part of tube development proximal convoluted tubule development proximal convoluted tubule segment 1 development GO:0072031 mah 2010-01-25T02:55:57Z S1 development biological_process The process whose specific outcome is the progression of the S1 portion of the proximal convoluted tubule over time, from its formation to the mature structure. The S1 portion is the initial portion of the proximal convoluted tubule and is responsible for avid reabsorption of water and solutes.