Zygotically activated genes are suppressed in mouse nuclear transferred embryos

Area of Science:

• Developmental Biology
• Reproductive Science
• Genomics

Background:

• Mammalian oocytes can reprogram somatic cell nuclei, enabling cloning via somatic cell nuclear transfer (SCNT).
• Despite successful cloning in various species, SCNT efficiency remains low across all mammals.
• Previous studies focused on gene expression differences in later developmental stages of SCNT embryos.

Purpose of the Study:

• To investigate gene expression patterns in SCNT embryos at the early 2-cell stage.
• To identify molecular abnormalities that may contribute to the low developmental success of cloned embryos.

Main Methods:

• Differential display reverse transcription PCR (DDRT-PCR) was employed to compare gene expression between SCNT and in vitro fertilization (IVF) embryos.
• Analysis focused on the 2-cell stage to detect early developmental aberrations.

Main Results:

• Significant aberrant gene expression was observed in SCNT embryos compared to IVF embryos.
• Specific genes (MuERV-L, Dnaja2) were downregulated, while others (Inpp5b, Chst12) were upregulated in SCNT embryos.
• Expression of zygotically activated genes, including Interferon-gamma and Dub-1, was suppressed in SCNT embryos.

Conclusions:

• Early-stage SCNT embryos exhibit distinct gene expression profiles compared to normally fertilized embryos.
• The observed gene dysregulation suggests that the nuclear reprogramming process in SCNT is not fully efficient.
• These findings highlight critical molecular events occurring early in SCNT development that impact subsequent viability.