JAGN1 deficiency causes aberrant myeloid cell homeostasis and congenital neutropenia

Genetic backgrounds and clinical characteristics of congenital neutropenias in Israel

BACKGROUND

Congenital neutropenias are characterized by severe infections and a high risk of myeloid transformation; the causative genes vary across ethnicities. The Israeli population is characterized by an ethnically diverse population with a high rate of consanguinity.

OBJECTIVE

To evaluate the clinical and genetic spectrum of congenital neutropenias in Israel.

METHODS

We included individuals with congenital neutropenias listed in the Israeli Inherited Bone Marrow Failure Registry. Sanger sequencing was performed for ELANE or G6PC3, and patients with wild-type ELANE/G6PC3 were referred for next-generation sequencing.

RESULTS

Sixty-five patients with neutropenia were included. Of 51 patients with severe congenital neutropenia, 34 were genetically diagnosed, most commonly with variants in ELANE (15 patients). Nine patients had biallelic variants in G6PC3, all of consanguineous Muslim Arab origin. Other genes involved were SRP54, JAGN1, TAZ, and SLC37A4. Seven patients had cyclic neutropenia, all with pathogenic variants in ELANE, and seven had Shwachman-Diamond syndrome caused by biallelic SBDS variants. Eight patients (12%) developed myeloid transformation, including six patients with an unknown underlying genetic cause. Nineteen (29%) patients underwent hematopoietic stem cell transplantation, mostly due to insufficient response to treatment with granulocyte-colony stimulating factor or due to myeloid transformation.

CONCLUSIONS

The genetic spectrum of congenital neutropenias in Israel is characterized by a high prevalence of G6PC3 variants and an absence of HAX1 mutations. Similar to other registries, for 26% of the patients, a molecular diagnosis was not achieved. However, myeloid transformation was common in this group, emphasizing the need for close follow-up.

Neutropenia in Childhood-A Narrative Review and Practical Diagnostic Approach

Neutropenia refers to a decrease in the absolute neutrophil count according to age and race norms and poses a common concern in pediatric practice. Neutrophils serve as host defenders and act crucially in acute inflammation procedures. In this narrative review, we systematically present causes of neutropenia in childhood, mainly adopting the pathophysiological classification of Frater, thereby studying (1) neutropenia with reduced bone marrow reserve, (2) secondary neutropenia with reduced bone marrow reserve, and (3) neutropenia with normal bone marrow reserve. Different conditions in each category are thoroughly discussed and practically approached from the clinician's point of view. Secondary mild to moderate neutropenia is usually benign due to childhood viral infections and is expected to resolve in 2-4 weeks. Bacterial and fungal agents are also associated with transient neutropenia, although fever with severe neutropenia constitutes a medical emergency. Drug-induced and immune neutropenias should be suspected following a careful history and a detailed clinical examination. Cytotoxic chemotherapies treating malignancies are responsible for severe neutropenia and neutropenic shock. Rare genetic neutropenias usually manifest with major infections early in life. Our review of taxonomies clinical findings and associates them to specific neutropenia disorders. We consequently propose a practical diagnostic algorithm for managing neutropenic children.

Extracellular traps development in canine neutrophils induced by infective stage Toxocara canis larvae

Neutrophils, a crucial element of the host defense system, develop extracellular traps against helminth parasites. Neutrophils accumulate around the larvae of Toxocara canis (T. canis) in the tissues of the organism. This study aimed to determine the reaction in canine neutrophils after incubation with infective stage T. canis larvae (L3) in vitro. Most L3 were still active and moved between the extracellular traps (NETs) after 60-min incubation. NETs were not disintegrated by L3 movement. The L3 was only immobilized by NETs, entrapped larvae were still motile between the traps at the 24 h incubation. NETs were observed not only to accumulate around the mouth, excretory pole or anus but also the entire body of live L3. The extracellular DNA amount released from the canine neutrophils after being induced with phorbol 12-myristate 13-acetate was not affected by T. canis excretory/secretory products obtained from 250 L3. To the Authors'knowledge, the extracellular trap structures was firstly observed in canine neutrophils against T. canis L3 in vitro. NETs decorated with myeloperoxidase, neutrophil elastase and histone (H3) were observed under fluorescence microscope. There were not significant differences in the amount of extracellular DNA (P > 0.05), but the morphological structure of NETs was different in the live and head-inactivated T. canis larvae.

Discerning clinicopathological features of congenital neutropenia syndromes: an approach to diagnostically challenging differential diagnoses

The congenital neutropenia syndromes are rare haematological conditions defined by impaired myeloid precursor differentiation or function. Patients are prone to severe infections with high mortality rates in early life. While some patients benefit from granulocyte colony-stimulating factor treatment, they may still face an increased risk of bone marrow failure, myelodysplastic syndrome and acute leukaemia. Accurate diagnosis is crucial for improved outcomes; however, diagnosis depends on familiarity with a heterogeneous group of rare disorders that remain incompletely characterised. The clinical and pathological overlap between reactive conditions, primary and congenital neutropenias, bone marrow failure, and myelodysplastic syndromes further clouds diagnostic clarity.We review the diagnostically useful clinicopathological and morphological features of reactive causes of neutropenia and the most common primary neutropenia disorders: constitutional/benign ethnic neutropenia, chronic idiopathic neutropenia, cyclic neutropenia, severe congenital neutropenia (due to mutations in ELANE, GFI1, HAX1, G6PC3, VPS45, JAGN1, CSF3R, SRP54, CLPB and WAS), GATA2 deficiency, Warts, hypogammaglobulinaemia, infections and myelokathexis syndrome, Shwachman-Diamond Syndrome, the lysosomal storage disorders with neutropenia: Chediak-Higashi, Hermansky-Pudlak, and Griscelli syndromes, Cohen, and Barth syndromes. We also detail characteristic cytogenetic and molecular factors at diagnosis and in progression to myelodysplastic syndrome/leukaemia.

Association of neutrophil defects with oral ulcers but undetermined role of neutrophils in recurrent aphthous stomatitis

Objective

Recurrent oral ulcers and severe periodontal diseases in patients with quantitative or qualitative neutrophil defects highlight the important role of neutrophils in maintaining oral mucosal barrier homeostasis. Recurrent aphthous stomatitis (RAS) is a common oral mucosal disease affecting up to 25% of the population, yet its etiopathogenesis remains unclear, and management is unsatisfactory. This review aims to gain insight into the pathogenesis of RAS.

Design

This narrative review examines the characteristics of oral and blood neutrophils, the associations between neutrophil defects and the occurrence of oral ulcers, and the evidence for the involvement of neutrophils in RAS. To conduct the review, relevant literature was searched in PubMed and Google Scholar, which was then thoroughly reviewed and critically appraised.

Results

Neutropenia, specifically a decrease in the number of oral neutrophils, impaired extravasation, and defective ROS production appear to be associated with oral ulcers, while defects in granule enzymes or NETosis are unlikely to have a link to oral ulcers. The review of the histopathology of RAS shows that neutrophils are concentrated in the denuded area but are latecomers to the scene and early leavers. However, the evidence for the involvement of neutrophils in the pathogenesis of RAS is inconsistent, leading to the proposal of two different scenarios involving either impaired or hyperactive neutrophils in the pathogenesis of RAS.

