Seasonal study of apoptotic markers in lizard oviduct

Lizard oviduct is a very dynamic organ that undergoes high tissue remodelling as a function of the cyclic reproductive activity. Until today there are no studies of molecular actors involved in cell death in the lizard oviduct. Therefore, this report is focused on some of apoptotic markers responsible of programmed cell death in this organ during the main significant phases of reproductive cycle. Apoptotic cell recognition was based on the estimation of known following markers: cleaved caspase-9 and-3; tissue transglutaminase (tTG) and DNA fragmentation. By Western blotting, expected band sizes of 29 and 17 kDa, recognizing the anti-caspase-9 and caspase-3, respectively, showed a stronger expression during the ovulation and postovulation. Enzymatic activity of caspase-9 shows the highest value at ovulation, whereas that of caspase-3 is recorded at postovulation. The expression and the activation of tTG protein are in line with the fragmentation of DNA. No tTG positive cells are detected at quiescence, when either no TdT-mediated dUTP-biotin nick end labeling (TUNEL)-positive nuclei or DNA fragmentation is observed. At this time tTG activity is at a minimum. Indeed, a consistent DNA smear is observed from the DNA extracted at postovulation, when tTG activity reached its maximum and several transglutaminase immunoreactivity cells and TUNEL positive nuclei are observed. The temporal and dynamic outlines of apoptotic parameters match with seasonal modifications of the oviduct. Taken together, our results demonstrate that the seasonal apoptotic activity of the oviduct represents a key process in the remodelling of this tissue during the reproductive cycle.