Combined immunodeficiency and hypoglycemia associated with mutations in hypoxia upregulated 1

Loss of Grp170 results in catastrophic disruption of endoplasmic reticulum function

GRP170 (Hyou1) is required for mouse embryonic development, and its ablation in kidney nephrons leads to renal failure. Unlike most chaperones, GRP170 is the lone member of its chaperone family in the ER lumen. However, the cellular requirement for GRP170, which both binds nonnative proteins and acts as nucleotide exchange factor for BiP, is poorly understood. Here, we report on the isolation of mouse embryonic fibroblasts obtained from mice in which LoxP sites were engineered in the Hyou1 loci (Hyou1LoxP/LoxP). A doxycycline-regulated Cre recombinase was stably introduced into these cells. Induction of Cre resulted in depletion of Grp170 protein which culminated in cell death. As Grp170 levels fell we observed a portion of BiP fractionating with insoluble material, increased binding of BiP to a client with a concomitant reduction in its turnover, and reduced solubility of an aggregation-prone BiP substrate. Consistent with disrupted BiP functions, we observed reactivation of BiP and induction of the unfolded protein response (UPR) in futile attempts to provide compensatory increases in ER chaperones and folding enzymes. Together, these results provide insights into the cellular consequences of controlled Grp170 loss and provide hypotheses as to why mutations in the Hyou1 locus are linked to human disease.

Monogenic etiologies of persistent human papillomavirus infections: A comprehensive systematic review

PURPOSE

Persistent human papillomavirus infection (PHPVI) causes cutaneous, anogenital, and mucosal warts. Cutaneous warts include common warts, Treeman syndrome, and epidermodysplasia verruciformis, among others. Although more reports of monogenic predisposition to PHPVI have been published with the development of genomic technologies, genetic testing is rarely incorporated into clinical assessments. To encourage broader molecular testing, we compiled a list of the various monogenic etiologies of PHPVI.

METHODS

We conducted a systematic literature review to determine the genetic, immunological, and clinical characteristics of patients with PHPVI.

RESULTS

The inclusion criteria were met by 261 of 40,687 articles. In 842 patients, 83 PHPVI-associated genes were identified, including 42, 6, and 35 genes with strong, moderate, and weak evidence for causality, respectively. Autosomal recessive inheritance predominated (69%). PHPVI onset age was 10.8 ± 8.6 years, with an interquartile range of 5 to 14 years. GATA2,IL2RG,DOCK8, CXCR4, TMC6, TMC8, and CIB1 are the most frequently reported PHPVI-associated genes with strong causality. Most genes (74 out of 83) belong to a catalog of 485 inborn errors of immunity-related genes, and 40 genes (54%) are represented in the nonsyndromic and syndromic combined immunodeficiency categories.

CONCLUSION

PHPVI has at least 83 monogenic etiologies and a genetic diagnosis is essential for effective management.

Excess dietary sodium partially restores salt and water homeostasis caused by loss of the endoplasmic reticulum molecular chaperone, GRP170, in the mouse nephron

The maintenance of fluid and electrolyte homeostasis by the kidney requires proper folding and trafficking of ion channels and transporters in kidney epithelia. Each of these processes requires a specific subset of a diverse class of proteins termed molecular chaperones. One such chaperone is GRP170, which is an Hsp70-like, endoplasmic reticulum (ER)-localized chaperone that plays roles in protein quality control and protein folding in the ER. We previously determined that loss of GRP170 in the mouse nephron leads to hypovolemia, electrolyte imbalance, and rapid weight loss. In addition, GRP170-deficient mice develop an AKI-like phenotype, typified by tubular injury, elevation of clinical kidney injury markers, and induction of the unfolded protein response (UPR). By using an inducible GRP170 knockout cellular model, we confirmed that GRP170 depletion induces the UPR, triggers an apoptotic response, and disrupts protein homeostasis. Based on these data, we hypothesized that UPR induction underlies hyponatremia and volume depletion in rodents, but that these and other phenotypes might be rectified by supplementation with high salt. To test this hypothesis, control and GRP170 tubule-specific knockout mice were provided with a diet containing 8% sodium chloride. We discovered that sodium supplementation improved electrolyte imbalance and reduced clinical kidney injury markers, but was unable to restore weight or tubule integrity. These results are consistent with UPR induction contributing to the kidney injury phenotype in the nephron-specific GR170 knockout model, and that the role of GRP170 in kidney epithelia is essential to both maintain electrolyte balance and cellular protein homeostasis.

