Gene expression and protein distribution of leptin and its receptor in bovine oocytes and preattachment embryos produced in vitro

Abstract

Many investigations point out the important role of leptin during the preimplantation development. Transcripts for the leptin gene (LEP) and its receptor (LEPR) have been identified in several tissues related to reproduction (e.g. ovaries, testis and oviduct) in both human and mouse. This work shows for the first time the expression and distribution patterns of LEP and LEPR in bovine oocytes and in vitro-produced embryos. Gene expression was analysed by reverse transcription PCR and real-time PCR, and the proteins were localised by immunostaining. This study included immature and mature oocytes, zygotes, two-, four-, eight-to 16-cell embryos, morulae and blastocysts and the LEP transcript was identified throughout all stages of bovine preimplantation development. However, mRNA for the LEPR gene was detected at all stages, excluding four-cell embryos. Expression of both LEP and LEPR genes was reduced at the eight-to 16-cell stage. This in addition to the absence of LEPR mRNA in four-blastomere embryos may suggest that maternally derived transcripts degenerate towards the eight-to 16-cell stage coinciding with embryonic genome activation at eight-to 16-cell stage and subsequent appearance of embryonic mRNA. Immunofluorescent staining demonstrated that LEP and LEPR proteins form a spherical rim beneath the oolemma. After maturation, however, the proteins became evenly distributed within the cytoplasm. In two-to eight-cell embryos, fluorescence was observed in the apical surface of the blastomeres, and from 10-to 16-cell stage in the apical region of outer blastomeres. This pattern persisted to the blastocyst stage, leading to LEP and LEPR distribution within trophoblast cells, but not in the inner cell mass. These results support previous findings on polar distribution of proteins within mammalian oocytes and embryos, as well as suggests leptin's potential role during early mammalian development and implantation.

Leptin in farm animals: where are we and where can we go?

“…Leptin in pregnancy ObR mRNA in immature and mature bovine oocytes and embryos suggested a role for leptin in implantation and embryo development (Madeja et al, 2009b) as well as in ovary development and steroidogenesis (Henson and Castracane, 2006). Maternal leptin drives conceptus growth and placental angiogenesis but placental leptin may also be involved.…”

Involvement of plasma adipokines in metabolic and reproductive parameters in Holstein dairy cows fed with diets with differing energy levels

“…Recently, the expression of leptin (Madeja et al, 2009), adiponectin (Lagaly et al, 2008;Maillard et al, 2010), and resistin (Maillard et al, 2011;Spicer et al, 2011) were documented in ovarian cells, including oocytes, granulosa, and theca cells. In vitro, these adipokines modulate ovarian steroidogenesis in dairy cows (Spicer et al, 2000(Spicer et al, , 2011Maillard et al, 2011).…”

Expression pattern of STAT5A gene during early bovine embryogenesis

“…In contrast, expression of the related factor STAT3 declines steadily from the oocyte to the 16-cell stage and then increases until hatched blastocyst (Leidenfrost et al ., 2011). A similar expression pattern to STAT3 has also been observed for the related LEP gene in in vitro produced bovine embryos (Madeja et al ., 2009). In the same experiment LEPR mRNA expression was detected in all but 4-cell bovine embryos (Madeja et al ., 2009).…”

“…In the study by Madeja et al . (2009), the expression of leptin and its functional receptor was shown in mouse oocytes and preimplantation embryos.…”