P–055 Methylation dynamics of the sperm epigenome after chemotherapy: a case study
Authors: Neyroud A S , Rolland A , Evrard B , Alary N , Dejucq-Rainsford N , Jégou B , Bujan L , Ravel C , Chalmel F 
Published: August 2021

Abstract

Study question
What is the evolution of the sperm epigenome after chemotherapy in a patient with testicular cancer (TC)?

Summary answer
These new data on epigenetic recovery profil after TC are useful tools for counseling and reassuring these patients.

What is known already
An important issue for young men affected TC is how TC and its treatment will affect, transiently or permanently, their future reproductive health. The consequences of cancer treatment on the sperm epigenome during the recovery periods are topical issues of ascendant significance as epigenetic modifications to the paternal genome may have deleterious effects on the offspring.

Study design, size, duration
Here we report the epigenomic profiling of frozen sperm from a TC patient before and after the treatment at different time points (6, 9, 12 and 24 months) by using RRBS analysis (Reduced representation bisulfite sequencing method).

Participants/materials, setting, methods
A testicular tumor (testicular germ cell tumor) was diagnosed in a 30 years old patient. A cryopreservation of spermatozoa was proposed before treatment.Semen samples were obtained 2 times before treatment and 4 times after treatment (6, 9, 12 and 24 months following the initiation of treatment).

Main results and the role of chance
Upon collection, sampling after chemotherapy ranged from 0,6 to 4,2 million per sperm straw between 6 and 24 months after the treatment, always increasing.
In order to capture the direct effect of the treatment on the methylation changes, the DMR detection has been operated between pre-chemotherapy samples (pair-wise) and the time point of 6 months. Among the 179 hqDMRs, 74 are differentially methylated between the PreCT and PostCT6m samples (16 hyper- and 68 hypo-methylated) associated with 49 DMGs (15 hyper- and 34 hypo-methylated).
We further sub-clustered the 74 hqDMRs between PreCT and PostCT6m into 6 patterns, 3 hyper- and 3 hypo-methylated. Briefly, patterns P1 and P4 include hqDMRs that quickly get back to their pre-treatment methylation status just after 9th months onwards. Patterns P2 and P5 include hqDMRs that slowly get back to their pre-treatment methylation status between 12 and 24 months after treatment. Patterns P3 and P6 include hqDMRs that remain hyper- or hypo-methylated even after 24 months.
We have intersected the genes (DMGs) associated with the detected hqDMRs with those known to be important or expressed during embryogenesis. We thus detected that 7 hyper-methylated and 6 hypomethylated DMGs were involved (or expressed) during embryonic / fetal development.

Limitations, reasons for caution
This study involves a single patient. As the patient made no major changes in his personal way of life, we hypothesized that sperm parameter variations may be attributable to the BEP treatment.
Wider implications of the findings: The altered methylated status of those DMGs important for early development might modify their expression pattern and thus affect their function during key stages of embryogenesis leading to potential developmental disorders. It is important to notice that among the 110 DMGs none of them correspond to known imprinted genes.

Trial registration number
Not applicable