Erythrocyte Heterokaryons — A Model System for the Analysis of Cell Determination and Gene Regulation

Abstract

Embryological studies using cell and nuclear transplantation techniques have shown that during early development, cells undergo a stepwise restriction in their potential to undergo all forms of cell differentiation. This process has been termed determination. Genetic evidence suggests that the determined state is heritable and may occur several cell generations before it results in altered gene expression and altered cellular phenotypes, i.e. in differentiation. The formation of terminally differentiated cells such as erythrocytes and nerve cells, most likely consists of a well-ordered series of determination events followed by sequential phenotypic changes. While it is now well established that differentiation is associated with altered patterns of transcription and mRNA translation, very little is known about the molecular basis of determination. Among the mechanisms which have been considered are rearrangements of nucleotide sequences (recombination, amplification, deletion etc.), DNA methylation and altered DNA-protein interactions.