Lymphocytes Utilize Somatic Mutations, Epigenetic Silencing, and the Proteasome to Escape Truncated WASP Expression.

Wiskott-Aldrich Syndrome Protein (WASP) deficiency causes Wiskott-Aldrich Syndrome (WAS), a sex-linked disorder characterized by combined immunodeficiency, microthrombocytopenia, and eczema. Like WASP-deficient humans, WASP-deficient mice produce normal numbers of functionally defective T cells. Here, we report a WAS patient with a novel germline frameshifting WAS mutation encoding a truncated form of WASP lacking the C-terminal cofilin homology (C) and the acidic region (A) domains (WASPΔCA). Although stably overexpressed in embryonic kidney cell lines, WASPΔCA was undetectable in circulating patient leukocytes. Deep sequencing, transcript profiling, and protein degradation analyses demonstrated patient lymphocytes employ an array of genetic, epigenetic, and proteasomal strategies to avoid expressing WASPΔCA.

Constrained chromatin accessibility in PU.1-mutated agammaglobulinemia patients.

The pioneer transcription factor (TF) PU.1 controls hematopoietic cell fate by decompacting stem cell heterochromatin and allowing nonpioneer TFs to enter otherwise inaccessible genomic sites. PU.1 deficiency fatally arrests lymphopoiesis and myelopoiesis in mice, but human congenital PU.1 disorders have not previously been described. We studied six unrelated agammaglobulinemic patients, each harboring a heterozygous mutation (four de novo, two unphased) of SPI1, the gene encoding PU.1. Affected patients lacked circulating B cells and possessed few conventional dendritic cells. Introducing disease-similar SPI1 mutations into human hematopoietic stem and progenitor cells impaired early in vitro B cell and myeloid cell differentiation. Patient SPI1 mutations encoded destabilized PU.1 proteins unable to nuclear localize or bind target DNA. In PU.1-haploinsufficient pro-B cell lines, euchromatin was less accessible to nonpioneer TFs critical for B cell development, and gene expression patterns associated with the pro- to pre-B cell transition were undermined. Our findings molecularly describe a novel form of agammaglobulinemia and underscore PU.1's critical, dose-dependent role as a hematopoietic euchromatin gatekeeper.

Identification and characterization of agnuside, a natural proangiogenic small molecule.

Due to its important role in regulating angiogenesis, vascular homeostasis and remodeling, and arteriogenesis in blood vascular and lymphatic endothelial cells, VEGFR2 stimulation has demonstrated promise in preclinical studies as an endovascular treatment for ischemic myocardial and peripheral disease. However, the short half-life of protein- and cytokine-based strategies and transduction inefficiency of vector-based modalities have hindered its clinical therapeutic applications. In the present study, we used a streamlined bioinformatics strategy combining ligand-based pharmacophore development and validation, virtual screening, and molecular docking to identify agnuside, a non-toxic, natural small molecule extract of Vitex agnus-castus possessing strong binding affinity, druggable physiochemical properties, and conformationally stable hydrogen bond and hydrophobic interactions with catalytically important residues within VEGFR2's active and allosteric sites. In-vitro proliferation, tube formation, and scratch wound migration assays provide evidence that agnuside promotes endothelial cell angiogenesis. Agnuside increases HUVEC proliferation with an EC50 of 1.376 µg/mL, stimulates tubulogenesis dose-dependently, and increases scratch wound migration rate. An additional angiogenesis assay suggests that agnuside may actively compete with a VEGFR2 inhibitor for VEGFR2 binding site occupancy to increase total length and branching length of HUVEC tubular networks. Chemometric analysis of molecular interaction fields (MIFs) by partial least squares (PLS)-derived quantitative structure activity relationship (QSAR) analysis and MIF contours provides the framework for the formulation of agnuside analogues possessing greater potency. Our research supports that agnuside may be a lead molecule for therapeutic angiogenesis.