OC 53.3 - Syntaxin-2 deficiency results in reduced von Willebrand factor expression in vitro and in vivo

Tuesday, July 12, 2022

11:15 AM – 11:30 AM

Location: ExCel Center, ICC Capital Suite Room 7&12

Presentation Format: Virtual

Presenting Author(s)

MB

Mackenzie Bowman, PhD

Research Associate
Department of Medicine, Queen's University
Gananaque, Ontario, Canada

Co-Author(s)

MH

Megan Hinds

Research Technologist
Department of Medicine, Queen's University, Kingston, Canada
Kingston, Ontario, Canada
PL

Patricia D.A. Lima

Scientist
Department of Medicine, Queen's University, Kingston, Canada
Kingston, Ontario, Canada
EB

Erin Burnett

Veterinary Technician
Queen's University, Pathology and Molecular Medicine
Kingston, Ontario, Canada
CN

Christopher Ng, MD

Assistant Professor
Department of Pediatrics, University of Colorado - Anschutz Medical Campus, Aurora, USA
Aurora, Colorado, United States
David Lillicrap, MD

Professor
Department of Pathology and Molecular Medicine, Queen's University
Kingston, Ontario, Canada
Paula James, MD

Professor
Department of Medicine, Queen's University, Kingston, ON, Canada
Kingston, Ontario, Canada

Background: The genetic association data derived from the original CHARGE analysis identified syntaxin-2 (STX2) as a candidate gene for influencing von Willebrand factor (VWF) plasma levels. STX2 is known to be involved in vesicular transport and protein trafficking. In endothelial cells (ECs) it may play important roles in mediating Weibel-Palade body (WPB) exocytosis.

Aims: To investigate the in vitro and in vivo effect of STX2 deficiency on VWF synthesis and secretion.

Methods: STX2 expression in ECs was assessed via qRT-PCR, western blot and confocal immunofluorescence microscopy. STX2 was depleted in human umbilical vein endothelial cells (HUVECs) using siRNA. Cell supernatants and lysates were collected 72 hours later and VWF:Ag measured via ELISA. VWF mRNA expression was assessed in cell lysates using qRT-PCR. Epimorphin/Stx2 knock out (Stx2-/-) mice were used to evaluate the in vivo effect of STX2 deficiency on VWF. Blood was collected from male and female 8-12 week old wild-type (WT), heterozygous (Stx2+/-) and Stx2-/- mice for the assessment of plasma VWF levels. Tissues were harvested (kidney, lung, liver) for qRT-PCR analysis of VWF in WT, Stx2+/- and Stx2-/- mice.

Results: STX2 was observed in ECs but did not associate with VWF in WPBs (Figure 1A). Depletion of STX2 in HUVECs resulted in significantly lower VWF in the media compared to siCTRL HUVECs (Figure 1B). VWF mRNA levels were lower in siSTX2 HUVEC compared to siCTRL (Figure 1C). In vivo, Stx2-/- mice had lower plasma VWF levels compared to Stx2+/- and WT littermates (Figure 2A). VWF mRNA expression was lower in kidney and lung tissues of Stx2-/- mice compared to WT (Figure 2B).

Conclusion(s): STX2 deficiency leads to a decrease in VWF expression both in vitro and in vivo. The mechanism underlying this remains to be determined, as well as the role of STX2 in von Willebrand disease.