Congenital neutropenia: From lab bench to clinic bedside and back

Neutropenia is a hematological condition characterized by a decrease in absolute neutrophil count (ANC) in peripheral blood, typically classified in adults as mild (1-1.5 × 109/L), moderate (0.5-1 × 109/L), or severe (< 0.5 × 109/L). It can be categorized into two types: congenital and acquired. Congenital severe chronic neutropenia (SCN) arises from mutations in various genes, with different inheritance patterns, including autosomal recessive, autosomal dominant, and X-linked forms, often linked to mitochondrial diseases. The most common genetic cause is alterations in the ELANE gene. Some cases exist as non-syndromic neutropenia within the SCN spectrum, where genetic origins remain unidentified. The clinical consequences of congenital neutropenia depend on granulocyte levels and dysfunction. Infants with this condition often experience recurrent bacterial infections, with approximately half facing severe infections within their first six months of life. These infections commonly affect the respiratory system, digestive tract, and skin, resulting in symptoms like fever, abscesses, and even sepsis. The severity of these symptoms varies, and the specific organs and systems affected depend on the genetic defect. Congenital neutropenia elevates the risk of developing acute myeloid leukemia (AML) or myelodysplastic syndromes (MDS), particularly with certain genetic variants. SCN patients may acquire CSF3R and RUNX1 mutations, which can predict the development of leukemia. It is important to note that high-dose granulocyte colony-stimulating factor (G-CSF) treatment may have the potential to promote leukemogenesis. Treatment for neutropenia involves antibiotics, drugs that boost neutrophil production, or bone marrow transplants. Immediate treatment is essential due to the heightened risk of severe infections. In severe congenital or cyclic neutropenia (CyN), the primary therapy is G-CSF, often combined with antibiotics. The G-CSF dosage is gradually increased to normalize neutrophil counts. Hematopoietic stem cell transplants are considered for non-responders or those at risk of AML/MDS. In cases of WHIM syndrome, CXCR4 inhibitors can be effective. Future treatments may involve gene editing and the use of the diabetes drug empagliflozin to alleviate neutropenia symptoms.

Severe congenital neutropenia due to jagunal homolog 1 (JAGN1) mutation: a case report and literature review

Severe congenital neutropenia caused by jagunal homolog 1 (JAGN1) mutation is a rare condition resulting from maturation arrest secondary to endoplasmic reticulum stress response from impaired neutrophil protein glycosylation. Here, we report a case of a 4-year-old boy who presented with a history of recurrent infections and manifestations, including recurrent intracranial hemorrhage. A review of similar cases reported in the literature indicates that a bleeding diathesis has not been previously described in these patients. We hypothesize that this newly described association of bleeding complications in this patient with JAGN1 mutation is secondary to defective glycosylation in the normal functioning of platelets or clotting factors. Recurrent infections with intracranial hemorrhage, new focal neurologic defects, or altered mental status in a child should warrant a suspicion for this immunodeficiency for the prompt initiation of treatment and prophylaxis for life-threatening infections or trauma.

A deficiency screen of the 3rd chromosome for dominant modifiers of the Drosophila ER integral membrane protein, Jagunal

The mechanism surrounding chromosome inheritance during cell division has been well documented, however, organelle inheritance during mitosis is less understood. Recently, the endoplasmic reticulum (ER) has been shown to reorganize during mitosis, dividing asymmetrically in proneuronal cells prior to cell fate selection, indicating a programmed mechanism of inheritance. ER asymmetric partitioning in proneural cells relies on the highly conserved ER integral membrane protein, Jagunal (Jagn). Knockdown of Jagn in the compound Drosophila eye displays a pleotropic rough eye phenotype in 48% of the progeny. To identify genes involved in Jagn dependent ER partitioning pathway, we performed a dominant modifier screen of the 3rd chromosome for enhancers and suppressors of this Jagn-RNAi-induced rough eye phenotype. We screened through 181 deficiency lines covering the 3L and 3R chromosomes and identified 12 suppressors and 10 enhancers of the Jagn-RNAi phenotype. Based on the functions of the genes covered by the deficiencies, we identified genes that displayed a suppression or enhancement of the Jagn-RNAi phenotype. These include Division Abnormally Delayed (Dally), a heparan sulfate proteoglycan, the γ-secretase subunit Presenilin, and the ER resident protein Sec63. Based on our understanding of the function of these targets, there is a connection between Jagn and the Notch signaling pathway. Further studies will elucidate the role of Jagn and identified interactors within the mechanisms of ER partitioning during mitosis.

Historical Cohort of Severe Congenital Neutropenia in Iran: Clinical Course, Laboratory Evaluation, Treatment, and Survival

INTRODUCTION

Severe congenital neutropenia (SCN) is one of the primary immunodeficiency diseases developed by genetic alterations. Mutations in several genes including HAX-1 , G6PC3 , jagunal , and VPS45 account for autosomal recessive SCN.

PATIENTS AND METHODS

Patients with SCN registered in the Iranian Primary Immunodeficiency Registry and referred to our clinic at the Children's Medical Center were reviewed.

RESULTS

Thirty-seven eligible patients with a mean age of 28.51 ± 24.38 months at the time of diagnosis were included. Nineteen cases had consanguineous parents and 10 cases had confirmed or unconfirmed positive family history. The most prevalent infectious symptoms were oral infections followed by respiratory infections. We identified HAX-1 mutation in 4, ELANE mutation in 4 cases, G6PC3 mutation in 1, and WHIM syndrome in 1 case. Other patients remained genetically unclassified. After the median follow-up of 36 months from the time of diagnosis, the overall survival was 88.88%. The mean event-free survival was 185.84 months (95% CI: 161.02, 210.66).

DISCUSSION

Autosomal recessive SCN is more common in countries with high rates of consanguinity like Iran. The genetic classification was possible only for a few patients in our study. This might suggest that there are other autosomal recessive genes causative of neutropenia that have yet to be described.

