79 - Comparative Genome Methylation of Continual Nephrogenesis in the Reptile Kidney

Poster Board Number: 79
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Abstract Body : In mammals, nephrogenesis is a process strictly confined to embryonic development, during which a finite number of nephrons are formed. Progenitor cells, termed cap mesenchyme, become depleted prior to or just after birth in mammals. As a result, nephrogenesis ceases and generation of new nephrons for homeostasis or repair can no longer occur. Reptiles (non-avian reptiles) possess the same definitive kidney as mammals called the metanephric kidney. However, unlike in mammals, the progenitor cap mesenchyme cells in reptiles are maintained in adulthood where they contribute to continual nephrogenesis. We have detected the process of continual adult nephrogenesis throughout reptiles including crocodiles, turtles, lizards, and snakes. To investigate the mechanisms of why kidney progenitor cells are maintained in reptiles we used the red-eared slider turtle, Trachemys scripta, as a model system. To further examine continual nephrogenesis, embryonic and adult T. scripta kidney tissue was used for comparative gene studies. Gene expression detection using either PCR or in situ hybridization found conserved expression of key kidney development regulators in the embryonic and adult reptile kidney such as Six2, Eya1, and Wt1. Conserved expression between progenitor cell life stages suggests that 1) the adult progenitor cells are a continuation of the embryonic program and 2) differential gene regulation may be responsible for progenitor cell maintenance in reptiles. To begin to investigate the hypothesis of differential gene regulation, we next looked into the potential differences in epigenetic regulation between mammal and reptile adult kidneys. Mouse and red-eared slider adult kidneys were used to extract genomic DNA for whole genome bisulfite sequencing. Cortical tissue was dissected from mouse kidneys while for turtles, observable zones of nephrogenesis on the kidney surface were dissected and utilized for DNA extraction. Comparative analysis of genome methylation provided new insights into the maintenance of kidney progenitor cells in reptiles. Future work will continue to focus on possible mechanisms of differential gene regulation needed to maintain adult kidney progenitor cells.