Comparative Study of Reprogramming Efficiency and Regulatory Mechanisms of Placental- and Fibroblast-Derived Induced Pluripotent Stem Cells (iPSCs) in Mules.

As an interspecies hybrid inheriting genetic material from horse and donkey lineages, mules provide a unique model for studying allele-specific regulatory dynamics. Here, we isolated adult fibroblasts (AFs) and placental fibroblasts (PFs) from mule tissues and reprogrammed them into induced pluripotent stem cells (iPSCs). Intriguingly, placental fibroblast-derived iPSCs (mpiPSCs) exhibited reduced reprogramming efficiency compared to adult fibroblast-derived iPSCs (maiPSCs). Through allele-specific expression (ASE) analysis, we systematically dissected transcriptional biases in parental cell types and their reprogrammed counterparts, revealing conserved preferential expression of asinine alleles in core pluripotency regulators (e.g., POU5F1/OCT4, SOX2, NANOG) across both cell lineages. Strikingly, mpiPSCs displayed stronger asinine allele dominance than maiPSCs, suggesting tissue-specific parental genomic imprinting. Mechanistic exploration implicated PI3K-AKT signaling as a potential pathway mediating the reprogramming inefficiency in placental fibroblasts. By integrating transcriptomic profiling with ASE technology, this study uncovers allele selection hierarchies during somatic cell reprogramming in hybrids and establishes a framework for understanding how parental genomic conflicts shape pluripotency establishment. These findings advance interspecies iPSC research by delineating allele-specific regulatory networks and providing insights into the molecular constraints of hybrid cellular reprogramming.