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Respir Physiol Neurobiol. 2016 Apr;224:2-10. doi: 10.1016/j.resp.2015.06.010. Epub 2015 Jul 6.

Testing the evolutionary conservation of vocal motoneurons in vertebrates.

Author information

1
Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
2
Department of Biological Sciences, Columbia University, New York, NY 10027, USA; Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA.
3
Department of Exercise Science, Faculté des Sciences, Université du Québec à Montréal, Montréal, Québec H3C 3P8, Canada; Department of Neuroscience, Université de Montréal, Montréal, Québec H3C 3J7, Canada.
4
Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA.
5
Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
6
Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA.
7
Hotchkiss Brain Institute and ACH Research Institute, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N4N1, Canada.
8
Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, MO 63110, USA. Electronic address: pgray@mac.com.

Abstract

Medullary motoneurons drive vocalization in many vertebrate lineages including fish, amphibians, birds, and mammals. The developmental history of vocal motoneuron populations in each of these lineages remains largely unknown. The highly conserved transcription factor Paired-like Homeobox 2b (Phox2b) is presumed to be expressed in all vertebrate hindbrain branchial motoneurons, including laryngeal motoneurons essential for vocalization in humans. We used immunohistochemistry and in situ hybridization to examine Phox2b protein and mRNA expression in caudal hindbrain and rostral spinal cord motoneuron populations in seven species across five chordate classes. Phox2b was present in motoneurons dedicated to sound production in mice and frogs (bullfrog, African clawed frog), but not those in bird (zebra finch) or bony fish (midshipman, channel catfish). Overall, the pattern of caudal medullary motoneuron Phox2b expression was conserved across vertebrates and similar to expression in sea lamprey. These observations suggest that motoneurons dedicated to sound production in vertebrates are not derived from a single developmentally or evolutionarily conserved progenitor pool.

KEYWORDS:

Hypoglossal; Lamprey; Midshipman; Respiration; Vocalization; Zebra Finch

PMID:
26160673
PMCID:
PMC4703570
DOI:
10.1016/j.resp.2015.06.010
[Indexed for MEDLINE]
Free PMC Article

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