BACKGROUND: Dnmt3L, a member of the DNA methyltransferase 3 family, lacks enzymatic activity but is required for de-novo methylation of imprinted genes in oocytes and for transposon repression in male germ cells. METHODS: We used northern blots, RT-PCR, 5' rapid amplification of complementary DNA (cDNA) ends (RACE), RNase H mapping, real-time/quantitative RT-PCR and in situ hybridization to identify and characterize Dnmt3L transcripts produced during germ cell development. RESULTS: Mouse Dnmt3L uses three sex-specific promoters, not the single promoter previously thought. A promoter active in prospermatogonia drives transcription of an mRNA encoding the full-length protein in perinatal testis, where de-novo methylation occurs. Late pachytene spermatocytes activate a second promoter in intron 9 of the Dnmt3L gene. After this stage, the predominant transcripts are three truncated mRNAs, which appear to be non-coding. We could also detect similar adult testis transcripts in humans. In the mouse ovary, an oocyte-specific promoter located in an intron of the neighbouring autoimmune regulator (Aire) gene produces a transcript with the full open reading frame (ORF). This is the only Dnmt3L transcript found in growing oocytes and is absent in the oocytes of Dnmt3L-/- females. CONCLUSIONS: Sex-specific promoters control Dnmt3L expression in the mouse germ line, mirroring the situation at the Dnmt1 and Dnmt3A loci.
Shovlin, T. C., Bourc'his, D., La Salle, S., O'Doherty, A., Trasler, J. M., Bestor, T. H., & Walsh, C. (2007). Sex-specific promoters regulate Dnmt3L expression in mouse germ cells. Human Reproduction, 22(2), 457-467. https://doi.org/10.1093/humrep/de1379