimera , Recombinases/deficiency , Recombinases/genetics , Recombinases/physiology , Thrombocytopenia/congenital , Thrombocytopenia/geneticsABSTRACT
This report presents the case of a 15-year-old male with severe chronic neutropenia, leukopenia, and persistent tetraploid mosaicism in the bone marrow and peripheral blood. His father had mild neutropenia and bone marrow tetraploidy. Flow cytometric analysis of DNA content peripheral blood showed tetraploidy in 20% of granulocytes and 15% of monocytes. Sequence analysis of the ELA2 gene was normal, but the GFI1 gene exhibited transient appearance of single base changes the coding region and promoter. We speculate that an underlying genetic defect, inherited in an autosomal dominant pattern, leads to both disordered mitosis and neutropenia in this kindred.
Subject(s)
DNA-Binding Proteins/genetics , Mosaicism , Neutropenia/congenital , Polyploidy , Transcription Factors/genetics , Adolescent , Adult , Chronic Disease , Genes, Dominant , Granulocytes/ultrastructure , Humans , Leukemia/genetics , Leukopenia/congenital , Leukopenia/genetics , Lymphoma, Follicular/genetics , Male , Mitosis/genetics , Monocytes/ultrastructure , Mutagenesis , Neutropenia/genetics , Paraproteinemias/genetics , PedigreeSubject(s)
Leukopenia/congenital , Humans , Infant, Newborn , Leukopenia/complications , Leukopenia/diagnosis , MaleABSTRACT
Reticular dysgenesis is a rare congenital disorder characterized by severe combined immunodeficiency and profound neutropenia, curable to date, only by bone marrow transplantation. This report describes the association of bilateral sensorineural deafness with this disease.
Subject(s)
Deafness/congenital , Deafness/diagnosis , Leukopenia/congenital , Leukopenia/diagnosis , Lymphatic Diseases/congenital , Lymphatic Diseases/diagnosis , Severe Combined Immunodeficiency/congenital , Severe Combined Immunodeficiency/diagnosis , Thymus Gland , Audiometry , Bone Marrow Transplantation , Evoked Potentials, Auditory, Brain Stem , Female , Histocompatibility Testing , Humans , Incidence , Infant , Infant, Newborn , Leukocyte Count , Leukopenia/blood , Leukopenia/genetics , Leukopenia/therapy , Lymphatic Diseases/blood , Lymphatic Diseases/genetics , Lymphatic Diseases/therapy , Male , Retrospective Studies , Severe Combined Immunodeficiency/blood , Severe Combined Immunodeficiency/genetics , Severe Combined Immunodeficiency/therapySubject(s)
Fever of Unknown Origin/immunology , Immunologic Deficiency Syndromes/congenital , Leukopenia/congenital , Opportunistic Infections/immunology , Puerperal Infection/immunology , Adult , Female , Humans , Immunologic Deficiency Syndromes/immunology , Leukocyte Count , Leukopenia/immunologyABSTRACT
We report fatal reticular dysgenesis in a premature infant presenting with severely decreased blood and bone marrow granulocytes and lymphocytes, an absent thymic shadow by x-ray film, and generalized lymphoid hypoplasia. Immunologic and electron microscopic evaluation of his white blood cells demonstrated that, despite extremely low cell numbers, cells from all stages of both granulocytic and lymphocytic development were present. Immature bone marrow cells of both myeloid and lymphoid lineages were found in much greater proportions than were mature cells; pre-B cells outnumbered B cells by more than tenfold. Megakaryocytes and erythroid cells appeared to be present in normal numbers, and tritiated-thymidine incorporation by bone marrow nucleated cells was also normal, although it may have largely occurred in erythroblasts. These data suggest that the primary defect in reticular dysgenesis is not failure in initiation of stem cell differentiation along lymphoid and myelomonocytic lines but rather an, as yet, undefined abnormality that interferes with normal growth and maturation of immune cells committed to these differentiation pathways.
Subject(s)
Immunologic Deficiency Syndromes/congenital , Infant, Premature, Diseases/immunology , Leukocytes/immunology , Leukopenia/congenital , B-Lymphocytes/immunology , Erythroblasts/immunology , Granulocytes/immunology , Hematopoietic Stem Cells/immunology , Humans , Immunologic Deficiency Syndromes/immunology , Infant, Newborn , Leukocytes/ultrastructure , Leukopenia/immunology , Male , Megakaryocytes/immunology , Microscopy, Electron , Neutrophils/immunology , T-Lymphocytes/immunologyABSTRACT
Congenital dysgranulopietic neutropenia (CDN) is a recently proposed entity that describes a small subgroup of children with clinically severe neutropenia. We followed and studied a 3-year-old girl with neutropenia (less than 500/mm3) and recurrent severe infections in whom repeated marrow evaluations revealed large (30-50 microns) multinucleated promyelocytes to polymorphonuclear cells with as many as 4 to 16 nuclei or nuclear lobes, respectively. In addition to the nuclear endoreduplication, ultrastructural and cytochemical evaluation of these cells demonstrated abnormalities in granule genesis and centriole structure. Concomitantly, immunoperoxidase staining indicated that many of the granules were devoid of lactoferrin but not lysozyme. In vitro proliferation studies revealed normal to increased thymidine labeling, normal numbers of colony-forming cells, and normal colony-stimulating activity from blood and marrow mononuclear cells, findings consistent with ineffective myelopoiesis. However, serum folate, B12, and lysozyme levels were normal. The nuclear and cytoplasmic abnormalities in this patient result in an extreme example of CDN, distinct from previously described cases.