Loss of Grp170 results in catastrophic disruption of endoplasmic reticulum functions

GRP170, a product of the Hyou1 gene, is required for mouse embryonic development, and its ablation in kidney nephrons leads to renal failure. Unlike most chaperones, GRP170 is the lone member of its chaperone family in the ER lumen. However, the cellular requirement for GRP170, which both binds non-native proteins and acts as nucleotide exchange factor for BiP, is poorly understood. Here, we report on the isolation of embryonic fibroblasts from mice in which LoxP sites were engineered in the Hyou1 loci ( Hyou1 LoxP/LoxP ). A doxycycline-regulated Cre recombinase was also stably introduced into these cells. Induction of Cre resulted in excision of Hyou1 and depletion of Grp170 protein, culminating in apoptotic cell death. As Grp170 levels fell we observed increased steady-state binding of BiP to a client, slowed degradation of a misfolded BiP substrate, and BiP accumulation in NP40-insoluble fractions. Consistent with disrupted BiP functions, we observed reactivation of BiP storage pools and induction of the unfolded protein response (UPR) in futile attempts to provide compensatory increases in ER chaperones and folding enzymes. Together, these results provide insights into the cellular consequences of controlled Grp170 loss and insights into mutations in the Hyou1 locus and human disease.

Recurrent Infections and Immunodeficiency Caused by Severe Pancytopenia Associated with a Novel Life-Threatening Mutation in Hypoxia-Upregulated Protein 1

HYOU1 encodes a protein from the endoplasmic reticulum chaperone proteins, expressed to protect cellular mechanisms from stress such as hypoxia, insufficient energy and excessive or insufficient substances, and to restore cell homeostasis. In this study, we report a novel pathogenic variant in HYOU1. The proband, the second patient with pathogenic variant in HYOU1, was a female born to consanguineous parents. A novel homozygous pathogenic variant in HYOU1 (NM_001130991.3: c.1456C>T; p.Arg486Cys) was identified, causing anemia, thrombocytopenia and severe panleukopenia and immunodeficiency in the second month of age, leading to consistent high-grade fever, regression of brain functions and recurrent infections; ultimately resulting in the patient expiring at three and half months of age. Both parents are heterozygous for this variant and have no issues related to this study.

Novel Genetic Discoveries in Primary Immunodeficiency Disorders

The field of Immunology is one that has undergone great expansion in recent years. With the advent of new diagnostic modalities including a variety of genetic tests (discussed elsewhere in this journal), the ability to diagnose a patient with a primary immunodeficiency disorder (PIDD) has become a more streamlined process. With increased availability of genetic testing for those with suspected or known PIDD, there has been a significant increase in the number of genes associated with this group of disorders. This is of great importance as a misdiagnosis of these rare diseases can lead to a delay in what can be critical treatment options. At times, those options can include life-saving medications or procedures. Presentation of patients with PIDD can vary greatly based on the specific genetic defect and the part(s) of the immune system that is affected by the variation. PIDD disorders lead to varying levels of increased risk of infection ranging from a mild increase such as with selective IgA deficiency to a profound risk with severe combined immunodeficiency. These diseases can also cause a variety of other clinical findings including autoimmunity and gastrointestinal disease.

