Species: mouse
Mutation name: None
type: null mutation
fertility: infertile - ovarian defect
Comment: SUN1 Is Required for Telomere Attachment to Nuclear Envelope and Gametogenesis in Mice. Ding X et al. Prior to the pairing and recombination between homologous chromosomes during meiosis, telomeres attach to the nuclear envelope and form a transient cluster. However, the protein factors mediating meiotic telomere attachment to the nuclear envelope and the requirement of this attachment for homolog pairing and synapsis have not been determined in animals. Here we show that the inner nuclear membrane protein SUN1 specifically associates with telomeres between the leptotene and diplotene stages during meiotic prophase I. Disruption of Sun1 in mice prevents telomere attachment to the nuclear envelope, efficient homolog pairing, and synapsis formation in meiosis. Massive apoptotic events are induced in the mutant gonads, leading to the abolishment of both spermatogenesis and oogenesis. This study provides genetic evidence that SUN1-telomere interaction is essential for telomere dynamic movement and is required for efficient homologous chromosome pairing/synapsis during mammalian gametogenesis.

Species: mouse
Mutation name: None
type: null mutation
fertility: infertile - ovarian defect
Comment: Analysis of meiosis in SUN1 deficient mice reveals a distinct role of SUN2 in mammalian meiotic LINC complex formation and function. Link J 2014 et al. LINC complexes are evolutionarily conserved nuclear envelope bridges, composed of SUN (Sad-1/UNC-84) and KASH (Klarsicht/ANC-1/Syne/homology) domain proteins. They are crucial for nuclear positioning and nuclear shape determination, and also mediate nuclear envelope (NE) attachment of meiotic telomeres, essential for driving homolog synapsis and recombination. In mice, SUN1 and SUN2 are the only SUN domain proteins expressed during meiosis, sharing their localization with meiosis-specific KASH5. Recent studies have shown that loss of SUN1 severely interferes with meiotic processes. Absence of SUN1 provokes defective telomere attachment and causes infertility. Here, we report that meiotic telomere attachment is not entirely lost in mice deficient for SUN1, but numerous telomeres are still attached to the NE through SUN2/KASH5-LINC complexes. In Sun1(-/-) meiocytes attached telomeres retained the capacity to form bouquet-like clusters. Furthermore, we could detect significant numbers of late meiotic recombination events in Sun1(-/-) mice. Together, this indicates that even in the absence of SUN1 telomere attachment and their movement within the nuclear envelope per se can be functional. /////////////////////////