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T. L. Young, R. Metlapally, A. E. Shay, A. Bulusu, S. Zuchner, O. Sundin, Y.-J. Li; Hyperopia and Microphthalmia Are Not Associated With MFRP Sequence Variants. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1312. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The Membrane-type Frizzled-Related Protein (MFRP) gene is selectively expressed in the retinal pigment epithelium and ciliary body, and mutations of which cause nanophthalmos. MFRP is unnecessary for retinal function, and is thought to be primarily involved in axial length regulation. We screened for sequence variants in MFRP in moderate -high hyperopic and microphthalmic/anophthalmic patients.
Eleven hyperopic adults, ten microphthalmic/anophthalmic patients of varying ages, and one plano control adult patient were consented for genomic DNA testing. Sixteen primer pairs were designed to amplify the 13 exons of MFRP including intron /exon boundaries. Polymerase chain reactions were performed, and amplified products were sequenced using standard techniques. Normal and affected individual DNA sequences were compared alongside the known reference sequence (UCSC genome browser) for MFRP.
The average spherical refractive error of the hyperopic patient cohort was +4.21 diopters (range +2.00 to +9.25 D). A total of 9 single nucleotide polymorphisms (SNPs) were identified. A novel synonymous SNP in exon 5 was observed in 6 hyperopic (5 heterozygous, 1 substitution) and 6 microphthalmic/anophthalmic (all heterozygous) subjects. Two known SNPs were observed in the plano control (rs3814762: substitution; rs948411: substitution), hyperopic subjects (rs3814762: 6 heterozygous; rs948411: 4 heterozygous, 7 substitutions), and microphthalmic/anophthalmic subjects (rs3814762: 4 heterozygous, 1 substitution; rs948411: 3 heterozygous, 7 substitutions). In addition, 6 isolated novel SNPs were identified in exons 6 (non-synonymous), 8 (synonymous), 9 (non-synonymous), 13 (3’ untranslated region), and introns 8 and 11.
Sequence variants of MFRP do not appear to be associated with either less severe forms of hyperopia, or in extreme forms of limited eye growth and development. These results indicate that MFRP may not play a role in regulating axial length in these phenotypes.
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