Abstract: Objective To enhance the sensitivity of detecting the signal from mouse Ychromosome fluorescence in situ hybridization of brain slices direct tyramine signal amplification method was applied.Methods The RNA probe was labeled with pY353/B,a repeat sequence of mouse Ychromosome.Compared with the female mice,the brain tissue sections of the male mice were in situ hybridized with the RNAprobe,its fluorescence signal was detected with direct tyramine signal amplification method and "three antibodies method" respectively.The sensitivity of the detection Ychromosome positive cells was calculated as the percentage of the Ychromosome positive cell nuclei to that of all nuclei.The difference of sensitivity between the direct tyramine signal amplification and "three antibodies method" was compared and analyzed with statistic methods.Results The sensitivity and specificity of "three antibodies method" for detection of Ychromosome signal in brain tissue is 85.67% and 100%,respectively;the sensitivity and specificity of direct tyramine signal amplification method for detection of Ychromosome signal in brain tissue is 92.82% and 100%,respectively.Conclusion Compared with the "three antibodies method",the sensitivity for detection of the signal of Ychromosome fluorescence in situ hybridization in brain tissue sections of mice was enhanced significantly by the direct tyramine signal amplification method.This technique can be used in the tracing and analysis of the migration of bone marrow stem cells in the brain.

Key words: mouse, Y chromosome, in situ hybridization, fluorescence in situ hybridization, tyramine signal amplification