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G. Cheng, J.D. Porter; Comprehensive Evaluation of the Extraocular Muscle Critical Period Using Serial Analysis of Gene Expression (SAGE) in Dark-Reared Rats . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4809.
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Purpose:The extraocular muscle (EOM) critical period concept is based upon our prior report that dark rearing (DR) suppresses postnatal EOM-specific myosin expression. Here, we used gene profiling with SAGE to extend this concept. Methods:SAGE was used as a comprehensive means of quantifying alterations in EOM transcription in postnatal day 45 rats DR from birth. SAGE isolates and sequences 10 bp tags from defined locations in mRNA-derived cDNA. Tag sequences were used to extract transcript identity from a SAGE database; detection frequencies reflect mRNA abundance. Dark-reared data were compared with those from our prior normative EOM study (IOVS 43:1048-58, 2002). Results:31,776 SAGE tags were generated and sequenced from DR EOM, including 10,105 unique tags (quality controls: GC content of 46.4%, linker contamination of 0.05%). 54% of the unique tags matched known ESTs. Compared to normally reared control EOM, 280 unique tags had > 3-fold changes (p < 0.05). Most of the 280 transcripts represented either ESTs (51%) or novel tags (30%). The major pattern (62% of unique tags) observed here was transcript induction in DR EOM. Several muscle-specific genes (sarcosin, triadin , calpain 3, cardiac calsequestrin) were expressed at higher levels in DR EOM. Lipid metabolism-related transcripts (Acox1, Echs1, Me1, Dci) also were induced by DR. Transcripts downregulated by DR function in a range of cellular activities including glycolysis (Pfkm) and extracellular matrix organization (Col1a1, Pcolce). Conclusions: Postnatal EOM maturation is broadly susceptible to activity pattern-induced alterations resulting from visuomotor maldevelopment. These findings extend the concept of an EOM critical period and further suggest that strabismus and amblyopia may exert an important impact upon the EOM phenotype.
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