Zebrafish as a model for Catel–Manzke syndrome—identification and characterization of the zebrafish <scp> <i>TGDS</i> </scp> ortholog

Catel-Manzke syndrome (CMS) is a rare genetic disorder associated with mutations in the TDP-glucose 4,6-dehydratase (TGDS) gene, the function of which in vertebrates remains unclear. This study investigated the zebrafish ortholog tgds to assess its suitability for modeling the disease. During development, the tgds transcript exhibits a conserved biphasic expression pattern with an initial maternal contribution followed by a second wave of expression after gastrulation. Recombinant zebrafish Tgds expressed in Escherichia coli demonstrated UDP-D-glucose 4,6-dehydratase (EC4.2.1.76) activity, similar to TGDS orthologs in lower eukaryotes, where it acts as the first step in the L-rhamnose biosynthetic pathway. This finding suggests the presence of a yet unidentified pathway in vertebrates. Furthermore, CMS-associated mutations in conserved residues significantly impair enzyme activity and stability. CRISPR/Cas9-mediated F₀ knockout of tgds resulted in a range of developmental defects in zebrafish. In particular, craniofacial cartilage alterations, associated with a decrease in sulfate glycosaminoglycan content, mirrored some skeletal features observed in humans with CMS. These findings establish the zebrafish as a relevant model to further explore CMS pathogenesis and the in vivo function of tgds.