title: The subventricular zone is the developmental milestone of a 6-layered neocortex: comparisons in metatherian and eutherian mammals.
abstract: The major lineages of mammals (Eutheria, Metatheria, and Monotremata) diverged more than 100 million years ago and have undergone independent changes in the neocortex. We found that adult South American gray short-tailed opossum (Monodelphis domestica) and tammar wallaby (Macropus eugenii) possess a significantly lower number of cerebral cortical neurons compared with the mouse (Mus musculus). To determine whether the difference is reflected in the development of the cortical germinal zones, the location of progenitor cell divisions was examined in opossum, tammar wallaby, and rat. The basic pattern of the cell divisions was conserved, but the emergence of a distinctive band of dividing cells in the subventricular zone (SVZ) occurred relatively later in the opossum (postnatal day [P14]) and the tammar wallaby (P40) than in rodents. The planes of cell divisions in the ventricular zone (VZ) were similar in all species, with comparable mRNA expression patterns of Brn2, Cux2, NeuroD6, Tbr2, and Pax6 in opossum (P12 and P20) and mouse (embryonic day 15 and P0). In conclusion, the marsupial neurodevelopmental program utilizes an organized SVZ, as indicated by the presence of intermediate (or basal) progenitor cell divisions and gene expression patterns, suggesting that the SVZ emerged prior to the Eutherian-Metatherian split.
authors.affiliation: Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3QX, UK.
authors.forename: Amanda F P
authors.initials: AF
authors.lastname: Cheung
authors.forename: Shinichi
authors.initials: S
authors.lastname: Kondo
authors.forename: Omar
authors.initials: O
authors.lastname: Abdel-Mannan
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Chodroff
authors.forename: Tamara M
authors.initials: TM
authors.lastname: Sirey
authors.forename: Lisa E
authors.initials: LE
authors.lastname: Bluy
authors.forename: Natalie
authors.initials: N
authors.lastname: Webber
authors.forename: Jamin
authors.initials: J
authors.lastname: DeProto
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Karlen
authors.forename: Leah
authors.initials: L
authors.lastname: Krubitzer
authors.forename: Helen B
authors.initials: HB
authors.lastname: Stolp
authors.forename: Norman R
authors.initials: NR
authors.lastname: Saunders
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Molnár
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002452:Cell Count / Q000379:methods; D004622:Embryo, Mammalian; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D018398:Homeodomain Proteins / Q000378:metabolism; D020547:Lateral Ventricles / Q000166:cytology / Q000196:embryology / Q000254:growth & development; D007614:Macropodidae; D048309:Monodelphis / Q000033:anatomy & histology / Q000196:embryology / Q000254:growth & development; D019579:Neocortex / Q000166:cytology / Q000196:embryology / Q000254:growth & development; D009474:Neurons / Q000378:metabolism; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D008941:Spindle Apparatus / Q000648:ultrastructure
chemical_list: D018398:Homeodomain Proteins