Animal Molecular Breeding 2024, Vol.14, No.4, 262-270 http://animalscipublisher.com/index.php/amb 264 demethylase inhibitors as future treatments, as well as the use of microRNAs as diagnostic and prognostic biomarkers (Figure 1) (Montaner-Angoiti et al., 2023). Figure 1 Scheme of miRNA biogenesi (Adopted from Montaner-Angoiti et al., 2023) Image caption: In the nucleus, miRNA is transcribed by RNA polymerase II as primary transcripts (pri-miRNA). The Drosha enzyme cuts this pri-miRNA to form a premiRNA, which is actively transported to the cytoplasm by the nuclear transport receptor exportin 5 (XPO5). In the cytoplasm, the pre-miRNA is cut by a second enzyme, Dicer, to form a mature and short double-stranded miRNA molecule. The miRNA duplex is incorporated into the RISC protein complex (Adopted from Montaner-Angoiti et al., 2023) Montaner-Angoiti et al. (2023) explored the critical processes of miRNA biogenesis, shedding light on the sequential stages of miRNA maturation. In the nucleus, miRNA transcription produces primary transcripts (pri-miRNA), which are processed by the Drosha enzyme. This early processing step is essential to convert pri-miRNA into pre-miRNA, a necessary precursor for downstream maturation. Afterward, exportin 5 (XPO5) mediates the active export of pre-miRNA to the cytoplasm. Once in the cytoplasm, the Dicer enzyme further refines pre-miRNA by cleaving it into a mature double-stranded miRNA duplex. Importantly, the mature miRNA is subsequently integrated into the RNA-induced silencing complex (RISC), which is responsible for gene silencing activities such as mRNA degradation or translational repression. This pathway underlines the precise regulatory role of miRNAs in post-transcriptional gene expression, providing potential targets for therapeutic interventions. 3.2 Advances in epigenomic technologies for marker identification Advances in epigenomic technologies have significantly enhanced the identification of epigenetic markers in canine health. Techniques such as bisulphite sequencing, real-time methylation-specific PCR, and chromatin immunoprecipitation followed by quantitative PCR (ChIP-qPCR) have been employed to study the epigenetic regulation of genes associated with disease resistance. For example, bisulphite sequencing and real-time methylation-specific PCR were used to reveal hypermethylation and hypomethylation patterns in the CpG islands of the ABCB1 gene in different canine lymphoid tumor cell lines (Ling and Rönn, 2016). Furthermore, ChIP-qPCR has been utilized to assess histone modifications, providing insights into the epigenetic landscape of drug-resistant and drug-sensitive cell lines (Izquierdo and Crujeiras, 2019).
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