Increasing complexity of ocular genetic diseases : the case of BEST disease

Purpose Monogenic diseases until recently appeared simple from a molecular genetics point of view but correlations between genotypes and phenotypes still remain difficult to establish in many diseases and for many genes. For autosomal dominant diseases such as Best Vitelliform Macular Dystrophy, supposed to be a juvenile disease, it appears that mutations of BEST1 gene can cause multiple phenotypes including early onset and late onset phenotypes as well as unexpected phenotypes such as RP. We report several novel mutations and their associated phenotypes and describe phenotypes linked to previously reoported mutations for which the phenotype had not been describe at all previously. The role of SOX9, MITF and OTX2 in the incomplete penetrance and the variable expressivity of BVMDs is duscussed as well the potential roles of SNPs occuring in coding exons Methods We used genomic PCR with appropriate primers flanking all the exons of the BEST1 gene in order to amplify them. This Genomic PCR was followed by automated sequencing and careful analysis of the sequences obtained. Results We report the case of an unusual family where the Mother II2 of the proband III1, his maternal aunt II3, his brother III3 and his first cousin IIIIV, the son of his maternal aunt, carry a missense mutatation causing apparently only electrophysiological abnormalities. The Father II1 of the proband III1 turned out to carry a stop codon instead of the fifth normal BEST1 codon. The father did not display any electrophysiological nor any clinical abnormality and has a perfect monocular and binocular vision. In contrast the proband III1 carries both mutations with a severe phenotype. Conclusion This report exemplifies the necessity to study all family members in the case of BVMDs.