FIGURE 8

FIGURE 8

Summary schematic explaining how the zebrafish thalamiceminence (EmT) reveals ancestral topological relationships to posterior medial amygdala and olfactory pallium. (A–F2) Comparing topographically rostral and posterior ends of the telencephalon in transgenic lines Tg(vGlut2a:GFP) and Tg(lhx5:GFP) with distribution of parvalbumin, otp-a, and GFAP indicated a complex EmT. In sites classically defined as “telencephalic,” we identified the rostral (EmTr = vGlut2a+, lhx5+, otp-a+) and lateral (EmTl) vlgut2a+;lhx5-). At diencephalic side of the diencephalic-telencephalic junction, the EmTm can be easily identified based on vGlut2a-driven GFP expression and absence of lhx5-driven GFP, whereas the otp-a negative bed nucleus of the stria medullaris (BNSM) shows both vlgut2a- and lhx5-driven GFP. Note, that we consider the rostral and posteriormost parts of the newly defined nLOT a derivative of the EmT consistent with the absence of radial glia somata and processes in their most lateral (pial) aspects. (G–L) Schematics comparing brain of adult zebrafish (dorsal view) with adult rodent (idealized side view), and developmental stage to determine various EmT derivatives. The study identifies topographically rostral and posterior EmT territories based on differential expression of vGluta- and lhx5-driven GFP in comparison to otp-a expression. The dorsal view on the zebrafish telencephalon highlights “diencephalic” medial (EmTm) versus “telencephalic” rostral (EmTr) and lateral (EmTl) at the diencephalic-telencephalic junction (DTJ). The distribution of vGlut2a-driven GFP and lhx5-driven GFP in adult zebrafish strikingly resembles the situation shown in mammals (mouse) (Ruiz-Reig et al., 2017). Our complexly everted telencephalon model considers both rostral (nLOTr) and posterior portions of the most ventro-lateral expression domains of vGlut2a-driven GFP as radial extensions of the EmTl. The integrative olfactory pallium (IOP) is most likely a derivative of the newly defined lateral pallium of the prosomeric model and thus homologous to the entorhinal cortex.