301 Imprinted Gene Expression Patterns in Cultured Primordial Germ Cells Derived From Porcine Embryos Between Day 25 and 30

Abstract

Although epigenetic reprogramming during germ cell development has extensively been studied in the mouse, little is known about the timing of imprinting accomplishment in the pig. Therefore, the aim of this study was to investigate the timing of epigenetic reprogramming in porcine primordial germ cells (PGC) through short-term culture as well as to confirm the differences of epigenetic features between PGC and embryonic germ cells (EGC). The present study aimed to investigate mRNA expression pattern of imprinted genes in cultured PGC that were derived from embryos at Day 25 to 30 of pregnancy. The overall expression pattern can be separated into 3 different features: no changes in all PGC regardless of embryonic day, gradual increases through embryonic day, and extreme increases in PGC derived from embryos at Day 30. Of 8 imprinted genes, Grb10, Peg10, and Snrpn transcripts were retained through all stages. The expression level of H19, Igf2, Igf2r, and Peg1/Mest progressively increased in PGC derived at later stages of embryo development. Interestingly, Xist and Nnat transcripts showed extremely high levels of expression in PGC derived from embryo at Day 30 of pregnancy. The expression level of these transcripts was 3- to 4-fold higher in PGC derived from embryo at Day 30 of pregnancy compared with that of the others. Our results indicated that analysis of the imprinted gene expression level in short-term cultured PGC may in part reflect epigenetic modifications during germ cell development in pig. This study could help us understand how epigenetic reprogramming is maintained or lost during germ cell development. Further study will be carried out to compare imprinted gene expression patterns between the porcine PGC and EGC. This work was supported by the BioGreen 21 Program (#20070401034031, #20080401034031), Rural Development Administration, Republic of Korea (HK).