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Ataxia-Telangiectasia (A-T) is a multisystem disorder caused by loss of A-T mutated (ATM) protein activity, characterized clinically by immunodeficiency and cerebellar ataxia. ATM is a master regulator of DNA damage responses and loss of ATM function is accompanied by persistent activation of PARP1 leading to depletion of intracellular NAD and dysfunction of a series of cellular signalling pathways dependent on NAD , providing a mechanistic rationale for NAD augmentation therapy. We performed a clinical trial of NAD augmentation with nicotinamide riboside (NR) over 24 months in A-T patients where we observed improved coordination and eye movements in A-T patients. Here, by using peripheral blood mononuclear cells, we performed longitudinal transcriptome profiling to define molecular signatures of A-T and to assess pathway-level responses to NR supplementation. A-T patients exhibited reproducible transcriptomic alterations involving immune, vascular, and inflammatory pathways. NAD augmentation was associated with suppression of interferon response genes and modulation of networks correlated with neurological improvement. These findings establish systemic molecular signatures of A-T and identify potential blood-based biomarkers that reflect disease processes and therapeutic response, supporting the use of NAD augmentation as a disease-modifying strategy in A-T by dampening interferon signalling.

In 2012, the Norwegian newborn screening program (NBS) was expanded (eNBS) from screening for two diseases to that for 23 diseases (20 inborn errors of metabolism, IEMs) and again in 2018, to include a total of 25 conditions (21 IEMs). Between 1 March 2012 and 29 February 2020, 461,369 newborns were screened for 20 IEMs in addition to phenylketonuria (PKU). Excluding PKU, there were 75 true-positive (TP) (1:6151) and 107 (1:4311) false-positive IEM cases. Twenty-one percent of the TP cases were symptomatic at the time of the NBS results, but in two-thirds, the screening result directed the exact diagnosis. Eighty-two percent of the TP cases had good health outcomes, evaluated in 2020. The yearly positive predictive value was increased from 26% to 54% by the use of the Region 4 Stork post-analytical interpretive tool (R4S)/Collaborative Laboratory Integrated Reports 2.0 (CLIR), second-tier biochemical testing and genetic confirmation using DNA extracted from the original dried blood spots. The incidence of IEMs increased by 46% after eNBS was introduced, predominantly due to the finding of attenuated phenotypes. The next step is defining which newborns would truly benefit from screening at the milder end of the disease spectrum. This will require coordinated international collaboration, including proper case definitions and outcome studies.

Christoph Klein and colleagues identify loss-of-function mutations in SMARCD2 ( BAF60b ) that lead to neutropenia, specific granule deficiency and myelodysplasia. They show that SMARCD2 controls differentiation of myeloid–erythroid progenitor cells through interaction with CEBPɛ and that reduced SMARCD2 levels cause transcription and chromatin alterations in acute myeloid leukemia cells. We identify SMARCD2 (SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily D, member 2), also known as BAF60b (BRG1/Brahma-associated factor 60b), as a critical regulator of myeloid differentiation in humans, mice, and zebrafish. Studying patients from three unrelated pedigrees characterized by neutropenia, specific granule deficiency, myelodysplasia with excess of blast cells, and various developmental aberrations, we identified three homozygous loss-of-function mutations in SMARCD2 . Using mice and zebrafish as model systems, we showed that SMARCD2 controls early steps in the differentiation of myeloid–erythroid progenitor cells. In vitro , SMARCD2 interacts with the transcription factor CEBPɛ and controls expression of neutrophil proteins stored in specific granules. Defective expression of SMARCD2 leads to transcriptional and chromatin changes in acute myeloid leukemia (AML) human promyelocytic cells. In summary, SMARCD2 is a key factor controlling myelopoiesis and is a potential tumor suppressor in leukemia.

Forkhead winged-helix transcription factor Foxp3 serves as the dedicated mediator of the genetic program governing CD25⁺CD4⁺ regulatory T cell$(T_{R})$development and function in mice. In humans, its role in mediating$T_{R}$development has been controversial. Furthermore, the fate of$T_{R}$precursors in FOXP3 deficiency has yet to be described. Making use of flow cytometric detection of human FOXP3, we have addressed the relationship between FOXP3 expression and human$T_{R}$development. Unlike murine Foxp3⁻ T cells, a small subset of human CD4⁺ and CD8⁺ T cells transiently upregulated FOXP3 upon in vitro stimulation. Induced FOXP3, however, did not alter cell-surface phenotype or suppress T helper 1 cytokine expression. Furthermore, only ex vivo FOXP3⁺$T_{R}$cells persisted after prolonged culture, suggesting that induced FOXP3 did not activate a$T_{R}$developmental program in a significant number of cells. FOXP3 flow cytometry was also used to further characterize several patients exhibiting symptoms of immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome (IPEX) with or without FOXP3 mutations. Most patients lacked FOXP3-expressing cells, further solidifying the association between FOXP3 deficiency and immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome. Interestingly, one patient bearing a FOXP3 mutation enabling expression of stable$FOXP3^{mut}$protein exhibited$FOXP3^{mut}-expressing$cells among a subset of highly activated CD4⁺ T cells. This observation raises the possibility that the severe autoimmunity in FOXP3 deficiency can be attributed, in part, to aggressive T helper cells that have developed from$T_{R}$precursors.

