ASSIGNMENT OF THE NTRK4 (TRKE) GENE TO CHROMOSOME 6P21

Reverse transcriptase-polymerase chain reactions using foetal brain RN A with reverse and forward primers of the first, second and third NTRK 4 region allowed us to obtain three amplified NTRK4 fragments. The spe cificity of amplified fragments was checked by digestion with restrict ion endonucleases AvrII, HindIII and PspII for the first, second and t hird regions, respectively. Each restriction site was specific for eac h amplified fragment. The fragment of the NTRK4 first region was also sequenced and the sequence determined was identical to the human NTRK4 sequence. The three amplified fragments were cloned in pBS. For the S outhern technique, plasmid pBS-NTRK4a (with an insert of 1052 bp) dete cted a human 9-kb HindIII sequence which was localised unambiguously o n chromosome 6. For fluorescence in situ hybridisation, the three plas mids, pBS-NTRK4a, pBS-NTRK4b (insert 924 bp) and pBS-NTRK4c (insert 11 14 bp) were pealed and used as a probe. This NTRK4 probe was localised on 6p21. Of 50 metaphases analysed, 49 contained twin spot signals on both sister chromatids.