Wiskott-Aldrich Syndrome in four male siblings from a consanguineous family from Lebanon

A Novel Splicing Mutation Leading to Wiskott-Aldrich Syndrome from a Family

Wiskott-Aldrich syndrome (WAS) is a rare X-linked recessive genetic disease characterized by clinical symptoms such as eczema, thrombocytopenia with small platelets, immune deficiency, prone to autoimmune diseases, and malignant tumors. This disease is caused by mutations of the WAS gene encoding WASprotein (WASP). The locus and type of mutations of the WAS gene and the expression quantity of WASP were strongly correlated with the clinical manifestations of patients. We found a novel mutation in the WAS gene (c.931 + 5G > C), which affected splicing to produce three abnormal mRNA, resulting in an abnormally truncated WASP. This mutation led to a reduction but not the elimination of the normal WASP population, resulting in causes X-linked thrombocytopenia (XLT) with mild clinical manifestations. Our findings revealed the pathogenic mechanism of this mutation.

The opposing effects of two gene defects in STX11 and SLP76 on the disease in a patient with an inborn error of immunity

BACKGROUND

Inborn errors of immunity are mostly monogenic. However, disease phenotype and outcome may be modified by the coexistence of a second gene defect.

OBJECTIVE

We sought to identify the genetic basis of the disease in a patient who experienced bleeding episodes, pancytopenia, hepatosplenomegaly, and recurrent pneumonia that resulted in death.

METHODS

Genetic analysis was done using next-generation sequencing. Protein expression and phosphorylation were determined by immunoblotting. T-cell proliferation and F-actin levels were studied by flow cytometry.

RESULTS

The patient harbored 2 homozygous deletions in STX11 (c.369_370del, c.374_376del; p.V124fs60∗) previously associated with familial hemophagocytic lymphohistiocytosis and a novel homozygous missense variant in SLP76 (c.767C>T; p.T256I) that resulted in an approximately 85% decrease in SLP76 levels and absent T-cell proliferation. The patient's heterozygous family members showed an approximately 50% decrease in SLP76 levels but normal immune function. SLP76-deficient J14 Jurkat cells did not express SLP76 and had decreased extracellular signal-regulated kinase signaling, basal F-actin levels, and polymerization following T-cell receptor stimulation. Reconstitution of J14 cells with T256I mutant SLP76 resulted in low protein expression and abnormal extracellular signal-regulated kinase phosphorylation and F-actin polymerization after T-cell receptor activation compared with normal expression and J14 function when wild-type SLP76 was introduced.

CONCLUSIONS

The hypomorphic mutation in SLP76 tones down the hyperinflammation due to STX11 deletion, resulting in a combined immunodeficiency that overshadows the hemophagocytic lymphohistiocytosis phenotype. To our knowledge, this study represents the first report of the opposing effects of 2 gene defects on the disease in a patient with an inborn error of immunity.

A novel homozygous mutation in RASGRP1 that predisposes to immune dysregulation and immunodeficiency associated with uncontrolled Epstein-Barr virus-induced B cell proliferation

BACKGROUND

RASGRP1-deficiency results in an immune dysregulation and immunodeficiency that manifest as autoimmunity, lymphoproliferation, lymphopenia, defective T cell function, and increased incidence of Epstein-Bar Virus infections and lymphomas.

OBJECTIVE

To investigate the mechanism of autoimmune hemolytic anemia and infections in a male patient of consanguineous parents from Lebanon.

METHODS

Genetic diagnosis was obtained using next generation and Sanger sequencing. Protein expression and phosphorylation were determined by immunoblotting. T and B cell development and function were studied by flow cytometry. Cytokine and immunoglobulin secretions were quantified by enzyme-linked immunosorbent assay.

RESULTS

The patient suffered from severe lymphopenia especially affecting the T cell compartment. Genetic analysis revealed a homozygous insertion of adenine at position 1396_1397 in RASGRP1 that abolished protein expression and downstream Ras signaling. T cells from the patient showed severe activation defects resulting in uncontrolled Epstein-Bar Virus-induced B cell proliferation. B cells from the patient were normal.

