RAPID DETECTION OF CHROMOSOMES BY IN-SITU HYBRIDIZATION OF LABELED OLIGONUCLEOTIDES AND COMPARISON WITH PRINS

We propose a simple, fast and inexpensive method of identification of human centromeres on metaphasic chromosomes and interphasic nuclei. Th is is based on in situ hybridization of labelled oligonucleotides. The efficiency of the methodology was demonstrated on cytogenetic prepara tions from human heteroploid and human x hamster hybrid cell lines and also on frozen tissue sections using an oligonucleotide specific for the alpha-satellite DNA of chromosome 1. Three versions of this oligon ucleotide respectively labelled with 1, 4 and 10 fluorescein molecules were synthesized. The signal intensity provided by the oligonucleotid e coupled with 4 fluoresceins allowed unambiguously the detection of t he chromosome and the establishment of its ploidy using a classical cy togenetic microscope without the need for an amplification procedure. The use of different fluorochromes and possibly combination with an un labelled elongation in 3' of the oligonucleotides which stabilize its hybridization, lead to a simple multicolour method. Preliminary quanti fication of the signals obtained by in situ hybridization of labelled oligonucleotides and comparison with those obtained by primed in situ labelling (PRINS) using the same nucleotides as primers, suggest that the elongation generated by PRINS may be very short compared with a PC R in solution. This limited efficiency of the in situ elongation may r eflect the present difficulties of PRINS and DISC PCR (direct in situ single copy polymerase chain reaction) with primers specific for non-r epetitive sequencies.