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Expression of APXL in human placenta
DEL MÓNACO, S.; DAMIANO, A.; ZOTTA, E.; IBARRA, C.; KOTSIAS, B.
Embu das Artes, São Paulo, Brasil
Simposio; I Simposio Latino Americano sobre Interacción Materno-Fetal Placenta: Pesquisa y Clínica.; 2003
International Federation of Placenta Associations
The syncytiotrophoblast is the outermost covering of the fetal placental villi and acts as a physiological barrier between maternal and fetal blood. It controls transcellular movement of water and solutes helping to maintain normal fetal growth and homeostasis. In our studies we have found that there are high amounts of a protein called APXL, (Apical Protein of Xenopus Like) in human placental syncytiotrophoblast. This protein was also detected in other human tissues (lung, pancreas and retina) although its physiological function is still unknown. The name APXL comes from the homology with another protein, APX (Apical Protein of Xenopus), associated to an apical Na+ channel purified from A6 Xenopus laevis kidney cells. In order to study the function of APXL and its relation to Na+ placental transport we firstly confirmed its presence in human syncytiotrophoblast by RT-PCR, western blot and immunohistochemical analysis. The RT-PCR amplified fragment was cloned and sequenced, resulting in 100% homology with the sequence from retina reported by Schiaffino et al., (1995). We are currently screening a cDNA library from placenta to obtain the full APXL gene. As our project includes the expression of this protein in Bufo arenarum oocytes to perform voltage clamp and kinetic analysis, we proved the absence of APX and APXL in these oocytes by immunohistochemical analysis and the absence of amiloride sensitive currents by voltage clamp. These results confirm that our model is appropriate to complete the study.