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Interspecies avian brain chimeras reveal that large brain size differences are influenced by cell-interdependent
Chun-Chun Chen1, Evan Balaban, Erich D Jarvis
1Department of Neurobiology, Howard Hughes Medical Institute, Duke University, Durham, North Carolina, United States of America. cc229@duke.edu
Plos One
|August 4, 2012
Summary
Vocal learning in birds is linked to telencephalon development. Transplanting brains revealed that telencephalon size is partly cell-interdependent, with distinct mechanisms controlling different brain region sizes.
Area of Science:
- Neuroscience
- Developmental Biology
- Evolutionary Biology
Background:
- Vocal learning, observed in humans and certain bird species, is associated with delayed telencephalon maturation.
- This developmental difference leads to smaller prenatal brains but larger adult telencephala in vocal learners compared to non-learners.
Purpose of the Study:
- To investigate whether evolutionary differences in telencephalon size between vocal learning and non-learning species are due to cell-autonomous or cell-interdependent developmental processes.
- To understand the developmental mechanisms underlying brain size evolution in vocal learners.
Main Methods:
- Early embryonic neural tube transplantation of telencephala from zebra finches (vocal learners) into Japanese quail hosts (vocal non-learners).
- Chimeric embryos were analyzed at later developmental stages (9-12 days of incubation).
- Assessment of tissue fusion, neural connections, brain region sizes, cell density, and cell nucleus size.
Main Results:
- Successful fusion and major fiber pathway connections were observed between donor (zebra finch) and host (Japanese quail) tissues.
- Chimeric zebra finch telencephala were larger than normal finch telencephala, indicating cell-interdependent growth.
- Despite innervation by a smaller zebra finch brain, chimeric quail midbrains showed no significant size changes.
- Cell density in chimeric finch telencephala decreased, but species-specific cell nucleus sizes were maintained.
Conclusions:
- Telencephalon size development is influenced by cell-interdependent factors.
- Mechanisms regulating the size of different brain regions appear to operate independently.
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