Rbm8a deficiency causes hematopoietic defects by modulating Wnt/PCP signaling.

Defects in blood development frequently occur among syndromic congenital anomalies. Thrombocytopenia-Absent Radius (TAR) syndrome is a rare congenital condition with reduced platelets (hypomegakaryocytic thrombocytopenia) and forelimb anomalies, concurrent with more variable heart and kidney defects. TAR syndrome associates with hypomorphic gene function for RBM8A/Y14 that encodes a component of the exon junction complex involved in mRNA splicing, transport, and nonsense-mediated decay. How perturbing a general mRNA-processing factor causes the selective TAR Syndrome phenotypes remains unknown. Here, we connect zebrafish rbm8a perturbation to early hematopoietic defects via attenuated non-canonical Wnt/Planar Cell Polarity (PCP) signaling that controls developmental cell re-arrangements. In hypomorphic rbm8a zebrafish, we observe a significant reduction of cd41-positive thrombocytes. rbm8a-mutant zebrafish embryos accumulate mRNAs with individual retained introns, a hallmark of defective nonsense-mediated decay; affected mRNAs include transcripts for non-canonical Wnt/PCP pathway components. We establish that rbm8a-mutant embryos show convergent extension defects and that reduced rbm8a function interacts with perturbations in non-canonical Wnt/PCP pathway genes wnt5b, wnt11f2, fzd7a, and vangl2. Using live-imaging, we found reduced rbm8a function impairs the architecture of the lateral plate mesoderm (LPM) that forms hematopoietic, cardiovascular, kidney, and forelimb skeleton progenitors as affected in TAR Syndrome. Both mutants for rbm8a and for the PCP gene vangl2 feature impaired expression of early hematopoietic/endothelial genes including runx1 and the megakaryocyte regulator gfi1aa. Together, our data propose aberrant LPM patterning and hematopoietic defects as consequence of attenuated non-canonical Wnt/PCP signaling upon reduced rbm8a function. These results also link TAR Syndrome to a potential LPM origin and a developmental mechanism.

SIDT2 Associates with Apolipoprotein A1 (ApoA1) and Facilitates ApoA1 Secretion in Hepatocytes.

SIDT2 is a lysosomal protein involved in the degradation of nucleic acids and the transport of cholesterol between membranes. Previous studies identified two "cholesterol recognition/interaction amino acid consensus" (CRAC) motifs in SIDT1 and SIDT2 members. We have previously shown that the first CRAC motif (CRAC-1) is essential for protein translocation to the PM upon cholesterol depletion in the cell. In the present study, we show that SIDT2 and the apolipoprotein A1 (ApoA1) form a complex which requires the second CRAC-2 motif in SIDT2 to be established. The overexpression of SIDT2 and ApoA1 results in enhanced ApoA1 secretion by HepG2 cells. This is not observed when overexpressing the SIDT2 with the CRAC-2 domain mutated to render it unfunctional. All these results provide evidence of a novel role for SIDT2 as a protein forming a complex with ApoA1 and enhancing its secretion to the extracellular space.

Therapeutic Intranasal Vaccine HB-ATV-8 Prevents Atherogenesis and Non-alcoholic Fatty Liver Disease in a Pig Model of Atherosclerosis.

BACKGROUND AND AIMS: Atherosclerosis as an inflammatory disease involved in the etiology of cardiovascular disease worldwide, in our days demands an array of different therapeutic approaches in order to soon be able to visualize an effective prevention. Based on an immunotherapeutic approach, we designed a non-invasive vaccine (HB-ATV-8), contained in a micellar nanoparticle composed of lipids and a peptide segment derived from the C-terminus of the cholesterol-ester transfer protein (CETP). Now we extend our successful proof of concept from the rabbit to a porcine model and investigated its effect in an attempt to undoubtedly establish the efficacy of vaccination in a model closer to the human. METHODS: A preclinical trial was designed to study the efficacy of vaccine HB-ATV-8 in pigs (Large White × Landrace). Male experimental animals were fed with standard diet (control), high fat diet (HFD) or the same HFD but treated with HB-ATV-8 (HFD + Vaccine) applied nasally for up to 7 months. All biochemical and enzymatic analyses were performed in peripheral venous blood and thoracic aorta and liver samples examined using conventional, two-photon excitation and second harmonic generation microscopy to identify atherosclerotic and hepatic lesions. mRNA concentrations for KLF2, ACTA2, SOD1, COL1A1 genes and protein levels for PPARα and ABCA1 were quantified in aorta and liver respectively using qPCR and Western blot analysis. RESULTS: The administration of vaccine HB-ATV-8 induced anti-CETP IgG antibodies and reduced atherosclerotic and hepatic lesions promoted by the high fat diet. In addition, plasma triglyceride levels of vaccine treated pigs fed the HFD were similar to those of control group, in contrast to high concentrations reached with animals exclusively fed with HFD. Moreover, HFD promotes a tendency to decrease hepatic PPARα levels and increase in aorta gene expression of KLF2, ACTA2, SOD1 and COL1A1, while vaccine application promotes recovery close to control values. CONCLUSIONS: Vaccine HB-ATV-8 administration constitutes a promissory preventive approach useful in the control of atherogenesis and fatty liver disease. The positive results obtained, the non-invasive characteristics of the vaccine, the simple design employed in its conception and its low production cost, support the novelty of this therapeutic strategy designed to prevent the process of atherogenesis and control the development of fatty liver disease.