CONCLUSION

This report expands the spectrum of mutations in patients with RasGRP1 deficiency, and provides evidence for the important role RasGRP1 plays in the ability of T cells to control Epstein-Bar Virus-induced B cell proliferation.

CLINICAL IMPLICATIONS

Following diagnosis, the patient will be maintained on oral valganciclovir and monitored regularly for Epstein-Bar Virus infections to avoid the development of Epstein-Bar Virus- induced B cell lymphoma. He is also candidate for hematopoietic stem cell transplantation.

Sinonasal diffuse large B-cell lymphoma in a patient with Wiskott-Aldrich syndrome: A case report and literature review

Wiskott-Aldrich syndrome (WAS) is a rare primary immunodeficiency disease with a predisposition towards autoimmunity and lymphoproliferative diseases. Non-Hodgkin lymphoma (NHL) is reported to be the predominant form of malignant tumor in WAS sufferers. Diffuse large B-cell lymphoma (DLBCL) is one of the most common types of NHL while it is uncommon to occur in paranasal sinuses and especially when associated with WAS. In this article, we report a unique case of WAS associated with DLBCL in paranasal sinuses and review the major publications of WAS-related lymphomas that occurred in the head and neck area. This study extends the available therapies for WAS-related lymphomas and emphasizes the significance of recognition for sinonasal lymphomas in WAS patients presenting with sinusitis.

Identification of discriminative gene-level and protein-level features associated with pathogenic gain-of-function and loss-of-function variants

Identifying whether a given genetic mutation results in a gene product with increased (gain-of-function; GOF) or diminished (loss-of-function; LOF) activity is an important step toward understanding disease mechanisms because they may result in markedly different clinical phenotypes. Here, we generated an extensive database of documented germline GOF and LOF pathogenic variants by employing natural language processing (NLP) on the available abstracts in the Human Gene Mutation Database. We then investigated various gene- and protein-level features of GOF and LOF variants and applied machine learning and statistical analyses to identify discriminative features. We found that GOF variants were enriched in essential genes, for autosomal-dominant inheritance, and in protein binding and interaction domains, whereas LOF variants were enriched in singleton genes, for protein-truncating variants, and in protein core regions. We developed a user-friendly web-based interface that enables the extraction of selected subsets from the GOF/LOF database by a broad set of annotated features and downloading of up-to-date versions. These results improve our understanding of how variants affect gene/protein function and may ultimately guide future treatment options.

WIP, YAP/TAZ and Actin Connections Orchestrate Development and Transformation in the Central Nervous System

YAP (Yes-associated protein) and TAZ (transcriptional coactivator with PDZ-binding motif) are transcription co-regulators that make up the terminal components of the Hippo signaling pathway, which plays a role in organ size control and derived tissue homeostasis through regulation of the proliferation, differentiation and apoptosis of a wide variety of differentiated and stem cells. Hippo/YAP signaling contributes to normal development of the nervous system, as it participates in self-renewal of neural stem cells, proliferation of neural progenitor cells and differentiation, activation and myelination of glial cells. Not surprisingly, alterations in this pathway underlie the development of severe neurological diseases. In glioblastomas, YAP and TAZ levels directly correlate with the amount of the actin-binding molecule WIP (WASP interacting protein), which regulates stemness and invasiveness. In neurons, WIP modulates cytoskeleton dynamics through actin polymerization/depolymerization and acts as a negative regulator of neuritogenesis, dendrite branching and dendritic spine formation. Our working hypothesis is that WIP regulates the YAP/TAZ pools using a Hippo-independent pathway. Thus, in this review we will present some of the data that links WIP, YAP and TAZ, with a focus on their function in cells from the central and peripheral nervous systems. It is hoped that a better understanding of the mechanisms involved in brain and nervous development and the pathologies that arise due to their alteration will reveal novel therapeutic targets for neurologic diseases.