Genomic structure and organization of the high grade Myopia-2 locus (MYP2) critical region: mutation screening of 9 positional candidate genes.

Purpose: Myopia is a common complex eye disorder, with implications for blindness due to increased risk of retinal detachment, chorioretinal degeneration, premature cataracts, and glaucoma. A genomic interval of 2.2 centiMorgans (cM) was defined on chromosome band 18p11.31 using 7 families diagnosed with autosomal dominant high myopia and was designated the MYP2 locus. To characterize this region, we analyzed 9 known candidate genes localized to within the 2.2 cM interval by direct sequencing.

Methods: Using public databases, a physical map of the MYP2 interval was compiled. Gene expression studies in ocular tissues using complementary DNA library screens, microarray experiments, reverse transcription techniques, and expression data identified in external databases aided in prioritizing gene selection for screening. Coding regions, intron-exon boundaries and untranslated exons of all known genes [Clusterin-like 1 (CLUL1), elastin microfibril interfacer 2 (EMILIN2), lipin 2 (LPIN2), myomesin 1 (MYOM1), myosin regulatory light chain 3 (MRCL3), myosin regulatory light chain 2 (MRLC2), transforming growth beta-induced factor (TGIFbeta), large Drosophila homolog associated protein 1 (DLGAP1), and zinc finger protein 161 homolog (ZFP161)] were sequenced using genomic DNA samples from 9 affected and 6 unaffected MYP2 pedigree members, and from 5 external controls (4 unaffected and 1 affected). Gene sequence changes were compared to known variants from public single nucleotide polymorphism (SNP) databases.

Results: In total, 103 polymorphisms were found by direct sequencing; 10 were missense, 14 were silent, 26 were not translated, 49 were intronic, 1 insertion, and 3 were homozygous deletions. Twenty-seven polymorphisms were novel. Novel SNPs were submitted to the public database; observed frequencies were submitted for known SNPs. No sequence alterations segregated with the disease phenotype.

Conclusions: Mutation analysis of 9 encoded positional candidate genes on MYP2 loci did not identify sequence alterations associated with the disease phenotype. Further studies of MYP2 candidate genes, including analysis of putative genes predicted in silico, are underway.