Purpose GATA2 deficiency is a rare primary immunodeficiency that has become increasingly recognized due to improved molecular diagnostics and clinical awareness. The only cure for GATA2 deficiency is allogeneic hematopoietic stem cell transplantation (allo-HSCT). The inconsistency of genotype–phenotype correlations makes the decision regarding “who and when” to transplant challenging. Despite considerable morbidity and mortality, the reported proportion of patients with GATA2 deficiency that has undergone allo-HSCT is low (~ 35%). The purpose of this study was to explore if detailed clinical, genetic, and bone marrow characteristics could predict end-point outcome, i.e., death and allo-HSCT. Methods All medical genetics departments in Norway were contacted to identify GATA2 deficient individuals. Clinical information, genetic variants, treatment, and outcome were subsequently retrieved from the patients’ medical records. Results Between 2013 and 2020, we identified 10 index cases or probands, four additional symptomatic patients, and no asymptomatic patients with germline GATA2 variants. These patients had a diverse clinical phenotype dominated by cytopenia (13/14), myeloid neoplasia (10/14), warts (8/14), and hearing loss (7/14). No valid genotype–phenotype correlations were found in our data set, and the phenotypes varied also within families. We found that 11/14 patients (79%), with known GATA2 deficiency, had already undergone allo-HSCT. In addition, one patient is awaiting allo-HSCT. The indications to perform allo-HSCT were myeloid neoplasia, disseminated viral infection, severe obliterating bronchiolitis, and/or HPV-associated in situ carcinoma. Two patients died, 8 months and 7 years after allo-HSCT, respectively. Conclusion Our main conclusion is that the majority of patients with symptomatic GATA2 deficiency will need allo-HSCT, and a close surveillance of these patients is important to find the “optimal window” for allo-HSCT. We advocate a more offensive approach to allo-HSCT than previously described.

Human NK cell deficiencies are rare yet result in severe and often fatal disease, particularly as a result of viral susceptibility. NK cells develop from hematopoietic stem cells, and few monogenic errors that specifically interrupt NK cell development have been reported. Here we have described biallelic mutations in IRF8, which encodes an interferon regulatory factor, as a cause of familial NK cell deficiency that results in fatal and severe viral disease. Compound heterozygous or homozygous mutations in IRF8 in 3 unrelated families resulted in a paucity of mature CD56dim NK cells and an increase in the frequency of the immature CD56bright NK cells, and this impairment in terminal maturation was also observed in Irf8-/-, but not Irf8+/-, mice. We then determined that impaired maturation was NK cell intrinsic, and gene expression analysis of human NK cell developmental subsets showed that multiple genes were dysregulated by IRF8 mutation. The phenotype was accompanied by deficient NK cell function and was stable over time. Together, these data indicate that human NK cells require IRF8 for development and functional maturation and that dysregulation of this function results in severe human disease, thereby emphasizing a critical role for NK cells in human antiviral defense.

Inborn errors of immunity (IEIs) caused by mutations in are associated with a broad range of clinical manifestations, ranging from relatively mild to life-threatening. Our aim was to give a clinical and molecular description of a Norwegian cohort with STAT1-related disease. This is a descriptive epidemiological study. We present 23 patients with heterozygous mutations, from 12 unrelated Norwegian families. Eighteen individuals had (GOF) variants. Chronic mucocutaneous candidiasis (CMC) was the most common manifestation, observed in 94% of patients. Herpesviruses caused morbidity in one-third of patients, with severe complications such as varicella meningitis, varicella retinitis and ulcerative CMV esophagitis seen in 17%. Autoimmune hypertriglyceridemia with GPIHBP1 autoantibodies was diagnosed in one patient, adding a new entity to STAT1 GOF. Fifty percent of patients suffered chronic ophthalmologic manifestations. Severe gastrointestinal manifestations were observed in 22% of patients. Five of the 23 patients had (LOF) variants. Mendelian susceptibility to mycobacterial disease (MSMD) was detected in three patients. Malignancy and autoimmunity were observed in two patients, both were heterozygous for the p.Ala246Thr variant, which is likely associated with a more complex phenotype. Significant viral infections were also observed. Presently, our cohort represents the largest nationwide study on STAT1-related disease. We report novel clinical manifestations in STAT1 GOF, and suggest that heterozygous STAT1 LOF might be a more complex condition than originally presumed.

