Expression of circadian clock proteins during peri-implantation period in mice

15th International Congress of Histochemistry and Cytochemistry, Antalya, Türkiye, 18 - 21 Mayıs 2017, ss.384-385

Dileyra Adıgüzel1, Merve Gürsoy2, Soner Çelik1, Pınar Şahin1, Çiler Çelik Özenci1

1Faculty of Medicine Department of Histology and Embryology, Akdeniz University, Antalya, Turkey

2Faculty of Medicine, Akdeniz University, Antalya, Turkey

OBJECTIVE: Embryo implantation is a complex process that requires the spatiotemporal hormonal orchestration and reciprocal interactions

between implantation-competent blastocyst and the receptive uterus. Internally synchronized circadian clock contains 4 genes/proteins at

molecular level: CLOCK, BMAL1, Cry (1-2) and Per (1-3). Additionally, NPAS-2 is a compansator protein for BMAL1. The cellular clock regulates

various processes including cell cycle control, DNA damage responses and hormone oscillations. The aim of this study was to investigate the

expression of circadian clock proteins in mouse uterus during early pregnancy and also in pseudopregnancy and artificial decidualization

models.

MATERIALS-METHOD: From 6 weeks old BALB/C female mice; estrous phase and pregnancy days of 1–8 uteri sections were obtained. In

addition, pseudopregnancy and artificial decidualization models were established to understand whether expressions of circadian clock

proteins are blastocyst and/or ovarian steroid hormone dependent or not (Figure1). Immunohistochemical analyses were performed for

CLOCK, BMAL1, and NPAS-2 in all groups (n=6 in each group).

RESULTS: At the time of implantation on day 5 of pregnancy, NPAS-2 expression was strong in stromal cell nuclei at implantation sites

while its expression was weak at inter-implantation sites where no embryo was present. This was true for day 6 as well (Figure 2). BMAL1

expression was nuclear in endometrial luminal epithelium and glands at implantation sites while its expression was almost absent at

inter-implantation sites. This was true for day 6 as well (Figure 3). There was an extensive but day independent expression of CLOCK protein

during peri-implantation period (Figure 4). When expressions of these proteins in pseudopregnancy and artificial decidualization models

were evaluated, we found that their expressions seem to be regulated by steroid hormones, except for CLOCK protein (Figure2-4).

CONCLUSION: Disruption of the circadian system, due to irregular lifestyle such as rotating shift work, frequent travel across time-zones,

or chronic stress, is correlated with several diseases such as infertility, cancer, and neurological disorders. Our findings indicate for the first

time that Clock proteins are differentially expressed throughout early pregnancy and they may have important roles in mouse embryo

implantation, uterus receptivity and decidualization processes.

This project was supported by TÜBİTAK (project number:215S868)

Keywords: mouse, peri-implantation, clock proteins, NPAS-2, BMAL1, CLOCK