Mammalian meiotic telomeres: composition and ultrastructure in telomerase-deficient mice

During early meiotic prophase chromosome ends become attached to the nuclear envelope, a process that is essential for faithful homologue pairing and segregation. The factors involved in this attachment are largely unknown. Here we investigated the possible involvement of telomere chromatin by using late generation (G5 and G6) Terc(-/-) mice. These mice lack telomerase activity and show progressive telomere shortening with increasing mouse generations. We show here that in meiotic chromosome ends of late generation Terc(-/-) mice telomeric TTAGGG repeats and the TRF1 telomere-binding protein are significantly reduced or below detection level. In spite of this, electron microscopy showed no apparent structural differences at the attachment sites of meiotic chromosomes to the nuclear envelope between wild-type and G6 Terc(-/-) meiocytes. These results suggest, as already shown in yeast, that most telomere chromatin is dispensable for proper attachment of mammalian meiotic chromosome ends to the nuclear envelope.