Sage J, Yuan L, Martin L, Mattei M G, Guénet J L, Liu J G, Hoög C, Rassoulzadegan M, Cuzin F
Unité 470, Institut National de la Santé et de la Recherche Médicale, Université de Nice, France.
Genomics. 1997 Aug 15;44(1):118-26. doi: 10.1006/geno.1997.4832.
The murine Sycp1 gene is expressed at the early stages of meiosis. We show that it is composed of a number of small exons and localized on mouse chromosome 3. In the laboratory strains, two retrogenes were also identified. The first one (Sycp1-ps1), on chromosome 7, has accumulated point mutations and deletions and is not transcribed. A second retrogene (Sycp1-ps2), on chromosome 8, is inserted within the continuity of a moderately repeated element, in an intron of another gene (Cad11). The two retroposition events can be dated to distinct periods in the evolution of the Muridae. Sycp1-ps2 has kept features indicative of a relatively recent origin, namely a nearly intact coding region, a poly(A) tail, and 14-bp terminal repeats. Its recent origin was confirmed by the fact that it is found in all the laboratory strains of mice, but neither in a recent isolate from Mus musculus domesticus wild stocks nor in the closely related subspecies M. musculus musculus, M. m. molossinus, M. m. castaneus, and M. m. bactrianus. Appearance of the more ancient Sycp1-ps1 retrogene is concomitant with the radiation of the genus. It is present in various Mus species (M. spretus, M. spicilegus, M. macedonicus, and M. cookii), but neither in the rat nor in the more closely related Pyromis genus. Transposition of retrotranscripts during meiosis and their hereditary establishment thus appear to occur relatively frequently. They may, therefore, play a significant role in the evolutionary process.
小鼠的Sycp1基因在减数分裂早期表达。我们发现它由多个小外显子组成，定位于小鼠3号染色体上。在实验室菌株中，还鉴定出两个反转录基因。第一个（Sycp1-ps1）位于7号染色体上，已积累了点突变和缺失，且不转录。第二个反转录基因（Sycp1-ps2）位于8号染色体上，插入到一个中度重复元件的连续区域内，位于另一个基因（Cad11）的一个内含子中。这两个反转录事件可以追溯到鼠科进化的不同时期。Sycp1-ps2保留了表明其起源相对较近的特征，即几乎完整的编码区、聚腺苷酸尾巴和14个碱基对的末端重复序列。它起源较近这一点得到了以下事实的证实：它存在于所有实验室小鼠菌株中，但在小家鼠野生种群的近期分离株中未发现，在近缘亚种小家鼠、日本小家鼠、印度小家鼠和阿富汗小家鼠中也未发现。更古老的Sycp1-ps1反转录基因的出现与该属的辐射同时发生。它存在于各种小鼠物种（西班牙小鼠、巢鼠、马其顿小鼠和库克氏小鼠）中，但大鼠和关系更密切的Pyromis属中均未发现。因此，减数分裂期间反转录转录本的转座及其遗传确立似乎相对频繁地发生。它们可能因此在进化过程中发挥重要作用。
