Identification of a Novel CCM1 Frameshift Mutation in a Chinese Han Family With Multiple Cerebral Cavernous Malformations

Molecular genetic features and clinical manifestations in Chinese familial cerebral cavernous malformation: from a novel KRIT1/CCM1 mutation (c.1119dupT) to an overall view

Cerebral cavernous malformations (CCMs) are common vascular anomaly diseases in the central nervous system associated with seizures, cerebral microbleeds, or asymptomatic mostly. CCMs can be classified as sporadic or familial, with familial cerebral cavernous malformations (fCCMs) being the autosomal dominant manner with incomplete penetrance. Germline mutations of KRIT1, CCM2, and PDCD10 are associated with the pathogenesis of fCCMs. Till now, little is known about the fCCMs mutation spectrum in the Han Chinese population. In this study, we enrolled a large, aggregated family, 11/26 of the family members were diagnosed with CCMs by pathological or neuroradiological examination, with a high percentage (5/9) of focal spinal cord involvement. Genomic DNA sequencing verified a novel duplication mutation (c.1119dupT, p.L374Sfs*9) in exon 9 of the Krev interaction trapped 1 (KRIT1) gene. The mutation causes a frameshift and is predicted to generate a truncated KRIT1/CCM1 protein of 381 amino acids. All our findings confirm that c.1119dupT mutation of KRIT1 is associated with fCCMs, which enriched the CCM genes' mutational spectrum in the Chinese population and will be beneficial for deep insight into the pathogenesis of Chinese fCCMs. Additionally, with a retrospective study, we analyzed the molecular genetic features of Chinese fCCMs, most of the Chinese fCCMs variants are in the KRIT1 gene, and all these variants result in the functional deletion or insufficiency of the C-terminal FERM domain of the KRIT1 protein.

Case Report: A novel heterozygous nonsense mutation in KRIT1 cause hereditary cerebral cavernous malformation

Cerebral cavernous malformation (CCM) is a vascular malformation of the central nervous system and mainly characterized by enlarged capillary cavities without intervening brain parenchyma. Genetic studies have identified three disease-causing genes (CCM1/KRIT1, CCM2/MGC4607 and CCM3/PDCD10) responsible for CCM. Here, we characterized a four-generation family diagnosed with CCM and identified a novel heterozygous mutation c.1159C>T, p.Q387X in KRIT1 gene by whole exome sequencing and Sanger sequencing. The Q387X mutation resulted in premature termination of KRIT1 protein, which was predicted to be deleterious by the ACMG/AMP 2015 guideline. Our results provide novel genetic evidence support that KRIT1 mutations cause CCM, and are helpful to the treatment and genetic diagnosis of CCM.

A Chinese Family With Cerebral Cavernous Malformation Caused by a Frameshift Mutation of the CCM1 Gene: A Case Report and Review of the Literature

Background

Familial cerebral cavernous malformation (FCCM) is a vascular malformation disease closely linked to three identified genes: KRIT1/CCM1, MGC4607/CCM2 and PDCD10/CCM3. Over the past decade, a few cases of cerebral cavernous malformation (CCM) caused by different gene mutations have been reported in Chinese families. Herein, we introduce a Chinese family affected by FCCM due to a kind of KRIT1/CCM1 frameshift mutation. At the same time, a literature review was conducted to identify case reports of familial cerebral cavernous malformation.

Case presentation

The proband in the family in question demonstrated a series of clinical symptoms and features, including headache and bleeding. The proband was hospitalized for headache twice and, both times was examined under suspicion of CCM and received surgical treatment. Magnetic resonance imaging results showed that the proband had multiple intracranial vascular lesions, including on the brain, brainstem, and cerebellum. Genetic test results showed that the classic KRIT1 gene in the proband had a pathogenic mutation. The family members of the proband also showed typical cerebral cavernous malformation when considering clinical manifestations, magnetic resonance imaging findings and genetic test results.

Conclusions

We report a case of Chinese FCCM and its associated symptoms with CCM1-deletion mutations in China. Our findings deepen our understanding of CCM mutations and related phenotypes, the investigation results of this clinical experiment further show that the gene mutation form we reported plays an important role in human FCCM, and this trial investigation is beneficial for genetic counseling for CCM patients.