CRISPR-Cas9n-mediated ELANE promoter editing for gene therapy of severe congenital neutropenia.

Severe congenital neutropenia (CN) is an inherited pre-leukemia bone marrow failure syndrome commonly caused by autosomal-dominant ELANE mutations (ELANE-CN). ELANE-CN patients are treated with daily injections of recombinant human granulocyte colony-stimulating factor (rhG-CSF). However, some patients do not respond to rhG-CSF, and approximately 15% of ELANE-CN patients develop myelodysplasia or acute myeloid leukemia. Here, we report the development of a curative therapy for ELANE-CN through inhibition of ELANE mRNA expression by introducing two single-strand DNA breaks at the opposing DNA strands of the ELANE promoter TATA box using CRISPR-Cas9D10A nickases-termed MILESTONE. This editing effectively restored defective neutrophil differentiation of ELANE-CN CD34+ hematopoietic stem and progenitor cells (HSPCs) in vitro and in vivo, without affecting the functions of the edited neutrophils. CRISPResso analysis of the edited ELANE-CN CD34+ HSPCs revealed on-target efficiencies of over 90%. Simultaneously, GUIDE-seq, CAST-Seq, and rhAmpSeq indicated a safe off-target profile with no off-target sites or chromosomal translocations. Taken together, ex vivo gene editing of ELANE-CN HSPCs using MILESTONE in the setting of autologous stem cell transplantation could be a universal, safe, and efficient gene therapy approach for ELANE-CN patients.

HAX1-related congenital neutropenia: Long-term observation in paediatric and adult patients enrolled in the European branch of the Severe Chronic Neutropenia International Registry (SCNIR).

HAX1-related congenital neutropenia (HAX1-CN) is a rare autosomal recessive disorder caused by pathogenic variants in the HAX1 gene. HAX1-CN patients suffer from bone marrow failure as assessed by a maturation arrest of the myelopoiesis revealing persistent severe neutropenia from birth. The disorder is strongly associated with severe bacterial infections and a high risk of developing myelodysplastic syndrome or acute myeloid leukaemia. This study aimed to describe the long-term course of the disease, the treatment, outcome and quality of life in patients with homozygous HAX1 mutations reported to the European branch of the Severe Chronic Neutropenia International Registry. We have analysed a total of 72 patients with different types of homozygous (n = 68), compound heterozygous (n = 3), and digenic (n = 1) HAX1 mutations. The cohort includes 56 paediatric (<18 years) and 16 adult patients. All patients were initially treated with G-CSF with a sufficient increase in absolute neutrophil counts. Twelve patients required haematopoietic stem cell transplantation for leukaemia (n = 8) and non-leukaemic indications (n = 4). While previous genotype-phenotype reports documented a striking correlation between two main transcript variants and clinical neurological phenotypes, our current analysis reveals novel mutation subtypes and clinical overlaps between all genotypes including severe secondary manifestations, e.g., high incidence of secondary ovarian insufficiency.

Differential transcriptional control of hematopoiesis in congenital and cyclic neutropenia patients harboring ELANE mutations.

Mutations in the ELANE gene, encoding the neutrophil elastase (NE) protein, are responsible for most CyN cases and approximately 25 % of CN cases. In CN and in CyN, a median of 2.8 % of CD34+ cells were early CD49f+ hematopoietic stem cells (eHSC) that did not express ELANE and thus escape from the unfolded protein response (UPR) caused by mutated NE. In CyN, the CD49f+ cells respond to G-CSF with a significant upregulation of the hematopoietic stem-cell-specific transcription factors, C/EBP/, MLL1, HOXA9, MEIS1, and HLF during the ascending arm of the cycle, resulting in the differentiation of myeloid cells to mature neutrophils at the cycle peak. However, NE protein released by neutrophils at the cycle's peak caused a negative feedback loop on granulopoiesis through the proteolytic digestion of G-CSF. In contrast, in CN patients, CD49f+ cells failed to express mRNA levels of HSC-specific transcription factors mentioned above. Rescue of C/EBP//expression in CN restored granulopoiesis.

