The novel zebrafish model pretzel demonstrates a central role for SH3PXD2B in defective collagen remodelling and fibrosis in Frank-Ter Haar syndrome.

Ivo J. H. M. de Vos,Jason Taslim,Arnette Shi Wei Wong,Maurice A. M. van Steensel,Julian L. Goggi,Thomas J. Carney,Sheena Li Ming Ong,Nicole C. Syder

doi:10.1242/bio.054270

Abstract

ABSTRACTFrank-Ter Haar syndrome (FTHS, MIM #249420) is a rare skeletal dysplasia within the defective collagen remodelling spectrum (DECORS), which is characterised by craniofacial abnormalities, skeletal malformations and fibrotic soft tissues changes including dermal fibrosis and joint contractures. FTHS is caused by homozygous or compound heterozygous loss-of-function mutation or deletion of SH3PXD2B (Src homology 3 and Phox homology domain-containing protein 2B; MIM #613293). SH3PXD2B encodes an adaptor protein with the same name, which is required for full functionality of podosomes, specialised membrane structures involved in extracellular matrix (ECM) remodelling. The pathogenesis of DECORS is still incompletely understood and, as a result, therapeutic options are limited. We previously generated an mmp14a/b knockout zebrafish and demonstrated that it primarily mimics the DECORS-related bone abnormalities. Here, we present a novel sh3pxd2b mutant zebrafish, pretzel, which primarily reflects the DECORS-related dermal fibrosis and contractures. In addition to relatively mild skeletal abnormalities, pretzel mutants develop dermal and musculoskeletal fibrosis, contraction of which seems to underlie grotesque deformations that include kyphoscoliosis, abdominal constriction and lateral folding. The discrepancy in phenotypes between mmp14a/b and sh3pxd2b mutants suggests that in fish, as opposed to humans, there are differences in spatiotemporal dependence of ECM remodelling on either sh3pxd2b or mmp14a/b. The pretzel model presented here can be used to further delineate the underlying mechanism of the fibrosis observed in DECORS, as well as screening and subsequent development of novel drugs targeting DECORS-related fibrosis.This paper has an associated First Person interview with the first author of the article.

Highlights

Frank-Ter Haar syndrome (FTHS, MIM #249420) is a skeletal dysplasia, characterised by craniofacial abnormalities, skeletal malformations, and a generalised reduction in bone mineral density
Quantitative polymerase chain reaction analysis of 2-month-old sh3pxd2bΔ/Δ homozygous mutants and their sh3pxd2b+/+ wild type (WT) clutch mates demonstrated that the CRISPR-induced mutation had no significant effect on sh3pxd2b mRNA expression (Fig. S1D; 8% increase in expression of mutant sh3pxd2b relative to WT sh3pxd2b, P=0.0706)
Regardless of this unexpected cleavage, all WT bands are larger than the mutant band, suggesting that we successfully generated a mutation in zebrafish sh3pxd2b with a similar truncating effect as mutations identified in FTHS patients

Summary

Introduction

Frank-Ter Haar syndrome (FTHS, MIM #249420) is a skeletal dysplasia, characterised by craniofacial abnormalities, skeletal malformations, and a generalised reduction in bone mineral density. SH3PXD2B encodes an adaptor protein with the same name, alternatively known as tyrosine kinase substrate with four SH3 domains (TKS4), with an amino (N-) PX domain that binds phosphoinositides [PI3P and PI(3,4)P2] in membranes, and four SH3 domains that bind other proteins (Buschman et al, 2009; Iqbal et al, 2010) It is involved in recruiting matrix metalloproteinase 14 (MMP14) to membrane structures called podosomes, which adhere to and degrade extracellular matrix (ECM) (Buschman et al, 2009; Murphy and Courtneidge, 2011; Hoshino et al, 2013). We previously generated an mmp14a/b knockout (KO) zebrafish and demonstrated that it primarily mimics the DECORS-related bone abnormalities

Methods

Results

Conclusion