Beyond marker expression: An ESC-informed framework for engineering and validating chicken induced pluripotent stem cells.

The chicken induced pluripotent stem cells (iPSCs) are still plagued by limitations such as low reprogramming efficiency, instability, and a lack of demonstrated germline competence, which are in part attributed to the absence of a precisely defined biological pluripotency reference. In this review, we propose an ESC-informed approach that positions a molecularly and functionally defined chicken embryonic stem cell (cESC) reference state as the standard against which chicken iPSC generation is designed and evaluated. Combined transcriptional, epigenetic, and signaling information reveals important pathways that are limiting, e.g., incomplete activation of pluripotency networks, epigenetic resistance, and species-specific signaling constraints, and rational strategies to overcome them. This approach does not emphasize induction of markers but rather state alignment to functional outcomes, with the most rigorous validation being germline contribution and, where demonstrated, transmission to offspring. This ESC-guided framework of interventions, including transcription factor optimization, RNA regulation, chemical modulation, and multi-omics integration, is proposed as a structured, mechanistically grounded strategy to improve the fidelity and reproducibility of reprogramming. This review outlines a standardized, mechanistically defined blueprint for chicken iPSC engineering, which has the potential to further chicken fundamental biology and applications in transgenic poultry production and conservation of avian genetic resources.