Novel genetic etiologies of severe congenital neutropenia

Novel Disease-Associated Missense Single-Nucleotide Polymorphisms Variants Predication by Algorithms Tools and Molecular Dynamics Simulation of Human TCIRG1 Gene Causing Congenital Neutropenia and Osteopetrosis

T Cell Immune Regulator 1, ATPase H + Transporting V0 Subunit A3 (TCIRG1 gene provides instructions for making one part, the a3 subunit, of a large protein complex known as a vacuolar H + -ATPase (V-ATPase). V-ATPases are a group of similar complexes that act as pumps to move positively charged hydrogen atoms (protons) across membranes. Single amino acid changes in highly conserved areas of the TCIRG1 protein have been linked to autosomal recessive osteopetrosis and severe congenital neutropenia. We used multiple computational approaches to classify disease-prone single nucleotide polymorphisms (SNPs) in TCIRG1. We used molecular dynamics analysis to identify the deleterious nsSNPs, build mutant protein structures, and assess the impact of mutation. Our results show that fifteen nsSNPs (rs199902030, rs200149541, rs372499913, rs267605221, rs374941368, rs375717418, rs80008675, rs149792489, rs116675104, rs121908250, rs121908251, rs121908251, rs149792489 and rs116675104) variants are likely to be highly deleterious mutations as by incorporating them into wild protein they destabilize the wild protein structure and function. They are also located in the V-ATPase I domain, which may destabilize the structure and impair TCIRG1 protein activation, as well as reduce its ATPase effectiveness. These mutants have not yet been identified in patients suffering from CN and osteopetrosis while (G405R, R444L, and D517N) reported in our study are already associated with osteopetrosis. Mutation V52L reported in our study was identified in a patient suspected for CN. Finally, these mutants can help to further understand the broad pool of illness susceptibilities associated with TCIRG1 catalytic kinase domain activation and aid in the development of an effective treatment for associated diseases.

Epigenetic Regulation of Gfi1 in Endocrine-Related Cancers: a Role Regulating Tumor Growth

Prostate and breast cancer constitute the most common cancers among men and women worldwide. The aging population is one of the main risk factors for prostate and breast cancer development and accumulating studies link aging with epigenetic changes. Growth factor independence-1 (Gfi1) is a transcriptional repressor with an important role in human malignancies, including leukemia, colorectal carcinoma, and lung cancer, but its role in prostate and breast cancer is unknown. We have found that Gfi1 epigenetic silencing is a common event in prostate and breast cancer. Gfi1 re-expression in prostate and breast cancer cell lines displaying Gfi1 epigenetic silencing decreases cell proliferation, reduced colony formation density, and tumor growth in nude mice xenografts. In addition, we found that Gfi1 repress alpha 1-anti-trypsin (AAT) and alpha 1-anti-chymotrypsin (ACT) expression, two genes with important functions in cancer development, suggesting that Gfi1 silencing promotes tumor growth by increasing AAT and ACT expression in our system. Finally, Gfi1 epigenetic silencing could be a promising biomarker for prostate cancer progression because it is associated with shorter disease-free survival. In conclusion, our findings strongly indicate that Gfi1 epigenetic silencing in prostate and breast cancer could be a crucial step in the development of these two-well characterized endocrine related tumors.

Novel ELANE Gene Mutation in a Newborn with Severe Congenital Neutropenia: Case Report and Literature Review

Severe neutropenia is defined as an absolute neutrophil count (ANC) of less than 0.5 × 10 ⁹ /L. Severe congenital neutropenia (SCN) is an inborn disorder with maturation arrest of granulocytes due to various genetic abnormalities, which may lead to immunodeficiency. Among several associated genetic mutations, the variants or heterozygous mutations of the ELANE gene coding neutrophil elastase comprise approximately 50% of the genetic causes of SCN. We present a newborn (male) with severe neutropenia due to a novel ELANE gene mutation. The newborn was born at 38 ^6/7 weeks gestation to a 25-year-old mother with hypertension and morbid obesity. Pregnancy and delivery were uncomplicated but the baby obtained a complete blood count (CBC) on day of life 2 for a work up of hyperbilirubinemia. He was noted to initially have an ANC of 0.2 × 10 ⁹ /L and 0 on subsequent blood counts. A bone marrow biopsy showed a left shift and consistent with myeloid maturation arrest. In direct DNA sequencing analysis, we found an ELANE gene mutation (Val119Glu, V119E), which may be a new gene mutation to cause SCN. The diagnosis of SCN in newborns is usually based on neutropenia identified on a routine CBC. Sufficient awareness and high suspicion of this rare disease can prevent missed or delayed diagnosis of SCN. Our analysis also suggests a new pathological mutation in the ELANE gene and supports the important role of molecular testing in SCN.

