Multiplex ligation-dependent probe amplification detects DCX gene deletions in band heterotopia.
BACKGROUND
Subcortical band heterotopia (SBH, or double cortex syndrome) is a neuronal migration disorder consisting of heterotopic bands of gray matter located between the cortex and the ventricular surface, with or without concomitant pachygyria. Most cases show diffuse or anteriorly predominant (A>P) migration abnormality. All familial and 53% to 84% of sporadic cases with diffuse or A>P SBH harbor a mutation of the DCX gene, leaving the genetic causes unexplained, and genetic counseling problematic, in the remaining patients. Our purpose was to verify the extent to which exonic deletions or duplications of the DCX gene would account for sporadic SBH with A>P gradient but normal gene sequencing.


METHODS
We identified 23 patients (22 women, 1 man) with sporadic, diffuse, or anteriorly predominant SBH. After sequencing the DCX gene and finding mutations in 12 (11 women, 1 man), we used multiplex ligation-dependent probe amplification (MLPA) to search for whole-exon deletions or duplications in the 11 remaining women. We used semiquantitative fluorescent multiplex PCR (SQF-PCR) and Southern blot to confirm MLPA findings.


RESULTS
MLPA assay uncovered two deletions encompassing exons 3 to 5, and one involving exon 6, in 3 of 11 women (27%) and raised the percentage of DCX mutations from 52% to 65% in our series. SQF-PCR performed in all three women and Southern blot analysis performed in two confirmed the deletions.


CONCLUSIONS
MLPA uncovers large genomic deletions of the DCX gene in a subset of patients with SBH in whom no mutations are found after gene sequencing. Deletions of DCX are an underascertained cause of SBH.
Mei
D
D
Pediatric Neurology Unit and Laboratories, Children's Hospital A. Meyer-University of Florence, via Luca Giordano 13, 50123, Florence, Italy.
Parrini
E
E
Pasqualetti
M
M
Tortorella
G
G
Franzoni
E
E
Giussani
U
U
Marini
C
C
Migliarini
S
S
Guerrini
R
R
D000293:Adolescent; D000328:Adult; D001921:Brain / Q000002:abnormalities*; D002648:Child; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D015342:DNA Probes / Q000235:genetics; D000089622:Doublecortin Domain Proteins; D000089662:Doublecortin Protein; D005260:Female; D017353:Gene Deletion; D020022:Genetic Predisposition to Disease / Q000235:genetics; D005820:Genetic Testing / Q000379:methods*; D006801:Humans; D008297:Male; D008869:Microtubule-Associated Proteins / Q000235:genetics*; D009421:Nervous System Malformations / Q000235:genetics*; D009479:Neuropeptides / Q000235:genetics*; D021141:Nucleic Acid Amplification Techniques / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
C000714328:DCX protein, human; D015342:DNA Probes; D000089622:Doublecortin Domain Proteins; D000089662:Doublecortin Protein; D008869:Microtubule-Associated Proteins; D009479:Neuropeptides