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I. Giuffre, G. Lando, I. Longo, S. Penco, A. Guala, E. Piozzi, P. Frezzotti, A. Caporossi, A. Marocchi, E. Maselli; Myoc Gene Analysis in Patients Affected by Congenital Glaucoma Who Are Carriers of Only One Cyp1b1 Mutation . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4616.
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Congenital glaucoma (CG) represents 0.01 to 0.04% of cases of severe blindness. Prevalence at birth is 1/10000. The mode of inheritance is autosomic recessive with variable penetrance, even if the disease has been described as poligenic and multifactorial. Linkage studies have shown a locus in the 2p21 region where the CYP1B1 gene was found mutated in a large part of CG patients. The mutation frequency in 40% of the pathological subjects hypothesizes the presence of one or more genes implicated in the pathology. In fact two other loci were identified on chromosomes 1 and 14, but the related genes are presently not known. Recent studies have reported CG cases with a mutation in CYP1B1 as well as in myocillin gene (MYOC/TIGR), associated with the juvanile form of glaucoma (JOAG); few JOAG patients were also carriers of mutations in the two genes proving a digenic inheritance. The aim of this study is to perform the MYOC/TIGR analysis in all the CG patients without or with only one mutation in CYP1B1 gene.
DNA analysis was performed to identify the presence of CYP1B1 gene.
We found two new aminoacidic variants in patients hetherozygotes for the most common G61E mutation in CYP1B1. The two variants (A447V, R76K) are localized in a highly conserved protein region.
This finding could suggest a presence of a digenic inheritance because of the presence of a double hetherozygote (CYP1B1/MYOC). Since frequence data of these two new aminoacidic variants are unknown, we are assessing their presence in a normal population. The segregation study of A447V identified that the variation derives from the healthy parent. We found no MYOC variants in all the others CYP1B1 hetherozygous patients.
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