In a groundbreaking advance that promises to reshape the future of genetic engineering and livestock biotechnology, researchers have successfully derived haploid androgenetic embryonic stem cells (haES cells) from cows and sheep and developed a novel method to generate offspring from these cells. The technique, termed intracytoplasmic haES cell injection (iCHI), builds upon previous rodent studies but breaks new ground in the realm of ruminants, animals notoriously resistant to earlier methods. This milestone not only enables the production of viable, full-term genetically modified livestock but also opens new avenues for precise genome editing in agricultural species of immense economic and ecological importance.
The story begins with the challenge posed by ruminants in reproductive biotechnology. While haploid androgenetic embryonic stem cells have been successfully injected into intact oocytes in rodents—allowing full-term development of offspring—equivalent success in large farm animals such as cows and sheep has eluded scientists. This limitation has stalled efforts to harness the power of haES cells in improving genetic traits or studying developmental biology in these species. The novel breakthrough comes with the derivation of stable haES cell lines from both cow and sheep embryos, marking a critical first step toward applying haploid stem cell technology beyond rodents.
What makes haES cells particularly valuable is their unique ploidy: they contain a single set of chromosomes derived solely from the paternal genome. This androgenetic origin permits precise genetic manipulation and rapid homozygosity for desired traits, which is difficult to achieve through conventional diploid embryonic stem cells or gametes. The team’s success in establishing haES cells from ruminants underscores their ability to navigate the complex developmental and epigenetic challenges inherent in these species, positioning haES cells as a transformative tool for livestock genomic innovation.
The researchers demonstrated that these ruminant haES cells possess characteristics associated with formative-state pluripotency—a developmental window between naïve and primed pluripotency states that is crucial for multi-lineage differentiation. Formative pluripotency endows cells with the capacity to give rise to derivatives of all three germ layers (ectoderm, mesoderm, and endoderm), both in vitro and after transplantation in vivo. This is a crucial attribute for generating genetically modified animals because successful integration and differentiation of the injected cells within host embryonic structures is paramount for normal development.
Building on the established foundation of haES cell pluripotency, the team developed iCHI, a novel reproductive technique inspired by intracytoplasmic sperm injection (ICSI), which traditionally entails direct injection of a sperm cell into an oocyte. iCHI substitutes the sperm cell with a haploid embryonic stem cell, enabling the former’s paternal genome to drive embryogenesis. This method proved successful in generating full-term offspring, a feat that had remained unattainable in ruminants until now. The implications of this are far-reaching, potentially eliminating the need for time-consuming and less efficient approaches such as somatic cell nuclear transfer or complex breeding schemes.
To further enhance the developmental competence of embryos generated via iCHI, the researchers introduced a bioengineering innovation: ectopic expression of protamine proteins within the haES cells prior to injection. Protamine is a small, arginine-rich nuclear protein typically expressed during spermiogenesis, responsible for replacing histones and enabling tight DNA packaging within sperm nuclei. By inducing protamine expression, the team created spermatid-like nuclear structures from haES cells, optimizing their chromatin architecture to mimic natural paternal genomes during fertilization.
This innovation, termed protamine intracytoplasmic haES cell injection (Pro-iCHI), substantially improved embryonic development rates and the proportion of offspring reaching full term. Generating spermatid-like nuclei enhances epigenetic remodeling and genome stability, facilitating more efficient reprogramming of haES cells upon injection. Pro-iCHI marks a pioneering technique that merges stem cell biology with reproductive technology to overcome species-specific developmental barriers and boost the viability of stem cell-derived embryos.
Not stopping at the generation of viable offspring, the team integrated the Pro-iCHI approach with cutting-edge prime editing genome engineering. Prime editing is a versatile CRISPR-based method enabling precise, efficient, and versatile gene modifications without inducing double-strand breaks. By applying prime editing directly in haES cells prior to conversion into spermatid-like nuclei and injection, researchers successfully generated genetically modified cows and sheep harboring precise edits. This synergy accelerates the pathway from genetic design to animal production, circumventing more traditional, laborious transgenic strategies reliant on viral vectors or embryonic microinjection.
The capacity to produce genetically modified livestock holds profound implications for agriculture, biomedicine, and sustainable food production. Precision gene editing could lead to animals with enhanced disease resistance, improved productivity traits, or altered physiological features reducing environmental footprint. Furthermore, livestock models with tailored genetic alterations can serve as vital platforms for biomedical research, including xenotransplantation and studies of complex human diseases. This work fundamentally expands the toolkit available for creating these advanced models.
Beyond practical applications, these findings also shine light on fundamental questions of developmental biology and epigenetic regulation in large mammals. Ruminants differ substantially from rodents in early embryogenesis, imprinting, and chromatin architecture. Successfully reprogramming haES cells and reconstructing fertile embryos from them illustrates not only technological innovation but also deepens understanding of mammalian developmental plasticity and gametogenesis across species. The creation of spermatid-like nuclei in particular offers a unique window into chromatin remodeling dynamics.
While this transformative study addresses many longstanding challenges in ruminant reproductive biotechnology, it also charts a course for future investigation. Further research will be needed to optimize editing efficiencies, increase embryo survival rates, and characterize the long-term health and reproductive capabilities of Pro-iCHI derived animals. Attention to regulatory and ethical frameworks governing genome editing in livestock will be essential as the field moves toward commercial and clinical applications.
The convergence of haploid stem cell technology, spermatid-like nuclear engineering, and prime editing embodies the continued evolution of synthetic biology and reproductive medicine. This study personifies how interdisciplinary collaboration—spanning stem cell biology, molecular genetics, reproductive physiology, and animal biotechnology—can generate breakthrough solutions with enormous potential to transform industries. The presence of such innovative techniques enables livestock breeding to shift from traditional selection toward rational, precise, and accelerated genetic improvement.
In conclusion, the generation of genetically modified cows and sheep from protamine-induced spermatid-like haploid embryonic stem cells via the Pro-iCHI method represents a landmark achievement. By overcoming species barriers and enhancing developmental competence through chromatin engineering, this work paves the way for next-generation livestock biotechnology. The integration with prime editing provides a versatile and powerful platform for precise genome manipulation, promising to accelerate the production of animals tailored for a future of sustainable agriculture and biomedical innovation. Undoubtedly, this leap forward will spark widespread excitement and vigorous exploration within the scientific community and agricultural industries alike.
Subject of Research: Generation of genetically modified livestock through haploid androgenetic embryonic stem cells and novel reproductive technologies.
Article Title: Generation of modified cows and sheep from spermatid-like haploid embryonic stem cells.
Article References:
Yang, L., Di, A., Song, L. et al. Generation of modified cows and sheep from spermatid-like haploid embryonic stem cells. Nat Biotechnol (2025). https://doi.org/10.1038/s41587-025-02832-4
Image Credits: AI Generated
