title: Structures and molecular mechanisms for common 15q13.3 microduplications involving CHRNA7: benign or pathological?
abstract: We have investigated four approximately 1.6-Mb microduplications and 55 smaller 350-680-kb microduplications at 15q13.2-q13.3 involving the CHRNA7 gene that were detected by clinical microarray analysis. Applying high-resolution array-CGH, we mapped all 118 chromosomal breakpoints of these microduplications. We also sequenced 26 small microduplication breakpoints that were clustering at hotspots of nonallelic homologous recombination (NAHR). All four large microduplications likely arose by NAHR between BP4 and BP5 LCRs, and 54 small microduplications arose by NAHR between two CHRNA7-LCR copies. We identified two classes of approximately 1.6-Mb microduplications and five classes of small microduplications differing in duplication size, and show that they duplicate the entire CHRNA7. We propose that size differences among small microduplications result from preexisting heterogeneity of the common BP4-BP5 inversion. Clinical data and family histories of 11 patients with small microduplications involving CHRNA7 suggest that these microduplications might be associated with developmental delay/mental retardation, muscular hypotonia, and a variety of neuropsychiatric disorders. However, we conclude that these microduplications and their associated potential for increased dosage of the CHRNA7-encoded alpha 7 subunit of nicotinic acetylcholine receptors are of uncertain clinical significance at present. Nevertheless, if they prove to have a pathological effects, their high frequency could make them a common risk factor for many neurobehavioral disorders.
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA.
authors.forename: Przemyslaw
authors.initials: P
authors.lastname: Szafranski
authors.forename: Christian P
authors.initials: CP
authors.lastname: Schaaf
authors.forename: Richard E
authors.initials: RE
authors.lastname: Person
authors.forename: Ian B
authors.initials: IB
authors.lastname: Gibson
authors.forename: Zhilian
authors.initials: Z
authors.lastname: Xia
authors.forename: Sangeetha
authors.initials: S
authors.lastname: Mahadevan
authors.forename: Joanna
authors.initials: J
authors.lastname: Wiszniewska
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Bacino
authors.forename: Seema
authors.initials: S
authors.lastname: Lalani
authors.forename: Lorraine
authors.initials: L
authors.lastname: Potocki
authors.forename: Sung-Hae
authors.initials: SH
authors.lastname: Kang
authors.forename: Ankita
authors.initials: A
authors.lastname: Patel
authors.forename: Sau Wai
authors.initials: SW
authors.lastname: Cheung
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Probst
authors.forename: Brett H
authors.initials: BH
authors.lastname: Graham
authors.forename: Marwan
authors.initials: M
authors.lastname: Shinawi
authors.forename: Arthur L
authors.initials: AL
authors.lastname: Beaudet
authors.forename: Pawel
authors.initials: P
authors.lastname: Stankiewicz
mesh_terms: D002648:Child; D002675:Child, Preschool; D002869:Chromosome Aberrations; D019457:Chromosome Breakage; D025063:Chromosome Disorders / Q000235:genetics / Q000473:pathology; D002884:Chromosomes, Human, Pair 15 / Q000235:genetics*; D055028:Comparative Genomic Hybridization; D002658:Developmental Disabilities / Q000473:pathology; D005192:Family Health; D005260:Female; D020440:Gene Duplication; D006801:Humans; D008607:Intellectual Disability / Q000473:pathology; D008297:Male; D001523:Mental Disorders / Q000473:pathology; D008969:Molecular Sequence Data; D009123:Muscle Hypotonia / Q000473:pathology; D010375:Pedigree; D011978:Receptors, Nicotinic / Q000235:genetics*; D017422:Sequence Analysis, DNA; D064569:alpha7 Nicotinic Acetylcholine Receptor
chemical_list: C579167:Chrna7 protein, human; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor