Post-gastrulation synthetic embryos generated ex utero from mouse naive ESCs.

In vitro cultured stem cells with distinct developmental capacities can contribute to embryonic or extraembryonic tissues after microinjection into pre-implantation mammalian embryos. However, whether cultured stem cells can independently give rise to entire gastrulating embryo-like structures with embryonic and extraembryonic compartments remains unknown. Here, we adapt a recently established platform for prolonged ex utero growth of natural embryos to generate mouse post-gastrulation synthetic whole embryo models (sEmbryos), with both embryonic and extraembryonic compartments, starting solely from naive ESCs. This was achieved by co-aggregating non-transduced ESCs, with naive ESCs transiently expressing Cdx2 or Gata4 to promote their priming toward trophectoderm and primitive endoderm lineages, respectively. sEmbryos adequately accomplish gastrulation, advance through key developmental milestones, and develop organ progenitors within complex extraembryonic compartments similar to E8.5 stage mouse embryos. Our findings highlight the plastic potential of naive pluripotent cells to self-organize and functionally reconstitute and model the entire mammalian embryo beyond gastrulation.

Lessons Learned From Five Years of Newborn Screening for Severe Combined Immunodeficiency in Israel.

BACKGROUND: Implementation of newborn screening (NBS) programs for severe combined immunodeficiency (SCID) have advanced the diagnosis and management of affected infants and undoubtedly improved their outcomes. Reporting long-term follow-up of such programs is of great importance. OBJECTIVE: We report a 5-year summary of the NBS program for SCID in Israel. METHODS: Immunologic and genetic assessments, clinical analyses, and outcome data from all infants who screened positive were evaluated and summarized. RESULTS: A total of 937,953 Guthrie cards were screened for SCID. A second Guthrie card was requested on 1,169 occasions (0.12%), which resulted in 142 referrals (0.015%) for further validation tests. Flow cytometry immune-phenotyping, T cell receptor excision circle measurement in peripheral blood, and expression of TCRVß repertoire for the validation of positive cases revealed a specificity and sensitivity of 93.7% and 75.9%, respectively, in detecting true cases of SCID. Altogether, 32 SCID and 110 non-SCID newborns were diagnosed, making the incidence of SCID in Israel as high as 1:29,000 births. The most common genetic defects in this group were associated with mutations in DNA cross-link repair protein 1C and IL-7 receptor α (IL-7Rα) genes. No infant with SCID was missed during the study time. Twenty-two SCID patients underwent hematopoietic stem cell transplantation, which resulted in a 91% survival rate. CONCLUSIONS: Newborn screening for SCID should ultimately be applied globally, specifically to areas with high rates of consanguineous marriages. Accumulating data from follow-up studies on NBS for SCID will improve diagnosis and treatment and enrich our understanding of immune development in health and disease.

Bariatric Surgery-Associated Myelopathy.

Bariatric surgery is gaining acceptance as an efficient treatment modality for adults and adolescents with morbid obesity. The early postbariatric period has the potential to induce an immunomodulatory imbalance due to the development or worsening of nutritional deficiencies, changes in hormonal balance (specifically after sleeve gastrectomy), and a shift in the proinflammatory cytokine profile along with a major change in the gut microbiome and permeability. These changes may induce encephalomyelitic T cell activity, change neural barrier permeability, and induce gut dysbioisis, favoring a proinflammatory metabolic profile. Such changes, in genetically prone individuals or those with additional risk factors, may lead to the development of myelopathy, particularly MS. Key Message: Postbariatric myelopathy is rare but should be considered in bariatric patients with relevant complaints in the postoperative period.

Principles of signaling pathway modulation for enhancing human naive pluripotency induction.

Isolating human MEK/ERK signaling-independent pluripotent stem cells (PSCs) with naive pluripotency characteristics while maintaining differentiation competence and (epi)genetic integrity remains challenging. Here, we engineer reporter systems that allow the screening for defined conditions that induce molecular and functional features of human naive pluripotency. Synergistic inhibition of WNT/ß-CATENIN, protein kinase C (PKC), and SRC signaling consolidates the induction of teratoma-competent naive human PSCs, with the capacity to differentiate into trophoblast stem cells (TSCs) and extraembryonic naive endodermal (nEND) cells in vitro. Divergent signaling and transcriptional requirements for boosting naive pluripotency were found between mouse and human. P53 depletion in naive hPSCs increased their contribution to mouse-human cross-species chimeric embryos upon priming and differentiation. Finally, MEK/ERK inhibition can be substituted with the inhibition of NOTCH/RBPj, which induces alternative naive-like hPSCs with a diminished risk for deleterious global DNA hypomethylation. Our findings set a framework for defining the signaling foundations of human naive pluripotency.

Varicella vaccine strain infection in a non-immunocompromised patient. A case report and review of literature.

