Morphogenesis underlying the development of the everted teleost telencephalon

Area of Science:

• Developmental Biology
• Neuroscience
• Comparative Vertebrate Anatomy

Background:

• Vertebrate brain regionalization shows conserved mechanisms but variable morphology.
• The telencephalon exhibits significant morphological diversity, notably the everted structure in ray-finned fish versus the evaginated structure in other vertebrates.
• Mechanisms driving these distinct telencephalic morphologies remain poorly understood.

Purpose of the Study:

• To investigate the developmental mechanisms underlying the everted telencephalon morphology in zebrafish.
• To elucidate the cellular and molecular events driving telencephalon morphogenesis from early development to 5 days post fertilization.

Main Methods:

• Analysis of forebrain ventricle formation in zebrafish embryos (12 hours post fertilization to 5 days post fertilization).
• Tracking gene and transgene expression patterns during development.
• Examining neuronal organization and performing fate mapping studies.

Main Results:

• Formation of the anterior intraencephalic sulcus (AIS) creates a posterior ventricular wall, displacing neuroepithelial territory laterally.
• Subsequent bulging of the pallial region into the AIS, alongside ventricular zone (VZ) expansion, forms the thin tela choroidea (tc).
• Anteroposterior growth of the pallial VZ results in an everted telencephalon by 5 days post fertilization.

Conclusions:

• The study challenges the conventional model of telencephalon eversion as a simple lateral outfolding.
• The described morphogenetic process provides new insights into the development of the adult fish telencephalon.
• Findings contribute to understanding the evolutionary diversification of vertebrate brain structures.