Reduction of H3K9 methylation by G9a inhibitors improves the development of mouse SCNT embryos

Silencing PsASH2 affects embryo development in the cotton mealybug

Mealybugs are highly aggressive pests that infest various plants and cause substantial economic losses. Histone lysine methyltransferases (KMT) are evolutionarily conserved and proposed to be essential in early embryo development in animals. However, few KMTs have been reported in mealybugs. Here, we identified a novel KMT gene, PsASH2, in the cotton mealybug, Phenacoccus solenopsis Tinsley. This gene was highly expressed in the ovary of female adults. Through RNA interference (RNAi) of PsASH2 by dsRNA microinjection, we found a reduction in the number of male embryos and total embryos in the ovaries of pregnant females. Continuous downregulation of PsASH2 in mated females until their death resulted in few changes in sex ratio but significant decreases in the number of both male and female offspring. Therefore, we believe that PsASH2 plays essential roles in embryo survival for both sexes of the cotton mealybug which may provide a potential target gene for the management of cotton mealybug by disrupting embryo development.

Enhancing embryonic and full-term development during mouse cloning through post-activation treatment with JNJ-7706621

Somatic cell nuclear transfer (SCNT) is widely researched for animal cloning. However, SCNT embryos frequently exhibit reduced developmental potential compared to those generated through natural reproduction. This study aimed to improve SCNT mouse embryo development by assessing the effects of JNJ-7706621 (JNJ, a specific inhibitor of cyclin-dependent kinase 1 and aurora kinases) as a post-activation treatment, replacing cytochalasin B (CB). Parthenogenetically activated (PA) mouse embryos were cultured with CB (5 μg/mL) or JNJ (1, 10, or 50 μM) to determine the optimal concentration. The 10 μM JNJ and CB groups showed significantly higher developmental competency compared to the 1 and 50 μM JNJ groups. The 10 μM JNJ group also exhibited an increase in total cell number and a decrease in apoptotic cells compared to the CB group. SCNT mouse embryos treated with 10 μM JNJ showed improved development (CB: 39.9 % ± 6.4; JNJ: 61.4 % ± 4.4), with increases in total cell number (CB: 52.7 ± 3.6; JNJ: 70.7 ± 2.9), inner cell mass (CB: 10.4 ± 0.7; JNJ: 15.4 ± 1.1), and trophectoderm cells (CB: 42.3 ± 3.3; JNJ: 55.3 ± 2.5). JNJ treatment significantly reduced aberrant F-actin and tubulin compared to CB. It also reduced abnormal spindles in one-cell embryos and decreased blastomere fragmentation and DNA damage in two-cell SCNT embryos compared to CB. Importantly, JNJ treatment led to significantly higher implantation (CB: 50.8 % ± 3.7; JNJ: 68.3 % ± 4.3) and live birth rates (CB: 2.4 % ± 2.4; JNJ: 10.9 % ± 2.8) compared to CB. These results demonstrate that JNJ enhances cytoskeletal integrity and chromosome stability, ultimately improving both preimplantation development and full-term success in mouse SCNT embryos.

Trichostatin A-Induced Epigenetic Modifications and Their Influence on the Development of Porcine Cloned Embryos Derived from Bone Marrow-Mesenchymal Stem Cells

Abnormal epigenetic reprogramming of nuclear-transferred (NT) embryos leads to the limited efficiency of producing cloned animals. Trichostatin A (TSA), a histone deacetylase inhibitor, improves NT embryo development, but its role in histone acetylation in porcine embryos cloned with mesenchymal stem cells (MSCs) is not fully understood. This study aimed to compare the effects of TSA on embryo development, histone acetylation patterns, and key epigenetic-related genes between in vitro fertilization (IVF), NT-MSC, and 40 nM TSA-treated NT-MSC (T-NT-MSC). The results demonstrated an increase in the blastocyst rate from 13.7% to 32.5% in the T-NT-MSC, and the transcription levels of CDX2, NANOG, and IGF2R were significantly elevated in T-NT-MSC compared to NT-MSC. TSA treatment also led to increased fluorescence intensity of acH3K9 and acH3K18 during early embryo development but did not differ in acH4K12 levels. The expression of epigenetic-related genes (HDAC1, HDAC2, CBP, p300, DNMT3a, and DNMT1) in early pre-implantation embryos followed a pattern similar to IVF embryos. In conclusion, TSA treatment improves the in vitro development of porcine embryos cloned with MSCs by increasing histone acetylation, modifying chromatin structure, and enhancing the expression of key genes, resulting in profiles similar to those of IVF embryos.

Targeting SETDB1 in cancer and immune regulation: Potential therapeutic strategies in cancer

SET domain bifurcated histone lysine methyltransferase 1 (SETDB1/ESET), a pivotal H3K9 methyltransferase, has been extensively studied since its discovery over two decades ago. SETDB1 plays critical roles in immune regulation, including B cell maturation, T-cell activity modulation, and endogenous retrovirus (ERV) silencing. While essential for normal immune cell function, SETDB1 overexpression in cancer cells disrupts immune responses by suppressing tumor immunogenicity and facilitating immune evasion. This is achieved through the repression of anti-tumor immune cell production, ERV silencing, and interference with the type I interferon pathway leading to inhibiting immune checkpoint blockade (ICB) efficacy. Beyond its immunological implications, SETDB1 overexpression fosters tumor growth and metastasis via transcriptional silencing of tumor suppressor genes through histone regulation and activating oncogenic signaling by non-histone regulation. These multifaceted roles make SETDB1 an attractive epigenetic target for novel cancer therapies. This review explores SETDB1's dual function in immune regulation and tumor progression, emphasizing its potential in the development of innovative cancer treatments targeting epigenetic dysregulation and oncogenic signaling.

H3K9 post-translational modifications regulate epiblast/primitive endoderm specification in rabbit blastocysts

Post-translational modifications of histone H3 on lysine 9, specifically acetylation (H3K9ac) and tri-methylation (H3K9me3), play a critical role in regulating chromatin accessibility. However, the role of these modifications in lineage segregation in the mammalian blastocyst remains poorly understood. We demonstrate that di- and tri-methylation marks, H3K9me2 and H3K9me3, decrease during cavitation and expansion of the rabbit blastocyst. Notably, H3K9me3 levels are particularly low in inner cell mass cells at the onset of blastocyst formation but increase again just before gastrulation. Conversely, H3K9ac is abundant in early blastocyst stages but decreases during the transition from the inner cell mass to the epiblast. These distinct distribution patterns correlate with high expression levels of methyltransferases (EHMT1, EHMT2, SETDB1) and deacetylases (HDAC1, HDAC2, HDAC5) in expanding blastocysts. Functionally, inhibiting H3K9me2/3 through an EHMT1/2 inhibitor disrupts primitive endoderm segregation, whereas enhancing histone acetylation (including H3K9ac) using a class I HDAC inhibitor promotes epiblast expansion at the expense of the primitive endoderm. These modifications impact the expression of genes associated with pluripotency and lineage determination, underscoring the importance of H3K9 modifications in embryonic cell fate decisions.