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Keri Allen, Maria Janessian, Kevin Linkroum, Wael Abdrabou, Janey Wiggs; Multiplex Ligation-dependent Probe Amplification (MLPA) for detection of large deletions in CYP1B1 in congenital glaucoma patients from the US. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1354.
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Mutations in CYP1B1 were first identified in consanguineous Saudi Arabian and Turkish primary congenital glaucoma (PCG) pedigrees. However, this gene accounts for only a small percentage of PCG cases in ethnically heterogeneous populations such as the United States. In a previous study conducted at the Massachusetts Eye and Ear infirmary (MEEI), a collection of 50 U.S. congenital glaucoma families were screened for mutations in CYP1B1 and only five probands were found to have causative mutations for CYP1B1. Testing for copy number variation using fragment analysis can significantly increase the detection rate of many genetic disorders. The purpose of this study is to test for whole gene, or whole exon deletions in CYP1B1 that are not detected by Sanger sequencing methods using Multiplex Ligation-dependent Probe amplification (MLPA) in MEEI congenital glaucoma families who previously tested negative for mutations for CYP1B1.
Genomic DNA samples from 32 of the original MEEI PCG probands were selected to be screened using MLPA. The MRC Holland SALSA MLPA P128-B2 Cytochrome P-450 probemix kit was used to assess copy number variation, specifically whole gene or whole exon deletion of CYP1B1.
MLPA analysis showed deletion of both exons in the CYP1B1 gene in 1 out of the 32 (3%) probands in the MEEI collection of congenital glaucoma families.
MLPA was able to detect a large deletion that includes the entire coding sequence of CYP1B1 in 1/32 of MEEI PCG probands who previously tested negative for a CYP1B1 mutation. MLPA should be used to exclude large deletions of CYP1B1 as the causative mutation in congenital glaucoma patients. Overall these results are consistent with the findings that CYP1B1 mutations are rare causes of congenital glaucoma in affected patients residing in the U.S. These results also suggest that other genes, not yet discovered, are responsible for the majority of congenital glaucoma cases in the U.S.
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