Staphylococcus aureus, phagocyte NADPH oxidase and chronic granulomatous disease

Dysfunction of phagocytes is a relevant risk factor for staphylococcal infection. The most common hereditary phagocyte dysfunction is chronic granulomatous disease (CGD), characterized by impaired generation of reactive oxygen species (ROS) due to loss of function mutations within the phagocyte NADPH oxidase NOX2. Phagocytes ROS generation is fundamental to eliminate pathogens and to regulate the inflammatory response to infection. CGD is characterized by recurrent and severe bacterial and fungal infections, with Staphylococcus aureus as the most frequent pathogen, and skin and lung abscesses as the most common clinical entities. Staphylococcus aureus infection may occur in virtually any human host, presumably because of the many virulence factors of the bacterium. However, in the presence of functional NOX2, staphylococcal infections remain rare and are mainly linked to breaches of the skin barrier. In contrast, in patients with CGD, S. aureus readily survives and frequently causes clinically apparent disease. Astonishingly, little is known why S. aureus, which possesses a wide range of antioxidant enzymes (e.g. catalase, SOD), is particularly sensitive to control through NOX2. In this review, we will evaluate the discovery of CGD and our present knowledge of the role of NOX2 in S. aureus infection.

Periodontal and other oral manifestations of immunodeficiency diseases

The list of immunodeficiency diseases grows each year as novel disorders are discovered, classified, and sometimes reclassified due to our ever-increasing knowledge of immune system function. Although the number of patients with secondary immunodeficiencies (SIDs) greatly exceeds those with primary immunodeficiencies (PIDs), the prevalence of both appears to be on the rise probably because of scientific breakthroughs that facilitate earlier and more accurate diagnosis. Primary immunodeficiencies in adults are not as rare as once thought. Globally, the main causes of secondary immunodeficiency are HIV infection and nutritional insufficiencies. Persons with acquired immune disorders such as AIDS caused by the human immunodeficiency virus (HIV) are now living long and fulfilling lives as a result of highly active antiretroviral therapy (HAART). Irrespective of whether the patient's immune-deficient state is a consequence of a genetic defect or is secondary in nature, dental and medical practitioners must be aware of the constant potential for infections and/or expressions of autoimmunity in these individuals. The purpose of this review was to study the most common conditions resulting from primary and secondary immunodeficiency states, how they are classified, and the detrimental manifestations of these disorders on the periodontal and oral tissues.

Gene correction of HAX1 reversed Kostmann disease phenotype in patient-specific induced pluripotent stem cells

Severe congenital neutropenia (SCN, Kostmann disease) is a heritable disorder characterized by a granulocytic maturation arrest. Biallelic mutations in HCLS1 associated protein X-1 (HAX1) are frequently detected in affected individuals, including those of the original pedigree described by Kostmann in 1956. To date, no faithful animal model has been established to study SCN mediated by HAX1 deficiency. Here we demonstrate defective neutrophilic differentiation and compensatory monocyte overproduction from patient-derived induced pluripotent stem cells (iPSCs) carrying the homozygous HAX1^W44X nonsense mutation. Targeted correction of the HAX1 mutation using the CRISPR-Cas9 system and homologous recombination rescued neutrophil differentiation and reestablished an HAX1 and HCLS1-centered transcription network in immature myeloid progenitors, which is involved in the regulation of apoptosis, apoptotic mitochondrial changes, and myeloid differentiation. These findings made in isogenic iPSC-derived myeloid cells highlight the complex transcriptional changes underlying Kostmann disease. Thus, we show that patient-derived HAX1^W44X -iPSCs recapitulate the Kostmann disease phenotype in vitro and confirm HAX1 mutations as the disease-causing monogenic lesion. Finally, our study paves the way for nonvirus-based gene therapy approaches in SCN.

Haematological abnormalities in mitochondrial disorders

INTRODUCTION

This study aimed to assess the kind of haematological abnormalities that are present in patients with mitochondrial disorders (MIDs) and the frequency of their occurrence.