Registries for study of nonmalignant hematological diseases: the example of the Severe Chronic Neutropenia International Registry.

PURPOSE OF REVIEW: Registries provide 'real world' perspectives on the natural history and outcomes for many clinical conditions. The purpose of this review is to identify registries for nonmalignant hematological disease and to describe the operation of a successful long-term registry for patients with severe chronic neutropenia. RECENT FINDINGS: There was an upswing in registries about 20 years ago, based on optimism about their utility to improve patient care. To show value, registries must define outcomes for populations of patients with specific medical conditions and the effects of treatment. This is challenging for many reasons. The Severe Chronic Neutropenia International Registry is an example of a successful registry. This report describes underlying reasons for its success. SUMMARY: Registries are important to organize and analyze clinical information across geographic, ethnic and social boundaries. They are also challenging to organize, administer and support.

CRISPR/Cas9-mediated ELANE knockout enables neutrophilic maturation of primary hematopoietic stem and progenitor cells and induced pluripotent stem cells of severe congenital neutropenia patients.

A Autosomal-dominant ELANE mutations are the most common cause of severe congenital neutropenia. Although the majority of congenital neutropenia patients respond to daily granulocyte colony stimulating factor, approximately 15 % do not respond to this cytokine at doses up to 50 µg/kg/day and approximately 15 % of patients will develop myelodysplasia or acute myeloid leukemia. "Maturation arrest," the failure of the marrow myeloid progenitors to form mature neutrophils, is a consistent feature of ELANE associated congenital neutropenia. As mutant neutrophil elastase is the cause of this abnormality, we hypothesized that ELANE associated neutropenia could be treated and "maturation arrest" corrected by a CRISPR/Cas9-sgRNA ribonucleoprotein mediated ELANE knockout. To examine this hypothesis, we used induced pluripotent stem cells from two congenital neutropenia patients and primary hematopoietic stem and progenitor cells from four congenital neutropenia patients harboring ELANE mutations as well as HL60 cells expressing mutant ELANE We observed that granulocytic differentiation of ELANE knockout induced pluripotent stem cells and primary hematopoietic stem and progenitor cells were comparable to healthy individuals. Phagocytic functions, ROS production, and chemotaxis of the ELANE KO (knockout) neutrophils were also normal. Knockdown of ELANE in the mutant ELANE expressing HL60 cells also allowed full maturation and formation of abundant neutrophils. These observations suggest that ex vivo CRISPR/Cas9 RNP based ELANE knockout of patients' primary hematopoietic stem and progenitor cells followed by autologous transplantation may be an alternative therapy for congenital neutropenia.

Neutropenia in glycogen storage disease Ib: outcomes for patients treated with granulocyte colony-stimulating factor.

PURPOSE OF REVIEW: Glycogen storage disease Ib (GSD Ib) is characterized by hepatomegaly, hypoglycemia, neutropenia, enterocolitis and recurrent bacterial infections. It is attributable to mutations in G6PT1, the gene for the glucose-6-phosphate transporter responsible for transport of glucose into the endoplasmic reticulum. Neutropenia in GSD Ib is now frequently treated with granulocyte colony-stimulating factor (G-CSF). We formed a cooperative group to review outcomes of the long-term treatment of GSD Ib patients treated with G-CSF. RECENT FINDINGS: The study enrolled 103 patients (48 men and 55 women), including 47 currently adult patients. All of these patients were treated with G-CSF, starting at a median age of 3.8 years (range 0.04-33.9 years) with a median dose of 3.0 mcg/kg/day (range 0.01-93.1 mcg/kg/day) for a median of 10.3 years (range 0.01-29.3 years). Neutrophils increased in response to G-CSF in all patients (median values before G-CSF 0.2 × 10/l, on G-CSF 1.20 x 10/l). Treatment increased spleen size (before G-CSF, 47%, on treatment on G-CSF 76%), and splenomegaly was the dose-limiting adverse effect of treatment (pain and early satiety). Clinical observations and records attest to reduce frequency of infectious events and the severity of inflammatory bowel symptoms, but fever and recurrent infections remain a significant problem. In the cohort of patients followed carefully through the Severe Chronic Neutropenia International Registry, four patients have developed myelodysplasia or acute myeloid leukemia and we are aware of four other cases, (altogether seven on G-CSF, one never treated with G-CSF). Liver transplantation in five patients did not correct neutropenia. Four patients had hematopoietic stem cell transplantation; two adults and two children were transplanted; one adult and one child survived. SUMMARY: GSD Ib is a complex disorder of glucose metabolism causing severe chronic neutropenia. G-CSF is effective to raise blood neutrophil counts and reduce fevers and infections in most patients. In conjunction with other therapies (salicylates, mesalamine sulfasalazine and prednisone), G-CSF ameliorates inflammatory bowel symptoms, but doses must be limited because it increases spleen size associated with abdominal pain.

