Cloned transgenic mouse fetuses from embryonic stem cells.

Area of Science:

• * Developmental Biology
• * Reproductive Biotechnology
• * Mammalian Genetics

Background:

• * Efficient genetic modification and large-scale cloning are crucial for agriculture, biotechnology, and human medicine.
• * Mice serve as an ideal model organism for fundamental genetic modification research.
• * Embryonic stem (ES) cells offer a promising avenue for generating cloned and genetically modified animals.

Purpose of the Study:

• * To investigate the production of cloned mice from an established embryonic stem cell line using nuclear transfer.
• * To explore the feasibility of producing cloned transgenic mouse fetuses and offspring using EGFP-modified ES cells.
• * To assess the developmental potential of reconstructed oocytes and cloned embryos derived from ES cells.

Main Methods:

• * Nuclear transfer into reconstructed oocytes using an established TT2 embryonic stem cell line (at least 15 passages).
• * Modification of ES cells with the enhanced green fluorescent protein (EGFP) marker gene.
• * Transfer of modified embryos into surrogate mothers (pseudopregnant females) and monitoring of fetal development.

Main Results:

• * Reconstructed oocytes developed into various embryonic stages, reaching blastocysts at a rate of 44.8%.
• * 17.2% of reconstructed oocytes developed to term (19.5 days post-coitum).
• * Transfer of EGFP-modified embryos resulted in live fetuses expressing GFP, although none survived beyond 19.5 dpc.

Conclusions:

• * Embryonic stem cells are a viable tool for producing cloned mice.
• * The study provides evidence for the successful generation of cloned transgenic mouse fetuses using ES cell nuclear transfer.
• * Further optimization is needed to improve the survival rates of cloned transgenic offspring beyond the fetal stage.