Sporadic cerebral cavernous malformations: report of further mutations of CCM genes in 40 Italian patients

Abstract

Cerebral cavernous malformations (CCMs) are vascular lesions characterized by abnormally enlarged capillary cavities, affecting the central nervous system. CCMs can occur sporadically or as a familial autosomal dominant condition with incomplete penetrance and variable clinical expression attributable to mutations in three different genes: CCM1 (K-Rev interaction trapped 1 (KRIT1)), CCM2 (MGC4607), and CCM3 (PDCD10). CCMs occur as a single or multiple malformations that can lead to seizures, focal neurological deficits, hemorrhagic stroke, and headache. However, patients are frequently asymptomatic. In our previous mutation screening, performed in a cohort of 95 Italian patients, both sporadic and familial, we have identified several mutations in CCM genes, three of which in three distinct sporadic patients. In this study, representing further molecular screening of the three CCM genes, in a south Italian cohort of CCM patients enrolled by us in the last three years, we report the identification of other four new mutations in 40 sporadic patients with either single or multiple CCM.

Figure 1

Identification of two mutations in 3′UTR of the CCM1 gene in a sporadic CCM patient. (a) Left: partial wild-type sequence of 3′UTR of the CCM1 gene; right: mutated sequence of 3′UTR of the CCM1 gene showing the variants c.*132T>G and c.*137delC (arrows) in heterozygous condition. (b) Left: schematic representation of the sequence alignment of the hsa-miR-324-3p and hsa-miR-1913 with wild-type (WT) CCM1 mRNA (sequence target); right: schematic representation of the sequence alignment of hsa-miR-1281 with mutated CCM1 mRNA (sequence target). The “seed region” at the 5′ end of miRNA is shown in blue. While c.*132T>G is located 2 bp upstream of the predicted target sequence for has-miR-324-3p and hsa-miR-1913, the c.*137delC resides inside a sequence matching the seed of miRNAs. The c.*137 C deletion totally abolishes the interaction of hsa-miR-324-3p and hsa-miR-1913 with the sequence target. The two mutations together create a seed site in the 3′ UTR of mutated CCM1 mRNA for the interaction with hsa-miR-1281.

Figure 2

Identification of a mutation in exon 10 of CCM2 gene in a sporadic CCM patient. (a) At the top: partial wild-type sequence of exon 10 of CCM2 gene; at the bottom: partial mutated sequence of exon 10 of CCM2 gene showing the mutation c.1280 A>G (arrow) in heterozygous condition. (b) The D427 residue, highlighted in yellow in the figure, is highly conserved among species. (c) Web informatics tools used for the in silico analysis and prediction results.

Figure 3

Identification of an intronic mutation in CCM1 gene, c.1254+14 T>A (IVS12+14 T>A).