GM-CSF treatment is not effective in congenital neutropenia patients due to its inability to activate NAMPT signaling.

Severe congenital neutropenia (CN) is a bone marrow failure syndrome characterized by an absolute neutrophil count (ANC) below 500 cells/µL and recurrent, life-threatening bacterial infections. Treatment with granulocyte colony-stimulating factor (G-CSF) increases the ANC in the majority of CN patients. In contrary, granulocyte-monocyte colony-stimulating factor (GM-CSF) fails to increase neutrophil numbers in CN patients in vitro and in vivo, suggesting specific defects in signaling pathways downstream of GM-CSF receptor. Recently, we detected that G-CSF induces granulopoiesis in CN patients by hyperactivation of nicotinamide phosphoribosyl transferase (NAMPT)/Sirtuin 1 signaling in myeloid cells. Here, we demonstrated that, in contrast to G-CSF, GM-CSF failed to induce NAMPT-dependent granulopoiesis in CN patients. We further identified NAMPT signaling as an essential downstream effector of the GM-CSF pathway in myelopoiesis.

ELANE mutant-specific activation of different UPR pathways in congenital neutropenia.

A number of studies have demonstrated induction of the unfolded protein response (UPR) in patients with severe congenital neutropenia (CN) harbouring mutations of ELANE, encoding neutrophil elastase. Why UPR is not activated in patients with cyclic neutropenia (CyN) carrying the same ELANE mutations is unclear. We evaluated the effects of ELANE mutants on UPR induction in myeloid cells from CN and CyN patients, and analysed whether additional CN-specific defects contribute to the differences in UPR induction between CN and CyN patients harbouring identical ELANE mutations. We investigated CN-specific p.C71R and p.V174_C181del (NP_001963.1) and CN/CyN-shared p.S126L (NP_001963.1) ELANE mutants. We found that transduction of haematopoietic cells with p.C71R, but not with p.V174_C181del or p.S126L ELANE mutants induced expression of ATF6, and the ATF6 target genes PPP1R15A, DDIT3 and HSPA5. Recently, we found that levels of secretory leucocyte protease inhibitor (SLPI), a natural ELANE inhibitor, are diminished in myeloid cells from CN patients, but not CyN patients. Combined knockdown of SLPI by shRNA and transduction of ELANE p.S126L in myeloid cells led to elevated levels of ATF6, PPP1R15A and HSPA5 RNA, suggesting that normal levels of SLPI in CyN patients might protect them from the UPR induced by mutant ELANE. In summary, different ELANE mutants have different effects on UPR activation, and SLPI regulates the extent of ELANE-triggered UPR.

Bortezomib inhibits STAT5-dependent degradation of LEF-1, inducing granulocytic differentiation in congenital neutropenia CD34(+) cells.

