CDKN2A and Rectal prolapse: However, p16INK4a deficiency showed no effect on c-Abl deficiency-caused megaesophagus and only a minor effect on rectal prolapse, suggesting that these two aging-related disorders may not involve aging-promoting gene p16Ink4a. This is in contrast to the pro-aging roles for p16INK4a in bone formation, pancreases, and other organs21, 44–46.