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We report a recurrent microdeletion syndrome causing mental retardation, epilepsy and variable facial and digital dysmorphisms. We describe nine affected individuals, including six probands: two with de novo deletions, two who inherited the deletion from an affected parent and two with unknown inheritance. The proximal breakpoint of the largest deletion is contiguous with breakpoint 3 (BP3) of the Prader-Willi and Angelman syndrome region, extending 3.95 Mb distally to BP5. A smaller 1.5-Mb deletion has a proximal breakpoint within the larger deletion (BP4) and shares the same distal BP5. This recurrent 1.5-Mb deletion contains six genes, including a candidate gene for epilepsy (CHRNA7) that is probably responsible for the observed seizure phenotype. The BP4-BP5 region undergoes frequent inversion, suggesting a possible link between this inversion polymorphism and recurrent deletion. The frequency of these microdeletions in mental retardation cases is approximately 0.3% (6/2,082 tested), a prevalence comparable to that of Williams, Angelman and Prader-Willi syndromes.

Original publication

DOI

10.1038/ng.93

Type

Journal article

Journal

Nat Genet

Publication Date

03/2008

Volume

40

Pages

322 - 328

Keywords

Adolescent, Child, Child, Preschool, Chromosome Breakage, Chromosomes, Human, Pair 15, Female, Gene Deletion, Gene Frequency, Humans, Inheritance Patterns, Intellectual Disability, Male, Pedigree, Receptors, Nicotinic, Seizures, Syndrome, alpha7 Nicotinic Acetylcholine Receptor