The transcription factor lymphoid enhancer-binding factor 1 (LEF-1), which plays a definitive role in granulocyte colony-stimulating factor (G-CSF) receptor-triggered granulopoiesis, is downregulated in granulocytic progenitors of severe congenital neutropenia (CN) patients. However, the exact mechanism of LEF-1 downregulation is unclear. CN patients are responsive to therapeutically high doses of G-CSF and are at increased risk of developing acute myeloid leukemia. The normal expression of LEF-1 in monocytes and lymphocytes, whose differentiation is unaffected in CN, suggests the presence of a granulopoiesis-specific mechanism downstream of G-CSF receptor signaling that leads to LEF-1 downregulation. Signal transducer and activator of transcription 5 (STAT5) is activated by G-CSF and is hyperactivated in acute myeloid leukemia. Here, we investigated the effects of activated STAT5 on LEF-1 expression and functions in hematopoietic progenitor cells. We demonstrated that constitutively active STAT5a (caSTAT5a) inhibited LEF-1-dependent autoregulation of the LEF-1 gene promoter by binding to the LEF-1 protein, recruiting Nemo-like kinase and the E3 ubiquitin-ligase NARF to LEF-1, leading to LEF-1 ubiquitination and a reduction in LEF-1 protein levels. The proteasome inhibitor bortezomib reversed the defective G-CSF-triggered granulocytic differentiation of CD34(+) cells from CN patients in vitro, an effect that was accompanied by restoration of LEF-1 protein levels and LEF-1 messenger RNA autoregulation. Taken together, our data define a novel mechanism of LEF-1 downregulation in CN patients via enhanced ubiquitination and degradation of LEF-1 protein by hyperactivated STAT5.

A lack of secretory leukocyte protease inhibitor (SLPI) causes defects in granulocytic differentiation.

We identified diminished levels of the natural inhibitor of neutrophil elastase (NE), secretory leukocyte protease inhibitor (SLPI), in myeloid cells and plasma of patients with severe congenital neutropenia (CN). We further found that downregulation of SLPI in CD34(+) bone marrow (BM) hematopoietic progenitors from healthy individuals resulted in markedly reduced in vitro myeloid differentiation accompanied by cell-cycle arrest and elevated apoptosis. Reciprocal regulation of SLPI by NE is well documented, and we previously demonstrated diminished NE levels in CN patients. Here, we found that transduction of myeloid cells with wild-type NE or treatment with exogenous NE increased SLPI messenger RNA and protein levels, whereas transduction of mutant forms of NE or inhibition of NE resulted in downregulation of SLPI. An analysis of the mechanisms underlying the diminished myeloid differentiation caused by reduced SLPI levels revealed that downregulation of SLPI with short hairpin RNA (shRNA) upregulated nuclear factor κB levels and reduced phospho-extracellular signal-regulated kinase (ERK1/2)-mediated phosphorylation and activation of the transcription factor lymphoid enhancer-binding factor-1 (LEF-1). Notably, microarray analyses revealed severe defects in signaling cascades regulating the cell cycle, including c-Myc-downstream signaling, in myeloid cells transduced with SLPI shRNA. Taken together, these results indicate that SLPI controls the proliferation, differentiation, and cell cycle of myeloid cells.

Cooperativity of RUNX1 and CSF3R mutations in severe congenital neutropenia: a unique pathway in myeloid leukemogenesis.

Severe congenital neutropenia (CN) is a preleukemic bone marrow failure syndrome with a 20% risk of evolving into leukemia or myelodysplastic syndrome (MDS). Patterns of acquisition of leukemia-associated mutations were investigated using next-generation deep-sequencing in 31 CN patients who developed leukemia or MDS. Twenty (64.5%) of the 31 patients had mutations in RUNX1. A majority of patients with RUNX1 mutations (80.5%) also had acquired CSF3R mutations. In contrast to their high frequency in CN patients who developed leukemia or MDS, RUNX1 mutations were found in only 9 of 307 (2.9%) patients with de novo pediatric acute myeloid leukemia. A sequential analysis at stages prior to overt leukemia revealed RUNX1 mutations to be late events in leukemic transformation. Single-cell analyses in 2 patients showed that RUNX1 and CSF3R mutations were present in the same malignant clone. Functional studies demonstrated elevated granulocyte colony-stimulating factor (G-CSF)-induced proliferation with diminished myeloid differentiation of hematopoietic CD34(+) cells coexpressing mutated forms of RUNX1 and CSF3R. The high frequency of cooperating RUNX1 and CSF3R mutations in CN patients suggests a novel molecular pathway of leukemogenesis: mutations in the hematopoietic cytokine receptor (G-CSFR) in combination with the second mutations in the downstream hematopoietic transcription fator (RUNX1). The detection of both RUNX1 and CSF3R mutations could be used as a marker for identifying CN patients with a high risk of progressing to leukemia or MDS.

