Cerebral cavernous malformations: somatic mutations in vascular endothelial cells.

Area of Science:

• Genetics
• Molecular Biology
• Vascular Biology

Background:

• Cerebral cavernous malformations (CCMs) are linked to germline mutations in specific genes.
• A "2-hit" mechanism involving somatic and germline mutations in KRIT1 has been previously identified in CCM lesions.
• Understanding the cellular origin of somatic mutations is crucial for CCM pathogenesis.

Purpose of the Study:

• To investigate somatic, nonheritable mutations in additional CCM lesions.
• To identify the specific cell types within CCM lesions harboring somatic mutations.
• To further elucidate the "2-hit" mechanism in CCM development.

Main Methods:

• Somatic mutations were screened in DNA from excised CCM lesions using polymerase chain reaction and cloning.
• KRIT1 and PDCD10 coding regions were analyzed for mutations.
• Laser capture microdissection isolated endothelial and nonendothelial cells for mutation analysis.

Main Results:

• Somatic KRIT1 mutations were identified in the vascular endothelial cells of CCM lesions from two patients.
• These somatic mutations, along with germline mutations, result in biallelic inactivation and protein truncation.
• No conclusive somatic mutations were found in other lesions, potentially due to technical limitations or cell composition.

Conclusions:

• The "2-hit" mechanism in CCMs involves somatic mutations occurring in vascular endothelial cells.
• This cellular localization was observed in patients with both somatic and germline KRIT1 mutations.
• Future diagnostic strategies for somatic mutations should prioritize vascular endothelial cells within pristine CCM caverns.