Varicella live attenuated vaccine led to a significant reduction in morbidity and mortality from varicella zoster disease. Vaccine adverse effects are mostly mild. Immunosuppression is the main risk factor for severe varicella. Risk factors for disease following vaccination are less studied. We report a 12-month-old infant with no T-cell immunodeficiency who developed severe varicella infection by vaccine strain.

Novel NCF2 Mutation Causing Chronic Granulomatous Disease.

Chronic granulomatous disease (CGD) is a rare primary immunodeficiency disorder caused by defects in the NADPH oxidase complex. Mutations in NCF2 encoding the cytosolic factor p67phox result in autosomal recessive CGD. We describe three patients with a novel c.855G>C NCF2 mutation presenting with diverse clinical phenotype. Two siblings were heterozygous for the novel mutation and for a previously described exon 8-9 duplication, while a third unrelated patient was homozygous for the novel mutation. Mutation pathogenicity was confirmed by abnormal DHR123 assay and absent p67phox production and by sequencing of cDNA which showed abnormal RNA splicing. Clinically, the homozygous patient presented with suspected early onset interstitial lung disease and NCF2 mutation was found on genetic testing performed in search for surfactant-related defects. The two siblings also had variable presentation with one having history of severe pneumonia, lymphadenitis, and recurrent skin abscesses and the other presenting in his 30s with discoid lupus erythematosus and without significant infectious history. We therefore identified a novel pathogenic NCF2 mutation causing diverse and unusual clinical phenotype.

Minor Clinical Impact of COVID-19 Pandemic on Patients With Primary Immunodeficiency in Israel.

In the last few months the world has witnessed a global pandemic due to severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection causing coronavirus disease 2019 (COVID-19). Obviously, this pandemic affected individuals differently, with a significant impact on populations considered to be at high-risk. One such population, was assumed to be patients with primary genetic defect involving components or pathways of the immune system. While human immunity against COVID-19 is not fully understood, it is, so far, well documented, that both adaptive and innate cells have a critical role in protection against SARS-CoV-2. Here, we aimed to summarize the clinical and laboratory data on primary immunodeficiency (PID) patients in Israel, who were tested positive for SARS-CoV-2, in order to estimate the impact of COVID-19 on such patients. Data was collected from mid-February to end-September. During this time Israel experienced two "waves" of COVID-19 diseases; the first, from mid-February to mid-May and the second from mid-June and still ongoing at the end of data collection. A total of 20 PID patients, aged 4 months to 60 years, were tested positive for SARS-CoV-2, all but one, were detected during the second wave. Fourteen of the patients were on routine monthly IVIG replacement therapy at the time of virus detection. None of the patients displayed severe illness and none required hospitalization; moreover, 7/20 patients were completely asymptomatic. Possible explanations for the minimal clinical impact of COVID-19 pandemic observed in our PID patients include high level of awareness, extra-precautions, and even self-isolation. It is also possible that only specific immune pathways (e.g. type I interferon signaling), may increase the risk for a more severe course of disease and these are not affected in many of the PID patients. In some cases, lack of an immune response actually may be a protective measure against the development of COVID-19 sequelae.

Primary Cutaneous Clonal CD8+ T-Cell Lymphoproliferative Disorder Associated With Immunodeficiency due to RAG1 Mutation.

The development of T-cell lymphomas, granulomatous reactions, and autoimmunity has been observed in immunodeficiency due to milder forms of recombination activating gene (RAG) deficiency. A few cases of cutaneous clonal papulonodular CD8 lymphocytic infiltrates and cutaneous CD8 granulomatous T-cell lymphoma have been described in association with common variable immunodeficiency, and with X-linked agammaglobulinemia. We describe a 15-year-old girl with several autoimmune disorders and recurrent infections that presented with several nodules on her cheek. Histopathological studies demonstrate histological, immunohistochemical, and molecular findings compatible with a primary cutaneous clonal CD8 T-cell lymphoproliferative disorder. Vacuolar interface changes were also seen in the involved skin, reminiscent of cutaneous lupus erythematosus. Molecular genetic analysis revealed a germline novel homozygous missense mutation in RAG1 (T1003>C). The parents were heterozygous carriers. The facial cutaneous lesions recurred despite local radiation therapy. Because of recurrent life-threatening systemic infections, allogeneic bone marrow transplantation was performed. The pathogenesis of this primary cutaneous clonal CD8 T-cell lymphoproliferative disorder may have been related to a chronic stimulation of autoreactive T cells in the involved skin paired with reduced RAG1 activity.

Deterministic Somatic Cell Reprogramming Involves Continuous Transcriptional Changes Governed by Myc and Epigenetic-Driven Modules.

