Viable calves produced by somatic cell nuclear transfer using meiotic-blocked oocytes

Area of Science:

• Reproductive Biology
• Developmental Biology
• Animal Science

Background:

• Somatic cell nuclear transfer (SCNT) is crucial for animal cloning but faces limitations due to procedural complexity and low efficiency.
• Oocyte meiotic arrest presents a strategy to enhance SCNT flexibility and increase cloned embryo production.

Purpose of the Study:

• To investigate the efficacy of meiotic arrest using butyrolactone I and brain-derived neurotrophic factor (BDNF) in bovine oocytes for SCNT.
• To assess the impact of meiotic arrest on cloned embryo development, viability markers, and mitochondrial DNA copy number.

Main Methods:

• Bovine oocytes were subjected to meiotic arrest for 24 hours using butyrolactone I and BDNF prior to in vitro maturation.
• SCNT was performed using arrested and non-arrested oocytes, followed by embryo culture and analysis of gene expression (POU5F1, IFNT2) and mitochondrial DNA (mtDNA) copy number.

Main Results:

• Meiotically arrested oocytes supported the development of blastocysts and full-term cloned calves with efficiency comparable to non-arrested oocytes.
• Cloned blastocysts from arrested oocytes showed increased expression of POU5F1 (1.5-fold) and IFNT2 (2-fold), indicating enhanced viability.
• While mtDNA copy number decreased in immature arrested oocytes, it remained stable in mature oocytes and blastocysts.

Conclusions:

• Meiotic arrest of bovine oocytes using butyrolactone I and BDNF is a viable strategy for improving SCNT efficiency and producing cloned offspring.
• This method offers significant implications for SCNT applications and in vitro embryo production in animal science.
• The study reports the first instance of cloned offspring derived from prematurely arrested oocytes.