Mutations in the gene encoding KRIT1, a Krev-1/rap1a binding protein, cause cerebral cavernous malformations (CCM1).

Cerebral cavernous malformations (CCM) are congenital vascular anomalies of the brain that can cause significant neurological disabilities, including intractable seizures and hemorrhagic stroke. One locus for autosomal dominant CCM ( CCM1 ) maps to chromosome 7q21-q22. Recombination events in linked family members define a critical region of approximately 2 Mb and a shared disease haplotype associated with a presumed founder effect in families of Mexican-American descent points to a potentially smaller region of interest. Using a genomic sequence-based positional cloning strategy, we have identified KRIT1, encoding a protein that interacts with the Krev-1/rap1a tumor suppressor, as the CCM1 gene. Seven different KRIT1 mutations have been identified in 23 distinct CCM1 families. The identical mutation is present in 16 of 21 Mexican-American families analyzed, substantiating a founder effect in this population. Other Mexican-American and non-Hispanic Caucasian CCM1 kindreds harbor other KRIT1 mutations. Identification of a common Mexican-American mutation has potential clinical significance for presymptomatic diagnosis of CCM in this population. In addition, these data point to a key role for the Krev-1/rap1a signaling pathway in angiogenesis and cerebrovascular disease.

Evidence for a novel gene for familial febrile convulsions, FEB2, linked to chromosome 19p in an extended family from the Midwest.

Febrile convulsions are a common form of childhood seizure. It is estimated that between 2 and 5% of children will have a febrile convulsion before the age of 5. It has long been recognized that there is a significant genetic component for susceptibility to this type of seizure. Wallace, Berkovic and co-workers recently reported linkage of a putative autosomal dominant febrile convulsion gene to chromosome 8q13-21. We report here another autosomal dominant febrile convulsion locus on chromosome 19p. Linkage analysis in this large multi-generational family gave a maximum pairwise lod score of 4.52 with marker Mfd120 at locus D19S177. Linkage to the chromosome 8 locus was excluded in this family. Haplotype analysis using both affected and unaffected family members indicates that this febrile convulsion gene, which we call FEB2 , can be localized to an 11.7 cM, 1-2 Mb section of chromosome 19p13.3, between loci D19S591 and D19S395.