Cerebral cavernous malformations: somatic mutations in vascular endothelial cells.
OBJECTIVE
Germline mutations in 3 genes have been found in familial cases of cerebral cavernous malformations (CCMs). We previously discovered somatic and germline truncating mutations in the KRIT1 gene, supporting the "2-hit" mechanism of CCM lesion formation in a single lesion. The purpose of this study was to screen for somatic, nonheritable mutations in 3 more lesions from different patients and identify the cell type(s) in which somatic mutations occur.


METHODS
Somatic mutations were sought in DNA from 3 surgically excised, fresh-frozen CCM lesions by cloning and screening polymerase chain reaction products generated from KRIT1 or PDCD10 coding regions. Laser capture microdissection was used on isolated endothelial and nonendothelial cells to determine whether somatic mutations were found in endothelial cells.


RESULTS
CCM lesions harbor somatic and germline KRIT1 mutations on different chromosomes and are therefore biallelic. Both mutations are predicted to truncate the protein. The KRIT1 somatic mutations (novel c.1800delG mutation and previously identified 34 nucleotide deletion) in CCMs from 2 different patients were found only in the vascular endothelial cells lining caverns. No obvious somatic mutations were identified in the 2 other lesions; however, the results were inconclusive, possibly owing to the technical limitations or the fact that these specimens had a small proportion of vascular endothelial cells lining pristine caverns.


CONCLUSIONS
The "2-hit" mechanism occurs in vascular endothelial cells lining CCM caverns from 2 patients with somatic and Hispanic-American KRIT1 germline mutations. Methods for somatic mutation detection should focus on vascular endothelial cells lining pristine caverns.
Gault
Judith
J
Department of Neurosurgery, University of Colorado, Denver, Aurora, Colorado, USA. Judith.Gault@UCDenver.edu
Awad
Issam A
IA
Recksiek
Peter
P
Shenkar
Robert
R
Breeze
Robert
R
Handler
Michael
M
Kleinschmidt-DeMasters
Bette K
BK
D000293:Adolescent; D051017:Apoptosis Regulatory Proteins / Q000235:genetics*; D002675:Child, Preschool; D004252:DNA Mutational Analysis / Q000379:methods; D042783:Endothelial Cells / Q000473:pathology*; D005260:Female; D005787:Gene Frequency; D005838:Genotype; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000473:pathology*; D000075927:KRIT1 Protein; D008279:Magnetic Resonance Imaging; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008875:Middle Aged; D017354:Point Mutation / Q000235:genetics*; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism*
D051017:Apoptosis Regulatory Proteins; D000075927:KRIT1 Protein; C107928:KRIT1 protein, human; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; C495390:PDCD10 protein, human; D011518:Proto-Oncogene Proteins