CRISPR screens identify novel regulators of cFLIP dependency and ligand-independent, TRAIL-R1-mediated cell death

Kaposi's sarcoma-associated herpesvirus (KSHV) causes primary effusion lymphoma (PEL). PEL cell lines require expression of the cellular FLICE inhibitory protein (cFLIP) for survival, although KSHV encodes a viral homolog of this protein (vFLIP). Cellular and viral FLIP proteins have several functions, including, most importantly, the inhibition of pro-apoptotic caspase 8 and modulation of NF-κB signaling. To investigate the essential role of cFLIP and its potential redundancy with vFLIP in PEL cells, we first performed rescue experiments with human or viral FLIP proteins known to affect FLIP target pathways differently. The long and short isoforms of cFLIP and molluscum contagiosum virus MC159L, which are all strong caspase 8 inhibitors, efficiently rescued the loss of endogenous cFLIP activity in PEL cells. KSHV vFLIP was unable to fully rescue the loss of endogenous cFLIP and is therefore functionally distinct. Next, we employed genome-wide CRISPR/Cas9 synthetic rescue screens to identify loss of function perturbations that can compensate for cFLIP knockout. Results from these screens and our validation experiments implicate the canonical cFLIP target caspase 8 and TRAIL receptor 1 (TRAIL-R1 or TNFRSF10A) in promoting constitutive death signaling in PEL cells. However, this process was independent of TRAIL receptor 2 or TRAIL, the latter of which is not detectable in PEL cell cultures. The requirement for cFLIP is also overcome by inactivation of the ER/Golgi resident chondroitin sulfate proteoglycan synthesis and UFMylation pathways, Jagunal homolog 1 (JAGN1) or CXCR4. UFMylation and JAGN1, but not chondroitin sulfate proteoglycan synthesis or CXCR4, contribute to TRAIL-R1 expression. In sum, our work shows that cFLIP is required in PEL cells to inhibit ligand-independent TRAIL-R1 cell death signaling downstream of a complex set of ER/Golgi-associated processes that have not previously been implicated in cFLIP or TRAIL-R1 function.

JAGN1 mutation with distinct clinical features; two case reports and literature review

Jagunal homolog 1 (JAGN1) has been recognized as an essential protein in neutrophil function. The mutated JAGN1 is responsible for immunodeficiency related to innate and humoral defense mechanisms. This deficiency impairs neutrophil development and function, leading to recurrent infections and facial dysmorphism as phenotypic consequences of severe congenital neutropenia (SCN). We report two siblings having the reported JAGN1 mutation with different clinical manifestations. Recurrent abscess formation unresponsive to antibiotic therapy, a history of delayed umbilical separation, frequent bacterial or fungal infection, dysmorphic face, failure to thrive, and other coexisting organ abnormalities should prompt physicians to syndromic immunodeficiencies involving neutrophils. Genetic investigations to elucidate the responsible mutation is critical as clinical management varies. Once the diagnosis is confirmed, a multi-disciplinary team should perform further workups to investigate other coexisting malformations and neurodevelopmental evaluation.

Human genetic defects in SRP19 and SRPRA cause severe congenital neutropenia with distinctive proteome changes

The mechanisms of coordinated changes in proteome composition and their relevance for the differentiation of neutrophil granulocytes are not well studied. Here, we discover 2 novel human genetic defects in signal recognition particle receptor alpha (SRPRA) and SRP19, constituents of the mammalian cotranslational targeting machinery, and characterize their roles in neutrophil granulocyte differentiation. We systematically study the proteome of neutrophil granulocytes from patients with variants in the SRP genes, HAX1, and ELANE, and identify global as well as specific proteome aberrations. Using in vitro differentiation of human induced pluripotent stem cells and in vivo zebrafish models, we study the effects of SRP deficiency on neutrophil granulocyte development. In a heterologous cell-based inducible protein expression system, we validate the effects conferred by SRP dysfunction for selected proteins that we identified in our proteome screen. Thus, SRP-dependent protein processing, intracellular trafficking, and homeostasis are critically important for the differentiation of neutrophil granulocytes.

Potential roles of Toxocara canis larval excretory secretory molecules in immunomodulation and immune evasion

Toxocara canis larvae invade various tissues of different vertebrate species without developing into adults in paratenic host. The long-term survival of the larvae despite exposure to the well-armed immune response is a notable achievement. The larvae modulate the immune response to help the survival of both the host and the larvae. They skew the immune response to type 2/regulatory phenotype. The outstanding ability of the larvae to modulate the host immune response and to evade the immune arms is attributed to the secretion of Toxocara excretory-secretory products (TESPs). TESPs are complex mixture of differing molecules. The present review deals with the molecular composition of the TESPs, their interaction with the host molecules, their effect on the innate immune response, the receptor recognition, the downstream signals the adaptive immunity and the repair of tissues. This review also addresses the role of TESPs molecules in the immune evasion strategy and the potential effect of the induced immunomodulation in some diseases. Identification of parasite components that influence the nematode-host interactions could enhance understanding the molecular basis of nematode pathogenicity. Furthermore, the identification of helminths molecules with immunomodulatory potential could be used in immunotherapies for some diseases.

Case Report: Association between cyclic neutropenia and SRP54 deficiency

Autosomal dominant mutations in the signal recognition particle (SRP) 54 gene were recently described in patients with severe congenital neutropenia (SCN). SRP54 deficiency cause a chronic and profound neutropenia with maturation arrest at the promyelocyte stage, occurring in the first months of life. Nearly all reported patients with SRP54 mutations had neutropenia without a cyclic pattern and showed a poor or no response to granulocyte colony-stimulating factor (G-CSF) therapy. We report here an 11-year-old female patient with cyclic neutropenia and recurrent heterozygous p.T117del (c.349_351del) in-frame deletion mutation in SRP54, who showed remarkable therapeutic response to G-CSF treatment. The diagnosis of cyclic pattern of neutropenia was established by acceptable standards. ELANE gene mutation was excluded by using various genetic approaches. The patient described here also had dolichocolon which has not been described before in association with SCN.

Lymphocyte cytosolic protein 1 (L-plastin) I232F mutation impairs granulocytic proliferation and causes neutropenia

Neutrophils migrate into inflamed tissue, engage in phagocytosis, and clear pathogens or apoptotic cells. These processes require well-coordinated events involving the actin cytoskeleton. We describe a child with severe neutropenia and episodes of soft tissue infections and pneumonia. Bone marrow examination showed granulocytic hypoplasia with dysplasia. Whole-exome sequencing revealed a de novo heterozygous missense mutation in LCP1, which encodes the F-actin-binding protein Lymphocyte Cytosolic Protein 1. To determine its pathophysiological significance, we stably transduced cells with doxycycline-inducible wild-type LCP1 and LCP1 I232F lentiviral constructs. We observed dysplastic granulocytic 32D cells expressing LCP1 I232F cells. These cells showed decreased proliferation without a block in differentiation. In addition, expression of LCP1 I232F resulted in a cell cycle arrest at the G2/M phase, but it did not lead to increased levels of genes involved in apoptosis or the unfolded protein response. Both 32D and HeLa cells expressing mutant LCP1 displayed impaired cell motility and invasiveness. Flow cytometry showed increased F-actin. However, mutant LCP1-expressing 32D cells exhibited normal oxidative burst upon stimulation. Confocal imaging and subcellular fractionation revealed diffuse intracellular localization of LCP1, but only the mutant form was found in the nucleus. We conclude that LCP1 is a new gene involved in granulopoiesis, and the missense variant LCP1 I232F leads to neutropenia and granulocytic dysplasia with aberrant actin dynamics. Our work supports a model of neutropenia due to aberrant actin regulation.

