Transglutaminase (TG) involvement in early embryogenesis.

Area of Science:

• Biochemistry
• Developmental Biology
• Cell Biology

Background:

• Transglutaminase (TG) is a family of enzymes that catalyze cross-linking reactions.
• Preimplantation embryogenesis involves significant cellular and structural remodeling.
• The role of TG in early mouse embryo development is not fully understood.

Purpose of the Study:

• To investigate the activity and substrates of transglutaminase (TG) during preimplantation mouse embryogenesis.
• To determine the relationship between TG activity and cytoskeletal changes in developing embryos.

Main Methods:

• Assaying TG specific activity in soluble fractions of mouse embryos at different developmental stages (2-cell, 8-cell, blastocyst).
• Utilizing N,N'-dimethylcasein or endogenous substrates for TG activity measurement.
• Identifying TG acyl donors using [3H]putrescine and analyzing protein components via electrophoresis and immunoblotting.
• Comparing the suitability of assembled and monomeric cytoskeleton proteins as TG substrates.

Main Results:

• TG specific activity in the soluble cellular fraction increased 2-fold from 2-cell to 8-cell embryos and 4-fold by the blastocyst stage.
• Microtubules, particularly tubulin, were identified as major acyl donors for TG.
• A high molecular weight (HMW) cross-linked product was also a significant TG product.
• Assembled microtubules served as more efficient acyl donors than monomeric cytoskeleton proteins.

Conclusions:

• TG activity is dynamically regulated during preimplantation mouse development.
• TG likely modulates the microtubule cytoskeleton to meet the changing structural demands of blastomeres.
• These findings highlight TG's crucial role in early embryonic development and cell structure maintenance.