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Editorial on the Research Topic Sperm epigenetic code: implications in reproductive health and paternal contribution to embryo development For decades, the study of human reproduction and offspring health has predominantly focused on the maternal contribution to embryo development, often overlooking the molecular complexity of spermatozoa, traditionally considered merely as vectors of paternal genetic information. The Research Topic “Sperm Epigenetic Code: Implications in Reproductive Health and Paternal Contribution to Embryo Development” provides multidisciplinary insights into the establishment and maintenance of sperm epigenetic landscape. Since harmful perturbations in the sperm epigenome have been consistently linked to altered sperm quality, male infertility and compromised offspring health, these Research Topic are extensively addressed in this Research Topic. [...]the study by Pastore et al. sheds light on the intergenerational transmission of dysmetabolic traits via paternal inheritance. [...]the concept of the sperm epigenetic code radically reshapes our understanding on paternal heredity, extending it beyond DNA sequence to include dynamic, heritable, and environmentally sensitive epigenetic modifications.

Small non-coding RNAs (ncRNAs), particularly miRNAs, play key roles in a plethora of biological processes both in health and disease. Although largely operative in the cytoplasm, emerging data indicate their shuttling in different subcellular compartments. Given the central role of mitochondria in cellular homeostasis, here we systematically profiled their small ncRNAs content across mouse tissues that largely rely on mitochondria functioning. The ubiquitous presence of piRNAs in mitochondria (mitopiRNA) of somatic tissues is reported for the first time, supporting the idea of a strong and general connection between mitochondria biology and piRNA pathways. Then, we found groups of tissue-shared and tissue-specific mitochondrial miRNAs (mitomiRs), potentially related to the “basic” or “cell context dependent” biology of mitochondria. Overall, this large data platform will be useful to deepen the knowledge about small ncRNAs processing and their governed regulatory networks contributing to mitochondria functions.

The etiology of human asthenozoospermia is multifactorial. The need to unveil molecular mechanisms underlying this state of infertility is, thus, impelling. Circular RNAs (circRNAs) are involved in microRNA (miRNA) inhibition by a sponge activity to protect mRNA targets. All together they form the competitive endogenous RNA network (ceRNET). Recently, we have identified differentially expressed circRNAs (DE-circRNAs) in normozoospermic and asthenozoospermic patients, associated with high-quality (A-spermatozoa) and low-quality (B-spermatozoa) sperm. Here, we carried out a differential analysis of CRISP2, CATSPER1 and PATE1 mRNA expression in good quality (A-spermatozoa) and low quality (B-spermatozoa) sperm fractions collected from both normozoospermic volunteers and asthenozoospermic patients. These sperm fractions are usually separated on the basis of morphology and motility parameters by a density gradient centrifugation. B-spermatozoa showed low levels of mRNAs. Thus, we identified the possible ceRNET responsible for regulating their expression by focusing on circTRIM2, circEPS15 and circRERE. With the idea that motility perturbations could be rooted in quantitative changes of transcripts in sperm, we evaluated circRNA and mRNA modulation in A-spermatozoa and B-spermatozoa after an oral amino acid supplementation known to improve sperm motility. The profiles of CRISP2, CATSPER1 and PATE1 proteins in the same fractions of sperm well matched with the transcript levels. Our data may strengthen the role of circRNAs in asthenozoospermia and shed light on the molecular pathways linked to sperm motility regulation.

