MCM3APandPOMPMutations Cause a DNA-Repair and DNA-Damage-Signaling Defect in an Immunodeficient Child

Abstract

Immunodeficiency patients with DNA repair defects exhibit radiosensitivity and proneness to leukemia/lymphoma formation. Though progress has been made in identifying the underlying mutations, in most patients the genetic basis is unknown. Two de novo mutated candidate genes, MCM3AP encoding germinal center-associated nuclear protein (GANP) and POMP encoding proteasome maturation protein (POMP), were identified by whole-exome sequencing (WES) and confirmed by Sanger sequencing in a child with complex phenotype displaying immunodeficiency, genomic instability, skin changes, and myelodysplasia. GANP was previously described to promote B-cell maturation by nuclear targeting of activation-induced cytidine deaminase (AID) and to control AID-dependent hyperrecombination. POMP is required for 20S proteasome assembly and, thus, for efficient NF-κB signaling. Patient-derived cells were characterized by impaired homologous recombination, moderate radio- and cross-linker sensitivity associated with accumulation of damage, impaired DNA damage-induced NF-κB signaling, and reduced nuclear AID levels. Complementation by wild-type (WT)-GANP normalized DNA repair and WT-POMP rescued defective NF-κB signaling. In conclusion, we identified for the first time mutations in MCM3AP and POMP in an immunodeficiency patient. These mutations lead to cooperative effects on DNA recombination and damage signaling. Digenic/polygenic mutations may constitute a novel genetic basis in immunodeficiency patients with DNA repair defects.

Biallelic germline BRCA1 mutations in a patient with early onset breast cancer, mild Fanconi anemia‐like phenotype, and no chromosome fragility

“…Given the close association between HR deficiency and the pathogenicity of BRCA1 mutations (Bouwman et al, ), we applied an EGFP‐based DNA double‐strand break (DSB) repair assay on fresh PBLs derived from the index patient, her unaffected mother and two female healthy donors functionally representing wild‐type controls (Deniz, ; Gatz et al, ; Keimling et al, ) (Figure a). HR analysis indicated threefold reduced HR frequencies in PBLs from the patient as well as from the mother compared to the wild‐type reference, although not reaching statistical significance ( p = .1000), most likely due to the limited number of measurements.…”

“…Thawed PBLs were cultivated in PB‐MAXTM Karyotyping Medium (Gibco/Invitrogen, Carlsbad, CA, USA) including 2% phytohemagglutinin (PAA, Pasching, Germany) for 72 hr. LCLs were cultivated as previously described (Gatz et al, ) and used for HR measurements at passage 2–6.…”

“…For in situ analysis of DSB repair by HR, we performed immunofluorescence microscopic analysis of the DNA damage marker γH2AX and the recombinase RAD51 in PBLs after exposure to 2 Gy of ionizing radiation (IR) as previously described (Gatz et al, ; Obermeier et al, ). Briefly, PBLs were harvested by cytospinning at the indicated time points postirradiation, fixed with 3.7% formaldehyde followed by permeabilization with 0.5% TritionX‐100.…”

Inhibition of tryptophan 2,3-dioxygenase impairs DNA damage tolerance and repair in glioma cells

“…There was a notable depletion of MCM3AP, which acetylates MCM3 and inhibits replication initiation (49). Mutations in MCM3AP have been shown to result in defective HR-mediated repair of DSBs (50), and failed activation of canonical NF-kB signaling caused by MCM3AP mutation may be responsible for the defect in HR repair. Such a scenario is consistent with the break repair defects we observed for TDO-deficient cells exposed to BCNU (Fig.…”

Clinical case of proteasome-associated autoinflammatory syndrome-2 (PRAAS2)

“…На сегодняшний день в гене POMP описана гомозиготная мутация -делеция нуклеотида c. -95 в 5'-нетранслируемой области (5'-НТО) и гетерозиготная мутация с нарушением рамки считывания [2,8]. Описано также сочетание мутаций POMP и MCM3AP, приводящее к нарушению репарации и сигнальных механизмов ДНК у ребенка с В-клеточным иммунодефицитом [9].…”