PARENT SESSION
SLIDE SESSION 17: PREIMPLANTATION DEVELOPMENT
Chairs: Richard Leach, Carol Brenner, David Natale (Trainee)
Arts Hall 026
1:30 PM-3:30 PM

GLUT8 EXPRESSION AND TRANSLOCATION ARE CRITICAL FOR MURINE BLASTOCYST SURVIVAL.

Pinto, Anil¹, Carayannopoulos, Mary¹, Moley, Kelle^{1, 2}, ^{1 2}

ABSTRACT- GLUT8 is a facilitative glucose transporter expressed predominantly in the murine blastocyst. Unlike other glucose transporters, GLUT8 resides intracellularly in vesicles that, upon IGF-1/insulin stimulation, appear to translocate to the plasma membrane. To determine if GLUT8 has a physiologic role in blastocyst survival, as do the other glucose transporters, two-cell embryos were cultured to a blastocyst stage in the presence of antisense or sense oligonucleotides to GLUT8. Apoptosis was assessed using the TUNEL techniques and recorded as %TUNEL-positive nuclei/total nuclei. Embryos culture in GLUT8 antisense (n=17) experienced 46% TUNEL-positive nuclei as compared to sense embryos at 6% (n=19). A control antisense oligonucleotide, specific for Hsp70-2 and known not to have an effect on blastocysts, was used. These blastocysts showed a rate of apoptosis that was similar to sense. To determine the outcome of these apoptotic embryos, blastocysts exposed to sense vs antisense were transferred back into foster mice and the pregnancy continued until day 14.5 at which time the uteri were examine for the normal gestational sacs and resorptions. Embryos exposed to GLUT8 antisense experienced higher rates of resorptions (86.5 ± 5.2% vs 40.0 ± 8.5%; p=0.0002) and lower normal pregnancy rates (10.5 ± 4.3% vs 59.6 ± 8.5%; p<0.0001) as compared to embryos cultured in GLUT8 sense. To examine what effect, if any, a decrease in IGF-1receptor (IGF-1R) expression and signalling has on GLUT8 translocation, embryos were cultured in IGF-1R sense vs antisense to a blastocyst stage. Using confocal immunofluorescent microscopy, GLUT8 was localized within the blastocysts acutely treated with insulin or not treated. Comparison was made between embryos cultured in IGF-1R antisense vs sense. Exposure to insulin in the sense-treated embryos (n=12) induced translocation from intracellular compartments to the plasma membrane. Blastocysts exposed to IGF-1R antisense (n=10), however, failed to demonstrate any change in intracellular location with insulin treatment. These IGF-1R antisense embryos also displayed significantly greater TUNEL staining as compared to sense. These data suggest that GLUT8 expression and translocation in response to insulin are critical for blastocyst survival.

KEY WORDS: glucose transport, blastocyst, insulin signalling