Feasibility of Human Telomerase Reverse Transcriptase mRNA Expression in Individual Blastomeres as an Indicator of Early Embryo Development

Abstract

Purpose : The study was undertaken to test whether human telomerase reverse transcriptase (hTERT) transcripts in an individual blastomere could be used as an indicator for embryo development. Methods : Group A consisted of day 3 normal cleaving embryos at 4-to 8-cell stage, which were surplus and not allocated for uterine transfer. Group B consisted of arrested or fragmented embryos at the same stage, which were considered to be compromised. After blastomere dissociation, RNA purification, reverse transcription, and hTERT PCR amplification, the amplified product was separated by 3% gel electrophoresis. Results : Eighty-six (90.5%) of the 95 intact blastomeres in group A and 78 (70.9%) of the 110 blastomeres in group B demonstrated hTERT mRNA expression. The difference was statistically significant (P < 0.05, chi-square). Eight (38.1%) of the 21 embryos in group A and 22 (62.9%) of the 35 embryos in group B had at least one blastomere that did not express hTERT mRNA under this procedure. The difference was not significant (P > 0.05, chi-square). Conclusions : General hTERT mRNA transcripts can be detected in most of the individual blastomeres but cannot be used as an indicator for early embryo development. Further investigations are necessary to elucidate its clinical application.

Totipotency: What It Is and What It Is Not

“…Zygotic transcription commences during the first cell cycle in both mouse [48][49][50][51] and human [52][53][54][55][56][57][58][59] embryos. While some studies have seen no difference in gene expression between early blastomeres [60], there is evidence from several groups suggesting that as early as the 4-8-cell stage, blastomeres have unique molecular properties [61][62][63][64][65][66][67][68][69][70][71] that translate into distinct developmental capabilities after dissociation and reaggregation [72,73]. Substantial evidence stretching back over 60 years indicates that when cells with distinct developmental states are aggregated, cell sorting plays a significant role in re-establishing the initial pattern [74,75].…”

“…There is clear evidence from multiple laboratories that by the four-to eight-cell stage these two processes have resulted in blastomeres that have distinct molecular, functional, and developmental properties [61][62][63][64][65][66][67][68][69][70][71]157,158], indicating that from the four-cell stage onward, mammalian development is mosaic to some extent.…”