METHODS

The blood cell counts of a cohort of patients with syndromic and non-syndromic MIDs were retrospectively reviewed. MIDs were classified as 'definite', 'probable' or 'possible' according to clinical presentation, instrumental findings, immunohistological findings on muscle biopsy, biochemical abnormalities of the respiratory chain and/or the results of genetic studies. Patients who had medical conditions other than MID that account for the haematological abnormalities were excluded.

RESULTS

A total of 46 patients ('definite' = 5; 'probable' = 9; 'possible' = 32) had haematological abnormalities attributable to MIDs. The most frequent haematological abnormality in patients with MIDs was anaemia. 27 patients had anaemia as their sole haematological problem. Anaemia was associated with thrombopenia (n = 4), thrombocytosis (n = 2), leucopenia (n = 2), and eosinophilia (n = 1). Anaemia was hypochromic and normocytic in 27 patients, hypochromic and microcytic in six patients, hyperchromic and macrocytic in two patients, and normochromic and microcytic in one patient. Among the 46 patients with a mitochondrial haematological abnormality, 78.3% had anaemia, 13.0% had thrombopenia, 8.7% had leucopenia and 8.7% had eosinophilia, alone or in combination with other haematological abnormalities.

CONCLUSION

MID should be considered if a patient's abnormal blood cell counts (particularly those associated with anaemia, thrombopenia, leucopenia or eosinophilia) cannot be explained by established causes. Abnormal blood cell counts may be the sole manifestation of MID or a collateral feature of a multisystem problem.

Genetic analysis and clinical picture of severe congenital neutropenia in Israel

BACKGROUND

The relative frequency of mutated genes among patients with severe congenital neutropenia (SCN) may differ between various ethnic groups. To date, few population-based genetic studies have been reported. This study describes the genetic analysis of 32 Israeli patients with SCN.

PROCEDURES

Clinical data were retrieved from the prospective Israeli Inherited Bone Marrow Failure Registry. Recruitment included living and deceased patients who were diagnosed between 1982 and 2012, for whom molecular diagnosis was performed. ELANE, HAX1 and G6PC3 genes were sequenced in all patients, and GFI-1 and WAS genes were sequenced if other genes were wildtype.

RESULTS

Eleven patients (34%) had heterozygous mutations in ELANE (10 kindreds), eight (25%) had homozygous mutations in G6PC3 (5 kindreds) and 13 (41%) had no detected mutations. No patients had mutations in HAX1 or WAS. Four of the eight patients with G6PC3 mutations had congenital anomalies. The probability of survival for all patients was 50% at age of 18. Deaths were mainly due to sepsis (5 patients, 4/5 not responding to G-CSF, none with G6PC3 mutation). Two patients developed acute myelogenous leukemia (AML) and one myelodysplastic syndrome (MDS), none with G6PC3 mutation.

CONCLUSIONS

We found a unique pattern of SCN mutations in Israel with homozygous G6PC3 mutations in eight (25%) patients, the highest frequency described so far. HAX1 mutations, reported mainly in Sweden and Iran, were absent. Patients with G6PC3 mutations had congenital anomalies, appeared to have a better response to G-CSF, and so far have not developed AML or MDS.

Neutropenia in the newborn

PURPOSE OF REVIEW

The aim is to review normal blood neutrophil concentrations and the clinical approach to neutropenia in the neonatal period. A literature search on neonatal neutropenia was performed using the databases PubMed, EMBASE, and Scopus, and the electronic archive of abstracts presented at the annual meetings of the Pediatric Academic Societies.

RECENT FINDINGS

The review summarizes current knowledge on the causes of neutropenia in premature and critically ill neonates, focusing on common causes such as maternal hypertension, neonatal sepsis, twin-twin transfusion, alloimmunization, and hemolytic disease. The article provides a rational approach to diagnosis and treatment of neonatal neutropenia, including current evidence on the role of recombinant hematopoietic growth factors.

SUMMARY

Neutrophil counts should be carefully evaluated in premature and critically ill neonates. Although neutropenia is usually benign and runs a self-limited course in most neonates, it can be prolonged, and it constitutes a serious deficiency in antimicrobial defense in some infants.

Global and single gene DNA methylation in umbilical cord blood cells after elective caesarean: a pilot study

OBJECTIVE

To evaluate global and single gene methylation patterns as a sign for epigenetic modulation of the immune system in infants born by elective cesarean section (CS) and vaginal delivery (VD).

