The ADPKD genespkd1a/bandpkd2regulate extracellular matrix formation

Abstract

SUMMARYMutations in polycystin1 (PKD1) account for the majority of autosomal dominant polycystic kidney disease (ADPKD). PKD1 mutations are also associated with vascular aneurysm and abdominal wall hernia, suggesting a role for polycystin1 in extracellular matrix (ECM) integrity. In zebrafish, combined knockdown of the PKD1 paralogs pkd1a and pkd1b resulted in dorsal axis curvature, hydrocephalus, cartilage and craniofacial defects, and pronephric cyst formation at low frequency (10-15%). Dorsal axis curvature was identical to the axis defects observed in pkd2 knockdown embryos. Combined pkd1a/b, pkd2 knockdown demonstrated that these genes interact in axial morphogenesis. Dorsal axis curvature was linked to notochord collagen overexpression and could be reversed by knockdown of col2a1 mRNA or chemical inhibition of collagen crosslinking. pkd1a/b-and pkd2-deficient embryos exhibited ectopic, persistent expression of multiple collagen mRNAs, suggesting a loss of negative feedback signaling that normally limits collagen gene expression. Knockdown of pkd1a/b also dramatically sensitized embryos to low doses of collagen-crosslinking inhibitors, implicating polycystins directly in the modulation of collagen expression or assembly. Embryos treated with wortmannin or LY-29400 also exhibited dysregulation of col2a1 expression, implicating phosphoinositide 3-kinase (PI3K) in the negative feedback signaling pathway controlling matrix gene expression. Our results suggest that pkd1a/b and pkd2 interact to regulate ECM secretion or assembly, and that altered matrix integrity may be a primary defect underlying ADPKD tissue pathologies.

Cathepsin-Mediated Alterations in TGFß-Related Signaling Underlie Disrupted Cartilage and Bone Maturation Associated With Impaired Lysosomal Targeting

“…S2). (21) Alcian blue stains showed that gnptab/col2a1a double morphants retained ML-like phenotypes ~94% of the time. Further, confocal analyses of immunohistochemically stained fli1a :EGFP confirmed that although type II collagen expression was reduced, MLII chondrocyte organization was not improved (Supplemental Fig.…”

Pkd1 Regulates Lymphatic Vascular Morphogenesis during Development

“…Previous studies investigating the consequences of depleting Polycystin1 (a and b) in zebrafish, found that MO-pkd1a/b embryos exhibit a specific body curvature phenotype (Mangos et al, 2010). We injected MO-pkd1b into our putative pkd1a mutant embryos and robustly induced this phenotype, confirming that the lyc1 mutation is a pkd1a loss-of-function allele (Figure 2C and Figure S4).…”

“…We injected MO-pkd1b into our putative pkd1a mutant embryos and robustly induced this phenotype, confirming that the lyc1 mutation is a pkd1a loss-of-function allele (Figure 2C and Figure S4). Pkd1 and Pkd2 can modulate extracellular matrix (ECM) formation (Mangos et al, 2010). Importantly, even the most phenotypically penetrant lyc1 (pkd1a) mutants for lymphangiogenesis do not display body curvature defects associated with altered ECM.…”

“…Morpholino against pkd1a (MO ex8), pkd1b (MO ex45) and pkd2 (MO ATG) were described in (Mangos et al, 2010, Obara et al, 2006) and were injected at 5, 7.5 or 10ng/embryo as described (Hogan et al, 2008). …”

Systems biology of polycystic kidney disease: a critical review

“…For example, Pkd2 morpholinos are reported to cause renal cysts but germline mutation of Pkd2 does not 49 . Curiously the cystic phenotype is incompletely penetrant in Pkd1 morphants despite complete knock-down of Pkd1 gene expression 50 .…”