HAX1 deficiency causes autosomal recessive severe congenital neutropenia (Kostmann disease).

Autosomal recessive severe congenital neutropenia (SCN) constitutes a primary immunodeficiency syndrome associated with increased apoptosis in myeloid cells, yet the underlying genetic defect remains unknown. Using a positional cloning approach and candidate gene evaluation, we identified a recurrent homozygous germline mutation in HAX1 in three pedigrees. After further molecular screening of individuals with SCN, we identified 19 additional affected individuals with homozygous HAX1 mutations, including three belonging to the original pedigree described by Kostmann. HAX1 encodes the mitochondrial protein HAX1, which has been assigned functions in signal transduction and cytoskeletal control. Here, we show that HAX1 is critical for maintaining the inner mitochondrial membrane potential and protecting against apoptosis in myeloid cells. Our findings suggest that HAX1 is a major regulator of myeloid homeostasis and underline the significance of genetic control of apoptosis in neutrophil development.

The diversity of mutations and clinical outcomes for ELANE-associated neutropenia.

PURPOSE OF REVIEW: Mutations in the gene for neutrophil elastase, ELANE, cause cyclic neutropenia (CyN) and severe congenital neutropenia (SCN). This study summarized data from the Severe Chronic Neutropenia International Registry (SCNIR) on genotype-phenotype relationships of ELANE mutations to important clinical outcomes. We also summarize findings for ELANE mutations not observed in SCNIR patients. RECENT FINDINGS: There were 307 SCNIR patients with 104 distinctive ELANE mutations who were followed longitudinally for up to 27 years. The ELANE mutations were diverse; there were 65 single amino acid substitutions; 61 of these mutations (94%) were 'probably' or 'possibly damaging' by PolyPhen-2 analysis, and one of the 'benign' mutations was associated with two cases of acute myeloid leukemia (AML). All frame-shift mutations (19/19) were associated with the SCN. The pattern of mutations in the SCN versus CyN was significantly different (P < 10), but some mutations were observed in both groups (overlapping mutations). The cumulative incidence of severe adverse events, that is, myelodysplasia, AML, stem cell transplantation, or deaths was significantly greater for patients with SCN versus those with CyN or overlapping mutations. Specific mutations (i.e. G214R or C151Y) had a high risk for evolution to AML. SUMMARY: Sequencing is useful for predicting outcomes of ELANE-associated neutropenia.

Outcome and management of pregnancies in severe chronic neutropenia patients by the European Branch of the Severe Chronic Neutropenia International Registry.

Long-term granulocyte-colony stimulating factor treatment has been shown to be safe and effective in severe chronic neutropenia patients. However, data on its use during pregnancy are limited. To address this issue, we analyzed all pregnancies reported to the European branch of the Severe Chronic Neutropenia International Registry since 1994. A total of 38 pregnancies in 21 women with chronic neutropenia (16 pregnancies in 10 women with congenital, 10 in 6 women with cyclic, 12 in 5 women with idiopathic neutropenia) were reported. Granulocyte-colony stimulating factor was administered throughout pregnancy in 16 women and for at least one trimester in a further 5 women. No major differences were seen between treated and untreated women with respect to pregnancy outcome, newborn complications and infections. In addition, we evaluated the genetic transmission of known or suspected genetic defects in 16 mothers having 22 newborns as well as in 8 men fathering 15 children. As a proof of inheritance, neutropenia was passed on to the newborn in 58% from female and in 62% from male patients with ELANE mutations, but also to some newborns from parents with unknown gene mutation. Based on our results, granulocyte-colony stimulating factor therapy has been shown to be safe for mothers throughout pregnancies and for newborns without any signs of teratogenicity. With an increasing number of adult patients, genetic counseling prior to conception and supportive care of mothers during pregnancy are crucial. The acceptance of having affected children may reflect the high quality of life obtained due to this treatment.

