Comparison of Pretectal Genoarchitectonic Pattern between Quail and Chicken Embryos

Abstract

Regionalization of the central nervous system is controlled by local networks of transcription factors that establish and maintain the identities of neuroepithelial progenitor areas and their neuronal derivatives. The conserved cerebral Bauplan of vertebrates must result essentially from conserved patterns of developmentally expressed transcription factors. We have previously produced detailed molecular maps for the alar plate of prosomere 1 (the pretectal region) in chicken (Ferran et al., 2007, 2008, 2009). Here we compare the early molecular signature of the pretectum of two closely related avian species of the family Phasianidae, Coturnix japonica (Japanese quail) and Gallus gallus (chicken), aiming to test conservation of the described pattern at a microevolutionary level. We studied the developmental pretectal expression of Bhlhb4, Dbx1, Ebf1, Gata3, Gbx2, Lim1, Meis1, Meis2, Pax3, Pax6, Six3, Tal2, and Tcf7l2 (Tcf4) mRNA, using in situ hybridization, and PAX7 immunohistochemistry. The genoarchitectonic profile of individual pretectal domains and strata was produced, using comparable section planes. Remarkable conservation of the combinatorial genoarchitectonic code was observed, fundamented in a tripartite anteroposterior subdivision. However, we found that at corresponding developmental stages the pretectal region of G. gallus was approximately 30% larger than that of C. japonica, but seemed relatively less mature. Altogether, our results on a conserved genoarchitectonic pattern highlight the importance of early developmental gene networks that causally underlie the production of homologous derivatives in these two evolutionarily closely related species. The shared patterns probably apply to sauropsids in general, as well as to more distantly related vertebrate species.

Molecular characterization of prosomeric and intraprosomeric subdivisions of the embryonic zebrafish diencephalon

“…These results suggested a subdivision of the pretectum into three molecularly distinct domains, a rostral dbx1a-, intermediate six3a, lhx5, emx2-, and caudal pax7a-positive domain. These molecularly defined domains of the zebrafish pretectal primordium were reminiscent of precommissural, juxtacommissural, and commissural pretectal subdivisions in tetrapods (Ferran et al, 2007(Ferran et al, , 2008(Ferran et al, , 2009Merch an et al, 2011;Morona et al, 2011).…”

“…In tetrapods, the expression sites of Pax genes in the alar diencephalon were used as diagnostic domains for definition of the anteroposterior extent of the pretectum (Ferran et al, 2007(Ferran et al, , 2008Merch an et al, 2011;Morona et al, 2011). We compared zebrafish pax3a and pax6a expression by two-color FISH (Fig.…”

“…Secondary subdivisions within the thalamic mantle have been proposed based on examination of cadherin protein expression in chick Yoon et al, 2000). A large set of regulatory gene and protein expression domains identified an anteroposterior tripartition of the pretectum into three histogenetic domains in Xenopus (Morona et al, 2011), chick (Ferran et al, 2007), and quail (Merch an et al, 2011) that were traced into later stages of differentiated nuclear architecture (Ferran et al, 2009). Initial comparative transcription factor expression analysis of Dbx1, Six3, and Pax3 confirmed the same set of three domains in the mouse pretectum (Ferran et al, 2008).…”

Transcriptional regulatory mechanisms underlying the GABAergic neuron fate in different diencephalic prosomeres

“…For analysis of P1, we performed fluorescence ISH for Tal2, Slc17a6 and Mab21l1 (a marker of IZ precursors in the glutamatergic precomissural and commissural parts of P1) (Vue et al, 2007) (Fig. 5A-H,L-N) as well as IHC for Slc17a6 and Pax7 (strongly expressed in the commissural part of P1) (Merchán et al, 2011) (Fig. 5C-F,L).…”

Architect genes of the brain: A look at brain evolution through genoarchitecture

“…In our example, the pretectal region seen in Figure 5 shows that the same active gene is expressed in the same subdivision of this region in both chicken and mouse. This, on the one hand, allows us to recognize the same area in two different species that in many cases are evolutionary very distant from each other; but, on the other hand, this example also reveals that birds and mammals are using the same genes in the construction of that region at early developmental stages (Ferran et al, 2008;Merchán, Bardet, Puelles, & Ferran, 2011;Morona, Ferran, Puelles, & González, 2011). …”