Abstract
Regionalization is a critical, highly conserved step in the development of the vertebrate brain. Discrepancies exist in how regionalization of the anterior vertebrate forebrain is conceived since the “preoptic area” is proposed to be a part of the telencephalon in tetrapods but not in teleost fish. To gain insight into this complex morphogenesis, formation of the anterior forebrain was analyzed in 3D over time in zebrafish embryos, combining visualization of proliferation and differentiation markers, with that of developmental genes. We found that the region containing the preoptic area behaves as a coherent morphogenetic entity, organized around the optic recess and located between telencephalon and hypothalamus. This optic recess region (ORR) makes clear borders with its neighbor areas and expresses a specific set of genes (dlx2a, sim1a and otpb). We thus propose that the anterior forebrain (secondary prosencephalon) in teleosts contains three morphogenetic entities (telencephalon, ORR and hypothalamus), instead of two (telencephalon and hypothalamus). The ORR in teleosts could correspond to “telencephalic stalk area” and “alar hypothalamus” in tetrapods, resolving current inconsistencies in the comparison of basal forebrain among vertebrates.
Highlights
Regionalization is a critical, highly conserved step in the development of the vertebrate brain
We found that the region containing the preoptic area behaves as a coherent morphogenetic entity, organized around the optic recess and located between telencephalon and hypothalamus
We found that the region containing the zebrafish preoptic area behaves as a morphogenetic entity, distinct from the telencephalon and the hypothalamus
Summary
Regionalization is a critical, highly conserved step in the development of the vertebrate brain. The hypothalamus is www.nature.com/scientificreports considered to be subdivided into alar and basal domains, and the telencephalon to be derived from the roof plate of the anterior neural tube[8,18]. These general events of regionalization are thought to be conserved among different vertebrate groups, notably at the developmental time point referred to as the ‘‘phylotypic period’’ during which progenitor cells acquire a positional identity. The preoptic area occupies a large part of the anterior forebrain in adult teleosts, the development of this region has not been well studied
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