Novel CCM2 missense variants abrogating the CCM1-CCM2 interaction cause cerebral cavernous malformations

Comprehensive analysis of Novel mutations in CCM1/KRIT1 and CCM2/MGC4607 and their clinical implications in Cerebral Cavernous malformations

BACKGROUND

Cerebral Cavernous Malformations (CCM) is a genetic disease characterized by vascular abnormalities in the brain and spinal cord, affecting 0.4-0.5 % of the population. We identified two novel pathogenic mutations, CCM1/KRIT1 c.811delT (p.Trp271GlyfsTer5) and CCM2/MGC4607 c.613_614insGG p.Glu205GlyfsTer31), which disrupt crucial protein domains and potentially alter disease progression.

OBJECTIVE

The study aims to comprehensively analyze a Brazilian cohort of CCM patients, integrating genetic, clinical, and structural aspects. Specifically, we sought to identify novel mutations within the CCM complex, and explore their potential impact on disease progression.

METHODS

We conducted a detailed examination of neuroradiological and clinical features in both symptomatic and asymptomatic CCM patients, performing genetic analyses through sequencing of the CCM1/KRIT1, CCM2/MGC4607, and CCM3/PDCD10 genes In silico structural predictions were carried out using PolyPhen-2, SIFT, and Human Genomics Community tools. Protein-protein interactions and docking analyses were explored using the STRING database.

RESULTS

Genetic analysis identifies 6 pathogenic mutations, 4 likely pathogenic, 1 variants of uncertain significance, and 7 unclassified mutations, including the novel mutations in CCM1 c.811delT and CCM2 c.613_614insGG. In silico structural analysis revealed significant alterations in protein structure, supporting their pathogenicity. Protein-protein interaction analysis indicated nuanced impacts on cellular processes. Clinically, we observed a broad spectrum of symptoms, including seizures and focal neurological deficits. However, no statistically significant differences were found in lesion burden, age of first symptom onset, or sex between the identified CCM1/KRIT1 and CCM2/MGC4607 mutations among all patients studied.

CONCLUSION

This study enhances the understanding of CCM by linking clinical variability, genetic mutations, and structural effects. The identification of these novel mutations opens new avenues for research and potential therapeutic strategies.

A Novel CCM2 Missense Variant Caused Cerebral Cavernous Malformations in a Chinese Family

Cerebral cavernous malformations (CCMs) are common vascular malformations in the central nervous system. Familial CCMs (FCCMs) are autosomal dominant inherited disease with incomplete penetrance and variable symptoms. Mutations in the KRIT1, CCM2, and PDCD10 genes cause the development of FCCM. Approximately 476 mutations of three CCM-related genes have been reported, most of which were case reports, and lack of data in stable inheritance. In addition, only a small number of causative missense mutations had been identified in patients. Here, we reported that 8/20 members of a Chinese family were diagnosed with CCMs. By direct DNA sequencing, we found a novel variant c.331G > C (p.A111P) in exon 4 of the CCM2 gene, which was a heterozygous exonic variant, in 7/20 family members. We consider this variant to be causative of disease due to a weaken the protein-protein interaction between KRIT1 and CCM2. In addition, we also found the exon 13 deletion in KRIT1 coexisting with the CCM2 mutation in patient IV-2, and this was inherited from her father (patient III-1H). This study of a Chinese family with a large number of patients with CCMs and stable inheritance of a CCM2 mutation contributes to better understanding the spectrum of gene mutations in CCMs.