DETECTION OF ANEUPLOIDY IN HUMAN OOCYTES AND CORRESPONDING FIRST POLAR BODIES BY FLUORESCENT IN-SITU HYBRIDIZATION

Purpose: The purpose of the study was to investigate the reliability o f the fluorescent in situ hybridization (FISH) analysis of the first p olar body (IPB) for cytogenetic evaluation of human oocytes as a metho d of choice in preimplantation diagnosis of chromosomal aneuploidies. Design: Human unfertilized oocytes and their extruded IPB were analyze d using the directly labeled fluorescence alpha-satellite DNA probes t o chromosomes X and 18. Results: Paired signals for chromosomes X and 18 were observed in the second meiotic prophase (MII) of unfertilized oocytes and their extruded IPB. In the series of 156 unfertilized oocy tes in which the number of X chromosome- and chromosome 18-specific si gnals were analyzed in both MII and IPB, Jive nondisjunction events ha ve been detected, with corresponding signals in MII and their IPB: mis sing signals in MII corresponded to extra signals in their IPB and ext ra signals in MII corresponded to missing signals in IPB. In one oocyt e chromosome 18 nondisjunction was detected, with both chromosome 18 s ignals in MII and no chromosome 18 signal in IPB. In foul oocytes chro matid malsegregations for chromosome X or chromosome 18 were detected: in two oocytes, three of four chromosome 18 signals were present in M II, with only one in IPB, and in the other two oocytes, three of four chromosome signals were present in MII, with only one left in IPB. Con clusions: The data suggest the possibility of detecting chromosomal an euploidy in oocytes through cytogenetic analysis of their correspondin g IPB by FISH as a possible approach for preimplantation diagnosis of major chromosomal trisomies.