Specific Interaction of DDX6 with an RNA Hairpin in the 3' UTR of the Dengue Virus Genome Mediates G1 Phase Arrest

The extent to which viral genomic RNAs interact with host factors and contribute to host response and disease pathogenesis is not well known. Here, we report that the human RNA helicase DDX6 specifically binds to the viral most conserved RNA hairpin in the A3 element in the dengue 3' UTR, with nanomolar affinities. DDX6 CLIP confirmed the interaction in HuH-7 cells infected by dengue virus serotype 2. This interaction requires three conserved residues-Lys³⁰⁷, Lys³⁶⁷, and Arg³⁶⁹-as well as the unstructured extension in the C-terminal domain of DDX6. Interestingly, alanine substitution of these three basic residues resulted in RNA-independent ATPase activity, suggesting a mechanism by which RNA-binding and ATPase activities are coupled in DEAD box helicases. Furthermore, we applied a cross-omics gene enrichment approach to suggest that DDX6 is functionally related to cell cycle regulation and viral pathogenicity. Indeed, infected cells exhibited cell cycle arrest in G₁ phase and a decrease in the early S phase. Exogenous expression of intact DDX6, but not A3-binding-deficient mutants, alleviated these effects by rescue of the DNA preinitiation complex expression. Disruption of the DDX6-binding site was found in dengue and Zika live-attenuated vaccine strains. Our results suggested that dengue virus has evolved an RNA aptamer against DDX6 to alter host cell states and defined DDX6 as a new regulator of G₁/S transition. IMPORTANCE Dengue virus (DENV) is transmitted by mosquitoes to humans, infecting 390 million individuals per year globally. About 20% of infected patients shows a spectrum of clinical manifestation, ranging from a mild flu-like syndrome, to dengue fever, to life-threatening severe dengue diseases, including dengue hemorrhagic fever and dengue shock syndrome. There is currently no specific treatment for dengue diseases, and the molecular mechanism underlying dengue pathogenesis remains poorly understood. In this study, we combined biochemical, bioinformatics, high-content analysis and RNA sequencing approaches to characterize a highly conserved interface of the RNA genome of DENV with a human factor named DDX6 in infected cells. The significance of our research is in identifying the mechanism for a viral strategy to alter host cell fates, which conceivably allows us to generate a model for live-attenuated vaccine and the design of new therapeutic reagent for dengue diseases.

Biological Function of HYOU1 in Tumors and Other Diseases

Various stimuli induce an unfolded protein response to endoplasmic reticulum stress, accompanied by the expression of endoplasmic reticulum molecular chaperones. Hypoxia-upregulated 1 gene (HYOU1) is a chaperone protein located in the endoplasmic reticulum. HYOU1 expression was upregulated in many diseases, including various cancers and endoplasmic reticulum stress-related diseases. HYOU1 does not only play an important protective role in the occurrence and development of tumors, but also is a potential therapeutic target for cancer. HYOU1 may also be used as an immune stimulation adjuvant because of its anti-tumor immune response, and a molecular target for therapy of many endoplasmic reticulum-related diseases. In this article, we summarize the updates in HYOU1 and discuss the potential therapeutic effects of HYOU1.

New primary immunodeficiency diseases: context and future

PURPOSE OF REVIEW

Primary immunodeficiency diseases (PIDs) are genetic disorders classically characterized by impaired host defense and an increased susceptibility to infections. It is now appreciated that these conditions broadly include variations in the genetic code that cause dysregulated immune function. This review highlights the newly defined PIDs in the 2017 International Union of Immunologic Societies (IUIS) report, current approaches to diagnosing PIDs, and the implications for the future management of PIDs.