STUDY DESIGN

For this prospective pilot study a two step approach was chosen. Initially 41 newborn infants comprising 23 delivered by VD and 18 delivered by elective CS were included. Global DNA methylation of umbilical cord blood was determined. In a second step, methylation status of 96 single genes linked to T cell activation, cytokine production, inflammatory response, and stem cell transcription was evaluated in 48 newborn infants, 20 delivered by VD and 28 delivered by CS.

RESULTS

Global methylation did not differ significantly between CS and VD (p=0.732). The methylation status was low (threshold: ≤3%) for the majority of single genes (n=92) in both groups. FOXP3, CD7, ELA2, and IRF1 showed hypermethylation in both groups. In the CS group, ELA2 (p<0.001) and IRF1(p =0.017) showed significantly higher methylation compared to the VD group.

CONCLUSION

We found no difference in global methylation between newborn infants in the VD group compared to the elective CS group. Methylation of single genes was significantly higher in newborn infants delivered by elective CS. Further research is needed to determine the significance of theses findings.

TCIRG1-associated congenital neutropenia

Severe congenital neutropenia (SCN) is a rare hematopoietic disorder, with estimated incidence of 1 in 200,000 individuals of European descent, many cases of which are inherited in an autosomal dominant pattern. Despite the fact that several causal genes have been identified, the genetic basis for >30% of cases remains unknown. We report a five-generation family segregating a novel single nucleotide variant (SNV) in TCIRG1. There is perfect cosegregation of the SNV with congenital neutropenia in this family; all 11 affected, but none of the unaffected, individuals carry this novel SNV. Western blot analysis show reduced levels of TCIRG1 protein in affected individuals, compared to healthy controls. Two unrelated patients with SCN, identified by independent investigators, are heterozygous for different, rare, highly conserved, coding variants in TCIRG1.

Potential roles for Gfi1 in the pathogenesis and proliferation of glioma

Glioblastoma multiforme (GBM) is a major form of adult brain tumour with relatively poor prognosis and high mortality. Temozolomide (TMZ)-based chemotherapy following neurosurgery and radiotherapy has been suggested as the first line of treatment and is proven to effectively prolong overall survival and enhance patient quality of life. However, not all patients benefit from this treatment because of drug resistance. Even patients with TMZ-sensitive GBM may become resistant, which is partly due to the restoration of activity of the DNA repair enzyme O(6)-methylguanine-DNA-methyltransferase (MGMT); thus, patients cannot evade eventual tumour recurrence. The cellular activity of MGMT is the most important determinant of TMZ-resistance. However, some patients with a low level of activated MGMT are also TMZ-resistant. The aberrant expression of HOXA9, one of the 39 class I homeobox genes, is a marker of poor prognosis, and its level gradually increases with histologic malignant progression, shorter time to overall survival (OS) and free progression survival (FPS) in glioma patients, which further supports an oncogenic role for HOXA9 in gliomas. The HOXA9-PI3K signalling pathway is an important mechanism in GBM that is independent of MGMT promoter methylation status. The DNA binding sites of growth factor independent-1 (Gfi1) can overlap with the HOXA9 promoter through the "AATC" versus "GATT" core sequence. The competition for this binding site inhibits the expression of HOXA9 and induces different transcriptional outcomes, which suggests a new direction for investigation of the mechanism underlying targeted therapy of malignant gliomas.

A novel G6PC3 gene mutation in a patient with severe congenital neutropenia

Glucose-6-phosphatase catalytic subunit 3 (G6PC3) deficiency is a newly described syndromic type of severe congenital neutropenia, associated with multiple organ abnormalities including facial, cardiac, and urogenital abnormalities, and increased visibility of superficial veins. The molecular pathophysiology of G6PC3 deficiency is associated with the disturbed glucose homeostasis, increased endoplasmic reticulum stress, and apoptosis in neutrophils. We report a new case of G6PC3 deficiency caused by a novel homozygous G6PC3 gene mutation (p.Leu154Pro). Most remarkable is that the chronic neutropenia that originated from this novel G6PC3 genetic defect is also accompanied by some other unusual manifestations in this patient: myelokathexis and hypercholesterolemia.

