It seems that the process of enucleation is a variant of cell division. As you know erythrocytes divide several times as they mature from haemopoietic stem cells, and in each successive division both daughter cells get a full chromosome complement. However the final cell division before maturation is asymmetrical, and only one of the daughter cells gets both chromosome complements (and destined to be consumed by macrophages). The other daughter cell, with no genetic material, goes on to become the mature erythrocyte.
I found
this article describing the genes involved in the process, specifically the proteins Rac1 and Rac2, and the effector gene mDia2. These are all involved in co-ordinating the actin cytoskeleton which normally controls chromosome migration to opposite poles of the cell. The cited Nature Cell Biology article can be found
here
Couldn't find anything on mitochondria, or any other organelles, but since their distribution within the cell is dictated by their adhesion to the actin cytoskeleton also, it is likely that a similar process is involved.
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