Understanding neutropenia secondary to intrinsic or iatrogenic immune dysregulation

As a key member of the innate and adaptive immune response, neutrophils provide insights into the hematopoietic and inflammatory manifestations of inborn errors of immunity (IEI) and the consequences of immunotherapy. The facile recognition of IEI presenting with neutropenia provides an avenue for hematologists to facilitate early diagnosis and expedite biologically rationale care. Moreover, enhancing the understanding of the molecular mechanisms driving neutropenia in IEI-decreased bone marrow reserves, diminished egress from the bone marrow, and decreased survival-offers an opportunity to further dissect the pathophysiology driving neutropenia secondary to iatrogenic immune dysregulation, eg, immune checkpoint inhibitors and chimeric antigen receptor T-cell therapy.

Kostmann disease and other forms of severe congenital neutropenia

Congenital neutropenia with autosomal recessive inheritance was first described by the Swedish paediatrician Rolf Kostmann who coined the term 'infantile genetic agranulocytosis'. The condition is now commonly referred to as Kostmann disease. These patients display a maturation arrest of the myelopoiesis in the bone marrow and reduced neutrophil numbers and suffer from recurrent, often life-threatening infections. The molecular mechanism underlying congenital neutropenia has been intensively investigated, and mutations in genes that impinge on programmed cell death have been identified. The present review provides an overview of these studies.

Chronic neutropenia: how best to assess severity and approach management?

INTRODUCTION

Neutropenia is a relatively common finding in medical practice and the medical approach requires a gradual and pertinent diagnostic procedure as well as adapted management.

AREAS COVERED

The area of chronic neutropenia remains fragmented between diverse diseases or situations. Here physicians involved in different aspects of chronic neutropenia gather both the data from medical literature till the end of May 2021 and their experience to offer a global approach for the diagnosis of chronic neutropenia as well as their medical care.

EXPERT OPINION

In most cases, the neutropenia is transient, frequently related to a viral infection, and not harmful. However, neutropenia can be chronic (i.e. >3 months) and related to a number of etiologies, some clinically benign, such as so-called 'ethnic' neutropenia. Autoimmune neutropenia is the common form in young children, whereas idiopathic/immune neutropenia is a frequent etiology in young females. Inherited neutropenia (or congenital neutropenia) is exceptional, with approximately 30 new cases per 10⁶ births and 30 known subtypes. Such patients have a high risk of invasive bacterial infections, and oral infections. Supportive therapy, which is primarily based on daily administration of an antibiotic prophylaxis and/or treatment with granulocyte-colony stimulating factor (G-CSF), contributes to avoiding recurrent infections.

Identification of Toxocara canis Antigen-Interacting Partners by Yeast Two-Hybrid Assay and a Putative Mechanism of These Host-Parasite Interactions

Toxocara canis is a zoonotic roundworm that infects humans and dogs all over the world. Upon infection, larvae migrate to various tissues leading to different clinical syndromes. The host–parasite interactions underlying the process of infection remain poorly understood. Here, we describe the application of a yeast two-hybrid assay to screen a human cDNA library and analyse the interactome of T. canis larval molecules. Our data identifies 16 human proteins that putatively interact with the parasite. These molecules were associated with major biological processes, such as protein processing, transport, cellular component organisation, immune response and cell signalling. Some of these identified interactions are associated with the development of a Th2 response, neutrophil activity and signalling in immune cells. Other interactions may be linked to neurodegenerative processes observed during neurotoxocariasis, and some are associated with lung pathology found in infected hosts. Our results should open new areas of research and provide further data to enable a better understanding of this complex and underestimated disease.

Sanguisorba parviflora (Maxim.) Takeda alleviates cyclophosphamide-induced leukopenia by regulating haematopoietic cell-specific protein 1-associated protein X-1 gene expression

WHAT IS KNOWN AND OBJECTIVE

We have previously shown that the saponins of Sanguisorba parviflora (Maxim.) Takeda (Sp. T) relieved cyclophosphamide-induced myelosuppression in leukopenic mice. Haematopoietic cell-specific protein 1-associated protein X-1 (HAX-1) participated in the survival of neutrophils through the regulation of mitochondrial function. The aim of the present study was to comprehensively identify the role of HAX-1 in the mechanism of leukopenia alleviation by Sp. T.

METHODS

HAX-1 gene and protein expression levels in peripheral blood neutrophils were examined using real-time quantitative reverse transcription-polymerase chain reaction, western blot and immunohistochemical assays. Neutrophil apoptosis was measured using flow cytometry. Mitochondrial function was determined via assessments of the reactive oxygen species (ROS) generation and mitochondrial membrane potential (ΔΨm) integrity levels.

RESULTS AND DISCUSSION

The HAX-1 gene expression level in the peripheral blood neutrophils was significantly lower in patients with leukopenia than in healthy donors. The saponins of Sp. T induced HAX-1 expression and promoted myeloid progenitor cell (mEB8-ER cell) viability. HAX-1 overexpression reduced the production of ROS and maintained ΔΨm integrity. Cyclophosphamide-induced mitochondrial dysfunction and apoptosis could be abrogated by treatment with Sp. T or metformin.

WHAT IS NEW AND CONCLUSION

Our data suggest a mechanism through which Sp. T protects against chemotherapy-induced leukopenia by regulating HAX-1 gene expression in a mitochondrial-dependent manner.

Sanguisorba parviflora (Maxim) Takeda alleviates cyclophosphamide-induced leukopenia via regulating the hematopoietic cell-specific protein 1-associated protein X-1 gene

WHAT IS KNOWN AND THE OBJECTIVE

Our previous studies have shown that saponins of Sanguisorba parviflora (Maxim) Takeda (Sp. T) relieved cyclophosphamide-induced myelosuppression in mice with leukopenia. The hematopoietic cell-specific protein 1-associated protein X-1 (HAX-1) participated in the survival of neutrophils through the regulation of mitochondrial function. This study aimed to comprehensively identify the role of HAX-1 in Sp. T to alleviate leukopenia.

METHODS

HAX-1 expression was examined in the peripheral blood neutrophils using real-time polymerase chain reaction (PCR), Western blot analysis and immunohistochemical staining. Neutrophil apoptosis was measured by flow cytometry. Mitochondrial function was evaluated via reactive oxygen species (ROS) generation and mitochondrial membrane potential (ΔΨm) integrity.

RESULTS AND DISCUSSION

Our study indicated that the expression of the HAX-1 gene was significantly decreased in the peripheral blood neutrophils of leukopenia patients compared with healthy donors. The saponins of Sp. T induced HAX-1 expression and promoted myeloid progenitor cell (mEB8-ER cell) viability, while overexpression of HAX-1 reduced the production of reactive oxygen species (ROS) and maintained the integrity of the mitochondrial membrane potential. Cyclophosphamide-induced mitochondrial dysfunction and apoptosis could be abrogated by treatment with Sp. T or the addition of metformin.

WHAT IS NEW AND OUR CONCLUSION

Our data support a mechanism where Sp. T protects against chemotherapy-induced leukopenia by regulating HAX-1 gene expression in a mitochondrial-dependent manner.

