Somatic cell nuclear transfer (SCNT) successfully clones cynomolgus monkeys, but the efficiency remains low due to a limited understanding of the reprogramming mechanism. Notably, no rhesus monkey has been cloned through SCNT so far. Our study conducts a comparative analysis of multi-omics datasets, comparing embryos resulting from intracytoplasmic sperm injection (ICSI) with those from SCNT. Our findings reveal a widespread decrease in DNA methylation and the loss of imprinting in maternally imprinted genes within SCNT monkey blastocysts. This loss of imprinting persists in SCNT embryos cultured in-vitro until E17 and in full-term SCNT placentas. Additionally, histological examination of SCNT placentas shows noticeable hyperplasia and calcification. To address these defects, we develop a trophoblast replacement method, ultimately leading to the successful cloning of a healthy male rhesus monkey. These discoveries provide valuable insights into the reprogramming mechanism of monkey SCNT and introduce a promising strategy for primate cloning.
© 2024. The Author(s).

Somatic cell nuclear transfer (SCNT) has been used to clone cynomolgus monkeys, but cloning of other non-human primate species remains to be achieved. Our histological examination indicated severe calcification of the placenta of implanted SCNT macaque embryos. By replacing SCNT-derived trophoblast with ICSI-derived trophoblast, endowing a normal placenta for the SCNT fetus, we obtained a healthy SCNT rhesus monkey. Thus, trophoblast replacement represents a useful approach for rhesus monkeys cloning.