Glypican4 promotes cardiac specification and differentiation by attenuating canonical Wnt and Bmp signaling

Abstract

Glypicans are heparan sulphate proteoglycans (HSPGs) attached to the cell membrane by a glycosylphosphatidylinositol (GPI) anchor, and interact with various extracellular growth factors and receptors. The Drosophila division abnormal delayed (dally) was the first glypican lossof-function mutant described that displays disrupted cell divisions in the eye and morphological defects in the wing. In human, as in most vertebrates, six glypican-encoding genes have been identified (GPC1-6), and mutations in several glypican genes cause multiple malformations including congenital heart defects. To understand better the role of glypicans during heart development, we studied the zebrafish knypek mutant, which is deficient for Gpc4. Our results demonstrate that knypek/gpc4 mutant embryos display severe cardiac defects, most apparent by a strong reduction in cardiomyocyte numbers. Cell-tracing experiments, using photoconvertable fluorescent proteins and genetic labeling, demonstrate that Gpc4 'Knypek' is required for specification of cardiac progenitor cells and their differentiation into cardiomyocytes. Mechanistically, we show that Bmp signaling is enhanced in the anterior lateral plate mesoderm of knypek/gpc4 mutants and that genetic inhibition of Bmp signaling rescues the cardiomyocyte differentiation defect observed in knypek/gpc4 embryos. In addition, canonical Wnt signaling is upregulated in knypek/gpc4 embryos, and inhibiting canonical Wnt signaling in knypek/gpc4 embryos by overexpression of the Wnt inhibitor Dkk1 restores normal cardiomyocyte numbers. Therefore, we conclude that Gpc4 is required to attenuate both canonical Wnt and Bmp signaling in the anterior lateral plate mesoderm to allow cardiac progenitor cells to specify and differentiate into cardiomyocytes. This provides a possible explanation for how congenital heart defects arise in glypican-deficient patients.

Glypican 4 and Mmp14 interact in regulating the migration of anterior endodermal cells by limiting extracellular matrix deposition

“…Recently, it was shown that, in the pLLP, Gpc4 affects the expression of sonic hedgehog (Shh) during the development of muscle cells, which express the chemokine that directs LLP migration (Venero Galanternik et al, 2016). Similarly, Gpc4 regulates the specification and differentiation of cardiac mesoderm by attenuating Wnt and Bmp signaling in the anterior lateral plate mesoderm where cardiac cells are located (Strate et al, 2015). In the zebrafish gastrula, gpc4 is expressed ubiquitously (Topczewski et al, 2001).…”

Agonists and Antagonists of TGF-β Family Ligands

“…Both glypican-1 and -3 also bind BMP-2 and block BMP-2 signaling in cranial osteogenesis (Dwivedi et al 2013). In zebrafish, glypican-4 attenuates BMP signaling to regulate cardiac development (Strate et al 2015). As glypicans also regulate Wnt, hedgehog, and FGF signaling (Bernfield et al 1999;Lin and Perrimon 2000;Fico et al 2011), the six vertebrate glypicans may differentially modulate overlapping and distinct signaling pathways during vertebrate embryogenesis and homeostasis.…”

Developmental Alterations in Heart Biomechanics and Skeletal Muscle Function in Desmin Mutants Suggest an Early Pathological Root for Desminopathies

“…The following lines were used in this study: wild-type AB, desma ct122Gta and desma ct122aRGt lines (Trinh et al, 2011), desma sa5 (Kettleborough et al, 2013), Tg(myl7:egfp) (Huang et al, 2003), Tg(myl7:ras-eGFP) s883 (D'Amico et al, 2007), Tg(fli1a:neGFP) y7 (Roman et al, 2002), Tg(fli:gal4FF ubs ; UAS:kaede) (Herwig et al, 2011), Tg(myl7:GalFF; UAS:RFP) hu6228 (Strate et al, 2015), and Tg(UAS:gcamp3.0; Gal4s1020t) (Warp et al, 2012) and were described previously. Embryos were staged according to hours (hpf) and days postfertilization (dpf).…”