Characterization of the segmental duplication LCR7-20 in the human genome.
Our previous study described the amplification of a genomic sequence containing exon 9 of CFTR in the human genome. Here we report that this CFTR sequence is part of a large duplicated sequence unit, provisionally named LCR7-20. Through successive screening of two human chromosome 7-specific cosmid libraries to construct a cosmid contig, we assembled two sequenced BAC clones into a single contig containing a prototypic LCR7-20 unit. Subsequent searches of existing human genome sequences identified additional six copies of LCR7-20-like sequences with more than 90% sequence homology. Additional genomic clones containing LCR7-20-like sequences were then isolated from total genomic BAC and PAC libraries. Restriction fragment analysis and limited sequencing data indicated that there could be around 30 copies of LCR7-20-like sequences in the human genome and that the average region of homology could extend over 120 kb. As indicated by fluorescence in situ hybridization analysis, LCR7-20-like sequences are dispersed on different chromosomes, mainly in the centromeric and pericentromeric regions, and some may exist in tandem copies. Our study also indicates that many genomic regions containing LCR7-20's either have been misassembled or are missing in current versions of the human genome sequence.
Liu
Xiangdong
X
The Centre for Applied Genomics, Research Institute, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada.
Li
Xiaobin
X
Li
Martin
M
Acimovic
Yugo J
YJ
Li
Zhenzhong
Z
Scherer
Stephen W
SW
Estivill
Xavier
X
Tsui
Lap-Chee
LC
D015139:Blotting, Southern; D002897:Chromosomes, Human, Pair 7; D020451:Contig Mapping; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics*; D030561:Databases, Nucleic Acid; D020440:Gene Duplication; D015894:Genome, Human; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid
C505032:CFTR protein, human; D019005:Cystic Fibrosis Transmembrane Conductance Regulator