Ultrastructure, protein phosphorylation and mRNA status of equine oocytes matured in vivo and in vitro.

The research article presents a study investigating the structure, protein phosphorylation, and mRNA status of horse oocytes matured both in living beings and the lab. The study looked into details such as the number, position, and interaction of different cell components, how they altered with time during lab maturation, and the differences between in-lab and in vivo maturation process.

Ultrastructure of Oocytes

• The researchers used electron microscopy to study the ultrastructure of equine oocytes. They observed a smooth nuclear membrane in oocytes that had a compact cumulus, while oocytes in all other groups had an undulated nuclear membrane.
• Oocytes with a more compact cumulus showed fewer microvilli (small protrusions that increase the cell’s surface area), while those with expanded cumulus exhibited more microvilli.
• The study found that oocytes with a compact cumulus had cortical granules and clusters of mitochondria mostly in the peripheral ooplasm. However, oocytes with expanded cumuli presented an increased number of these cell components, and the Golgi complexes in these cells were smaller than in other oocytes.

Oocyte Maturation In Vitro

• By observing the oocytes at 10, 20, and 30 hours of in vitro maturation, the study noticed some changes. The mitochondria migrated centrally, the number of cortical granules near the oolemma (cell membrane) gradually increased, and the presence of membrane-bound smooth endoplic reticulum (a cell organelle) decreased over time.

Protein Phosphorylation and mRNA Status

• The research detected phosphorylated proteins with a molecular mass ranging from 20 to 150 kDa in both oocytes and cumulus cells.
• The phosphorylation pattern of these proteins varied in oocytes developed through natural in vivo methods and the ones cultured in labs (16 and 32 hours).
• Different cumulus types did not show distinct bands of phosphorylated proteins.
• The study found mainly repressed mRNAs (molecules that carry instructions from DNA for protein synthesis) in oocytes with compact cumuli, whereas oocytes with expanded cumuli had the translationally active form of mRNA.