Pfeifer Charlotte, Scherthan Harry, Thomsen Preben D
Royal Veterinary and Agricultural University, Department of Anatomy and Physiology, Grønnegårdsvej 7, DK-1870, Frederiksberg C, Denmark.
Dev Biol. 2003 Mar 15;255(2):206-15. doi: 10.1016/s0012-1606(02)00093-3.
The process of homolog pairing is well characterised in meiosis of male mammals, but much less information is available from female meiosis. We have therefore studied telomere dynamics by FISH and synapsis formation by immunostaining of synaptonemal complex proteins (SCP3, SCP1) on ovarian sections from 15 bovine fetuses, which covered the entire female prophase I. Telomeres displayed a dispersed intranuclear distribution in oogonia and relocated to the nuclear periphery during the preleptotene stage. Tight telomere clustering (bouquet formation) coincided with synapsis initiation at the leptotene/zygotene transition. Clustering of telomeres persisted during zygotene and even into the pachytene stage in a subset of nuclei, while it was absent in diplotene/dictyotene stage nuclei. Thus, the bouquet stage in the bovine female lasts significantly longer than in the male. Further, we observed that synapsis in the female initiated both terminally and interstitially in earliest zygotene stage oocytes, which contrasts with the predominantly terminal synapsis initiation in early zygotene spermatocytes of the bovine male. Altogether, our data disclose a sex-specific difference in telomere dynamics and synapsis initiation patterns in male and female bovine germ cells that may be related to the sex-specific differences in recombination rates observed in this and other mammalian species.
同源配对过程在雄性哺乳动物减数分裂中已得到充分表征，但关于雌性减数分裂的信息则少得多。因此，我们通过荧光原位杂交（FISH）研究了端粒动态，并通过对15头牛胎儿卵巢切片上的联会复合体蛋白（SCP3、SCP1）进行免疫染色来研究联会形成，这些胎儿涵盖了整个雌性减数分裂前期I。端粒在卵原细胞中呈分散的核内分布，并在细线前期阶段重新定位到核周边。紧密的端粒聚集（花束形成）与细线期/偶线期转变时的联会起始同时发生。端粒聚集在偶线期持续存在，甚至在一部分细胞核中持续到粗线期，而在双线期/核网期细胞核中则不存在。因此，牛雌性的花束期比雄性持续的时间长得多。此外，我们观察到雌性的联会在最早的偶线期卵母细胞中既在末端也在中间起始，这与牛雄性早期偶线期精母细胞中主要在末端起始的联会形成对比。总之，我们的数据揭示了雄性和雌性牛生殖细胞中端粒动态和联会起始模式的性别特异性差异，这可能与在该物种和其他哺乳动物物种中观察到的重组率的性别特异性差异有关。
