A comparative study of digoxigenin, 2,4-dinitrophenyl, and alkaline phosphatase as deoxyoligonucleotide labels in non-radioisotopic in situ hybridisation

Aim-To determine the optimum form of labelling and the most efficient reporter molecule for non-radioisotopic in situ hybridisation (ISH). Methods-Nine deoxyoligonucleotides complementary to histone mRNA were synthesised and labelled either enzymatically or during solid-phase synthesis with the reporter molecules digoxigenin, 2,4-dinitrophenyl (DNP), or alkaline phosphatase. Pooled deoxyoligonucleotide cocktails were then used in nonradioisotopic ISH detection of histone mRNA in human tonsil. Hybrid detection was by nitroblue tetrazoleum/5-bromo-4-chloro-3-indolyl phosphate colorimetric development. Results-The use of a spacer in 3' enzymatic labelling and when labelling with alkaline phosphatase significantly increased ISH signal. The 3' and 5' labelling of oligonucleotides with triple DNP groups during solid-phase synthesis produced the strongest signal as determined by the highest cell. signal intensity and shortest development time. Conclusions-3' and 5' solid-phase labelling with triple DNP groups produced the best labelling for non-isotopic ISH using deoxyoligonucleotide cocktails.