CCM1 gene mutations in families segregating cerebral cavernous malformations Article abstract—Cerebral cavernous malformations (CCM) are vascular anomalies, sometimes inherited as an autosomal dominant trait, which can cause strokes and seizures. Recently, mutations of the CCM1 gene (chromo- some 7q) have been found in a subset of families. The authors found 10 new mutations by screening 29 families and five seemingly sporadic cases of CCM. The mutations predicted truncation of the Krit1 mRNA encoded by CCM1, supporting the contention that CCM result from loss of Krit1 protein function and the possibility that this protein acts as a tumor suppressor. NEUROLOGY 2001;56:540 –543 W.J. Davenport, MD; A.M. Siegel, MD; J. Dichgans, MD; P. Drigo, MD; I. Mammi, MD; P. Pereda, MD; N.W. Wood, MD; and G.A. Rouleau, MD Cerebral cavernous malformations (CCM) are vascu- lar anomalies (dilated vessels) constituting approxi- mately 10 to 20% of cerebral vascular lesions. They occur singly or in multiple and can lead to focal neu- rologic signs, seizures, or hemorrhagic stroke. Sei- zure is the most common presentation. 1 Although the defining lesions of CCM are cerebral, lesions can oc- cur in the spinal cord and skin. Ophthalmologists also report instances of cerebral cavernous angiomas in patients with retinal cavernous hemangiomas. 2 The vascular malformations occur in families and in individuals without a family history of the disease. Imaging of asymptomatic members of affected fami- lies shows that CNS lesions can be clinically silent, and because all first-degree relatives of patients with CCM may not be screened radiologically, the ratio of true sporadic to familial cases may be underestimated. 1,3 Recently, a gene causing cerebral cavernous mal- formations in a subset of families with the disease was identified. 4,5 CCM1 encodes the ankyrin repeat- containing protein Krit1 (Genbank cDNA sequence accession number U90268). 6 In addition to CCM1 (Mendelian Inheritance in Man [MIM] #116860; *604214), two other loci with purported genes CCM2 (MIM *603284) and CCM3 (MIM *603285) are linked to distinct subsets of families. 7 In vitro the CCM1 protein product Krit1 binds a putative tumor sup- pressor protein, Krev-1/rap1a, which in turn may participate in angiogenesis. Krit1 also has a domain that regulates cytoskeletal–plasma membrane in- teractions, the FERM domain of the erzin/radixin/ moesin protein family. 6 This FERM domain, in com- bination with ankyrin repeats, has not been found in any protein other than Krit1. 4 Although the initial study identifying Krit1 noted expression in heart, muscle, and brain but not in other tissues, 6 subse- quent experiments showed varying levels of expres- sion in these organs and also in placenta, lung, liver, skeletal muscle, kidney, and pancreas. 4 The clinical phenotype in CCM of scattered lesions plus the structure and protein associates of Krit1 suggest that the disease may be caused by sporadic loss of a single remaining functional gene in het- erozygous individuals. 4,5 To explain the peculiarity of uniquely vascular lesions restricted to a few organs, especially the CNS, requires better definition of the role of Krit1 and its gene, CCM1. Methods. Patients. We screened DNA from 29 families and five apparently sporadic cases of CCM for mutations in CCM1. The families participated in the International Familial Cavernous Angioma Study (IFCAS). 8 Twenty- nine families and five sporadic cases of CCM were identi- fied in our DNA sample collection. One of these families has been described elsewhere (IFCAS-7). 9 DNA was col- lected with informed consent. Families were from Switzer- land, Italy, Uruguay, United States, Japan, Israel, Germany, United Kingdom, and Canada. One of the fami- lies in the United States was Mexican-American. Diagno- sis of CCM included brain MRI or CT in at least two affected family members and, in some cases, biopsy, surgi- cal excision, or autopsy. In all familial cases, the diagnosis of cerebral angiomas was verified by MRI. Additionally, in five families the proband had surgical confirmation of dis- ease. In all seemingly sporadic cases, the diagnosis was confirmed by surgery. The diagnosis of hepatic hemangio- mas and confirmation of the diagnosis of skin angiomas were by ultrasound. Neurologic signs and symptoms in- cluded visual deficits, paresis, seizures, and paresthesias; headache was commonly reported. Onset of symptoms ranged from the first to sixth decade, sometimes earlier in later generations, as has been reported. 10 Gene analysis. DNA from 29 families (plus six control spouses) and five seemingly sporadic patients was ex- tracted from whole blood or from cultured lymphocytes by phenol and chloroform extraction. Each of the 12 exons of From the Center for Research in the Neurosciences, Montreal General Hospital, and Department of Neurology and Neurosurgery (Drs. Davenport and Rouleau), McGill University, Montreal, Quebec, Canada; Epilepsy Pro- gram (Dr. Siegel), Department of Neurology, University Hospital Zürich, Switzerland; Department of Neurology (Dr. Dichgans), University of Tübin- gen, Germany; Department of Pediatrics (Drs. Drigo and Mammi), Univer- sity of Padua, Italy; Clinica Neurologica (Dr. Pereda), Ospedalo Universitario, Montevideo, Uruguay; and the Institute of Neurology and Neurogenetics (Dr. Wood), National Hospital for Neurology and Neurosur- gery, London, United Kingdom. Supported by the Schweizerischer Nationalfonds (Swiss National Research Foundation), the Kommission zur Förderung des akademischen Nachwuch- ses des Kt.Zürichs, and the Julius Klaus-Stiftung (A.M.S). Also supported by the Medical Research Council of Canada (G.A.R.). Received June 2, 2000. Accepted in final form October 27, 2000. Address correspondence and reprint requests to Dr. Guy Rouleau, Center for Research in Neurosciences, Montreal General Hospital, and Department of Neurology and Neurosurgery, McGill University, 1650 Cedar Avenue, Montreal, Quebec, H3G 1A4 Canada; e-mail: mi32@musica.mcgill.ca 540 Copyright © 2001 by AAN Enterprises, Inc.