Abstract
Introduction Collagen fibers from the marine sponge Chondrosia reniformis have been extensively studied for their biotechnological potential in regenerative medicine and drug delivery applications. However, the molecular characterization of the genes encoding these fibrillar collagens has not yet been clarified. Methods In this study, we used an integrated genomic, transcriptomic and experimental approach to identify and characterize the repertoire of fibrillar collagen genes in C. reniformis . Gene organization, predicted protein features, quantitative PCR expression analyses and in situ hybridization experiments were performed. Results Our analysis revealed the presence of five fibrillar collagen genes, two located on chromosome 2 and three on chromosome 13. Gene size, exon–intron organization and predicted protein features closely resemble those observed in bilaterian fibrillar collagens. Quantitative PCR analyses demonstrated that all five genes are expressed in adult specimens, with Colf1 and Colf4 representing the most abundant transcripts. Although Colf3 showed generally low expression levels, particularly in the choanosome, it was significantly enriched in the ectosome region, suggesting a possible functional specialization related to extracellular matrix organization and collagen fiber dynamics. This hypothesis is supported by specific features of the predicted triple-helical domain of Colf3, including five glycine substitutions that may confer increased fiber flexibility. In situ hybridization analyses revealed distinct spatial expression patterns, with numerous lophocytes expressing fibrillar collagen genes in the mesohyl, while transcript production in the ectosome appeared restricted to a limited number of highly active cells. Discussion Overall, these findings provide new molecular insights into fibrillar collagen diversity and tissue-specific expression in C. reniformis , supporting its relevance as a model for sponge extracellular matrix biology and as a reference framework for future studies on collagen-based biomaterials.