COMBINED IMMUNOCYTOGENETIC AND MOLECULAR CYTOGENETIC ANALYSIS OF MEIOSIS-I HUMAN SPERMATOCYTES

We have used a combination of immunocytogenetic and molecular cytogene tic technology on human spermatocytes to investigate (1) meiosis I chr omosome pairing, and (2) organization of synaptonemal complex (SC)-ass ociated chromatin with respect to whole chromosome paints, unique DNA sequences and repetitive DNA of heterochromatic blocks, centromeres an d telomeres. It is evident that synapsis normally starts at the termin i of homologues. In general, synapsis proceeds synchronously from term ini towards the centre of bivalents without any indication of intersti tial initiation. Some aberrant meiosis I spermatocytes showed asynchro nous pairing, demonstrating not only large differences in the degree o f SC formation between bivalents, but also chromosome alignment withou t synapsis as well as clear interstitial synaptic initiation. it may b e the case that alignment normally takes place along the entire length of homologues before synapsis occurs and that the potential for synap tic initiation exists along the length of chromosomes. Telomeric seque nces were seen tightly associated with the SCs, as might be expected c onsidering their kinetic properties in relation to the nuclear membran e, Other repetitive DNA, i,e. centromeric alpha-satellites and classic al satellites of the heterochromatic blocks 1qh and 9qh, were all foun d to form loops that are associated with SCs only at their bases. A un ique DNA cosmid probe (21q22.3) was found to produce a hybridization p attern consisting of spots located outside SC. The fluorescence in sit u hybridization (FISH) signals of these spread DNA sequences have a gr anular appearance, probably reflecting the pattern of coiling and chro matin condensation of the target DNAs.