About this Research Topic
The brain is not a cloistered organ. Increasing evidence for evolutionary variation in neurogenesis, coupled with decades of documentation on interspecific differences in maternal investment during fetal development, suggest that evolution of the mammalian brain may largely be a product of maternal-fetal conflict. In support of this, experimental and theoretical work have demonstrated the evolution in mammals of a platform for genomic conflict between mothers and developing embryos, as well as between maternal and paternal genomes, that inspires intense conflict between mother and embryo and results, through genomic-imprinting or sex-linked gene expression, in rapid evolution of postzygotic phenotypes preferential to either the maternal or fetal genome. Furthermore, because placentation has been shown to be adaptive in its effect on maternal investment in the developing fetal brain, we may now expect brain and placenta to be under strong collaborative selection along the mammalian lineage. In order to understand this collaboration and how variability in brain size and cortical organization has been achieved over evolutionary time, we must advance both our conception and knowledge of the constraints acting on neurogenesis during embryonic development. Workers have shown that these constraints may be stabilized either within fetal brain development, such that the array of neurogenetic events (i.e., sequence heterochrony) is generally conserved across species, or by the timing and duration of nutrient transfer (temporal heterochrony) provided by the mother throughout gestation. It is important, therefore, to (i) consolidate interspecific data on neurogenesis, (ii) examine those data against the well established field of comparative placentation and reproduction, (iii) synthesize the lot with rigorous evolutionary theory, and (iv) propose future channels for investigating the influence of maternal-fetal conflict on neurogenesis at the genomic and cell-biological level.
In this Research Topic, we wish to summarize what is known about neurogenesis in different species and review that knowledge in light of heterochrony and maternal-fetal conflict. We are interested in all article types, especially (ongoing) original research. Work focusing on mammalian neurogenesis, but also on non-mammalian species that either asserts fundamental constraints on vertebrate neurogenesis or highlights derived aspects of mammalian neurogenesis, is welcome.
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