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Nat Commun. 2010 Jul 27;1:49. doi: 10.1038/ncomms1045.

Ancestry of motor innervation to pectoral fin and forelimb.

Author information

1
Department of Physiology and Neuroscience, NYU Langone Medical Center, New York, New York 10016, USA.

Abstract

Motor innervation to the tetrapod forelimb and fish pectoral fin is assumed to share a conserved spinal cord origin, despite major structural and functional innovations of the appendage during the vertebrate water-to-land transition. In this paper, we present anatomical and embryological evidence showing that pectoral motoneurons also originate in the hindbrain among ray-finned fish. New and previous data for lobe-finned fish, a group that includes tetrapods, and more basal cartilaginous fish showed pectoral innervation that was consistent with a hindbrain-spinal origin of motoneurons. Together, these findings support a hindbrain-spinal phenotype as the ancestral vertebrate condition that originated as a postural adaptation for pectoral control of head orientation. A phylogenetic analysis indicated that Hox gene modules were shared in fish and tetrapod pectoral systems. We propose that evolutionary shifts in Hox gene expression along the body axis provided a transcriptional mechanism allowing eventual decoupling of pectoral motoneurons from the hindbrain much like their target appendage gained independence from the head.

PMID:
20975699
PMCID:
PMC2963806
DOI:
10.1038/ncomms1045
[Indexed for MEDLINE]
Free PMC Article

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