The epigenetic dynamics of induced pluripotent stem cell (iPSC) reprogramming in correctly reprogrammed cells at high resolution and throughout the entire process remain largely undefined. Here, we characterize conversion of mouse fibroblasts into iPSCs using Gatad2a-Mbd3/NuRD-depleted and highly efficient reprogramming systems. Unbiased high-resolution profiling of dynamic changes in levels of gene expression, chromatin engagement, DNA accessibility, and DNA methylation were obtained. We identified two distinct and synergistic transcriptional modules that dominate successful reprogramming, which are associated with cell identity and biosynthetic genes. The pluripotency module is governed by dynamic alterations in epigenetic modifications to promoters and binding by Oct4, Sox2, and Klf4, but not Myc. Early DNA demethylation at certain enhancers prospectively marks cells fated to reprogram. Myc activity drives expression of the essential biosynthetic module and is associated with optimized changes in tRNA codon usage. Our functional validations highlight interweaved epigenetic- and Myc-governed essential reconfigurations that rapidly commission and propel deterministic reprogramming toward naive pluripotency.

Neutralizing Gatad2a-Chd4-Mbd3/NuRD Complex Facilitates Deterministic Induction of Naive Pluripotency.

Mbd3, a member of nucleosome remodeling and deacetylase (NuRD) co-repressor complex, was previously identified as an inhibitor for deterministic induced pluripotent stem cell (iPSC) reprogramming, where up to 100% of donor cells successfully complete the process. NuRD can assume multiple mutually exclusive conformations, and it remains unclear whether this deterministic phenotype can be attributed to a specific Mbd3/NuRD subcomplex. Moreover, since complete ablation of Mbd3 blocks somatic cell proliferation, we aimed to explore functionally relevant alternative ways to neutralize Mbd3-dependent NuRD activity. We identify Gatad2a, a NuRD-specific subunit, whose complete deletion specifically disrupts Mbd3/NuRD repressive activity on the pluripotency circuitry during iPSC differentiation and reprogramming without ablating somatic cell proliferation. Inhibition of Gatad2a facilitates deterministic murine iPSC reprogramming within 8 days. We validate a distinct molecular axis, Gatad2a-Chd4-Mbd3, within Mbd3/NuRD as being critical for blocking reestablishment of naive pluripotency and further highlight signaling-dependent and post-translational modifications of Mbd3/NuRD that influence its interactions and assembly.

First Year of Israeli Newborn Screening for Severe Combined Immunodeficiency-Clinical Achievements and Insights.

Severe combined immunodeficiency (SCID), the most severe form of T cell immunodeficiency, is detectable through quantification of T cell receptor excision circles (TRECs) in dried blood spots obtained at birth. Herein, we describe the results of the first year of the Israeli SCID newborn screening (NBS) program. This important, life-saving screening test is available at no cost for every newborn in Israel. Eight SCID patients were diagnosed through the NBS program in its first year, revealing an incidence of 1:22,500 births in the Israeli population. Consanguine marriages and Muslim ethnic origin were found to be a risk factor in affected newborns, and a founder effect was detected for both IL7Rα and DCLRE1C deficiency SCID. Lymphocyte subset analysis and TREC quantification in the peripheral blood appear to be sufficient for confirmation of typical and leaky SCID and ruling out false positive (FP) results. Detection of secondary targets (infants with non-SCID lymphopenia) did not significantly affect the management or outcomes of these infants in our cohort. In the general, non-immunodeficient population, TREC rises along with gestational age and birth weight, and is significantly higher in females and the firstborn of twin pairs. Low TREC correlates with both gestational age and birth weight in extremely premature newborns. Additionally, the rate of TREC increase per week consistently accelerates with gestational age. Together, these findings mandate a lower cutoff or a more lenient screening algorithm for extremely premature infants, in order to reduce the high rate of FPs within this group. A significant surge in TREC values was observed between 28 and 30 weeks of gestation, where median TREC copy numbers rise by 50% over 2 weeks. These findings suggest a maturational step in T cell development around week 29 gestation, and imply moderate to late preterms should be screened with the same cutoff as term infants. The SCID NBS program is still in its infancy, but is already bearing fruit in the early detection and improved outcomes of children with SCID in Israel and other countries.

Transient acquisition of pluripotency during somatic cell transdifferentiation with iPSC reprogramming factors.

Somatic cells can be transdifferentiated to other cell types without passing through a pluripotent state by ectopic expression of appropriate transcription factors. Recent reports have proposed an alternative transdifferentiation method in which fibroblasts are directly converted to various mature somatic cell types by brief expression of the induced pluripotent stem cell (iPSC) reprogramming factors Oct4, Sox2, Klf4 and c-Myc (OSKM) followed by cell expansion in media that promote lineage differentiation. Here we test this method using genetic lineage tracing for expression of endogenous Nanog and Oct4 and for X chromosome reactivation, as these events mark acquisition of pluripotency. We show that the vast majority of reprogrammed cardiomyocytes or neural stem cells obtained from mouse fibroblasts by OSKM-induced 'transdifferentiation' pass through a transient pluripotent state, and that their derivation is molecularly coupled to iPSC formation mechanisms. Our findings underscore the importance of defining trajectories during cell reprogramming by various methods.