Severe combined immunodeficiency (SCID) and other T cell lymphopenias can be detected during newborn screening (NBS) by measuring T cell receptor excision circles (TRECs) in dried blood spot (DBS) DNA. Second tier next generation sequencing (NGS) with an amplicon based targeted gene panel using the same DBS DNA was introduced as part of our prospective pilot research project in 2015. With parental consent, 21 000 newborns were TREC-tested in the pilot. Three newborns were identified with SCID, and disease-causing variants in , and were confirmed by NGS on the initial DBS DNA. The molecular findings directed follow-up and therapy: the -SCID underwent early hematopoietic stem cell transplantation (HSCT) without any complications; the leaky SCID received prophylactic antibiotics, antifungals, and immunoglobulin infusions, and underwent HSCT at 1 year of age. The child with -SCID had complete Hirschsprung disease and died at 1 month of age. Since January 2018, all newborns in Norway have been offered NBS for SCID using 1st tier TRECs and 2nd tier gene panel NGS on DBS DNA. During the first 20 months of nationwide SCID screening an additional 88 000 newborns were TREC tested, and four new SCID cases were identified. Disease-causing variants in , and were molecularly confirmed on day 8, 15, 8 and 6, respectively after birth, using the initial NBS blood spot. Targeted gene panel NGS integrated into the NBS algorithm rapidly delineated the specific molecular diagnoses and provided information useful for management, targeted therapy and follow-up i.e., X rays and CT scans were avoided in the radiosensitive SCID. Second tier targeted NGS on the same DBS DNA as the TREC test provided instant confirmation or exclusion of SCID, and made it possible to use a less stringent TREC cut-off value. This allowed for the detection of leaky SCIDs, and simultaneously reduced the number of control samples, recalls and false positives. Mothers were instructed to stop breastfeeding until maternal (CMV) status was determined. Our limited data suggest that shorter time-interval from birth to intervention, may prevent breast milk transmitted CMV infection in classical SCID.

Increasing recognition of germline DDX41 variants in patients with hematological malignancies prompted us to provide DDX41‐specific recommendations for diagnosis, surveillance, and treatment. Causative germline variants in the DDX41 predispose to the development of myeloid neoplasms (MNs), especially myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). Almost 3%–5% of all patients with MDS or AML carry a pathogenic or likely pathogenic germline DDX41 variant, while half of them acquire a somatic second hit in the other allele. DDX41‐associated MNs exhibit unique clinical characteristics compared to other hematological malignancies with germline predisposition: MNs occur mostly at advanced age and follow an indolent clinical course. Male carriers are more prone to develop MDS or AML than females. DDX41‐associated MN is often hypoplastic, and the malignancy may be preceded by cytopenias.

Background With advances in next generation sequencing technologies and genomic capture techniques, exome sequencing has become a cost-effective approach for mutation detection in genetic diseases. However, computational prediction of copy number variants (CNVs) from exome sequence data is a challenging task. Whilst numerous programs are available, they have different sensitivities, and have low sensitivity to detect smaller CNVs (1–4 exons). Additionally, exonic CNV discovery using standard aCGH has limitations due to the low probe density over exonic regions. The goal of our study was to develop a protocol to detect exonic CNVs (including shorter CNVs that cover 1–4 exons), combining computational prediction algorithms and a high-resolution custom CGH array. Results We used six published CNV prediction programs (ExomeCNV, CONTRA, ExomeCopy, ExomeDepth, CoNIFER, XHMM) and an in-house modification to ExomeCopy and ExomeDepth (ExCopyDepth) for computational CNV prediction on 30 exomes from the 1000 genomes project and 9 exomes from primary immunodeficiency patients. CNV predictions were tested using a custom CGH array designed to capture all exons (exaCGH). After this validation, we next evaluated the computational prediction of shorter CNVs. ExomeCopy and the in-house modified algorithm, ExCopyDepth, showed the highest capability in detecting shorter CNVs. Finally, the performance of each computational program was assessed by calculating the sensitivity and false positive rate. Conclusions In this paper, we assessed the ability of 6 computational programs to predict CNVs, focussing on short (1–4 exon) CNVs. We also tested these predictions using a custom array targeting exons. Based on these results, we propose a protocol to identify and confirm shorter exonic CNVs combining computational prediction algorithms and custom aCGH experiments.