Sperm DNA Fragmentation as a Marker of Chromoanagenesis Occurrence During Spermatogenesis

Chromothripsis and chromoanasynthesis have been described as new complex chromosomal rearrangements and are grouped under the term chromoanagenesis.Various mechanisms of formation of these rearrangements have been identified and reproduced experimentally, including the sequestration of chromosomes in micronuclei, the premature condensation of chromosomes, or abortive apoptosis. All these phenomena can occur during human spermatogenesis, particularly abortive apoptosis which leads to DNA fragmentation in spermatozoa.Given the paternal origin of most cases of chromothripsis and chromoanasynthesis, their presence is researched in human sperm samples with high DNA fragmentation rate.Magnetic-activated cell sorting (MACS) is performed on sperm samples to separate spermatozoa according to their fragmentation rate. Sorting efficiency is assessed by using the Annexin V-FITC staining and the fragmentation rate is assessed by using TUNEL (Terminal deoxynucleotidyl transferase-mediated dUTP Nick-End Labeling) assay.Pools of spermatozoa with a high DNA fragmentation rate are thus constituted, on which genomic analysis can be performed to identify complex rearrangements, such as chromothripsis and chromoanasynthesis.