RECENT FINDINGS

With the advances in and increased commercial availability of genetic testing and the adoption of the TREC assay into the US Newborn Screening program, the number of identified PIDs has exponentially risen in the past few decades, reaching over 350 disorders. The IUIS Inborn Errors of Immunity committee acknowledged at least 50 new disorders between 2015 and 2017. Furthermore, given the greater recognition of disorders with primarily immune dysregulation, the committee proposed a more inclusive term of 'inborn errors of immunity' to encompass primary immunodeficiencies and immune dysregulation disorders.

SUMMARY

This latest IUIS report underscores the rapid expansion in the PID field with technologic advancements in immunogenetics and clinical screening discovering new genetic diseases, and therefore, paving the way to novel therapeutics and precision medicine.

Advances and highlights in primary immunodeficiencies in 2017

This manuscript reviews selected topics in primary immunodeficiency diseases (PIDDs) published in 2017. These include (1) the role of follicular T cells in the differentiation of B cells and development of optimal antibody responses; (2) impaired nuclear factor κB subunit 1 signaling in the pathogenesis of common variable immunodeficiency, revealing an association between impaired B-cell maturation and development of inflammatory conditions; (3) autoimmune and inflammatory manifestations in patients with PIDDs in T- and B-cell deficiencies, as well as in neutrophil disorders; (4) newly described gene defects causing PIDDs, including exostosin-like 3 (EXTL3), TNF-α-induced protein 3 (TNFAIP3 [A20]), actin-related protein 2/3 complex-subunit 1B (ARPC1B), v-Rel avian reticuloendotheliosis viral oncogene homolog A (RELA), hypoxia upregulated 1 (HYOU1), BTB domain and CNC homolog 2 (BACH2), CD70, and CD55; (5) use of rapamycin and the phosphoinositide 3-kinase inhibitor leniolisib to reduce autoimmunity and regulate B-cell function in the activated phosphoinositide 3-kinase δ syndrome; (6) improved outcomes in hematopoietic stem cell transplantation for severe combined immunodeficiency (SCID) in the last decade, with an overall 2-year survival of 90% in part caused by early diagnosis through implementation of universal newborn screening; (7) demonstration of the efficacy of lentiviral vector-mediated gene therapy for patients with adenosine deaminase-deficient SCID; (8) the promise of gene editing for PIDDs using CRISPR/Cas9 and zinc finger nuclease technology for SCID and chronic granulomatous disease; and (9) the efficacy of thymus transplantation in Europe, although associated with an unexpected high incidence of autoimmunity. The remarkable progress in the understanding and management of PIDDs reflects the current interest in this area and continues to improve the care of immunodeficient patients.

Validation and Automation of a High-Throughput Multitargeted Method for Semiquantification of Endogenous Metabolites from Different Biological Matrices Using Tandem Mass Spectrometry

The use of metabolomics profiling to understand the metabolism under different physiological states has increased in recent years, which created the need for robust analytical platforms. Here, we present a validated method for targeted and semiquantitative analysis of 102 polar metabolites that cover major metabolic pathways from 24 classes in a single 17.5-min assay. The method has been optimized for a wide range of biological matrices from various organisms, and involves automated sample preparation and data processing using an inhouse developed R-package. To ensure reliability, the method was validated for accuracy, precision, selectivity, specificity, linearity, recovery, and stability according to European Medicines Agency guidelines. We demonstrated an excellent repeatability of retention times (CV < 4%), calibration curves (R² ≥ 0.980) in their respective wide dynamic concentration ranges (CV < 3%), and concentrations (CV < 25%) of quality control samples interspersed within 25 batches analyzed over a period of one year. The robustness was demonstrated through a high correlation between metabolite concentrations measured using our method and the NIST reference values (R² = 0.967), including cross-platform comparability against the BIOCRATES AbsoluteIDQp180 kit (R² = 0.975) and NMR analyses (R² = 0.884). We have shown that our method can be successfully applied in many biomedical research fields and clinical trials, including epidemiological studies for biomarker discovery. In summary, a thorough validation demonstrated that our method is reproducible, robust, reliable, and suitable for metabolomics studies.