Transcript isoforms of promyelocytic leukemia in mouse male and female gametes.

Promyelocytic leukemia (PML) nuclear bodies and proteins have been implicated in many functions of the nucleus. It is not known whether the PML gene is transcribed and expressed as PML nuclear bodies in gamete cells or in the early mammalian embryo. In this study using reverse transcription-polymerase chain reaction and immunocytochemistry we show the presence of PML transcripts and identify their variants in the mature mouse gametes. Mature sperm contains isoform II; however, oocyte contains transcript isoforms I, II, and possibly other unknown isoforms of PML. This indicates that the mature gametes may carry the transcripts to the newly created embryo. We also show that sperm and oocyte cells do not contain PML nuclear bodies. We find that the first appearance of PML nuclear bodies is in the 2-cell-stage mouse embryo. Appearance of PML nuclear bodies in the 2-cell-stage embryo may correspond to the major transcriptional activity of the embryonic genome. In summary, this report emphasizes the necessity to perform further experiments to investigate the presence and function of PML transcripts and nuclear bodies in earlier stages of germ cell and also later stages of the preimplantation development.