An exon-trapping system with a newly constructed trapping vector pEXT2; its application to the proximal region of the human chromosome 21 long arm

We have developed an exon-trapping system with a newly constructed trapping vector containing multiple cloning sites (designated pEXT2). The system revealed high sensitivity for trapping a control exon from several hundred kbp of DNA. We have applied the system to the cosmid clones located on human chromosome 21pll-q21, and identified two fragments highly homologous to neurofibromatosis 1 (NF1) gene and a clearly transcribed fragment hybridized with ~1.6 kb RNA from human brain and human glioblastoma A 172 cell.