Reviving rare chicken breeds using genetically engineered sterility in surrogate host birds

Area of Science:

• Reproductive Biology
• Conservation Genetics
• Cellular Biology

Background:

• Cryopreservation of avian oocytes and zygotes is hindered by large lipid content, preventing species regeneration from frozen material.
• Diploid primordial germ cells (PGCs) present a viable alternative for preserving avian genomes.
• Rare heritage chicken breeds are at risk due to limitations in current cryopreservation methods.

Purpose of the Study:

• To evaluate the efficacy of using genetically engineered (GE) sterile female chickens as surrogate hosts for cryopreserved avian PGCs.
• To determine the feasibility of regenerating rare heritage chicken breeds using PGC transplantation.
• To assess the genetic stability of PGCs during in vitro culture and cryopreservation.

Main Methods:

• Amplification of PGCs in culture, followed by cryopreservation.
• Transplantation of cryopreserved PGCs into GE sterile chicken embryos.
• Production of pure offspring from chimera hens using cryopreserved semen.
• Measurement of mutation rates (de novo single-nucleotide variants) and retroviral mobilization during PGC culture.

Main Results:

• All hatched offspring from chimera GE hens originated from donor heritage breed PGCs.
• Pure offspring were successfully produced from chimera hens using cryopreserved semen.
• The mutation rate of cultured PGCs was 2.7 × 10^-10 de novo SNVs per cell division, comparable to other stem cells.
• Endogenous avian leukosis virus (ALV) retroviral insertions remained stable during in vitro propagation.

Conclusions:

• Genetically engineered sterile avian surrogate hosts provide a viable platform for avian species conservation.
• Cryopreserved PGCs can be successfully used to regenerate avian breeds.
• The genetic stability of PGCs during culture and cryopreservation supports their use in conservation efforts.