Abstract
Purpose:
BCM is a rare X-linked disorder of color vision characterized by the absence of both red and green cone sensitivities. BCM is caused by discrete mutations in each of red (R) and green (G) opsin genes or a single mutation within the LCR in the upstream of R. We performed a fine analysis of the mutations in two Japanese families (W and N) with BCM.
Methods:
Affected males were examined clinically, and their DNA was obtained with informed consents. Various parts of R and G genes and the LCR were amplified by PCR, and direct sequencing was performed to find mutations. A PCR-based genomic walking was done to determine the unknown DNA sequence when necessary.
Results:
Affected males were examined clinically, and their DNA was obtained with informed consents. Various parts of R and G genes and the LCR were amplified by PCR, and direct sequencing was performed to find mutations. A PCR-based genomic walking was done to determine the unknown DNA sequence when necessary. In family W, a 16,803-bp deletion was found. The proximal boundary of the deletion was 8,845-bp upstream from the translation initiation codon of R gene, and the distal boundary was within intron 2 of R gene. While, family N revealed a complicated 87,355-bp deletion with 328-bp inversion and 3-bp insertion. The proximal boundary of the deletion was 28,144-bp upstream from the initiation codon of R gene, and the distal boundary was within the downstream region of the first G gene. In both cases, the deletion was associated with a highly repetitive sequence AluSz.
Conclusions:
In two Japanese families with BCM, the disease-causative mutations were the deletion of long region including the LCR. This is the first report of the single base-level analysis of BCM cases caused by the deletion including the LCR.
Keywords: 539 genetics •
533 gene/expression