Journal of Developmental Biology

High non-esterified fatty acids (NEFAs) during negative energy balance in dairy cattle can impair reproduction. While their effects on oocyte maturation and preimplantation embryo development are known, their impact during fertilisation is largely unexplored. This study examined the effects of high NEFA exposure exclusively during in vitro fertilisation (IVF). Bovine oocytes were matured in vitro and fertilised under physiological or high NEFA concentrations. High NEFA concentrations decreased fertilisation, cleavage, and blastocyst rates. Reactive oxygen species production in zygotes was not affected, but blastocysts derived from the High-NEFA group had fewer cells. Spermatozoa exposed to high NEFA concentrations exhibited increased plasma membrane and acrosome damage, higher DNA fragmentation, and reduced mitochondrial membrane potential. The expression of H3K27me3, a repressive histone mark normally erased from fertilisation to embryonic genome activation, was higher in 2-cell than in 4-cell embryos on day 2 after IVF, but only in the High-NEFA group. This delayed H3K27me3 loss, along with increased DNA damage, could partially explain the reduced blastocyst formation observed. In conclusion, high NEFA concentrations can impair pre-implantation embryo development during zygote formation, potentially via effects on both the oocyte and spermatozoon. The latter warrants further investigation using an intracytoplasmic sperm injection model.

We have previously established that bexarotene, a clinically approved agonist of retinoid X receptor (RXR), promotes the differentiation and fusion of skeletal myoblasts. We have also analyzed the genomic programs underlying rexinoid-enhanced myogenic differentiation to identify novel regulatory pathways. As such, we observed a significant upregulation of a transcript encoding a predicted transmembrane protein, Tmem182, during C2C12 myoblast differentiation. Despite the documentation of Tmem182 expression in skeletal muscles, its regulation had yet to be explored. Here, we show that Tmem182 gene expression is markedly augmented in early myoblast differentiation and further enhanced by RXR signaling. In addition, Tmem182 expression is specific to muscle tissues and related to muscle master regulator MyoD. We found that MyoD and histone acetyltransferase p300 are bound to the Tmem182 promoter, and Tmem182 expression is p300-dependent. Thus, our data display a putative epigenetic signature associated with p300 and histone acetylation in rexinoid-responsive locus activation and transcription of myogenic targets.

In recent years, assisted reproductive technology (ART) has developed rapidly with the delay in reproductive age and the rise in infertility rates. During ART, blastocyst quality is a key factor affecting the rate of implantation and clinical pregnancy, and blastocyst formation is dependent on the precise regulation of multiple signaling pathways in preimplantation embryo development. In this review, we systematically analyze the molecular mechanisms of the core pathways, including Hippo, Wnt/β-catenin, FGF, Nodal, and BMP, in blastocyst lineage differentiation and morphogenesis, and assess the feasibility of optimizing in vitro culture by targeting key signaling nodes, as well as provide theoretical support for constructing research models of preimplantation embryos.