Abstracts

Schizencephaly is a rare congenital defect of the cerebral cortex characterized by clefts of the cerebral mantle, extending from the pial surface to the lateral ventricles, and lined by heterotopic gray matter. The description of familial cases of schizencephaly raised the hypothesis that genetic factors could play a relevant role in the pathogenesis of this brain malformation. This evidence is supported by the presence, in a few patients, of germline mutations of the homeobox gene [italic]EMX2[/italic]. The objective of this study is to search for mutations in the [italic]EMX2 [/italic]gene in patients with schizencephaly
All patients included in this study had high resolution MRI scans performed in a 2T scanner with T1- and T2-weighted images in three orthogonal planes or CT scans. We searched for mutations in the three coding exons of EMX2 gene in all patients. In addition we genotyped 50 unrelated normal subjects. PCR reactions were performed with primers designed to amplify the entire coding region and intron/exon boundaries of the three exons of the [italic]EMX2[/italic] gene. PCR samples were analyzed by the single-strand conformation polymorphism (SSCP) method. The nucleotide sequence of all fragments showing an altered mobility in the SSCP experiment were subsequently determined using the Big Dye Terminator Sequencing kit for megaBACE[reg]1000.
A total of 34 patients were analyzed in this study. Only one of our patients had a familiar history of epilepsy but none of them had a positive family history for brain abnormalities, or mental impairment. Ten patients had bilateral open lip clefts, four patients had both types of clefts, four patients had unilateral closed lip cleft, nine patients had unilateral open lip cleft and seven patients had clefts not yet classified. SSCP analysis identified band shifts in exon-2 in four patients. Automatic sequencing has identified a C[rarr] A substitution that does not change the wild type amino acid arginine in position 156 of the protein. In addition, the [underline]same sequencing change[/underline] was found in 4 individuals of the [underline]control group.[/underline]
Although the C[rarr]A substitution has been previously reported as disease related in schizencephaly patients, our results clearly show that this mutation is not involved in the etiology of this disorder in our group of patients, since it was present in 8% of our control group. In addition, it is likely that abnormalities in [italic]EMX2[/italic] is not a major cause of brain malformation since only a few reports confirmed the presence of these mutations in patients with schizencephaly.
[Supported by: CAPES and FAPESP]