Adult pallium transcriptomes surprise in not reflecting predicted homologies across diverse chicken and mouse pallial sectors

• Published in: Proceedings of the National Academy of Sciences - PNAS 2013-08, Vol.110 (32), p.13150-13155
• Main Authors: Belgard, T. Grant, Montiel, Juan F., Wang, Wei Zhi, García-Moreno, Fernando, Margulies, Elliott H., Ponting, Chris P., Molnár, Zoltán
• Format: Article
• Language: English
• Subjects: Animal migration behavior; Animals; Biological and medical sciences; Biological Sciences; Birds; Brain; Brain - anatomy & histology; Brain - metabolism; Chickens; Evolution; Female; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression Profiling - methods; Gene Regulatory Networks; Genes; Globus Pallidus - anatomy & histology; Globus Pallidus - metabolism; Hippocampus; In Situ Hybridization; Male; Mammals; Medical research; Mice; Mice, Inbred C57BL; Models, Anatomic; Models, Genetic; Neocortex; Neurons; Telencephalon - anatomy & histology; Telencephalon - metabolism; Time Factors; Transcriptome - genetics; Transcriptomes; Vertebrates: nervous system and sense organs; Wildlife conservation
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1307444110

The thorniest problem in comparative neurobiology is the identification of the particular brain region of birds and reptiles that corresponds to the mammalian neocortex [Butler AB, Reiner A, Karten HJ (2011) Ann N Y Acad Sci 1225:14–27; Wang Y, Brzozowska-Prechtl A, Karten HJ (2010) Proc Natl Acad Sci USA 107(28):12676–12681]. We explored which genes are actively transcribed in the regions of controversial ancestry in a representative bird (chicken) and mammal (mouse) at adult stages. We conducted four analyses comparing the expression patterns of their 5,130 most highly expressed one-to-one orthologous genes that considered global patterns of expression specificity, strong gene markers, and coexpression networks. Our study demonstrates transcriptomic divergence, plausible convergence, and, in two exceptional cases, conservation between specialized avian and mammalian telencephalic regions. This large-scale study potentially resolves the complex relationship between developmental homology and functional characteristics on the molecular level and settles long-standing evolutionary debates.