Combined immunodeficiency: the Middle East experience

Previous reports about primary immunodeficiency disorders have shown variations in the frequency and distribution among populations from different ethnic and geographic backgrounds. In this review we describe peculiarities about combined immunodeficiencies (CIDs) in the Middle East. The frequency and type of genetic defects causing CIDs in this region differ in comparison with those in other populations because of the common practice of consanguineous marriage in the Middle East, which results in the relative increase in autosomal recessive diseases. We highlight some of the challenges in the awareness, diagnosis, and therapy of CIDs in the region and the research opportunities, especially those directed toward the identification of novel disease-causing genes.

Genetic lessons learned from X-linked Mendelian susceptibility to mycobacterial diseases

Mendelian susceptibility to mycobacterial disease (MSMD) is a rare syndrome conferring predisposition to clinical disease caused by weakly virulent mycobacteria, such as Mycobacterium bovis Bacille Calmette Guérin (BCG) vaccines and nontuberculous, environmental mycobacteria (EM). Since 1996, MSMD-causing mutations have been found in six autosomal genes involved in IL-12/23-dependent, IFN-γ-mediated immunity. The aim of this review is to provide the description of the two described forms of X-linked recessive (XR) MSMD. Germline mutations in two genes, NEMO and CYBB, have long been known to cause other human diseases-incontinentia pigmenti (IP) and anhidrotic ectodermal dysplasia with immunodeficiency (EDA-ID) (NEMO/IKKG), and X-linked chronic granulomatous disease (CGD) (CYBB)-but specific mutations in either of these two genes have recently been shown to cause XR-MSMD. NEMO is an essential component of several NF-κB-dependent signaling pathways. The MSMD-causing mutations in NEMO selectively affect the CD40-dependent induction of IL-12 in mononuclear cells. CYBB encodes gp91(phox) , which is an essential component of the NADPH oxidase in phagocytes. The MSMD-causing mutation in CYBB selectively affects the respiratory burst in macrophages. Mutations in NEMO and CYBB may therefore cause MSMD by selectively exerting their deleterious impact on a single signaling pathway (CD40-IL-12, NEMO) or a single cell type (macrophages, CYBB). These experiments of Nature illustrate how specific germline mutations in pleiotropic genes can dissociate signaling pathways or cell lineages, thereby resulting in surprisingly narrow clinical phenotypes.

Heterozygous M1V variant of ELA-2 gene mutation associated with G-CSF refractory severe congenital neutropenia

Severe congenital neutropenia is an autosomal recessive disorder characterized by maturation arrest at the promyelocyte/myelocyte phase in the bone marrow, absolute neutrophil count <0.5 × 10(9) /L and recurrent bacterial infections. Homozygous mutations of either HAX-1 or ELA-2 have been described. We report the case of a premature male infant with congenital neutropenia, associated with multiple infections, refractory to treatment with granulocyte colony stimulating factor who subsequently underwent matched sibling donor stem-cell transplant. He was found to be heterozygous for the M1V variant of the ELA-2 gene that we postulate to be causative for his severe neutropenia

Mutations in the ELANE gene are associated with development of periodontitis in patients with severe congenital neutropenia

Background

Patients with severe congenital neutropenia (SCN) often develop periodontitis despite standard medical and dental care. In light of previous findings that mutations in the neutrophil elastase gene, ELANE, are associated with more severe neutropenic phenotypes, we hypothesized an association between the genotype of SCN and development of periodontitis.

Methods

Fourteen Swedish patients with SCN or cyclic neutropenia harboring different genetic backgrounds were recruited for periodontal examination. Peripheral blood, gingival crevicular fluid (GCF), and subgingival bacterial samples were collected. The levels of cytokines and antibacterial peptides were determined in GCF and plasma by multiplex immunoassay and immunoblotting, respectively. Subgingival bacterial samples were analyzed using 16S rDNA pyrosequencing.

Results

ELANE mutations correlated with more severe periodontal status than the HAX1 or unknown mutations in patients with SCN. The subjects with mutant ELANE had higher levels of IL-1β in GCF. Using principal coordinate analysis of the subgingival microbiota, patients with ELANE mutations and reference subjects with periodontitis tended to cluster differently from patients with HAX1 or unknown mutations and non-periodontitis reference subjects.

Conclusion

This study demonstrates an association between ELANE mutations in SCN and the development of periodontitis with skewed subgingival microbiota, indicating a potential role of ELANE mutations in the pathogenesis of periodontitis.

