Reprogramming mechanism dissection and trophoblast replacement application in monkey somatic cell nuclear transfer

Area of Science:

• Reproductive biology
• Developmental biology
• Epigenetics

Background:

• Somatic cell nuclear transfer (SCNT) is a technique for cloning mammals, but its efficiency in primates, particularly rhesus monkeys, is hindered by incomplete epigenetic reprogramming.
• Understanding the molecular mechanisms underlying SCNT reprogramming is crucial for improving cloning success rates in non-human primates.

Purpose of the Study:

• To investigate the epigenetic landscape of SCNT-derived embryos in cynomolgus monkeys compared to intracytoplasmic sperm injection (ICSI) embryos.
• To identify reprogramming defects in SCNT embryos and placentas.
• To develop a novel strategy to overcome these defects and achieve successful cloning of rhesus monkeys.

Main Methods:

• Comparative analysis of multi-omics datasets (DNA methylation, gene expression) between ICSI and SCNT embryos.
• In vitro culture of SCNT embryos and histological examination of SCNT placentas.
• Development and application of a trophoblast replacement method for SCNT.

Main Results:

• SCNT cynomolgus monkey blastocysts exhibit widespread DNA hypomethylation and loss of imprinting in maternally imprinted genes.
• These epigenetic abnormalities persist in later-stage SCNT embryos and placentas, which also show hyperplasia and calcification.
• The developed trophoblast replacement strategy enabled the birth of a healthy, cloned male rhesus monkey.

Conclusions:

• Epigenetic reprogramming defects, including DNA hypomethylation and loss of imprinting, are significant barriers to successful SCNT in primates.
• A trophoblast replacement method can effectively correct these defects, paving the way for efficient primate cloning.
• This study provides critical insights into primate SCNT reprogramming and offers a viable strategy for future cloning efforts.