Identification of protein/mRNA network involving the PSORS1 locus gene CCHCR1 and the PSORS4 locus gene HAX1

CCHCR1 (Coiled-Coil alpha-Helical Rod 1), maps to chromosomal region 6p21.3, within the major psoriasis susceptibility locus PSORS1. CCHCR1 itself is a plausible psoriasis candidate gene, however its role in psoriasis pathogenesis remains unclear. We previously demonstrated that CCHCR1 protein acts as a cytoplasmic docking site for RNA polymerase II core subunit 3 (RPB3) in cycling cells, suggesting a role for CCHCR1 in vesicular trafficking between cellular compartments. Here, we report a novel interaction between CCHCR1 and the RNA binding protein HAX1. HAX1 maps to chromosomal region 1q21.3 within the PSORS4 locus and is over-expressed in psoriasis. Both CCHCR1 and HAX1 share subcellular co-localization with mitochondria, nuclei and cytoplasmic vesicles as P-bodies. By a series of ribonucleoprotein immunoprecipitation (RIP) assays, we isolated a pool of mRNAs complexed with HAX1 and/or CCHCR1 proteins. Among the mRNAs complexed with both CCHCR1 and HAX1 proteins, there are Vimentin mRNA, previously described to be bound by HAX1, and CAMP/LL37 mRNA, whose gene product is over-expressed in psoriasis.

A crucial role for Jagunal homolog 1 in humoral immunity and antibody glycosylation in mice and humans

Jagunal homolog 1 (JAGN1) has been identified as a critical regulator of neutrophil biology in mutant mice and rare-disease patients carrying JAGN1 mutations. Here, we report that Jagn1 deficiency results in alterations in the endoplasmic reticulum (ER) of antibody-producing cells as well as decreased antibody production and secretion. Consequently, mice lacking Jagn1 in B cells exhibit reduced serum immunoglobulin (Ig) levels at steady state and fail to mount an efficient humoral immune response upon immunization with specific antigens or when challenged with viral infections. We also demonstrate that Jagn1 deficiency in B cells results in aberrant IgG N-glycosylation leading to enhanced Fc receptor binding. Jagn1 deficiency in particular affects fucosylation of IgG subtypes in mice as well as rare-disease patients with loss-of-function mutations in JAGN1. Moreover, we show that ER stress affects antibody glycosylation. Our data uncover a novel and key role for JAGN1 and ER stress in antibody glycosylation and humoral immunity in mice and humans.

Efficacy of Low-Dose rhGM-CSF Treatment in a Patient With Severe Congenital Neutropenia Due to CSF3R Deficiency: Case Report of a Novel Biallelic CSF3R Mutation and Literature Review

This study reports the clinical manifestations, genetics, and efficacy of treatment with the efficacy of recombinant human granulocyte macrophage colony-stimulating factor (rhGM-GSF) of a 2-year-old female patient with severe congenital neutropenia (SCN) type 7 (SCN7) caused by novel biallelic mutations in the colony-stimulating factor 3 receptor (CSF3R) gene. Genetic diagnosis of the patient was performed by whole-exome and Sanger sequencing. Expression of the CSF3R gene in the peripheral neutrophils of the patient was detected by real-time PCR and Western blotting. The patient presented with recurrent suppurative tonsillitis and decreased absolute neutrophil count <0.5 × 10⁹/L. Novel heterozygous mutations were found to be inherited from each parent (maternal c.690delC [p.met231Cysfs^*32] and paternal c.64+5G>A). The patient's neutrophils had lower CSF3R mRNA and protein levels than those of the parents. Low-dose rhGM-CSF (3 μg/kg/day once a week) prevented recurrent infection in the patient. These results demonstrate that the clinical manifestations of SCN7 with biallelic CSF3R mutations and downregulated CSF3R can be effectively treated with rhGM-CSF.

Termini restraining of small membrane proteins enables structure determination at near-atomic resolution

Small membrane proteins are difficult targets for structural characterization. Here, we stabilize their folding by restraining their amino and carboxyl termini with associable protein entities, exemplified by the two halves of a superfolder GFP. The termini-restrained proteins are functional and show improved stability during overexpression and purification. The reassembled GFP provides a versatile scaffold for membrane protein crystallization, enables diffraction to atomic resolution, and facilitates crystal identification, phase determination, and density modification. This strategy gives rise to 14 new structures of five vertebrate proteins from distinct functional families, bringing a substantial expansion to the structural database of small membrane proteins. Moreover, a high-resolution structure of bacterial DsbB reveals that this thiol oxidoreductase is activated through a catalytic triad, similar to cysteine proteases. Overall, termini restraining proves exceptionally effective for stabilization and structure determination of small membrane proteins.

Severe congenital neutropenia-associated JAGN1 mutations unleash a calpain-dependent cell death programme in myeloid cells

Severe congenital neutropenia (SCN) of autosomal recessive inheritance, also known as Kostmann disease, is characterised by a lack of neutrophils and a propensity for life-threatening infections. Using whole-exome sequencing, we identified homozygous JAGN1 mutations (p.Gly14Ser and p.Glu21Asp) in three patients with Kostmann-like SCN, thus confirming the recent attribution of JAGN1 mutations to SCN. Using the human promyelocytic cell line HL-60 as a model, we found that overexpression of patient-derived JAGN1 mutants, but not silencing of JAGN1, augmented cell death in response to the pro-apoptotic stimuli, etoposide, staurosporine, and thapsigargin. Furthermore, cells expressing mutant JAGN1 were remarkably susceptible to agonists that normally trigger degranulation and succumbed to a calcium-dependent cell death programme. This mode of cell death was completely prevented by pharmacological inhibition of calpain but unaffected by caspase inhibition. In conclusion, our results confirmed the association between JAGN1 mutations and SCN and showed that SCN-associated JAGN1 mutations unleash a calcium- and calpain-dependent cell death in myeloid cells.

A Next-Generation Sequencing Test for Severe Congenital Neutropenia: Utility in a Broader Clinicopathologic Spectrum of Disease

Severe congenital neutropenia (SCN) is a collection of diverse disorders characterized by chronically low absolute neutrophil count in the peripheral blood, increased susceptibility to infection, and a significant predisposition to the development of myeloid malignancies. SCN can be acquired or inherited. Inherited forms have been linked to variants in a group of diverse genes involved in the neutrophil-differentiation process. Variants that promote resistance to treatment have also been identified. Thus, genetic testing is important for the diagnosis, prognosis, and management of SCN. Herein we describe clinically validated assay developed for assessing patients with suspected SCN. The assay is performed from a whole-exome backbone. Variants are called across all coding exons, and results are filtered to focus on 48 genes that are clinically relevant to SCN. Validation results indicated 100% analytical sensitivity and specificity for the detection of constitutional variants among the 48 reportable genes. To date, 34 individuals have been referred for testing (age range: birth to 67 years). Several pathogenic and likely pathogenic variants have been identified, including one in a patient with late-onset disease. The pattern of cases referred for testing suggests that this assay has clinical utility in a broader spectrum of patients beyond those in the pediatric population who have classic early-onset symptoms characteristic of SCN.

