The world's first cloned golden wild yak via interspecific SCNT: 4800m donor origin and 4200m vitrified blastocyst transfer

Abstract

Primarily inhabiting the harsh, high-altitude environment of the Qiangtang National Nature Reserve exceeding 5,000 meters above the sea (m.a.s.l.), the golden wild yak is critically endangered, with fewer than 300 individuals remaining in the world, a situation exacerbated by the significant challenges of conducting research and conservation of their genetic resources. Somatic cell nuclear transfer (SCNT) can be an effective method for their preservation, but facing several obstacles in this context, including the hypoxic stress at high altitude that impairs embryonic development due to in vitro manipulation, and constraints of long-distance embryo transport. In the present study, the ear tissue was collected from a childhood male golden wild yak at Xizang Geye Wildlife Rescue Station (4800 m.a.s.l.) and send to Institute of Animal Science at Beijing to derive fibroblast cells. Using fibroblast cells of the golden wild yak as nuclear donors, and bovine oocytes from a local slaughterhouse at Beijing as recipients, the interspecific SCNT (iSCNT) embryos were generated and in vitro developed to blastocysts. To maintain the embryonic viability after long-distance transportation from Beijing to Xizang, iSCNT blastocysts were subjected to cryopreservation by vitrification method. Thawing of vitrified iSCNT blastocysts were completed at Xizang Dangxiong Yak Breeding Innovation Base (4200 m.a.s.l.), and transferred into the uterine horn of domestic yaks. 257 days after blastocyst transfer, a cloned golden wild yak was successfully harvested on January 10, 2026. This work demonstrates, for the first time, that interspecies somatic cell nuclear transfer can successfully produce a cloned offspring under extreme conditions, spanning 4800 m.a.s.l. donor origin, long-distance vitrified embryo transportation, and high-altitude blastocyst transfer at 4200 m.a.s.l., establishing a viable strategy for conserving critically endangered high-altitude species.