Developmental bias in cleavage-stage mouse blastomeres.

Area of Science:

• Developmental Biology
• Genetics
• Embryology

Background:

• Cleavage-stage mouse embryos have seemingly equivalent blastomeres that form the inner cell mass (ICM) and trophectoderm (TE).
• It is unclear if blastomere contribution to ICM and TE is determined by chance.
• Understanding blastomere cell fate is crucial for preimplantation genetic diagnosis.

Purpose of the Study:

• To determine if blastomere allocation to the earliest lineages (ICM and TE) is random.
• To investigate the developmental potential of early embryonic cells.

Main Methods:

• Developed a noninvasive, recombination-mediated, combinatorial fluorescent labeling technique.
• Utilized this method for embryonic lineage tracing in mouse embryos.
• Employed Rainbow lineage tracing for tracking cell contributions.

Main Results:

• A statistically significant bias in blastomere contribution to TE or ICM was observed in a subset of embryos.
• No correlation was found between blastomere location (embryonic/abembryonic hemispheres) and TE-ICM allocation.
• The detected bias persists into postimplantation stages, indicating long-term developmental relevance.

Conclusions:

• Rainbow transgenic mice enable detection of lineage-dependent bias in early development.
• This method can assess the developmental equivalence of progenitor cells across various mammalian tissues.