Biallelic somatic and germ line CCM1 truncating mutations in a cerebral cavernous malformation lesion.
OBJECTIVE
Cerebral cavernous malformations (CCMs) are focal dysmorphic blood vessel anomalies that predispose patients to hemorrhagic stroke and epilepsy. CCMs are sporadic or inherited and 3 genes (CCM1, CCM2, and CCM3) have been identified. However, the role of somatic mutation in CCM genesis has been disputed. The hypothesis that somatic mutations contribute to CCM lesion genesis is tested.


METHODS
Mutations were identified by analysis of polymerase chain reaction (PCR) products spanning the 16 CCM1 coding exons with denaturing high-pressure liquid chromatography (DHPLC), cloning, and sequencing. Somatic mutation was verified 3 ways in lesion DNA and RNA samples. The somatic and germ line mutations were shown to be biallelic using allele specific reverse-transcribed PCR amplification and sequence analyses.


RESULTS
A somatic 34-nucleotide deletion in CCM1 is identified in a CCM lesion along with a germ line CCM1 mutation (Q455X). The somatic mutation is not present in DNA or RNA isolated from the patient's blood. These 2 genetic hits are biallelic.


CONCLUSIONS
Identification of biallelic CCM1 somatic and germ line truncating mutations strongly support the "two-hit" mechanism in this CCM lesion.
Gault
Judith
J
Department of Neurosurgery, University of Colorado Health Sciences Center, Denver, Colo, USA. judith.gault@uchsc.edu
Shenkar
Robert
R
Recksiek
Peter
P
Awad
Issam A
IA
D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D002851:Chromatography, High Pressure Liquid; D005091:Exons; D017353:Gene Deletion; D005819:Genetic Markers; D018095:Germ-Line Mutation; D020786:Hemangioma, Cavernous, Central Nervous System / Q000235:genetics*; D006470:Hemorrhage / Q000235:genetics*; D006801:Humans; D000075927:KRIT1 Protein; D008279:Magnetic Resonance Imaging; D008869:Microtubule-Associated Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D012313:RNA / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D020521:Stroke / Q000235:genetics
D005819:Genetic Markers; D000075927:KRIT1 Protein; C107928:KRIT1 protein, human; D008869:Microtubule-Associated Proteins; D011518:Proto-Oncogene Proteins; D012313:RNA