A novel human primary immunodeficiency syndrome caused by deficiency of the endosomal adaptor protein p14.

Lysosome-related organelles have versatile functions, including protein and lipid degradation, signal transduction and protein secretion. The molecular elucidation of rare congenital diseases affecting endosomal-lysosomal biogenesis has given insights into physiological functions of the innate and adaptive immune system. Here, we describe a previously unknown human primary immunodeficiency disorder and provide evidence that the endosomal adaptor protein p14, previously characterized as confining mitogen-activated protein kinase (MAPK) signaling to late endosomes, is crucial for the function of neutrophils, B cells, cytotoxic T cells and melanocytes. Combining genetic linkage studies and transcriptional profiling analysis, we identified a homozygous point mutation in the 3' untranslated region (UTR) of p14 (also known as MAPBPIP), resulting in decreased protein expression. In p14-deficient cells, the distribution of late endosomes was severely perturbed, suggesting a previously unknown role for p14 in endosomal biogenesis. These findings have implications for understanding endosomal membrane dynamics, compartmentalization of cell signal cascades, and their role in immunity.

LEF-1 is crucial for neutrophil granulocytopoiesis and its expression is severely reduced in congenital neutropenia.

We demonstrate here that lymphoid enhancer-binding factor 1 (LEF-1) mediates the proliferation, survival and differentiation of granulocyte progenitor cells. We initially documented the importance of this transcription factor in the bone marrow of individuals with severe congenital neutropenia (CN) with a 'differentiation block' at the promyelocytic stage of myelopoiesis. LEF-1 expression was greatly reduced or even absent in CN arrested promyelocytes, resulting in defective expression of the LEF-1 target genes CCND1, MYC and BIRC5, encoding cyclin D1 (ref. 2), c-Myc and survivin, respectively. In contrast, healthy individuals showed highest LEF-1 expression in promyelocytes. Reconstitution of LEF-1 in early hematopoietic progenitors of two individuals with CN corrected the defective myelopoiesis and resulted in the differentiation of these progenitors into mature granulocytes. Repression of endogenous LEF-1 by specific short hairpin RNA inhibited proliferation and induced apoptosis of CD34(+) progenitors from healthy individuals and of cells from two myeloid lines (HL-60 and K562). C/EBPalpha, a key transcription factor in granulopoiesis, was directly regulated by LEF-1. These observations indicate that LEF-1 is an instructive factor regulating neutrophilic granulopoiesis whose absence plays a critical role in the defective maturation program of myeloid progenitors in individuals with CN.

The European Guidelines on Diagnosis and Management of Neutropenia in Adults and Children: A Consensus Between the European Hematology Association and the EuNet-INNOCHRON COST Action.

Neutropenia, as an isolated blood cell deficiency, is a feature of a wide spectrum of acquired or congenital, benign or premalignant disorders with a predisposition to develop myelodysplastic neoplasms/acute myeloid leukemia that may arise at any age. In recent years, advances in diagnostic methodologies, particularly in the field of genomics, have revealed novel genes and mechanisms responsible for etiology and disease evolution and opened new perspectives for tailored treatment. Despite the research and diagnostic advances in the field, real world evidence, arising from international neutropenia patient registries and scientific networks, has shown that the diagnosis and management of neutropenic patients is mostly based on the physicians' experience and local practices. Therefore, experts participating in the European Network for the Innovative Diagnosis and Treatment of Chronic Neutropenias have collaborated under the auspices of the European Hematology Association to produce recommendations for the diagnosis and management of patients across the whole spectrum of chronic neutropenias. In the present article, we describe evidence- and consensus-based guidelines for the definition and classification, diagnosis, and follow-up of patients with chronic neutropenias including special entities such as pregnancy and the neonatal period. We particularly emphasize the importance of combining the clinical findings with classical and novel laboratory testing, and advanced germline and/or somatic mutational analyses, for the characterization, risk stratification, and monitoring of the entire spectrum of neutropenia patients. We believe that the wide clinical use of these practical recommendations will be particularly beneficial for patients, families, and treating physicians.