Functional analysis of the 5' flanking region of the human G6PC3 gene: regulation of promoter activity by glucose, pyruvate, AMP kinase and the pentose phosphate pathway

G6PC3 is a widely expressed isoform of glucose-6-phosphatase, found in many foetal and adult tissues. Mutations in this gene cause developmental abnormalities and severe neutropenia due to abolition of glucose recycling between the cytoplasm and endoplasmic reticulum. Low G6PC3 expression as a result of promoter polymorphisms or dysregulation could produce similar outcomes. Here we investigated the regulation of human G6PC3 promoter activity. HeLa and H4IIE cells were transiently transfected with G6PC3 promoter coupled to the firefly luciferase gene, and promoter activity was measured by dual luciferase assay. Activity was highest in a 453 bp segment of the G6PC3 promoter, from -455 to -3 relative to the transcriptional start site. This promoter was unresponsive to glucostatic hormones. Its activity increased significantly between 1 and 5.5 mM glucose, and was not elevated further by glucose concentrations up to 25 mM. Pyruvate increased its activity, but β-hydroxybutyrate and sodium acetate did not. Promoter activity was reduced by inhibitors of hexokinase, glyceraldehyde phosphate dehydrogenase and the oxidative branch of the pentose phosphate pathway, but not by a transketolase inhibitor. Deletion of two adjacent Enhancer-boxes (-274 to -279 and -299 to -304) reduced promoter activity and abolished the glucose effect, suggesting they could function as a glucose response element. Deletion of an additional downstream 140 bp (-140 to -306) restored activity, but not the glucose response, suggesting the presence of repressor elements in this region. 5-Aminoimidazole-4-carboxamide 1-β-D-ribofuranoside (AICAR) reduced promoter activity, showing dependence on AMP-kinase. Regulation of the G6PC3 promoter is thus radically different to that of the hepatic isoform, G6PC. It is sensitive to carbohydrate, but not to fatty acid metabolites, and at much lower physiological concentrations. Based on these findings, we speculate that reduced G6PC3 expression could occur during hypoglycemic episodes in vivo, which are common in utero and in the postnatal period. If such episodes lower G6PC3 expression they could place the foetus or infant at risk of impaired immune function and development, and this possibility requires further examination both in vitro and in vivo.

G6PC3 mutations are associated with a major defect of glycosylation: a novel mechanism for neutrophil dysfunction

Glucose-6-phosphatase, an enzyme localized in the endoplasmic reticulum (ER), catalyzes the hydrolysis of glucose-6-phosphate (G6P) to glucose and inorganic phosphate. In humans, there are three differentially expressed glucose-6-phosphatase catabolic genes (G6PC1-3). Recently, it has been shown that mutations in the G6PC3 gene result in a syndrome associating congenital neutropenia and various organ malformations. The enzymatic function of G6PC3 is dependent on G6P transport into the ER, mediated by G6P translocase (G6PT). Mutations in the gene encoding G6PT result in glycogen storage disease type-1b (GSD-1b). Interestingly, GSD-1b patients exhibit a similar neutrophil dysfunction to that observed in G6PC3-deficient patients. To better understand the causes of neutrophil dysfunction in both diseases, we have studied the neutrophil nicotinamide adenine dinucleotide phosphate (NADPH) oxidase of patients with G6PC3 and G6PT syndromes. Unexpectedly, sodium dodecyl sulfate-polyacrylamide gel electrophoresis experiments indicated hypo-glycosylation of gp91(phox), the electron-transporting component of the NADPH oxidase, in all of these patients. Rigorous mass spectrometric glycomic profiling showed that most of the complex-type antennae which characterize the neutrophil N-glycome of healthy individuals were severely truncated in the patients' neutrophils. A comparable truncation of the core 2 antenna of the O-glycans was also observed. This aberrant neutrophil glycosylation is predicted to have profound effects on the neutrophil function and merit designation of both syndromes as a new class of congenital disorders of glycosylation.

