Expression of growth-associated genes in various tissues of the fetal and adult rat.

4F1, 2A9 and 2F1 represent three of a number of cDNA sequences which have been identified because their cognate RNAs markedly increase when quiescent cells in culture are stimulated with serum. Studies using a variety of cell culture systems have shown that the expression of these genes is modulated by various growth factors and mitogens and thus such genes are considered to be 'growth-associated.' Thus far, little information has been obtained with these in vitro systems about the function of these genes. In an attempt to begin to elucidate the role of these genes (if any) in the physiology of the normal cell, we have analyzed the levels of 4F1, 2A9 and 2F1 transcripts in a variety of differentiated organs and tissues of adult and fetal rats. Our results show that each of these growth-associated genes exhibits its own unique pattern of expression, unrelated to the proliferative activity of the tissue. These data suggest that these genes most likely do have specific functions in normal tissue in addition to their role in the induction of DNA synthesis in quiescent cells in culture.