TRANSCRIPTOME PROFILING OF HISTONE WRITERS/ERASERS ENZYMES ACROSS SPERMATOGENESIS, MATURE SPERM AND PRE-CLEAVAGE EMBRYO: IMPLICATIONS IN PATERNAL EPIGENOME TRANSITIONS AND INHERITANCE MECHANISMS

CANDELA R. GONZALEZ; GASTON BARBERO; BETINA GONZALEZ

Zurich

Simposio; Epigenetic Inheritance: Impact for Biology and Society; 2023

Accumulating evidence points out that sperm carry epigenetic instructions to embryo in the form of retained histones marks and RNA cargo that can transmit metabolic and behavioral traits to offspring. In this sense, the role of epigenetic enzymes comes to focus as they are responsible for the histones post translational modifications (PTMs) writing and erasing balance. Even though histone modifying enzymes are the bridge linking the environment with epigenetic inheritance through retained histones PTMs, an in-depth analysis of their expression patterns throughout the spermatogenic process is still lacking. Here, we curated mouse germ cells RNA-seq data and analyzed the expression profile and dynamic changes of all the known families of histone lysine (K) acetyltransferases (HATs), deacetylases (HDACs), methyltransferases (KMTs) and demethylases (KDMs) and epigenetic enzymes of arginine (R) methylation (PRMTs) and citrullination (PADs) during spermatogonial, meiosis and spermiogenesis phase, unraveling the developmental windows at which they are upregulated. We found that the transition of undifferentiated spermatogonia to differentiated spermatogonia is characterized by specific Hdacs upregulation, decreased Hats expression and increased expression of activation marks H3K4me/H3K36me and repression marks H3K9me/H4K20me writers. Also, Prmt1 and Pad2 are characteristics of spermatogonial phase and decrease during meiosis entry. During meiosis I progression, Hats enzymes increase and there is a peak of Kmts and Kdms enzymes involved in DNA double-strand breaks, deposition and repair at synapsed chromatin, and epigenetic silencing of unpaired chromatin (MSUC) including meiotic sex chromosome inactivation (MSCI). Prmt4, also involved in the methylation of transition protein 2 (TNP2), together with Prmt5 and Pad4 peak at meiosis I. At round spermatid (RStid) stage, we found specific upregulation of Prmt7, associated with DNA damage repair, and Pad6, involved in chromatin assembly in early embryos. RStid stage showed several Hats enzymes expression, particularly the H4K16ac writer Msl3, an histone PTM essential for histone eviction which does not occur in the absence of this specific mark. Also, RStids showed high levels of the H3K79me writer Dot1l, the H3K27me writer Ezh2 and the H3K9me2 writer Ehmt2, consistent with the high global expression of these marks at spermiogenesis stage. Finally, we characterized the epigenetic enzymes signature in the mature sperm RNA cargo, showing most of them positive translation at pre-cleavage zygote, suggesting that paternally-derived enzymes mRNA cooperate with maternal factors to embryo chromatin assembly. Our study shows important mechanistic aspects behind transgenerational epigenetics, where enzymes not only can respond to environmental stressors, but could function as vectors of epigenetic information and participate in chromatin organization during maternal-to-zygote transition.