Sperm chromatin protamination influences embryo development in unsexed and sexed bull semen

Abstract

Summary Sex selection through sperm sorting offers advantages in regards selection pressure in high-producing livestock. However, the sex-sorting process results in sperm membrane and DNA damage that ultimately decrease fertility. We hypothesized that given the role of protamines in DNA packaging, protamine deficiency could account, at least partially, for the DNA damage observed following sperm sex sorting. To test this, we compared protamine status between unsexed and sexed spermatozoa from two bulls using the fluorochrome chromomycin A3 (CMA3) and flow cytometry. Then, we assessed embryo development following in vitro fertilization (IVF) using the same sperm treatments. Overall, sperm protamination was not different between sexed and unsexed semen. However, one of the two bulls displayed higher rates of protamine deficiency for both unsexed and sexed semen (P < 0.05). Moreover, unsexed semen from this bull yielded lower blastocyst (P < 0.05) and blastocyst hatching rates than unsexed sperm from the other bull. CMA3-positive staining was negatively correlated with cleavage (R2 85.1, P = 0.003) and blastocyst hatching (R2 87.6, P = 0.006) rates in unsexed semen. In conclusion, while the sex-sorting process had no effect on sperm protamine content, we observed a bull effect for sperm protamination, which correlated to embryo development rates following IVF.

Sperm chromatin condensation as an in vivo fertility biomarker in bulls: a flow cytometry approach

“…The present study successfully applied a flow cytometry protocol that allowed assessing sperm viability and Table 2 Receiver operating characteristic (ROC) curve analysis showing the area under the curve (AUC), standard deviation (SD), level of significance (P-value), cut-off value, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and ODDs ratio of all sperm parameters at 0 h post-thaw for discriminating between subfertile (n = 13) and highly fertile (n = 12) bulls chromatin condensation simultaneously. Previous studies evaluated in sperm by flow cytometry, using an excitation wavelength of 488 nm and fluorescence channels of 530/30 [31], 568/42 [32] and 585/42 [33][34][35]. However, as deoxyribonucleic acid-bound CMA3 is known to have an excitation peak of 430 nm (350 to 490 nm) and an emission peak of 590 nm (450 to 700 nm) [21], we used a 405-nm laser for excitation and collected emitting fluorescence through the Violet610 (610/20) channel.…”

SPAG17 mediates nuclear translocation of protamines during spermiogenesis

“…In contrast, PRM2 is primarily found in rodents and primates and is synthesized as a precursor that is processed by sequential cleavage to its mature form ( Balhorn et al, 2018 ; Arévalo et al, 2022b ). These male germ cell specific proteins are responsible for DNA hyper-condensation and chromatin structural reorganization thus protecting DNA strands from possible breaks and preserving the integrity of the genome ( Silva et al, 2021 ). This implies that any protamine-related changes can directly impact sperm DNA and nucleus, thus affecting sperm function ( Andraszek et al, 2014 ).…”