Friday, September 25, 2015

MicroRNAs act as transcriptomic modifiers of the preimplantation embryo even if the embryo is donated.

Endometrial fluid is a viscous fluid secreted by endometrial glands into the uterine cavity and its function is the nutrition of the embryo and gives an environment in which the first communication between the maternal endometrium and the embryo occurs during the window of implantation. This endometrial fluid contains different molecules such as proteins, glycodelin, lipids and cytokines, which are employed by the embryo for its development, but they can also create an impact in its physiology. A clear example are microRNAs from endometrial fluid (small, 19-22 nucleotide sequences of non-coding RNA), which can regulate the gene expression of endogenous genome (embryo). 
This study says that the mother can change the genetic information even when the egg has been donated. The finding shows an exchange between endometrial fluid and embryo, it had been though because of the physical similarity between mother and children of ovodonation, as well as disease incidence in children related with maternal pathologies during gestation, such as obesity and smoking (fig. 1).

Figure 1. Analysis of microRNAs content in endometrial fluid and evaluation of its biological function.
Transmission of molecules occurs during the window of implantation, it is because after fecundation, the embryo takes 5 days to move from fallopian tubes to the uterine cavity, and then are necessary around 24-36 hours to the implantation. In this period the embryo takes the genetic information of endometrial fluid and it can modify its development. These microRNAs prepare the embryo for implantation with specific protein expression (fig. 2). That communication can inhibit specific functions or on the other hand can express new functions.
With this information, researchers can employ the knowledge in future to avoid diseases such as obesity.
Figure 2. Endometrial fluid from the maternal endometrium modify the embryo transcriptome.
Vilella, F., Moreno-Moya, J. M., Balaguer, N., Grasso, A., Herrero, M., Martínez, S., ... & Simón, C. (2015). Hsa-miR-30d, secreted by the human endometrium, is taken up by the pre-implantation embryo and might modify its transcriptome. Development, 142(18), 3210-3221.