Grant: Discovery Grants Program - Individual

My research program focuses on the analysis of the molecular mechanisms underlying fin development in zebrafish with a special interest in the mechanisms that may have contributed to the evolution of the paired fins (pectoral, pelvic) into the limbs of tetrapod species. During embryogenesis, the pectoral fin bud shows a lot of similarity with the limb bud, but fin development quickly diverges starting with the formation of a fin fold that is supported by rigid fibers called actinotrichia. These fibers are also guiding the migration of mesenchyme to populate the developing fold. Later, the actinotrichia are located at the tip of the rays of adult fish. We previously identified actinodins as one of the components of the actinotrichia. Actinodins and actinotrichia are fish-specific as they disappear during evolution in tetrapod species during the fin-to-limb transition. Knock-out of two actinodin genes, and1 and2, results in an absence of actinotrichia in the double mutant fish that also present with fewer rays and with ray patterning defects. These findings support our hypothesis of an important contribution of actinotrichia loss during evolution of the vertebrate appendage. In the coming five years, my research program will integrate data and reagents from our previous work to further investigate actinotrichia composition, synthesis, regulation and contribution to fin formation and fish fitness. The long-term goal of this program will allow us to better understand fin development and provide a better insight into the fin-to-limb transition. More specifically, I propose the following 4 aims: 1)We will examine actinotrichia function in osteoblast organization and differentiation of developing rays by comparison of wildtype and actinodin double mutants. 2)We will examine actinotrichia function in endoskeletal patterning of the caudal fin and in fish fitness by comparing wildtype fish and actinodin double mutants. 3)We will examine regulation of and1 expression by Hox13 transcription factors by creating deletions of regulatory elements using CRISPR/Cas9. 4)We will use mass spectrometry to compare composition of actinotrichia and ceratotrichia from a shark species to get an insight at their functional relationships. Investigating the structure and the role of actinotrichia, that, we propose are essential for formation and patterning of fin rays but also for fish fitness and behaviour, provides a better insight into the evolutionary changes that may have resulted from the loss of these fibers during the fin-to-limb transition. In addition, understanding the regulatory link between And1 and Hox13 proteins will shed light on how regulatory changes contributed to the loss of the actinodin genes from the tetrapod genome. This program that provides a genetic view of fundamental changes taking place during vertebrate evolution, also offers excellent opportunities for trainees for hands-on learning in state-of-the-art experimental approaches.