Partial duplication of the APBA2 gene in chromosome 15q13 corresponds to duplicon structures.
BACKGROUND
Chromosomal abnormalities affecting human chromosome 15q11-q13 underlie multiple genomic disorders caused by deletion, duplication and triplication of intervals in this region. These events are mediated by highly homologous segments of DNA, or duplicons, that facilitate mispairing and unequal cross-over in meiosis. The gene encoding an amyloid precursor protein-binding protein (APBA2) was previously mapped to the distal portion of the interval commonly deleted in Prader-Willi and Angelman syndromes and duplicated in cases of autism.


RESULTS
We show that this gene actually maps to a more telomeric location and is partially duplicated within the broader region. Two highly homologous copies of an interval containing a large 5' exon and downstream sequence are located approximately 5 Mb distal to the intact locus. The duplicated copies, containing the first coding exon of APBA2, can be distinguished by single nucleotide sequence differences and are transcriptionally inactive. Adjacent to APBA2 maps a gene termed KIAA0574. The protein encoded by this gene is weakly homologous to a protein termed X123 that in turn maps adjacent to APBA1 on 9q21.12; APBA1 is highly homologous to APBA2 in the C-terminal region and is distinguished from APBA2 by the N-terminal region encoded by this duplicated exon.


CONCLUSIONS
The duplication of APBA2 sequences in this region adds to a complex picture of different low copy repeats present across this region and elsewhere on the chromosome.
Sutcliffe
James S
JS
Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA. james.s.sutcliffe@vanderbilt.edu
Han
Michael K
MK
Amin
Taneem
T
Kesterson
Robert A
RA
Nurmi
Erika L
EL
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001923:Brain Chemistry / Q000235:genetics; D015820:Cadherins; D002352:Carrier Proteins / Q000235:genetics*; D002884:Chromosomes, Human, Pair 15 / Q000235:genetics*; D002899:Chromosomes, Human, Pair 9 / Q000235:genetics; D018628:Gene Dosage; D020440:Gene Duplication; D020869:Gene Expression Profiling / Q000379:methods; D018507:Gene Expression Regulation, Developmental / Q000235:genetics; D023061:Gene Order / Q000235:genetics; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics*; D020161:Physical Chromosome Mapping / Q000379:methods*; D012689:Sequence Homology, Nucleic Acid; D016615:Telomere / Q000235:genetics
C079091:APBA1 protein, human; C491636:APBA2 protein, human; D048868:Adaptor Proteins, Signal Transducing; C513072:Apba1 protein, mouse; C491635:Apba2 protein, mouse; D015820:Cadherins; D002352:Carrier Proteins; D009419:Nerve Tissue Proteins