Stem cells. m6A mRNA methylation facilitates resolution of naïve pluripotency toward differentiation.

Naïve and primed pluripotent states retain distinct molecular properties, yet limited knowledge exists on how their state transitions are regulated. Here, we identify Mettl3, an N(6)-methyladenosine (m(6)A) transferase, as a regulator for terminating murine naïve pluripotency. Mettl3 knockout preimplantation epiblasts and naïve embryonic stem cells are depleted for m(6)A in mRNAs, yet are viable. However, they fail to adequately terminate their naïve state and, subsequently, undergo aberrant and restricted lineage priming at the postimplantation stage, which leads to early embryonic lethality. m(6)A predominantly and directly reduces mRNA stability, including that of key naïve pluripotency-promoting transcripts. This study highlights a critical role for an mRNA epigenetic modification in vivo and identifies regulatory modules that functionally influence naïve and primed pluripotency in an opposing manner.

Leukocyte adhesion deficiency type III: clinical features and treatment with stem cell transplantation.

Leukocyte adhesion deficiency type III (LADIII) is an autosomal recessive disorder that presents with a severe leukocyte adhesion defect and a Glanzmann-type thrombocytopathy. Hematopoietic stem cell transplantation (HSCT)--the only definitive treatment for LADIII--appears to have a high rate of complications. In this study, we describe a new group of patients with LADIII, highlighting further clinical and immunologic aspects of this disease, and reevaluating the effectiveness of HSCT for its treatment. The patients had clinical and laboratory findings consistent with LADIII. Molecular analysis confirmed the presence of a mutation in the kindlin-3 gene. HSCT was carried out in 3 patients and was successful in 2. The diagnosis of LADIII should be considered in all patients who present with recurrent infections and a bleeding diathesis, regardless of the leukocyte count. LADIII is a primary immune deficiency, which can be successfully corrected by bone marrow transplantation if applied early in the course of the disease using appropriate conditioning.

Leukocyte adhesion deficiencies.

Leukocyte trafficking from the blood stream to tissues is essential for continuous surveillance of foreign antigens. This dynamic process, designated as the leukocyte adhesion cascade, involves distinct steps. In leukocyte adhesion deficiency (LAD) I the firm adhesion of leukocyte to the endothelium is defective, due to mutations in the beta 2 integrin gene. LAD II is caused by mutations in the fucose transporter specific to the Golgi apparatus, leading to the absence of Sialyl Lewis X-the fucosylated ligand for the selectins-thus affecting the rolling phase, the first phase of the cascade. In LAD III, a primary activation defect occurs in beta integrins 1, 2, and 3. Recently, the genetic basis for LAD III has been revealed to involve mutations in kindlin-3, a newly recognized essential component of integrin activation-the second phase of the adhesion cascade. Until now, no human or animal models of defect in transmigration-the fourth and last phase of the cascade-has been described.

Functional aberrant expression of CCR2 receptor on chronically activated NK cells in patients with TAP-2 deficiency.

Chemokines play a pivotal role in homeostatic and inflammatory migration of naive and activated natural killer (NK) subsets. Recent studies have shown that aberrant chemokine receptor expression on certain immune cells underlies the pathogenesis of clinical conditions in which recruitment of such cells is altered. Progressive accumulation of activated NK cells, subsequently resulting in the formation of chronic granulomatous lesions in the respiratory tract and the skin, has been described in a number of patients with transporter associated with antigen processing 2 (TAP-2) deficiency in the later stages of disease. Therefore, the goal of the present study was to elucidate whether the dysregulation of chemoattracting receptor expression on NK cells could explain abnormal navigation of these cells in TAP-2 deficiency. High-throughput proteomic comparison, followed by verification with flow cytometry, revealed that chronically activated NK cells derived from 3 newly identified patients with TAP-2 deficiency consistently expressed aberrant levels of CC chemokine receptor 2 (CCR2) chemokine receptor in vitro and in vivo. This expression pattern translated into specific responsiveness of chronically activated NK cells derived from patients with TAP-2 deficiency to multiple ligands of CCR2. Moreover, the in vivo elevated levels of interleukin-2 (IL-2) and monocyte chemoattractant protein-1 (MCP-1) detected in serum and bronchoalveolar lavage samples derived from these patients highlight the potential involvement of the CCR2 pathway in aberrant NK-cell retention at chronic inflammatory sites.