Sperm Head Morphology Alterations Associated with Chromatin Instability and Lack of Protamine Abundance in Frozen-Thawed Sperm of Indonesian Local Bulls

SIMPLE SUMMARY: This study analyzed the association of various alterations in sperm morphology with the level of DNA damage, PRM deficiency, and the abundance of the PRM1 gene and protein in sperm. We found in this study that each parameter is associated with one another. Thus, gene expression and PRM1 protein abundance may play an essential role in the stability of sperm chromatin, especially concerning DNA damage and alterations in sperm head morphology. In addition, although it is not a novelty, the CMA3 in this study proved effective for bulls in Indonesia. It can be used as an alternative test to detect PRM content in sperm without having to carry out assessments at the molecular level, such as gene or protein expression assessments. ABSTRACT: This study aimed to analyze various alterations in the morphology of the sperm head and its association with nucleus instability and insufficient sperm protamine. Frozen-thawed semen from twenty local Indonesian bulls was used for all stages in this study. The results of sperm head defect assessments are used for bull grouping, high (HD) and low (LD). Sperm DNA damage was assessed using Acridine Orange and Halomax. The PRM1 protein abundance was carried out using an enzyme immunoassay, while PRM1 gene expression was carried out using the RT-qPCR. PRM deficiency was performed using CMA(3). Several kinds of sperm head defects in the HD were significantly higher (p < 0.05) than in the LD bulls. Sperm DNA damage showed a significant (p < 0.05) difference between the HD and LD bulls. PRM1 abundance was significantly (p < 0.05) decreased in HD bulls. PRM deficiency was significantly (p < 0.05) higher in HD bulls than in LD bulls. PRM deficiency in bulls correlated significantly (p < 0.01) with sperm head defects, DNA damage, and PRM1 abundance. The lack of sperm protamine might affect the sperm nucleus’s stability and induce morphological alterations in the sperm head.