Hepatocellular carcinoma (HCC) is among the most aggressive and lethal human tumors. Many functional studies have demonstrated the role of non-coding RNAs (ncRNA), particularly microRNAs (miRNA), in the regulation of hepatocarcinogenesis driving pathways. MiR-125a-5p (miR-125a) has been consistently reported as an oncosuppressive miRNA, as demonstrated in vivo and in vitro. However, its HCC relevant targets and molecular mechanisms are still largely unknown. Here, a genome-wide perspective of the whole miR-125a targetome has been achieved. In particular, two different HCC cell lines were subjected to a miRNA boosting by mimic transfections, and consequently many genes were de-regulated, as observed by a transcriptomic approach. The merging of down-regulated genes with results from bioinformatic predictive tools yielded a number of candidate direct targets that were further experimentally validated by luciferase-based reporter assays. Different novel targets were found, in particular ARID3A, CCNJ, LIPA, NR6A1, and NUP210, oncogenes in various tumors and here also related to HCC through miR-125a regulation. The RNA interactions investigated in this work could pave the way to piece together the RNA regulatory networks governed by the miRNA impacting on hepatocarcinogenesis, and be exploited in the future for identifying novel biomarkers and therapeutic targets in HCC.

This study aims to explore the complex role of cannabinoid type 1 receptor (CB1) signaling in the gastrocnemius muscle, assessing physiological processes in both CB1+/+ and CB1−/− mice. The primary focus is to enhance our understanding of how CB1 contributes to mitochondrial homeostasis. At the tissue level, CB1−/− mice exhibit a substantial miRNA-related alteration in muscle fiber composition, characterized by an enrichment of oxidative fibers. CB1 absence induces a significant increase in the oxidative capacity of muscle, supported by elevated in-gel activity of Complex I and Complex IV of the mitochondrial respiratory chain. The increased oxidative capacity is associated with elevated oxidative stress and impaired antioxidant defense systems. Analysis of mitochondrial biogenesis markers indicates an enhanced capacity for new mitochondria production in CB1−/− mice, possibly adapting to altered muscle fiber composition. Changes in mitochondrial dynamics, mitophagy response, and unfolded protein response (UPR) pathways reveal a dynamic interplay in response to CB1 absence. The interconnected mitochondrial network, influenced by increased fusion and mitochondrial UPR components, underlines the dual role of CB1 in regulating both protein quality control and the generation of new mitochondria. These findings deepen our comprehension of the CB1 impact on muscle physiology, oxidative stress, and MQC processes, highlighting cellular adaptability to CB1−/−. This study paves the way for further exploration of intricate signaling cascades and cross-talk between cellular compartments in the context of CB1 and mitochondrial homeostasis.

Bisphenol-A (BPA) is considered an endocrine disruptor with estrogenic activity. It is described as an environment-polluting industrial chemical whose adverse effects on the male reproductive system depend on the period of exposure (i.e., fetal, prepubertal, or adult life). We exposed male mice to BPA during the fetal-perinatal period (from 10 days post coitum to 31 days post partum) and investigated the impact of this early-life exposure on gamete health in adulthood animals at 78 days of age. Both in control and BPA-exposed mice, viability and motility of spermatozoa, as well as sperm motility acquisition and chromatin condensation of spermatozoa, have been evaluated. Results reveal harmful effect of BPA on viability and motility of sperm cells as well as on chromatin condensation status during epididymal maturation of spermatozoa. In particular, BPA exposure interferes with biochemical mechanism useful to stabilize sperm chromatin condensation, as it interferes with oxidation of thiol groups associated to chromatin.

