Background
Glucose metabolism is an essential energy source for mammalian preimplantation embryonic development. Therefore, we aimed to analyze the expression of all 12 known glucose transporters (facilitated solute carrier family 2, Slc2a) during early mouse embryo development.
Conclusion
The results unveil distinct expression patterns of individual Slc2a glucose transporters during early embryo development. Taken together, they provide novel insights into the understanding and management of glucose metabolic infertility in assisted-reproductive technologies (ART).
Methods
Gene and protein expression of Slc2a transporters in oocytes and embryos were assessed by the TaqMan gene expression assay and confocal immunofluorescence, respectively.
Results
Except for Slc2a2, the other 11 Slc2a transcripts were detected in oocytes. Transcripts of Slc2a1, Slc2a3, Slc2a4, and Slc2a8 were the most enriched and detected in preimplantation embryos. The transcription of other Slc2a isoforms was barely detectable or absent after fertilization; however, they were detected in blastocysts, except for Slc2a10 and Slc2a13. Embryo culture in the simple defined medium caused a reduction in transcription of Slc2a1, Slc2a3, Slc2a4, and Slc2a8 in blastocyst; yet, amino acids partially reversed this impaired transcription of Slc2a1 and Slc2a4. SLC2A1 and SLC2A4 proteins were detected at all embryonic stages with nuclear accumulation in the embryos at the early cleavage stage. SLC2A3 and SLC2A8 were not detected in embryos until the eight-cell stage. The cellular membrane localization of SLC2A1, SLC2A3, and SLC2A8 occurred after compaction and was characterized in blastocysts. SLC2A4 was evenly distributed in the cytoplasm and nuclei without its characteristic membrane localization. Indinavir sulfate (a SLC2A4 inhibitor) decreased the rate of development and prevented glucose utilization in embryos after compaction. These inhibitory activities were partially reversed by exogenous insulin.