Familial brain arteriovenous malformation maps to 5p13-q14, 15q11-q13 or 18p11: linkage analysis with clipped fingernail DNA on high-density SNP array

Familial arteriovenous malformations (AVM) in the brain is a very rare disease. It is defined as its occurrence in two or more relatives (up to third-degree relatives) in a family without any associated disorders, such as hereditary hemorrhagic telangiectasia. We encountered a Japanese family with brain AVM in which four affected members in four successive generations were observed. One DNA sample extracted from leukocytes of the proband and ten DNA samples from clipped finger nails of other members were available. A genome-wide linkage analysis was performed on this pedigree using Affymetrix GeneCip 10K 2.0 Xba Array and MERLIN software. We obtained sufficient performance of SNP genotyping in the fingernail samples with the mean SNP call rate of 92.49%, and identified 18 regions with positive LOD scores. Haplotype and linkage analyses with microsatellite markers at these regions confirmed three possible disease-responsible regions, i.e., 5p13.2-q14.1, 15q11.2-q13.1 and 18p11.32-p11.22. Sequence analysis was conducted for ten selected candidate genes at 5p13.2-q14.1, such as MAP3K1, DAB2, OCLN, FGF10, ESM1, ITGA1, ITGA2, EGFLAM, ERBB2IP, and PIK3R1, but no causative genetic alteration was detected. This is the first experience of adoption of fingernail DNA to genome-wide, high-density SNP microarray analysis, showing candidate brain AVM susceptible regions.

Combination of linkage and association studies for brain arteriovenous malformation

BACKGROUND AND PURPOSE

Genetic factors for brain arteriovenous malformation are unexplored because of the low incidence of familial cases, albeit local and familial clustering. We used a combination of a linkage study and an association study to explore the genetic background.

METHODS

A genome-wide linkage analysis was performed in 12 patients from 6 unrelated families using the GENEHUNTER program. A genome-wide association analysis of 26 cases and 30 controls was performed using a GeneChip 10K mapping array. Significance levels for linkage and single single-nucleotide polymorphism association analyses were set at P<0.05 and P<0.0001, respectively. Genotyping was also performed using 58 960 single-nucleotide polymorphisms for 2 sets of discordant twins.

RESULTS

The linkage analysis revealed 7 candidate regions, with the highest logarithm of odds score of 1.88 (P=0.002) at chromosome 6q25. A significant association was observed for 4 single-nucleotide polymorphisms and 2 haplotypes, but none of them overlapped with candidate linkage regions. Genotyping of the twins showed no genetic heterogeneity.

CONCLUSIONS

The present study failed to identify genetic factors for arteriovenous malformation although the low statistical power may have resulted in such evidence being missed.