Interspersed repetitive L1 family is differentially transcribed during the murine thymus ontogeny.

Repetitive L1 family in the first LINE (Long Interspersed Element) found in mammals. Structural and evolutionary studies demonstrated the capability of this family to play a functional role and several examples of L1 transcription have been reported in humans and mice especially in tumor cell lines.In this paper a general decrease in the L1 transcription level in different murine thymoma cell lines transformed by different means as compared to a normal counterpart represented by adult thymus is shown. When the same kind of analysis has been performed on normal thymus at different stages of differentiation (17th day embryos, new born, 30th day after birth) a modulated pattern of L1 transcription with a peak in the new born thymus was found. Furthermore, heterogeneous L1 transcription in all the above cases is demonstrated and its possible functional meaning discussed.