ALPHOID VARIANT-SPECIFIC FISH PROBES CAM DISTINGUISH AUTOSOMAL MEIOSIS-I FROM MEIOSIS-II NONDISJUNCTION IN HUMAN SPERM

Over the past few years, several groups have used fluorescence in situ hybridization (FISH) to study aneuploidy in human sperm. Several impo rtant observations have derived from these studies, including the demo nstration of chromosome-specific variation in non-disjunction frequenc ies, and the possible association of aneuploidy with environmental age nts and with increasing paternal age. However, an important technical limitation of these studies has been the inability to distinguish betw een autosomal non-disjunction occurring at meiosis I and meiosis II. I n the present report, we describe a simple FISH-based approach designe d to overcome this limitation. Using oligonucleotide probes capable of distinguishing subtle differences in the alpha satellite sequences of chromosome 17, we demonstrate that (in appropriate heterozygotes) it is possible to simultaneously identify disomic sperm and to determine the meiotic stage of origin of the additional chromosome. This novel a pproach has important implications for future FISH sperm studies, sinc e the ability to distinguish between meiosis I and meiosis II non-disj unction will make it possible to determine whether putative etiologica l agents affect chromosome segregation at both, or only one, of the tw o meiotic stages.