Molecular screening test in familial forms of cerebral cavernous malformation: the impact of the Multiplex Ligation-dependent Probe Amplification approach

PDCD10 gene mutations in multiple cerebral cavernous malformations

Cerebral cavernous malformations (CCMs) are vascular abnormalities that may cause seizures, intracerebral haemorrhages, and focal neurological deficits. Familial form shows an autosomal dominant pattern of inheritance with incomplete penetrance and variable clinical expression. Three genes have been identified causing familial CCM: KRIT1/CCM1, MGC4607/CCM2, and PDCD10/CCM3. Aim of this study is to report additional PDCD10/CCM3 families poorly described so far which account for 10-15% of hereditary cerebral cavernous malformations. Our group investigated 87 consecutive Italian affected individuals (i.e. positive Magnetic Resonance Imaging) with multiple/familial CCM through direct sequencing and Multiplex Ligation-Dependent Probe Amplification (MLPA) analysis. We identified mutations in over 97.7% of cases, and PDCD10/CCM3 accounts for 13.1%. PDCD10/CCM3 molecular screening revealed four already known mutations and four novel ones. The mutated patients show an earlier onset of clinical manifestations as compared to CCM1/CCM2 mutated patients. The study of further families carrying mutations in PDCD10/CCM3 may help define a possible correlation between genotype and phenotype; an accurate clinical follow up of the subjects would help define more precisely whether mutations in PDCD10/CCM3 lead to a characteristic phenotype.

Cavernous malformations

Cavernous malformations (CMs) are vascular lesions found in the central nervous system (CNS) and throughout the body and have been called cavernomas, cavernous angiomas, and cavernous hemangiomas. This article discusses the epidemiology, natural history, diagnosis, treatment and follow-up of children who are found to harbor these lesions. CMs affect children by causing hemorrhage, seizure, focal neurologic deficits, and headache. Diagnosis is best made with magnetic resonance imaging. Patients with multiple lesions should be referred for genetic evaluation and counseling. Individuals with symptomatic, growing, or hemorrhagic malformations should be considered for surgical resection. Close follow-up after diagnosis and treatment is helpful to identify lesion progression or recurrence.

Advances in the biology of cerebral cavernous malformations

OBJECT

To provide a review of current, high-impact scientific findings pertaining to the biology of cerebral cavernous malformations (CCMs).

METHODS

A comprehensive literature review was conducted using PubMed to examine the current literature regarding the molecular biology and pathophysiology of CCMs.

RESULTS

In this literature review, a comprehensive approach is taken to review the current scientific status of CCMs. This includes discussion of molecular biology and animal models, ultrastructure and angioarchitectural features and immunological methods and hypotheses.

CONCLUSIONS

Studies examining the molecular biology of CCMs have shown that genes involved in angiogenesis, blood-brain barrier formation, cell size regulation, vascular permeability and apoptosis play critical roles in the ontogeny of this disease. In vivo work suggests the likelihood of a "two-hit mechanism" resulting in somatic mosaicism and biallelic loss of angiogenic genes. The etiological effects of angioarchitecture and immune response within these lesions further complicate the pathophysiology. Future treatment endeavors will necessitate exploitation of the multiple facets of CCM formation to maximize success at CCM prevention or obliteration.

Small deletion at the 7q21.2 locus in a CCM family detected by real-time quantitative PCR

Cerebral cavernous malformations (CCMs) represent a common autosomal dominant disorder that predisposes patients to haemorrhagic strokes and focal neurological signs. About 56% of the hereditary forms of CCMs have been so far associated with mutations in the KRIT1 (Krev Interaction Trapped 1) gene, located at 7q21.2 (CCM1 locus). We described the complete loss of 7q21.2 locus encompassing the KRIT1 gene and 4 flanking genes in a CCM family by using a dense set of 12 microsatellite markers. The complete loss of the maternal copy of KRIT1 gene region was confirmed by Real-Time Quantitative Polymerase Chain Reaction (RT-QPCR) and the same approach was used for expression analysis. Additional RT-QPCR analysis showed the extension of the deletion, for a total of 700 kb, to the adjacent downstream and upstream-located genes, MTERF, AKAP9, CYP51A1, as well as a partial loss of the ANKIB1 gene. Here we report the molecular characterization of an interstitial small genomic deletion of the 7q21.2 region in a CCMs affected family, encompassing the KRIT1 gene. Our findings confirm the loss of function mechanism for the already known CCM1 locus, without any evident involvement of the other deleted genes. Moreover, our investigations highlight the usefulness of the RT-QPCR to the molecular characterization of the breakpoints genomic deletions and to the identification of internal deleted genes involved in the human genetic diseases.

Paediatric presentation of familial cerebral cavernoma

We report the case of a 13-year-old male who presented with headaches and was presumed to have a brain tumour. He was subsequently found to have multiple cerebral cavernomas with haemorrhage and positive family history. We review the literature on familial cavernomas. Cerebral cavernous malformations (CCMs) are characterized by abnormally enlarged capillary cavities without intervening brain parenchyma [Verlaan et al. Neurology 2005; 65:1982-1983] that may involve any part of the central nervous system. Focal neurologic deficit and haemorrhage occur in 45% of children, higher than in adults [Stoeter. Neurosurg Rev 2001; 24]. Paediatric patients with symptomatic cavernous malformations should be treated surgically because of the risk of haemorrhage [Lee et al. Child's Nervous Syst 2008; 24:321-327].