Characterizing the diverse cells that associate with the developing commissures of the zebrafish forebrain

Abstract

During embryonic development of bilateral organisms, neurons send axons across the midline at specific points to connect the two halves of the nervous system with a commissure. Little is known about the cells at the midline that facilitate this tightly regulated process. We exploit the con served process of vertebrate embryonic development in the zebrafish model system to elucidate the identity of cells at the midline that may facilitate postoptic (POC) and anterior commissure (AC) development. We have discovered that three differentgfap+ astroglial cell morphologies persist in contact with pathfinding axons throughout commissure formation. Similarly, olig2+ progenitor cells occupy delineated portions of the postoptic and anterior commissures. These early olig2+ progenitors demonstrate glial-like morphologies despite the lack of a myelination marker. Moreover, we conclude that both the gfap+ and olig2+progenitor cells give rise to neuronal populations in both the telencephalon and diencephalon. Interestingly, these varied cell populations showed significant developmental heterochrony between the telencephalon and diencephalon. Lastly, we also showed that fli1a+ mesenchymal cells migrate along the presumptive commissure regions before and during midline axon crossing. Furthermore, following commissure maturation, specific blood vessels formed at the midline of the POC and immediately ventral and parallel to the AC. This comprehensive account of the cellular populations that correlate with the timing and position of commissural axon pathfinding has supported the conceptual modeling and identification of the early forebrain architecture that may be necessary for proper commissure development.

Transcriptional control of visual neural circuit development by GS homeobox 1

“…These developmental instructions establish appropriate RGC axon pathfinding, synaptogenesis, and retinotopographic mapping, and many of these cues are conserved across mammalian and nonmammalian vertebrate visual systems (Baier, 2013;Bollmann, 2019;Contreras et al, 2019;Erskine and Herrera, 2007;Harada et al, 2007;Seabrook et al, 2017;Siu and Murphy, 2018). However, the majority of efforts to date have focused on identifying these mechanisms in primary visual processing areas, and how RGCs target other critical brain regions remains incompletely understood (Barresi et al, 2010(Barresi et al, , 2005Ross et al, 1992;Schnabl et al, 2021).…”