Novel Frameshift Autosomal Recessive Loss-of-Function Mutation in SMARCD2 Encoding a Chromatin Remodeling Factor Mediates Granulopoiesis

PURPOSE

Recently, a new form of congenital neutropenia that is caused by germline biallelic loss-of-function mutations in the SMARCD2 gene was described in four patients. Given the rarity of the condition, the clinical spectrum of the disease has remained elusive. We here report a new patient with a novel frameshift mutation and compare our patient with the previously reported SMARCD2-mutant patients, aiming to provide a more comprehensive understanding of the natural course of the disease.

METHODS

Clinical and laboratory findings of all reported patients were reviewed. Next-generation sequencing was performed to identify the causative genetic defect. Data on the hematopoietic stem cell transplantation including stem cell sources, conditioning regimen, engraftment, graft-versus-host disease, and infections were also collected.

RESULTS

An 11-year-old female patient had a variety of infections including sepsis, deep tissue abscesses, otitis, pneumonia, gingivitis, and diarrhea since infancy. A novel homozygous mutation in SMARCD2 (c.93delG, p.Ala32Argfs*80) was detected. Bone marrow examination showed hypocellularity and decreased neutrophils with diminished granules and myeloid dysplasia, but no blast excess as in previously reported patients. The neutropenia was non-responsive even to higher doses of granulocyte colony-stimulating factor (G-CSF); therefore, the patient was transplanted at 10 years of age from a HLA-A allele-mismatched unrelated donor using a reduced toxicity conditioning regimen and recovered successfully. Compared with the previous four cases, our patient showed longer survival before transplantation without blastic transformation.

CONCLUSION

Distinctive myeloid features and long-term follow-up including therapy options are presented for the newly described case of SMARCD2 deficiency. This disorder is apparent at infancy and requires early transplantation due to the unrelenting disease course despite conventional therapy.

JAGN1, tetraspanins, and Erv proteins: is common topology indicative of common function in cargo sorting?

The endoplasmic reticulum protein Jagunal (JAGN1) was first identified as a requirement for Drosophila melanogaster oocyte development. Subsequent studies in human patients linked mutations in JAGN1 to severe congenital neutropenia, as well as a broad range of additional symptoms, suggesting that JAGN1 function is required in many tissues. Moreover, JAGN1 orthologs are found throughout animal and plant phylogeny, suggesting that JAGN1 supports fundamental cellular processes not restricted to egg development or neutrophil function. JAGN1 lacks sequence similarity or recognizable domains other than a coatomer protein complex I-binding motif, and its cellular function is currently unknown. JAGN1 shares a tetraspanning membrane topology with two families of known cargo transporters: the tetraspanins and the endoplasmic reticulum vesicle (Erv) proteins. Herein, we discuss the similarities between JAGN1, tetraspanins, and Ervs and, based on those, suggest a role for JAGN1 in facilitating the traffic of cell-restricted and ubiquitously expressed proteins at the endoplasmic reticulum-Golgi interface.

Hereditary Predisposition to Hematopoietic Neoplasms: When Bloodline Matters for Blood Cancers

With the advent of precision genomics, hereditary predisposition to hematopoietic neoplasms- collectively known as hereditary predisposition syndromes (HPS)-are being increasingly recognized in clinical practice. Familial clustering was first observed in patients with leukemia, which led to the identification of several germline variants, such as RUNX1, CEBPA, GATA2, ANKRD26, DDX41, and ETV6, among others, now established as HPS, with tendency to develop myeloid neoplasms. However, evidence for hereditary predisposition is also apparent in lymphoid and plasma--cell neoplasms, with recent discoveries of germline variants in genes such as IKZF1, SH2B3, PAX5 (familial acute lymphoblastic leukemia), and KDM1A/LSD1 (familial multiple myeloma). Specific inherited bone marrow failure syndromes-such as GATA2 haploinsufficiency syndromes, short telomere syndromes, Shwachman-Diamond syndrome, Diamond-Blackfan anemia, severe congenital neutropenia, and familial thrombocytopenias-also have an increased predisposition to develop myeloid neoplasms, whereas inherited immune deficiency syndromes, such as ataxia-telangiectasia, Bloom syndrome, Wiskott Aldrich syndrome, and Bruton agammaglobulinemia, are associated with an increased risk for lymphoid neoplasms. Timely recognition of HPS is critical to ensure safe choice of donors and/or conditioning-regimen intensity for allogeneic hematopoietic stem-cell transplantation and to enable direction of appropriate genomics-driven personalized therapies. The purpose of this review is to provide a comprehensive overview of HPS and serve as a useful reference for clinicians to recognize relevant signs and symptoms among patients to enable timely screening and referrals to pursue germline assessment. In addition, we also discuss our institutional approach toward identification of HPS and offer a stepwise diagnostic and management algorithm.

Nonsense Suppression Therapy: New Hypothesis for the Treatment of Inherited Bone Marrow Failure Syndromes

Inherited bone marrow failure syndromes (IBMFS) are a group of cancer-prone genetic diseases characterized by hypocellular bone marrow with impairment in one or more hematopoietic lineages. The pathogenesis of IBMFS involves mutations in several genes which encode for proteins involved in DNA repair, telomere biology and ribosome biogenesis. The classical IBMFS include Shwachman–Diamond syndrome (SDS), Diamond–Blackfan anemia (DBA), Fanconi anemia (FA), dyskeratosis congenita (DC), and severe congenital neutropenia (SCN). IBMFS are associated with high risk of myelodysplastic syndrome (MDS), acute myeloid leukemia (AML), and solid tumors. Unfortunately, no specific pharmacological therapies have been highly effective for IBMFS. Hematopoietic stem cell transplantation provides a cure for aplastic or myeloid neoplastic complications. However, it does not affect the risk of solid tumors. Since approximately 28% of FA, 24% of SCN, 21% of DBA, 20% of SDS, and 17% of DC patients harbor nonsense mutations in the respective IBMFS-related genes, we discuss the use of the nonsense suppression therapy in these diseases. We recently described the beneficial effect of ataluren, a nonsense suppressor drug, in SDS bone marrow hematopoietic cells ex vivo. A similar approach could be therefore designed for treating other IBMFS. In this review we explain in detail the new generation of nonsense suppressor molecules and their mechanistic roles. Furthermore, we will discuss strengths and limitations of these molecules which are emerging from preclinical and clinical studies. Finally we discuss the state-of-the-art of preclinical and clinical therapeutic studies carried out for IBMFS.

