Approfondimenti sulle displasie scheletriche: generazione e caratterizzazione di un nuovo modello zebrafish

Osteogenesis imperfecta (OI) is a heritable connective tissue disorder characterized by bone fragility, recurrent fractures, and skeletal deformities. While most cases are caused by mutations in COL1A1 and COL1A2, an increasing number of recessive forms are associated with defects in genes encoding proteins involved in collagen post-translational modification, folding, and secretion as well as in osteoblast differentiation and activity. Recent studies have identified SUCO, a glycosylated transmembrane protein of the endoplasmic reticulum (ER), as a potential candidate gene in OI, although its function remains unknown. Evidence from a whole mouse knockout model indicates that Suco is essential for skeletal development and osteoblast differentiation, but perinatal lethality prevents detailed in vivo studies. To address this limitation, a zebrafish (Danio rerio) suco⁻/⁻ line was generated through ENU mutagenesis and validated by Sanger sequencing. A robust allele-specific PCR (AS-PCR) method was developed for genotyping, enabling the rapid genotype discrimination. Gene expression analysis revealed reduced suco transcript levels, consistent with nonsense-mediated mRNA decay (NMD) activation. Mutant fish exhibited high lethality, growth impairment, and severe skeletal abnormalities. Biochemical investigations further indicated overmodification of collagen type I, suggestive of defects in folding and maturation. Collectively, these findings demonstrate that loss of SUCO function results in a phenotype consistent with severe OI. Thus, the suco⁻/⁻ zebrafish line represents a valuable experimental model to investigate the SUCO role in collagen biosynthesis and skeletal development.