The Development of Porcine Parthenogenetic Diploid Oocytes with Homogeneous Genomic Components In Vitro.

Abstract

Abstract. The aim of this study was to determine the influence of the homogeneity of genomic components and ploidy on the in vitro development of porcine parthenogenetic oocytes to the blastocyst stage. In vitro matured oocytes were subjected to a single pulse of electro-stimulation (El-St; 100 µsec, 1,500 V/cm) for activation. First, the activated oocytes were cultured for 6, 16, 18, 20 and 22 h after El-St, and examined for the timing of the first cleavage of parthenogenetic haploids. Next, the effects of the timing and duration of cytochalasin B (CB) treatment on inhibition of the first cleavage of haploids were examined in order to produce homogenous parthenogenetic diploids. Then the developmental ability to the blastocyst stage was compared among activated oocytes with genomic components of haploid (without CB treatment), homogeneous diploid (nn-diploid, CB treatment for 6 h from 20 h after El-St), and heterogeneous diploid (nn'-diploid, CB treatment for 4 h immediately after El-St). Most haploids were at the prophase to telophase of the first cleavage between 16 and 22 h after El-St. When the haploids were treated with 5.0 µg/ml CB for 6 h from 20 h after El-St, their first cleavage was efficiently suppressed, and most of them (84%) became diploids. The frequency of parthenogenetic development to the blastocyst stage was significantly lower in haploids (5%) than in nn-diploids (48%, P<0.01) or nn'-diploids (57%, P<0.01). These results shows that ploidy of activated oocytes, but not the homology of genomic components, affects the development of porcine parthenogenetic oocytes to the blastocyst stage. Key words: Porcine parthenogenesis, Ploidy, In vitro development (J. Reprod. Dev. 48: [157][158][159][160][161][162][163][164][165][166] 2002) he genotype of the parthenogenetic embryo var ies d e pe nd ing on the ex per ime ntal conditions and on the postovulatory age of the oocyte. Matured oocytes have two genomic sets of chromosomes, one which is delivered to the egg and the other which is shared by the second polar body. Each chromosome consists of a mixture of paternal and maternal genomic components by the process of crossing-over during the meiotic prophase I. Thus the two genomic sets are not exactly identical. Therefore, the possible genotypes arising from parthenogenetic activation are uniform haploids with the extrusion of the second polar body (n), mosaic haploids through an immediately equal cell-division but not extrusion of the second polar body (n+n'), and heterogeneous diploids without the extrusion of the second polar body (nn') according to the theoretical classification by Kaufman [1]. It has been reported, however, that porcine oocytes matured less than 48 h followed by artificial activation actually yielded activated eggs of uniform haploid type (about 90%) or of heterogeneous diploid type with two haploid (n + n') nuclei or a single diploid (nn') nucleus (a few percentage each), but no mosaic-haploid activated oocytes [2,3].

Characteristics of Preimplantational Development of Porcine Parthenogenetic Diploids Relative to the Existence of Amino Acids In Vitro1

“…With in vitro fertilization, high developmental ability to the blastocyst stage is hardy expected because of the high incidence of polyspermy in the pig. Our previous reports have shown that electroactivated porcine oocytes that had been matured in vitro can develop to the blastocyst stage in vitro; furthermore, the characteristics of development of porcine parthenogenetic diploids to the blastocyst stage resembled those of in vitro fertilized eggs [40][41][42][43]. These results suggested that parthenogenetic diploids could be used as model embryos instead of fertilized oocytes for studies regarding the early development and establishment of culture systems in the pig.…”

Alpha-lipoic acid attenuates heat stress-induced apoptosis via upregulating the heat shock response in porcine parthenotes

“…In present study, parthenogenetic diploids were used due to the relatively high occurrence of polyspermy with in vitro fertilization of porcine embryos. However, the development of porcine parthenogenetic diploids to the blastocyst stage is comparable to the normal development of embryos [38][39][40] .…”

Polyamines inhibit apoptosis in porcine parthenotes developing in vitro

“…In the porcine system, a high incidence of polyspermy is seen with in vitro fertilization, and development to the blastocyst stage is compromised. However, development of porcine parthenogenetic diploids to the blastocyst stage resembles normal development (Kure-bayashi et al, 1996;Thuan et al, 2002;Cui and Kim, 2003). These results suggested that parthenogenetic diploids could be used as model embryos for studies regarding early development and establishment of in vitro culture systems in the pig.…”