Thesis prize SFBD 2023: Dr. Julien Leclerc
First prize :
→ Invitation to give a plenary lecture at the European Congress of Developmental Biology, from 25 to 28 September 2023 in Oxford (hubs in Paris and Barcelona).
→ Prize de 1000 €
The 2023 SFBD Thesis Prize has been awarded to Dr. Julien LECLERC for his thesis entitled “Evolution of the eye in Astyanax mexicanus: contribution of maternal and early developmental regulations”. Julien did his thesis under the supervision of Dr. Sylvie RÉTAUX, at Paris-Saclay University in Paris. His work has been published in the journals ‘eLife’ and ‘bioRxiv’.
About the winner :
During his PhD, Julien studied the genetic origins of morphological evolution. He focused on the developmental origins of differences in the eye formation between two morphotypes of the freshwater fish Astyanax mexicanus, one living in surface waters, and with normal eyes, and an eyeless cave-dwelling one. Julien first participated in demonstrating that gastrulation heterochronies between the two morphotypes cause differences in the migration of axial mesoderm cells, which may in turn have contributed to the lack of eyes in the cave morphotype. Experiments performed on hybrids between the two morphotypes strongly suggest a maternal control of this phenotype. This work is striking as it pushes the origin of morphological evolution (in this case the loss of eyes) towards very early development and even oogenesis. In second part of his work, Julien compared the transcriptome of embryos from the two morphotypes and hybrids to identify genes whose expression changed during eye development. This led him to focus on rx3 expression, a known transcriptional regulator of eye formation. Using transplantations and pharmacology he identified two differences in rx3 expression: cave fishes harbor a lower level of rx3 expression under the control of a cis-regulatory element, as well as a narrower expression domain controlled by Wnt signaling. Thus, this work illustrates the complexity of evolutionary events leading to a morphological change.
In parallel to this work, Julien also set up RNA knock-down by CRISPR-Cas13. The jury appreciated the evo-devo approach and was impressed by the diversity of experiments that the candidate mastered during his work on a non-model animal, as well as by the clarity and exhaustivity of the thesis manuscript.