Primary Immunodeficiencies With Defects in Innate Immunity: Focus on Orofacial Manifestations

The field of primary immunodeficiencies (PIDs) is rapidly evolving. Indeed, the number of described diseases is constantly increasing thanks to the rapid identification of novel genetic defects by next-generation sequencing. PIDs are now rather referred to as “inborn errors of immunity” due to the association between a wide range of immune dysregulation-related clinical features and the “prototypic” increased infection susceptibility. The phenotypic spectrum of PIDs is therefore very large and includes several orofacial features. However, the latter are often overshadowed by severe systemic manifestations and remain underdiagnosed. Patients with impaired innate immunity are predisposed to a variety of oral manifestations including oral infections (e.g., candidiasis, herpes gingivostomatitis), aphthous ulcers, and severe periodontal diseases. Although less frequently, they can also show orofacial developmental abnormalities. Oral lesions can even represent the main clinical manifestation of some PIDs or be inaugural, being therefore one of the first features indicating the existence of an underlying immune defect. The aim of this review is to describe the orofacial features associated with the different PIDs of innate immunity based on the new 2019 classification from the International Union of Immunological Societies (IUIS) expert committee. This review highlights the important role played by the dentist, in close collaboration with the multidisciplinary medical team, in the management and the diagnostic of these conditions.

Defective Sec61α1 underlies a novel cause of autosomal dominant severe congenital neutropenia

Background

The molecular cause of severe congenital neutropenia (SCN) is unknown in 30% to 50% of patients. SEC61A1 encodes the α-subunit of the Sec61 complex, which governs endoplasmic reticulum protein transport and passive calcium leakage. Recently, mutations in SEC61A1 were reported to be pathogenic in common variable immunodeficiency and glomerulocystic kidney disease.

Objective

Our aim was to expand the spectrum of SEC61A1-mediated disease to include autosomal dominant SCN.

Methods

Whole exome sequencing findings were validated, and reported mutations were compared by Western blotting, Ca2⁺ flux assays, differentiation of transduced HL-60 cells, in vitro differentiation of primary CD34 cells, quantitative PCR for unfolded protein response (UPR) genes, and single-cell RNA sequencing on whole bone marrow.

Results

We identified a novel de novo missense mutation in SEC61A1 (c.A275G;p.Q92R) in a patient with SCN who was born to nonconsanguineous Belgian parents. The mutation results in diminished protein expression, disturbed protein translocation, and an increase in calcium leakage from the endoplasmic reticulum. In vitro differentiation of CD34⁺ cells recapitulated the patient’s clinical arrest in granulopoiesis. The impact of Q92R-Sec61α1 on neutrophil maturation was validated by using HL-60 cells, in which transduction reduced differentiation into CD11b⁺CD16⁺ cells. A potential mechanism for this defect is the uncontrolled initiation of the unfolded protein stress response, with single-cell analysis of primary bone marrow revealing perturbed UPR in myeloid precursors and in vitro differentiation of primary CD34⁺ cells revealing upregulation of CCAAT/enhancer-binding protein homologous protein and immunoglobulin heavy chain binding protein UPR-response genes.

Conclusion

Specific mutations in SEC61A1 cause SCN through dysregulation of the UPR.

Management of a Patient With Congenital Biallelic CSF3R Mutation With GM-CSF

Severe Congenital Neutropenia (SCN) is a rare inherited disease characterized by an absolute neutrophil count (ANC) lower than 500/μL. Genetic heterogeneity and biallelic CSF3R mutation has rarely been identified as an underlying genetic defect in SCN. The majority of SCN patients respond to granulocyte colony stimulating factor treatment; however, in patients with inherited CSF3R mutation, ANC cannot generally be increased with granulocyte colony stimulating factor treatment. In such cases, granulocyte macrophage colony stimulating factor presents as an effective treatment option. Herein, we report a case of a 5-year-old SCN girl with homozygous c610-611 del ins AG (p.Q204R) mutation in the CSF3R gene, who was successfully treated with granulocyte macrophage colony stimulating factor.

Recent advances in primary immunodeficiency: from molecular diagnosis to treatment

The technological advances in diagnostics and therapy of primary immunodeficiency are progressing at a fast pace. This review examines recent developments in the field of inborn errors of immunity, from their definition to their treatment. We will summarize the challenges posed by the growth of next-generation sequencing in the clinical setting, touch briefly on the expansion of the concept of inborn errors of immunity beyond the classic immune system realm, and finally review current developments in targeted therapies, stem cell transplantation, and gene therapy.

CDG and immune response: From bedside to bench and back

Glycosylation is an essential biological process that adds structural and functional diversity to cells and molecules, participating in physiological processes such as immunity. The immune response is driven and modulated by protein-attached glycans that mediate cell-cell interactions, pathogen recognition and cell activation. Therefore, abnormal glycosylation can be associated with deranged immune responses. Within human diseases presenting immunological defects are congenital disorders of glycosylation (CDG), a family of around 130 rare and complex genetic diseases. In this review, we have identified 23 CDG with immunological involvement, characterized by an increased propensity to-often life-threatening-infection. Inflammatory and autoimmune complications were found in 7 CDG types. CDG natural history(ies) and the mechanisms behind the immunological anomalies are still poorly understood. However, in some cases, alterations in pathogen recognition and intracellular signaling (eg, TGF-β1, NFAT, and NF-κB) have been suggested. Targeted therapies to restore immune defects are only available for PGM3-CDG and SLC35C1-CDG. Fostering research on glycoimmunology may elucidate the involved pathophysiological mechanisms and open new therapeutic avenues, thus improving CDG patients' quality of life.

Screening of genetic variants in ELANE mutation negative congenital neutropenia by next generation sequencing

AIMS

Congenital neutropenia (CN) is a rare inherited disease that results in recurrent, life-threatening bacterial infections due to a deficiency of mature neutrophils. They are usually caused by heterozygous ELANE mutations although mutations in other genes like HAX-1, G6PC3 and GFI1 have also been reported. Identifying the causative mutation aids in the establishment of diagnosis and rules out other secondary causes of neutropenia like autoimmune cytopenia and evolving aplasia. We aimed to identify the molecular defects in CN patients who had no mutations in ELANE gene, by next generation sequencing (NGS) targeting a customised panel of genes.

METHODS

DNA samples were sequenced with an Illumina NextSeq sequencer using an in-house customised panel of genes at ≥100× depth. Bioinformatics analysis was carried out and the pathogenic variants were identified using a stepwise filtering and analysis strategy. Specific mutations identified were subsequently validated by Sanger sequencing.

RESULTS

The pathogenic variants identified in the study includes previously reported variants in SBDS (compound heterozygous c.258+2T>C and c.1A>T), GATA2 (heterozygous c.1186C>T) and novel variants in WAS (hemizygous c.812T>C), JAGN1 (homozygous c.70G>A) and RTEL1 (heterozygous c.2893G>C) genes.

CONCLUSION

This study highlights that the absence of ELANE mutations does not rule out the diagnosis of CN and this NGS based approach with a customised panel will help in diagnostic confirmation in such patients. The early onset of the disease, clinical severity and associated high risk of malignant transformation in CN strongly suggests the need for early diagnosis and therapeutic intervention.

