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Invest Ophthalmol Vis Sci. 2017 Apr 1;58(4):2388-2396. doi: 10.1167/iovs.16-21268.

Ocular Motor Nerve Development in the Presence and Absence of Extraocular Muscle.

Author information

1
Department of Neurology, Boston Children's Hospital, Boston, Massachusetts, United States 2F. M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, Massachusetts, United States 3Department of Neurology, Harvard Medical School, Boston, Massachusetts, United States 4University of North Carolina School of Medicine, Chapel Hill, North Carolina, United States 5Howard Hughes Medical Institute, Chevy Chase, Maryland, United States.
2
F. M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, Massachusetts, United States 6Department of Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, United States 7Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States.
3
Department of Neurology, Boston Children's Hospital, Boston, Massachusetts, United States 2F. M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, Massachusetts, United States 3Department of Neurology, Harvard Medical School, Boston, Massachusetts, United States 5Howard Hughes Medical Institute, Chevy Chase, Maryland, United States 8Duke University School of Medicine, Durham, North Carolina, United States.
4
F. M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, Massachusetts, United States 3Department of Neurology, Harvard Medical School, Boston, Massachusetts, United States.
5
F. M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, Massachusetts, United States 6Department of Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, United States.
6
Department of Neurology, Boston Children's Hospital, Boston, Massachusetts, United States 2F. M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, Massachusetts, United States 3Department of Neurology, Harvard Medical School, Boston, Massachusetts, United States 5Howard Hughes Medical Institute, Chevy Chase, Maryland, United States 6Department of Ophthalmology, Boston Children's Hospital, Boston, Massachusetts, United States 7Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, United States.

Abstract

Purpose:

To spatially and temporally define ocular motor nerve development in the presence and absence of extraocular muscles (EOMs).

Methods:

Myf5cre mice, which in the homozygous state lack EOMs, were crossed to an IslMN:GFP reporter line to fluorescently label motor neuron cell bodies and axons. Embryonic day (E) 11.5 to E15.5 wild-type and Myf5cre/cre:IslMN:GFP whole mount embryos and dissected orbits were imaged by confocal microscopy to visualize the developing oculomotor, trochlear, and abducens nerves in the presence and absence of EOMs. E11.5 and E18.5 brainstems were serially sectioned and stained for Islet1 to determine the fate of ocular motor neurons.

Results:

At E11.5, all three ocular motor nerves in mutant embryos approached the orbit with a trajectory similar to that of wild-type. Subsequently, while wild-type nerves send terminal branches that contact target EOMs in a stereotypical pattern, the Myf5cre/cre ocular motor nerves failed to form terminal branches, regressed, and by E18.5 two-thirds of their corresponding motor neurons died. Comparisons between mutant and wild-type embryos revealed novel aspects of trochlear and oculomotor nerve development.

Conclusions:

We delineated mouse ocular motor nerve spatial and temporal development in unprecedented detail. Moreover, we found that EOMs are not necessary for initial outgrowth and guidance of ocular motor axons from the brainstem to the orbit but are required for their terminal branching and survival. These data suggest that intermediate targets in the mesenchyme provide cues necessary for appropriate targeting of ocular motor axons to the orbit, while EOM cues are responsible for terminal branching and motor neuron survival.

PMID:
28437527
PMCID:
PMC5403115
DOI:
10.1167/iovs.16-21268
[Indexed for MEDLINE]
Free PMC Article

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