HAX1 mutations causing severe congenital neuropenia and neurological disease lead to cerebral microstructural abnormalities documented by quantitative MRI

Biallelic mutations in the gene encoding HCLS-associated protein X-1 (HAX1) cause autosomal recessive severe congenital neutropenia (SCN). Some of these patients have neurological abnormalities including developmental delay, cognitive impairment, and/or epilepsy. Recent genotype-phenotype studies have shown that mutations in HAX1 affecting transcripts A (NM_006118.3) and B (NM_001018837.1) cause the phenotype of SCN with neurological impairment, while mutations affecting isoform A but not B lead to SCN without neurological aberrations. In this study, we identified a consanguineous family with two patients suffering from SCN and neurological disease caused by a novel, homozygous genomic deletion including exons 4-7 of the HAX1 gene. Quantitative MRI analyses showed generalized alterations in cerebral proton density in both of the patients, as well as in an additional unrelated patient with another HAX1 mutation (Arg86X) known to be associated with neurological manifestations. This study provides first in vivo evidence of aberrant neuroimaging findings associated with HAX1 deficiency in SCN patients.

Genetic etiologies of severe congenital neutropenia

PURPOSE OF REVIEW

To review recent advances in severe congenital neutropenia (SCN) syndromes.

RECENT FINDINGS

The majority of patients with SCN bear monoallelic mutations in the neutrophil elastase (ELANE) gene. Biallelic mutations in the antiapoptotic gene HAX1 were identified in patients with autosomal recessive SCN. G6PC3 deficiency is a syndromic variant of SCN associating congenital neutropenia with various developmental defects including cardiac or urogenital malformations. The pathophysiology of these distinct genetic variants of SCN is complex. Increased apoptosis of neutrophil granulocytes may be caused by various molecular mechanisms including destabilization of the mitochondrial membrane potential and/or activation of the so-called 'unfolded protein response'.

SUMMARY

SCN represents a heterogenous group of disorders that may be caused by genetic defects in ELANE, GFI1, HAX1, G6PC3 or activating mutations in the Wiskott-Aldrich syndrome (WAS) gene. Ongoing research will uncover additional genetic defects in SCN patients.

Gfi1-cells and circuits: unraveling transcriptional networks of development and disease

PURPOSE OF REVIEW

The review will integrate current knowledge of transcriptional circuits whose dysregulation leads to autoimmunity, neutropenia and leukemia.

RECENT FINDINGS

Growth factor independent-1 (Gfi1) is a transcriptional repressor with essential roles in controlling hematopoietic stem cell biology, myeloid and lymphoid differentiation and lymphocyte effector functions. Recent work has suggested that Gfi1 competes or collaborates with other transcription factors to modulate transcription programs and lineage decisions.

SUMMARY

Gfi1 is central to several transcriptional circuits whose dysregulation leads to abnormal or malignant hematopoiesis. These functional relationships are conserved from Drosophila development. Such conserved pathways represent central oncogenic or 'gatekeeper' pathways that are pivotal to understanding the process of cellular transformation, and illustrate key targets for clinical intervention.

Primary immunodeficiencies of protective immunity to primary infections

The vast majority of primary immunodeficiencies (PIDs) predispose affected individuals to recurrent or chronic infectious diseases, because they affect protective immunity to both primary and secondary or latent infections. We discuss here three recently described groups of PIDs that seem to impair immunity to primary infections without compromising immunity to secondary and latent infections. Patients with mutations in IL12B or IL12RB1 typically present mycobacterial disease in childhood with a favorable progression thereafter. Cross-protection between mycobacterial infections has even been observed. Patients with mutations in IRAK4 or MYD88 suffer from pyogenic bacterial diseases, including invasive pneumococcal diseases in particular. These diseases often recur, although not always with the same serotype, but the frequency of these recurrences tails off, with no further infections observed from adolescence onwards. Finally, mutations in UNC93B1 and TLR3 are associated with childhood herpes simplex encephalitis, which strikes only once in most patients, with almost no recorded cases of more than two bouts of this disease. Unlike infections in patients with other PIDs, the clinical course of which typically deteriorates with age even if appropriate treatment is given, the prognosis of patients with these three newly described PIDs tends to improve spontaneously with age, provided, of course, that the initial infection is properly managed. In other words, although life-threatening in early childhood, these new PIDs are associated with a favorable outcome in adulthood. They provide proof-of-principle that infectious diseases of childhood striking only once may result from single-gene inborn errors of immunity.

Pathophysiology and management of inherited bone marrow failure syndromes

The inherited marrow failure syndromes are a diverse set of genetic disorders characterized by hematopoietic aplasia and cancer predisposition. The clinical phenotypes are highly variable and much broader than previously recognized. The medical management of the inherited marrow failure syndromes differs from that of acquired aplastic anemia or malignancies arising in the general population. Diagnostic workup, molecular pathogenesis, and clinical treatment are reviewed.