Characterization and mutagenesis of Chinese hamster ovary cells endogenous retroviruses to inactivate viral particle release

The Chinese hamster ovary (CHO) cells used to produce biopharmaceutical proteins are known to contain type‐C endogenous retrovirus (ERV) sequences in their genome and to release retroviral‐like particles. Although evidence for their infectivity is missing, this has raised safety concerns. As the genomic origin of these particles remained unclear, we characterized type‐C ERV elements at the genome, transcriptome, and viral particle RNA levels. We identified 173 type‐C ERV sequences clustering into three functionally conserved groups. Transcripts from one type‐C ERV group were full‐length, with intact open reading frames, and cognate viral genome RNA was loaded into retroviral‐like particles, suggesting that this ERV group may produce functional viruses. CRISPR‐Cas9 genome editing was used to disrupt the gag gene of the expressed type‐C ERV group. Comparison of CRISPR‐derived mutations at the DNA and RNA level led to the identification of a single ERV as the main source of the release of RNA‐loaded viral particles. Clones bearing a Gag loss‐of‐function mutation in this ERV showed a reduction of RNA‐containing viral particle release down to detection limits, without compromising cell growth or therapeutic protein production. Overall, our study provides a strategy to mitigate potential viral particle contaminations resulting from ERVs during biopharmaceutical manufacturing.

Homozygous c.130-131 ins A (pW44X) mutation in the HAX1 gene as the most common cause of congenital neutropenia in Turkey: Report from the Turkish Severe Congenital Neutropenia Registry

BACKGROUND

Severe congenital neutropenia is a rare disease, and autosomal dominantly inherited ELANE mutation is the most frequently observed genetic defect in the registries from North America and Western Europe. However, in eastern countries where consanguineous marriages are common, autosomal recessive forms might be more frequent.

METHOD

Two hundred and sixteen patients with severe congenital neutropenia from 28 different pediatric centers in Turkey were registered.

RESULTS

The most frequently observed mutation was HAX1 mutation (n = 78, 36.1%). A heterozygous ELANE mutation was detected in 29 patients (13.4%) in our cohort. Biallelic mutations of G6PC3 (n = 9, 4.3%), CSF3R (n = 6, 2.9%), and JAGN1 (n = 2, 1%) were also observed. Granulocyte colony-stimulating factor treatment was given to 174 patients (80.6%). Two patients died with infectious complications, and five patients developed myelodysplastic syndrome/acute myeloblastic leukemia. The mean (± mean standard error) follow-up period was 129.7 ± 76.3 months, and overall survival was 96.8% (CI, 94.4-99.1%) at the age of 15 years. In Turkey, severe congenital neutropenia mostly resulted from the p W44X mutation in the HAX1 gene.

CONCLUSION

In Turkey, mutation analysis should be started with HAX1, and if this is negative, ELANE and G6PC3 should be checked. Because of the very high percentage of consanguineous marriage, rare mutations should be tested in patients with a negative mutation screen.

Neutrophil Research, Quo Vadis?

In recent years, great progress has been made to understand how neutrophils contribute to homeostatic regulation, tumor progression, and chronic inflammation. Here, I highlight a few salient basic questions to be addressed in the field. Ideally, future investigations along these lines can contribute to identifying possible means of therapeutically interfering with neutrophil effector functions to fine-tune innate immunity.

Next-Generation Sequencing Reveals A JAGN1 Mutation in a Syndromic Child With Intermittent Neutropenia

BACKGROUND

Jagunal homolog 1 (JAGN1) gene was identified as a novel responsible for severe congenital neutropenia. The protein encoded by this gene is required for neutrophil differentiation, survival and function in microbial activity. JAGN1-deficient human neutrophils are characterized by alterations in trafficking within the endoplasmic reticulum and golgi compartments because of ultrastructural defects in endoplasmic reticulum and susceptibility to apoptosis.

OBSERVATIONS

We report a patient exhibiting an intermittent neutropenia, for which a next-generation sequencing revealed a homozygous mutation in the JAGN1 gene.

CONCLUSIONS

The patient extends the clinical variability associated to JAGN1 mutations, and this case highlights the importance of genetic investigations in patients with suspected neutropenia.

Congenital Neutropenia and Rare Functional Phagocyte Disorders in Children

Both profound neutropenia and functional phagocyte disorders render patients susceptible to recurrent, unusual, and/or life-threatening infections. Many disorders also have nonhematologic manifestations and a substantial risk of leukemogenesis. Diagnosis relies on clinical suspicion and interrogation of the complete blood count with differential/bone marrow examination coupled with immunologic and genetic analyses. Treatment of the quantitative neutrophil disorders depends on granulocyte colony-stimulating factor, whereas management of functional phagocyte disease is reliant on antimicrobials and/or targeted therapies. Hematopoietic stem cell transplant remains the only curative option for most disorders but is not used on a routine basis.

Congenital Neutropenia Patient With Hypomorphic Biallelic CSF3R Mutation Responding to GCSF

Congenital neutropenia (CN) is a rare disorder, and the most common gene responsible for CN is ELANE. Furthermore, the mutations of HAX1, G6PC3, and JAGN1 genes may cause CN. These patients generally find great benefit from subcutaneous administration of Granulocyte Colony Stimulating Factor (GCSF). In recent years, Biallelic Colony Stimulating Factor 3 Receptor (CSF3R) mutations have been described as an underlying defect of CN in several children. In contrast to the previous group, the patients who have a CSF3R mutation do not respond to GCSF treatment. Here, we present a CN patient with hypomorphic biallelic CSF3R mutation responding to GCSF.

Serpin B1 defect and increased apoptosis of neutrophils in Cohen syndrome neutropenia

Cohen syndrome (CS) is a rare genetic disorder due to mutations in VPS13B gene. Among various clinical and biological features, CS patients suffer from inconsistent neutropenia, which is associated with recurrent but minor infections. We demonstrate here that this neutropenia results from an exaggerate rate of neutrophil apoptosis. Besides this increased cell death, which occurs in the absence of any endoplasmic reticulum stress or defect in neutrophil elastase (ELANE) expression or localization, all neutrophil functions appeared to be normal. We showed a disorganization of the Golgi apparatus in CS neutrophils precursors, that correlates with an altered glycosylation of ICAM-1 in these cells, as evidenced by a migration shift of the protein. Furthermore, a striking decrease in the expression of SERPINB1 gene, which encodes a critical component of neutrophil survival, was detected in CS neutrophils. These abnormalities may account for the excessive apoptosis of neutrophils leading to neutropenia in CS. KEY MESSAGES: Cohen syndrome patients' neutrophils display normal morphology and functions. Cohen syndrome patients' neutrophils have an increased rate of spontaneous apoptosis compared to healthy donors' neutrophils. No ER stress or defective ELA2 expression or glycosylation was observed in Cohen syndrome patients' neutrophils. SerpinB1 expression is significantly decreased in Cohen syndrome neutrophils as well as in VPS13B-deficient cells.

Neutropenia in the age of genetic testing: Advances and challenges

Identification of genetic causes of neutropenia informs precision medicine approaches to medical management and treatment. Accurate diagnosis of genetic neutropenia disorders informs treatment options, enables risk stratification, cancer surveillance, and attention to associated medical complications. The rapidly expanding genetic testing options for the evaluation of neutropenia have led to exciting advances but also new challenges. This review provides a practical guide to germline genetic testing for neutropenia.