Rhesus Monkey Cloned with Breakthrough Technique Unlike Dolly the Sheep

Chinese scientists have made a breakthrough in cloning by successfully creating a rhesus monkey, named ReTro, using a novel approach that overcomes the developmental issues commonly seen in cloned embryos. Rhesus monkeys, sharing about 93% of their DNA with humans, are crucial in research related to human health and diseases. This new method, developed by researchers at the Chinese Academy of Sciences in Shanghai, differs significantly from the technique used to clone Dolly the sheep.

The innovative cloning process involved using a placenta from embryos created through in-vitro fertilization (IVF) instead of the one from the cloned embryo. This adjustment addressed the developmental flaws that typically affect the survival of cloned embryos, leading to this historic success in cloning a rhesus monkey.

Traditional cloning methods, like somatic cell nuclear transfer (SCNT), used for cloning Dolly the sheep, often result in low rates of birth and survival in cloned embryos, particularly in primates. Prior attempts at cloning long-tailed macaques in 2018 had a low success rate, and a rhesus monkey cloned in 2022 using SCNT survived less than a day.

The key issue identified by researchers was that the placentas of cloned embryos were not properly reprogrammed, leading to abnormal development. To tackle this, the team took the inner cells from the cloned embryo, responsible for forming the animal’s body, and implanted them into a non-cloned outer embryo. This created a cloned fetus with a “natural placenta”, enhancing its chances of survival.

Out of 11 cloned rhesus monkey embryos transferred to seven surrogate mothers, two pregnancies occurred, with one resulting in the birth of ReTro. This healthy male monkey has now lived for over two years. Despite this achievement, there are still hurdles to overcome in refining the cloning process.

Lluís Montoliu, a geneticist, noted the challenges in achieving success with such low efficiency rates in cloning experiments.

The potential applications of this advancement include using cloned monkeys for drug testing and behavioral research. The aim is to minimize the number of animals used in experiments and eliminate the variable of genetic differences.