Immunology and embryogenesis: the chromosomal editing hypothesis.
We have elaborated the chromosomal editing hypothesis of development. This hypothesis, based on evolutionary arguments, states that the immune system must have evolved from pre-existent cell receptor systems on other tissues. Therefore we feel that what we know about development in the immune system can serve as a provisional model for studying development in other organ systems. The model predicts that specifically programmed somatic-genetic events occur as lineages develop. These DNA cutting and splicing events, similar to those which generate antibody molecules, generate a wide diversity of specific cell receptors which allow the cell to properly orient itself in the developing organism. In addition, the chromosomal editing events occur sequentially and generate a temporal organization so that developmental events occur in an orderly fashion as lineages develop. At any point in development, epigenetic factors play a crucial role in triggering cells to undergo specific differentiative events. We believe that this hypothesis explains the apparent contradiction between rigid mosaic development and regulative development by proposing that the same general types of somatic-genetic and epigenetic events occur in both. In mosaic development, however, the organism does not have the residual and redundant stem cells which allow for the cell replacement, repair and regeneration seen in regulative development. We feel that by drawing analogies as we have from the development of the immune system one may gain insights into the genetic and epigenetic factors which govern the development of other tissues and formulate specific experiments to test the resulting hypothesis.
D005075:Biological Evolution; D002454:Cell Differentiation; D002875:Chromosomes / Q000502:physiology*; D005786:Gene Expression Regulation; D006412:Hematopoietic Stem Cells / Q000502:physiology; D007136:Immunoglobulins / Q000235:genetics*; D009030:Mosaicism; D011971:Receptors, Immunologic / Q000235:genetics
D007136:Immunoglobulins; D011971:Receptors, Immunologic