EXPRESSION OF THE SOLUBLE LECTIN L-14 GENE IS INDUCED BY TSH IN THYROID-CELLS AND SUPPRESSED BY RETINOIC ACID IN TRANSFORMED NEURAL CELLS

Expression of the soluble lectin L-14 is low in normal and very high i n transformed thyroid cells. We show that L-14 gene expression is tran siently induced upon thyrotropin stimulation of normal quiescent FRTL- 5 rat thyroid cells. Permanent activation of L-14 gene expression is o btained in the same cells infected with a wild-type and a temperature sensitive mutant of Kirsten murine sarcoma virus, both at the permissi ve and non permissive temperature for transformation. We also find tha t L-14 mRNA is undetectable in rat brain but is abundant in rat oligod endrocytes precursors transformed by polyoma middle T oncogene. Retino ic acid treatment of these transformed cells leads to acquisition of a differentiated phenotype accompanied by a 30-fold decrease of L-14 mR NA levels. Removal of retinoic acid restores both the transformed undi fferentiated phenotype and high L-14 expression. Taken together these results indicate that growth stimulation and induction of cell differe ntiation are accompanied by strong modulation of L-14 gene expression. (C) 1994 Academic Press, Inc.