“EVOLUTION OF BRAIN DEVELOPMENT”
Zoltán Molnár MD DPhil, Professor of Developmental Neuroscience, Department of Physiology, Anatomy and Genetics, University of Oxford, UK
Comparative developmental studies of the mammalian brain identify key changes that might have generated the diverse structure and function of this organ. The radial and tangential enlargement of the cortex was driven by changes in the cortical neurogenesis, in particular the elaboration and cytoarchitectonic compartmentalization of the germinal zone, with alterations in the proportions of various progenitor types (1,2). Clonal analysis from selected progenitor populations started to reveal the lineage in various pallial sectors of the mammalian and avian telencephalon (2,3). Some cortical cell populations, including some of the earliest generated subplate neurons, arrive to the cortex through tangential migration to converge in a specific area where the various cell populations organize themselves into precise neuronal circuits (4,5). Comparative analysis of the similarities and variation in these neurogenetic and migration patterns, together with the analysis of gene expression patterns hold the key to reveal conserved, diverged or converged development. A number of recent studies have begun to characterize the chick, mouse, human and non-human primate cortical transcriptome to understand how gene expression relates to the development, anatomical and functional organization of the neocortex (6). Understanding the molecular and cellular interactions regulating forebrain evolution illuminates the pathomechanisms of several cortical developmental disorders.
(1) The subventricular zone is the developmental milestone of a 6-layered neocortex: comparisons in metatherian and eutherian mammals. Cheung AF, Kondo S, Abdel-Mannan O, Chodroff RA, Sirey TM, Bluy LE, Webber N, DeProto J, Karlen SJ, Krubitzer L, Stolp HB, Saunders NR, Molnár Z. (2010) Cereb Cortex. 20(5):1071-81.
(2) Cortical and clonal contribution of Tbr2 expressing progenitors in the developing mouse brain. Vasistha NA, Garcia-Moreno F, Arora S, Cheung AFP, Arnold SJ, Robertson EJ and Molnár Z (2014) Cereb Cortex pii: bhu125. [Epub ahead of print].
(3) CLoNe is a new method to target single progenitors and study their progeny in mouse and chick. García-Moreno F, Vasistha NA, Begbie J, Molnár Z. (2014) Development. 141(7):1589-98.
(4) Pedraza M, Hoerder-Suabedissen A, Albert-Maestro MA, Molnár Z, De Carlos JA (2014) Extracortical origin of some murine subplate cell populations. Proc Natl Acad Sci USA. 111: 23. 8613-8618
(5) Development, evolution and pathology of neocortical subplate neurons. Hoerder-Suabedissen A, Molnár Z. (2015) Nature Reviews Neuroscience 16: 133-146
(6) Adult pallium transcriptomes surprise in not reflecting predicted homologies across diverse chicken and mouse pallial sectors. Belgard TG, Montiel JF, Wang WZ, García-Moreno F, Margulies EH, Ponting CP, Molnár Z. (2013) Proc Natl Acad Sci USA. 110(32):13150-5.