Determination of Lymphatic Vascular Identity and Developmental Timecourse in Zebrafish

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Zebrafish lymphatics have been shownto share a number of characteristics with theirhuman counterparts, making the fish a potentiallyuseful model for studying lymphaticdevelopment and disease. The utility of thezebrafish lymphatic model would be substantiallyenhanced by an improved understandingof the spatiotemporal development of theprimary lymphatic vasculature. The goal ofthis project is to identify and map the majorzebrafish lymphatic structures throughoutembryonic to early juvenile stages ofdevelopment. Two transgenic lines, kdrl:RASmCherryxfli1:GFP and stabilin1:YFP,were recently derived to assist in the study ofdeveloping lymphatic vasculature, but theirspecificity has not been rigorously tested.In the course of the present study, weexperimentally validate the utility of these twomarker lines as potential tools for establishinglymphatic vascular identity and visualizingdevelopmental lymphangiogenesis. Weintroduced twenty nanometer red florescentmicrospheres into the blood vasculature offli1:GFP zebrafish and collected tiled opticalz-sections at time intervals spanning earlydevelopment. Three-dimensional reconstructionsof the vasculature were used todifferentiate between blood and lymphaticvessels. Age-matched injected embryos werecompared to the two transgenic lines tofurther assess their specificity. We created aspatiotemporal map of the major lymphaticvessels in the developing zebrafish including apreviously unidentified lymphatic vessel in thegastrointestinal tract. We conclude that thekdr-l:RASmCherryxfli1:GFP line accuratelyidentifies developing lymphatic vessels withthe exception of those associated with thegastrointestinal tract. The stabilin1:YFP line,however, is less reliable, as it marks bothvenous vessels and lymphatic vessels.