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

Frank-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 (Src homology 3 and Phox homology domain-containing protein 2B; MIM #613293). 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 knockout zebrafish and demonstrated that it primarily mimics the DECORS-related bone abnormalities. Here, we present a novel mutant zebrafish, , which primarily reflects the DECORS-related dermal fibrosis and contractures. In addition to relatively mild skeletal abnormalities, 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 and mutants suggests that in fish, as opposed to humans, there are differences in spatiotemporal dependence of ECM remodelling on either or The 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.