The histone H4 hyperacetylation (i.e., acetylation of H4 at lysines -K5, -K8, -K12, and -K16, here reported as H4tetraAc) occurs in elongating spermatids (eSPTs) during spermiogenesis. Although it is critically involved in histone displacement, the mechanistic involvement of histone -acetyltransferases (HATs) and -deacetylases (HDACs) in the pathway underlying H4 hyperacetylation is poorly defined. Here, we investigate the involvement of SIRT1 deacetylase, and its functional interaction with the histone acetyltransferase MOF, in regulating H4 hyperacetylation underlying histone-to-protamine exchange. Exploiting the cannabinoid receptor 1 ( ) null mice (Cb1 ) as a model of impaired histone displacement, we assessed in eSPTs the expression and the localization of SIRT1 in combination with the enrichment of H4tetraAc and the relative monoacetylated forms (H4-K5ac, -K8ac, -K12ac and -K16ac), by Western Blot and immunohistochemistry analyses. Then, focusing on SIRT1 interaction with MOF HAT by protein immunoprecipitation experiments, we verified the H4K16ac and H4TetraAc enrichment in eSPTs in response to SIRT1 inhibition by using the selective EX-527 inhibitor. We show that the hyperacetylation of histone H4 occurs progressively in steps 8-9 eSPTs and bursts in step 10 eSPTs, appearing inversely correlated to the expression pattern of SIRT1, being SIRT1 present in step 8, detectable in step 9 and absent in step 10 eSPTs. The abnormal SIRT1 retention in step 10 eSPTs of Cb1 mice, despite the observed enrichment of H4-K5ac, -K8ac, and -K12ac, counteracts the H4 hyperacetylation burst by limiting the H4 acetylation at lysine K16. Mechanistically, SIRT1 directly or indirectly interacts with and negatively regulates MOF acetyltransferase, specifically affecting its acetylation status and protein content, thereby interfering with H4K16 acetylation. Counteracting the MOF/SIRT1 interaction by SIRT1 inhibition in Cb1 testis, both MOF protein content and acetylation status increase, downstream promoting recovery of H4K16ac and H4tetraAc in step 10 eSPT, and full rescue of histone displacement. These results underscore the key involvement of SIRT1-MOF axis in modulating H4K16 acetylation. Our findings provide mechanistic insights into H4K16 acetylation pathway in eSPTs and support the key role of H4K16ac in chromatin remodeling underlying histone displacement.

Paternal eating habits, before and at conception, have a strong impact on offspring future metabolism. By sending specific epigenetic signals through spermatozoa, paternal nutrition influences developing embryos and increases offspring risk of developing dysmetabolism and cardiovascular diseases. Among the intergenerational consequences, paternal epigenetic messages affect embryo DNA methylation altering programmed gene expression. The identification of offspring genetic loci that are epigenetically altered by paternal stimuli is of pivotal interest for timely post-natal treatment of offspring metabolic defects. We here use a murine model to show that, cyp19a1/aromatase , a gene coding for the cytochrome converting testosterone into 17-β estradiol (both potent hormonal mediators of embryo development and metabolism), is an epigenetic transducer of paternal intergenerational inheritance. By affecting cyp19a1 methylation status and alternative splicing, paternal diet coordinates androgens’ metabolism in the progeny affecting it in a sexually dimorphic way and promoting hypoandrogenism, growth retardation and diabetes in male pups.

The contribution of Cannabinoid type 1 receptor (CB1) in mitochondrial energy transduction mechanisms and mitochondrial activities awaits deeper investigations. Our study aims to assess the impact of CB1 absence on the mitochondrial compartment in the liver, focusing on both functional aspects and remodeling processes. We used CB1 and CB1 male mice. Cytochrome C Oxidase activity was determined polarographically. The expression and the activities of separated mitochondrial complexes and supercomplexes were performed by using Blue-Native Page, Western blotting and histochemical staining for in-gel activity. Key players of Mitochondrial Quality Control processes were measured using RT-qPCR and Western blotting. Liver fine sub-cellular ultrastructural features were analyzed by TEM analysis. In the absence of CB1, several changes in the liver occur, including increased oxidative capacity, reduced complex I activity, enhanced complex IV activity, general upregulation of respiratory supercomplexes, as well as higher levels of oxidative stress. The mitochondria and cellular metabolism may be affected by these changes, increasing the risk of ROS-related damage. CB1 mice show upregulation of mitochondrial fusion, fission and biogenesis processes which suggests a dynamic response to the absence of CB1. Furthermore, oxidative stress disturbs mitochondrial proteostasis, initiating the mitochondrial unfolded protein response (UPR ). We noted heightened levels of pivotal enzymes responsible for maintaining mitochondrial integrity, along with heightened expression of molecular chaperones and transcription factors associated with cellular stress reactions. Additionally, our discoveries demonstrate a synchronized reaction to cellular stress, involving both UPR and UPR pathways.