ABSTRACT
The present study examined transcription levels of the Oct4, DNMT1, DNMT3a, DNMT3b, HAT1 and HDAC1 genes in cloned felid embryos developing from single one-cell to blastocyst stages. IVF, cloned domestic and leopard cat embryos had low Oct4 and HAT1 levels during the early stages, but transcript expression increased at the eight-cell and blastocyst stages. In contrast, expression in the cloned marble cat embryos was low at all stages. Transcription patterns of HDAC1 were altered in cloned embryos compared with IVF embryos. Transcription levels of DNMT1 decreased markedly throughout development of both IVF and cloned embryos. In IVF embryos, DNMT3a transcripts rarely appeared in the four- to eight-cell stages, but levels increased in the morula to blastocyst stages. In contrast, in cloned embryos, DNMT3a transcript levels were high at the one- to two-cell stages, decreased during subsequent cell division and then increased again at the blastocyst stage. The IVF and cloned embryos showed similar DNMT3b transcription patterns, starting with low levels at the two-cell to morula stages and reaching a maximum at the blastocyst stage. These results suggest that the low level of Oct4 transcripts may be responsible, in part, for the failure of blastocyst production in the cloned marbled cat. However, higher transcription of the DNA methylation genes and lower transcription of the histone acetylation genes were observed in cloned compared with IVF embryos, suggesting that the felids' donor nucleus could not completely reprogramme the nuclear genome and so the re-establishment of embryonic totipotency was not achieved.
Subject(s)
Cloning, Organism/veterinary , Felidae/physiology , Gene Expression Regulation, Developmental , Animals , Cloning, Organism/methods , Conservation of Natural Resources/methods , DNA Methylation , Epigenesis, Genetic , Felidae/embryology , Felidae/genetics , Female , Histones/genetics , Histones/physiology , Linear Models , Male , Pregnancy , RNA, Messenger/genetics , RNA, Messenger/metabolism , Reverse Transcriptase Polymerase Chain Reaction/veterinary , Transcription, GeneticABSTRACT
We investigated the potential of vitrified-warmed buffalo oocytes to develop to blastocysts after parthenogenetic activation (PA) and somatic cell nuclear transfer (SCNT). In vitro-matured oocytes before and after enucleation (M-II oocytes and enucleated oocytes, respectively) were put in 7.5% DMSO and 7.5% ethylene glycol (EG) for 4, 7 and 10 min, and then vitrified (Cryotop device) after 1-min equilibration in 15% DMSO, 15% EG and 0.5M sucrose. Following 4-, 7- and 10-min exposure, proportions of the post-warm oocytes with a normal vitelline membrane were similar (66-71% in M-II oocytes and 69-71% in enucleated oocytes). However, 18-20% of the normal M-II oocytes had no detectable first polar body in their perivitelline space (no potential for subsequent enucleation). When the post-warm M-II oocytes were treated for PA by 7% ethanol, 10 microg/mL cycloheximide and 1.25 microg/mL cytochalasin-D, parthenogenetic development into Day-7 blastocysts occurred in 10-13% of cultured oocytes, lower (P<0.05) than fresh (control) oocytes (24%). In the absence of the cooling and warming, blastocyst rates in the 4-min exposure group (22%), but not in the 7-min and 10-min exposure groups (14-15%), were similar to that in the fresh group (23%). The total cell number (group average 117-132 cells) and the ICM ratio (22-24%) of the PA blastocysts derived from vitrified M-II oocytes were comparable with fresh oocytes (127 cells and 25%). After SCNT (with fibroblast cells and vitrified-warmed oocytes), blastocyst rates were similar for the three exposure periods for M-II oocytes (8-10%) and enucleated oocytes (7-9%), but were lower (P<0.05) than in the fresh group (15%). The total cell number of the SCNT blastocysts derived from vitrified M-II and enucleated oocytes (80-90 and 82-101 cells) was smaller (P<0.05) than from fresh oocytes (135 cells); the ICM ratio of blastocysts derived from the M-II and enucleated oocytes after vitrification in 7- or 10-min exposure groups (20-22%) was not different (P>0.05) from fresh control oocytes (24%) or those in 4-min exposure group (M-II 23%, enucleated 24%). Thus, SCNT of swamp buffalo oocytes following vitrification before or after enucleation resulted in blastocysts with a slightly decreased cell number.
