APPS November 2002 Meeting Abstract 2431

Chloride channels play a critical role in cell volume regulation, acidification of intracellular compartments and in the stabilisation of membrane potential¹. It is believed that Cl^- is transported by both paracellular² and transcellular mechanisms³ in the mouse blastocyst and that the expansion of the blastocoel cavity is largely reliant on Cl^- channels and a Cl^-/HCO₃^- exchanger⁴. The cystic fibrosis transmembrane conductance regulator (CFTR) can function not only as a Cl^- channel but also as a regulator of many other processes⁵. Defects in this channel have been linked to cystic fibrosis; the most common lethal heredity disorder of the Caucasian population⁵. The mRNA expression pattern of CFTR in the early mouse embryo was determined by RT-PCR. The results show that maternal stocks of CFTR mRNA persist in the embryo until the mid 2-cell stage when they are degraded. At the early 8-cell stage, the embryo starts to synthesise CFTR mRNA which then persists till the blastocyst stage and possibly later. Blastocysts are composed of two different cell types, the inner cell mass (ICM), which is found internally in the embryo and is not in direct contact with the uterus lumen, and the trophectoderm cells (TE) which form an impermeable single layer of cells around the embryo⁶. ICMs and TE cells were separated and RT-PCR was carried out for each cell type. The results showed that CFTR mRNA is only present in TE cells. Western blots were also carried out to confirm the presence of the CFTR protein in the blastocyst. The exact role that CFTR plays in embryo development is yet to be elucidated, however the results described above show that CFTR is present in the pre-implantation embryo at both the mRNA and protein level.