How does epigenetics affect body size of vertebrates ?

The longitudinal bone growth at the growth place is the key factor for determining the entire body size of vertebrates. With an increase of age, the plate goes through a programmed cell aging, making the longitudinal bone growth gradually to deteriorate. Indirect scientific data shown that stem-like cells have limit to proliferate in the growth plate resting zone and is worn out slowly. The same situation found on replication of different types of animal cells. It was know as the Hayflick phenomenon. In this study, the authors found that the number of population doublings of rabbit resting zone chondrocytes in culture did not depend on the age of the animal from which the cells were harvestedd”. Also, the observation displayed that the level of DNA methylation in resting zone chondrocytes declined in vivo, along with an increase of age. The slow proliferation of resting zone chondrocytes in vivo caused methylation to disappear particularly, whereas this phenomenon was not found in the rapid proliferation of proliferative zone chondrocytes in vivo. Therefore, during growth plate senescence, the level of methylation in DNA is decreased. Consequently, they assumed that the replication of growth plate chondrocytes in vivo is limited due to DNA methylation lost, which could be a natural mechanism that restricts longitudinal bone growth in vertebrates and, importantly, this is employed to determine the overall adult size(Nilsson et al. 2005).





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