A novel mutation in the POLE2 gene causing combined immunodeficiency

16sinonenoneFrugoni, Francesco; Dobbs, Kerry; Felgentreff, Kerstin; Aldhekri, Hasan; Al Saud, Bandar K.; Arnaout, Rand; Ali, Afshan Ashraf; Abhyankar, Avinash; Alroqi, Fayhan; Giliani, Silvia; Ojeda, Mayra Martinez; Tsitsikov, Erdyni; Pai, Sung-Yun; Casanova, Jean Laurent; Notarangelo, Luigi D.; Manis, John P.Frugoni, Francesco; Dobbs, Kerry; Felgentreff, Kerstin; Aldhekri, Hasan; Al Saud, Bandar K.; Arnaout, Rand; Ali, Afshan Ashraf; Abhyankar, Avinash; Alroqi, Fayhan; Giliani, Silvia Clara; Ojeda, Mayra Martinez; Tsitsikov, Erdyni; Pai, Sung Yun; Casanova, Jean Laurent; Notarangelo, Luigi D.; Manis, John P

Differential role of nonhomologous end joining factors in the generation, DNA damage response, and myeloid differentiation of human induced pluripotent stem cells

Nonhomologous end-joining (NHEJ) is a key pathway for efficient repair of DNA double-strand breaks (DSBs) and V(D)J recombination. NHEJ defects in humans cause immunodeficiency and increased cellular sensitivity to ionizing irradiation (IR) and are variably associated with growth retardation, microcephaly, and neurodevelopmental delay. Repair of DNA DSBs is important for reprogramming of somatic cells into induced pluripotent stem cells (iPSCs). To compare the specific contribution of DNA ligase 4 (LIG4), Artemis, and DNA-protein kinase catalytic subunit (PKcs) in this process and to gain insights into phenotypic variability associated with these disorders, we reprogrammed patient-derived fibroblast cell lines with NHEJ defects. Deficiencies of LIG4 and of DNA-PK catalytic activity, but not Artemis deficiency, were associated with markedly reduced reprogramming efficiency, which could be partially rescued by genetic complementation. Moreover, we identified increased genomic instability in LIG4-deficient iPSCs. Cell cycle synchronization revealed a severe defect of DNA repair and a G0/G1 cell cycle arrest, particularly in LIG4- and DNA-PK catalytically deficient iPSCs. Impaired myeloid differentiation was observed in LIG4-, but not Artemis- or DNA-PK-mutated iPSCs. These results indicate a critical importance of the NHEJ pathway for somatic cell reprogramming, with a major role for LIG4 and DNA-PKcs and a minor, if any, for Artemis

Inherited DOCK2 deficiency in patients with early-onset invasive infections

BACKGROUND: Combined immunodeficiencies (CIDs) denote inborn errors of T-cell immunity with T cells present but quantitatively or functionally deficient. Impaired humoral immunity, either due to a primary B cell defect or secondary to the T-cell defect, is also frequent. Consequently, patients with CID display severe infections and/or autoimmunity. The specific molecular, cellular, and clinical features of many types of CID remain unknown. METHODS: We performed genetic and cellular immunological studies in five unrelated children who shared a history of early-onset invasive bacterial and viral infections, with lymphopenia and defective T-, B-, and NK-cell responses. Two patients died early in childhood, whereas the other three underwent allogeneic hematopoietic stem cell transplantation with normalization of T cell function and clinical improvement. RESULTS: We identified bi-allelic mutations in the Dedicator Of Cytokinesis 2 (DOCK2) gene in these five patients. RAC1 activation was impaired in T cells. Chemokine-induced migration and actin polymerization were defective in T, B, and NK cells. NK-cell degranulation was also affected. The production of interferon (IFN)-α and -λ by peripheral blood mononuclear cells (PBMCs) was diminished following virus infection. Moreover, in DOCK2-deficient fibroblasts, virus replication was increased and there was enhanced virus-induced cell death, which could be normalized by treatment with IFN-α2β or upon expression of wild-type DOCK2. CONCLUSIONS: Autosomal recessive DOCK2 deficiency is a Mendelian disorder with pleiotropic defects of hematopoietic and non-hematopoietic immunity. Children with clinical features of CID, especially in the presence of early-onset, invasive infections may have this condition