Mutations in CYP1B1, the Gene for Cytochrome P4501B1, Are the Predominant Cause of Primary Congenital Glaucoma in Saudi Arabia

Abstract

The autosomal recessive disorder primary congenital glaucoma (PCG) is caused by unknown developmental defect(s) of the trabecular meshwork and anterior chamber angle of the eye. Homozygosity mapping with a DNA pooling strategy in three large consanguineous Saudi PCG families identified the GLC3A locus on chromosome 2p21 in a region tightly linked to PCG in another population. Formal linkage analysis in 25 Saudi PCG families confirmed both significant linkage to polymorphic markers in this region and incomplete penetrance, but it showed no evidence of genetic heterogeneity. For these 25 families, the maximum combined two-point LOD score was 15.76 at a recombination fraction of .021, with the polymorphic marker D2S177. Both haplotype analysis and homozygosity mapping in these families localized GLC3A to a 5-cM critical interval delineated by markers D2S2186 and D2S1356. Sequence analysis of the coding exons for cytochrome P4501B1 (CYP1B1) in these 25 families revealed three distinctive mutations that segregate with the phenotype in 24 families. Additional clinical and molecular data on some mildly affected relatives showed variable expressivity of PCG in this population. These results should stimulate a study of the genetic and environmental events that modify the effects of CYP1B1 mutations in ocular development. Furthermore, the small number of PCG mutations identified in this Saudi population makes both neonatal and population screening attractive public health measures.

Novel cytochrome P450 1B1 (CYP1B1) mutations in patients with primary congenital glaucoma in France

“…Numerous mutations of this gene have been characterized in PCG patients from different populations (Sarfarazi and Stoilov, 2000). In some ethnic groups, however, the diversity of mutations is restricted and founding effects are apparent (Bejjani et al, 1998;Plasilova et al, 1999;Belmouden et al, 2002;Sitorus et al, 2003). In the present study, we have investigated mutations of the CYP1B1 gene in 31 unrelated French PCG patients.…”

“…The coding region (exon II and III) of CYP1B1 was amplified from genomic DNA and sequenced as previously described (Bejjani et al, 1998;Stoilov et al, 1998). PCR products were gel-purified and subjected to dideoxy sequencing using sequencing primers described elsewhere (Bejjani et al, 1998).…”

“…PCR products were gel-purified and subjected to dideoxy sequencing using sequencing primers described elsewhere (Bejjani et al, 1998). DNA variants were confirmed by sequencing both strands from two different amplification products.…”

Accurate DNA Fragment Sizing by Capillary Electrophoresis with Laser-Induced Fluorescence Array for Detection of Sequence Specificity of DNA Damage

“…To create stand breaks at specific points; abasic sites have first to be created "specifically" at the damaged nucleobase sites. N-7 alkylated guanines 44 and N-3 alkylated adenines 45 depurinate at accelerated rates compared to intact guanines and adenines. However, depurination of intact nucleobases can be significant under certain conditions.…”

“…The predominant peaks within the range of the size standards are labeled 1-11. Using the correction table, these correspond to DNA fragments that are 29,31,33,40,45,48,50,63,65,69, and 72 bases, respectively. (Figure 2b).…”