Identification of <scp>MMP</scp> gene family and their expression profiles during scale development in <scp> <i>Gymnocypris przewalskii</i> </scp>

Biomineralization is a biological process whereby organisms synthesize mineralized tissues, such as bones and fish scales. The scales of Gymnocypris przewalskii are highly specialized, present only in specific body regions, making this species an excellent model for studying scale development and biomineralization. Our previous work identified elevated expression levels of several matrix metalloproteinase (MMP) family members at scale-embedded sites. In this study, we systematically analysed the genetic characteristics and expression patterns of the MMP family in G. przewalskii. A total of 20 MMP genes were identified across the entire genome and designated as GpMMPs. Transcriptional analysis demonstrated that GpMMPs, particularly GpMMP2, GpMMP9 and GpMMP13, exhibited high expression levels in the skin around the anal fin-a key site for scale development. Notably, GpMMP13 expression increased consistently throughout the scale development process, whereas GpMMP2 and GpMMP9 exhibited a transient expression pattern characterized by an initial rise followed by a decline. Furthermore, cellular experiments conducted with G. przewalskii myofibroblasts indicated that the expression of these GpMMPs was positively regulated by the TGF-β, Wnt and PI3K-Akt signalling pathways. Collectively, our findings provide novel insights into the role of MMPs in scale development and introduce new perspectives on biomineralization mechanisms.