Effect of the addition of a mental health specialist for evaluation of undiagnosed patients in centres for rare diseases (ZSE-DUO): a prospective, controlled trial with a two-phase cohort design.

Background: People with complex symptomatology but unclear diagnosis presenting to a centre for rare diseases (CRD) may present with mental (co-)morbidity. We hypothesised that combining an expert in somatic medicine with a mental health specialist working in tandem will improve the diagnostic outcome. Methods: Patients aged 12 years and older who presented to one of the 11 participating German CRDs with an unknown diagnosis were recruited into this prospective cohort trial with a two-phase cohort design. From October 1, 2018 to September 30, 2019, participants were allocated to standard care (SC, N = 684), and from October 1, 2019 to January 31, 2021 to innovative care (IC, N = 695). The cohorts consisted mainly of adult participants with only a minority of children included (N = 67). IC included the involvement of a mental health specialist in all aspects of care (e.g., assessing medical records, clinic visits, telehealth care, and case conferences). Clinicaltrials.gov identifier: NCT03563677. Findings: The proportion of patients with diagnoses established within 12 months after the first visit to the CRD explaining the entire symptomatology (primary outcome) was 19% (N = 131 of 672) in the SC and 42% (N = 286 of 686) in the IC cohort (OR adjusted for centre effects 3.45 [95% CrI: 1.99-5.65]). The difference was mainly due to a higher prevalence of mental disorders and non-rare somatic diseases in the IC cohort. The median time to explaining diagnoses was one month shorter with IC (95% CrI: 1-2), and significantly more patients could be referred to local regular care in the IC (27.5%; N = 181 of 659) compared to the SC (12.3%; N = 81 of 658) cohort (OR adjusted for centre effects 2.70 [95% CrI: 2.02-3.60]). At 12-month follow-up, patient satisfaction with care was significantly higher in the IC compared to the SC cohort, while quality of life was not different between cohorts. Interpretation: Our findings suggested that including a mental health specialist in the entire evaluation process of CRDs for undiagnosed adolescents and adults should become an integral part of the assessment of individuals with a suspected rare disease. Funding: The study was funded by the Global Innovation Fund from the Joint Federal Committee in Germany (Innovationsfonds des Gemeinsamen Bundesausschusses), grant number 01NVF17031.

A syndrome with congenital neutropenia and mutations in G6PC3.

BACKGROUND: The main features of severe congenital neutropenia are the onset of severe bacterial infections early in life, a paucity of mature neutrophils, and an increased risk of leukemia. In many patients, the genetic causes of severe congenital neutropenia are unknown. METHODS: We performed genomewide genotyping and linkage analysis on two consanguineous pedigrees with a total of five children affected with severe congenital neutropenia. Candidate genes from the linkage interval were sequenced. Functional assays and reconstitution experiments were carried out. RESULTS: All index patients were susceptible to bacterial infections and had very few mature neutrophils in the bone marrow; structural heart defects, urogenital abnormalities, and venous angiectasia on the trunk and extremities were additional features. Linkage analysis of the two index families yielded a combined multipoint lod score of 5.74 on a linkage interval on chromosome 17q21. Sequencing of G6PC3, the candidate gene encoding glucose-6-phosphatase, catalytic subunit 3, revealed a homozygous missense mutation in exon 6 that abolished the enzymatic activity of glucose-6-phosphatase in all affected children in the two families. The patients' neutrophils and fibroblasts had increased susceptibility to apoptosis. The myeloid cells showed evidence of increased endoplasmic reticulum stress and increased activity of glycogen synthase kinase 3beta (GSK-3beta). We identified seven additional, unrelated patients who had severe congenital neutropenia with syndromic features and distinct biallelic mutations in G6PC3. CONCLUSIONS: Defective function of glucose-6-phosphatase, catalytic subunit 3, underlies a severe congenital neutropenia syndrome associated with cardiac and urogenital malformations.