The evaluation of gonosomal mosaics: lymphocyte interphase nuclei analyzed by FISH

The reliable evaluation of chromosomal mosaics is still considered to be difficult in clinical diagnosis if aberrant metaphases are only present at low frequencies. Classical cytogenetic findings cannot significantly exclude low mosaic levels, obviously, because of the relatively low number of analyzed metaphases. To study this problem, the number of gonosomes in lymphocyte interphase nuclei was determined by FISH (fluorescence in situ hybridization) application of two satellite DNA probes. DXZI and DYZI. The results obtained with this method from lymphocytes of clinically and cytogenetically inconspicuous persons showed a high degree of reliability. The DNA probe yielded correct signals in more than 95% of the analyzed nuclei. Additionally, patients were examined who showed cytogenetically confirmed numerical gonosome aberrations. These results were compared with those obtained from the control group of inconspicuous patients and discussed with respect to the evaluation of gonosomal mosaics.