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An Altered Phenotype in a Conditional Knockout of Pitx2 in Extraocular Muscle

Zhou, Yuefang; Cheng, Georgiana; Dieter, Lisa; Hjalt, Tord LU ; Andrade, Francisco H.; Stahl, John S. and Kaminski, Henry J. (2009) In Investigative Ophthalmology & Visual Science 50(10). p.4531-4541
Abstract
PURPOSE. To determine the temporal and spatial expression of Pitx2, a bicoid-like homeobox transcription factor, during postnatal development of mouse extraocular muscle and to evaluate its role in the growth and phenotypic maintenance of postnatal extraocular muscle. METHODS. Mouse extraocular muscles of different ages were examined for the expression of Pitx2 by RT-PCR, q-PCR, and immunostaining. A conditional mutant mouse strain, in which Pitx2 function is inactivated at postnatal day (P)0, was generated with a Cre-loxP strategy. Histology, immunostaining, real-time PCR, in vitro muscle contractility, and in vivo ocular motility were used to study the effect of Pitx2 depletion on extraocular muscle. RESULTS. All three Pitx2 isoforms... (More)
PURPOSE. To determine the temporal and spatial expression of Pitx2, a bicoid-like homeobox transcription factor, during postnatal development of mouse extraocular muscle and to evaluate its role in the growth and phenotypic maintenance of postnatal extraocular muscle. METHODS. Mouse extraocular muscles of different ages were examined for the expression of Pitx2 by RT-PCR, q-PCR, and immunostaining. A conditional mutant mouse strain, in which Pitx2 function is inactivated at postnatal day (P)0, was generated with a Cre-loxP strategy. Histology, immunostaining, real-time PCR, in vitro muscle contractility, and in vivo ocular motility were used to study the effect of Pitx2 depletion on extraocular muscle. RESULTS. All three Pitx2 isoforms were expressed by extraocular muscle and at higher levels than in other striated muscles. Immunostaining demonstrated the presence of Pitx2 mainly in extraocular muscle myonuclei. However, no obvious expression patterns were observed in terms of anatomic region (orbital versus global layer), innervation zone, or muscle fiber types. The mutant extraocular muscle had no obvious pathology but had altered muscle fiber sizes. Expression levels of myosin isoforms Myh1, Myh6, Myh7, and Myh13 were reduced, whereas Myh2, Myh3, Myh4, and Myh8 were not affected by postnatal loss of Pitx2. In vitro, Pitx2 loss made the extraocular muscles stronger, faster, and more fatigable. Eye movement recordings found saccades to have a lower peak velocity. CONCLUSIONS. Pitx2 is important in maintaining the mature extraocular muscle phenotype and regulating the expression of critical contractile proteins. Modulation of Pitx2 expression can influence extraocular muscle function with long-term therapeutic implications. (Invest Ophthalmol Vis Sci. 2009; 50: 4531-4541) DOI:10.1167/iovs.08-2950 (Less)
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publication status
published
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in
Investigative Ophthalmology & Visual Science
volume
50
issue
10
pages
4531 - 4541
publisher
ASSOC RESEARCH VISION OPHTHALMOLOGY INC
external identifiers
  • wos:000270097200003
  • scopus:70349577528
ISSN
1552-5783
DOI
10.1167/iovs.08-2950
language
English
LU publication?
yes
id
e0db3ba1-5ad7-4a02-8e6c-bb90ce35747c (old id 1490041)
date added to LUP
2009-10-20 11:56:00
date last changed
2017-11-19 03:54:56
@article{e0db3ba1-5ad7-4a02-8e6c-bb90ce35747c,
  abstract     = {PURPOSE. To determine the temporal and spatial expression of Pitx2, a bicoid-like homeobox transcription factor, during postnatal development of mouse extraocular muscle and to evaluate its role in the growth and phenotypic maintenance of postnatal extraocular muscle. METHODS. Mouse extraocular muscles of different ages were examined for the expression of Pitx2 by RT-PCR, q-PCR, and immunostaining. A conditional mutant mouse strain, in which Pitx2 function is inactivated at postnatal day (P)0, was generated with a Cre-loxP strategy. Histology, immunostaining, real-time PCR, in vitro muscle contractility, and in vivo ocular motility were used to study the effect of Pitx2 depletion on extraocular muscle. RESULTS. All three Pitx2 isoforms were expressed by extraocular muscle and at higher levels than in other striated muscles. Immunostaining demonstrated the presence of Pitx2 mainly in extraocular muscle myonuclei. However, no obvious expression patterns were observed in terms of anatomic region (orbital versus global layer), innervation zone, or muscle fiber types. The mutant extraocular muscle had no obvious pathology but had altered muscle fiber sizes. Expression levels of myosin isoforms Myh1, Myh6, Myh7, and Myh13 were reduced, whereas Myh2, Myh3, Myh4, and Myh8 were not affected by postnatal loss of Pitx2. In vitro, Pitx2 loss made the extraocular muscles stronger, faster, and more fatigable. Eye movement recordings found saccades to have a lower peak velocity. CONCLUSIONS. Pitx2 is important in maintaining the mature extraocular muscle phenotype and regulating the expression of critical contractile proteins. Modulation of Pitx2 expression can influence extraocular muscle function with long-term therapeutic implications. (Invest Ophthalmol Vis Sci. 2009; 50: 4531-4541) DOI:10.1167/iovs.08-2950},
  author       = {Zhou, Yuefang and Cheng, Georgiana and Dieter, Lisa and Hjalt, Tord and Andrade, Francisco H. and Stahl, John S. and Kaminski, Henry J.},
  issn         = {1552-5783},
  language     = {eng},
  number       = {10},
  pages        = {4531--4541},
  publisher    = {ASSOC RESEARCH VISION OPHTHALMOLOGY INC},
  series       = {Investigative Ophthalmology & Visual Science},
  title        = {An Altered Phenotype in a Conditional Knockout of Pitx2 in Extraocular Muscle},
  url          = {http://dx.doi.org/10.1167/iovs.08-2950},
  volume       = {50},
  year         = {2009},
}