Changes in yolk platelet pH during Xenopus laevis development correlate with yolk utilization. A quantitative...

Area of Science:

• Cell Biology
• Developmental Biology
• Biochemistry

Background:

• Yolk platelets are essential nutrient stores in Xenopus oocytes.
• The pH of intracellular compartments plays a critical role in protein processing and degradation.
• Understanding yolk platelet pH dynamics is key to deciphering developmental processes.

Purpose of the Study:

• To investigate the pH variations within Xenopus yolk platelets during oogenesis and embryogenesis.
• To determine the role of yolk platelet pH in yolk degradation and cell differentiation.

Main Methods:

• Fluorescence confocal microscopy and computer image processing were used for pH estimation.
• pH-sensitive fluorescent dye DM-NERF, coupled to vitellogenin, was used for measurements in oocytes.
• Acridine Orange accumulation was measured in isolated yolk platelets and embryonic cells.
• Bafilomycin, a vacuolar H+-ATPase inhibitor, was employed to assess the role of acidification.

Main Results:

• Mature and primordial yolk platelets in oocytes are mildly acidic (pH 5.6-5.7).
• During embryogenesis, yolk platelets become significantly more acidic (pH < 5), correlating with yolk degradation.
• Inhibition of acidification with bafilomycin blocked yolk degradation and embryonic cell differentiation.

Conclusions:

• Yolk platelet pH is developmentally regulated in Xenopus.
• Yolk acidification is a critical trigger for yolk degradation and is linked to cell differentiation.
• Yolk acidification and degradation are associated with the formation of the endosomal/lysosomal compartment during development.