FISH assessment of aneuploidy frequencies in mature and immature human spermatozoa classified by the absence or presence of cytoplasmic retention

Previously, a relationship has been found between diminished cellular matur ity of human spermatozoa and low-level expression of the testis-specific ch aperone protein, HspA2. Because HspA2 is a component of the synaptonemal co mplex in rodents, and assuming that this is also the case in men, it was po stulated that the frequency of chromosomal aneuploidies would be higher in immature versus mature spermatozoa. This question was examined in spermatoz oa from semen and from 80% Percoll pellets (enriched for mature spermatozoa ) of the same ejaculate in 10 oligozoospermic men. Immature spermatozoa wit h retained cytoplasm, which signifies spermiogenetic arrest, were identifie d by immunocytochemistry, Using fluorescence in-situ hybridization (FISH), similar to 7000 sperm nuclei were evaluated in each of the 20 fractions (14 2 086 spermatozoa in all) using centromeric probes for the X, Y and 17 chro mosomes. The proportions of immature spermatozoa were 45.4 +/- 3.4 versus 2 6.6 +/- 2.2% in the two semen versus the Percoll groups (medians: 48.2 vers us 25%, P < 0,001, n = 300 spermatozoa per fraction, total 6000 spermatozoa ), There was also a concomitant decline in total disomy, total diploidy and total aneuploidy frequencies in the 80% Percoll versus semen fractions (0. 17 versus 0.54%, 0.14 versus 0.26% and 0.31 versus 0.81% respectively, P < 0.001 in all comparisons). The mean decline of aneuploidies was 2.7-fold. W ith regard to the hypothesis that aneuploidies are related to sperm immatur ity, there was a close correlation between the incidence of immature sperma tozoa and disomies (r = 0,7, P < 0.001) but no correlation with diploidies (r = 0,03), indicating that disomies originate primarily in immature sperma tozoa, It is suggested that the common factor underlying sperm immaturity a nd aneuploidies is the diminished expression of HspA2, In addition, the lac k of this chaperone may also cause diminished cellular transport of protein s, such as DNA-repair enzymes or of the retention of cytoplasm that is extr uded from normally maturing spermatozoa during spermiogenesis.