Midkine (Mdk) is a heparin-binding growth factor in development, reproduction, and repair. It plays a pivotal role in the etiology of inflammatory and malignant diseases. Thus, Mdk secretion and underlying gene transcription may serve as a biomarker for disease detection and monitoring. In the present work, the midkine gene in Piaractus orinoquensis (red-bellied pacu) was characterized using different sequencing techniques and bioinformatic analysis. Gene expression was also evaluated using RT-PCR and qPCR under a brain injury model. As a result, the complete open reading frame of midkine for red-bellied pacu was obtained with the presence of two orthologs (Mdka and Mdkb). Phylogenetic analysis grouped midkine with its other orthologs in teleost fish. In the sequence analysis, both P. orinoquensis midkines share highly conserved regions with teleosts and tetrapods. Both Mdka and Mdkb were expressed across all brain segments. For the expression analysis after brain injury, differential expression was obtained in brain segments with acute and chronic responses, suggesting its significant role in inflammatory and regenerative processes in the central nervous system. Together, these results support the role of midkine as a potential biomarker and highlight the possibility of the use of P. orinoquensis for the study of a brain injury model.

To Cite This Article: Rueda-Gómez DS, Zapata-Guerra NA and Rondón-Barragán IS, 2025. Molecular characterization and gene expression of Midkine (Mdk) in red-bellied pacu (Piaractus orinoquensis); Escobar, 2019. Pak Vet J. http://dx.doi.org/10.29261/pakvetj/2025.177