Peichel Catherine L, Ross Joseph A, Matson Clinton K, Dickson Mark, Grimwood Jane, Schmutz Jeremy, Myers Richard M, Mori Seiichi, Schluter Dolph, Kingsley David M
Department of Developmental Biology and Howard Hughes Medical Institute, Stanford University School of Medicine, Palo Alto, CA 94305, USA.
Curr Biol. 2004 Aug 24;14(16):1416-24. doi: 10.1016/j.cub.2004.08.030.
Many different environmental and genetic sex-determination mechanisms are found in nature. Closely related species can use different master sex-determination switches, suggesting that these developmental pathways can evolve very rapidly. Previous cytological studies suggest that recently diverged species of stickleback fish have different sex chromosome complements. Here, we investigate the genetic and chromosomal mechanisms that underlie sex determination in the threespine stickleback (Gasterosteus aculeatus).
Genome-wide linkage mapping identifies a single chromosome region at the distal end of linkage group (LG) 19, which controls male or female sexual development in threespine sticklebacks. Although sex chromosomes are not cytogenetically visible in this species, several lines of evidence suggest that LG 19 is an evolving sex chromosome system, similar to the XX female/XY male system in many other species: (1) males are consistently heterozygous for unique alleles in this region; (2) recombination between loci linked to the sex-determination region is reduced in male meiosis relative to female meiosis; (3) sequence analysis of X- and Y-specific bacterial artificial chromosome (BAC) clones from the sex-determination region reveals many sequence differences between the X- and Y-specific clones; and (4) the Y chromosome has accumulated transposable elements and local duplications.
Taken together, our data suggest that threespine sticklebacks have a simple chromosomal mechanism for sex determination based on a nascent Y chromosome that is less than 10 million years old. Further analysis of the stickleback system will provide an exciting window into the evolution of sex-determination pathways and sex chromosomes in vertebrates.
自然界中存在许多不同的环境和遗传性别决定机制。亲缘关系相近的物种可能使用不同的主要性别决定开关，这表明这些发育途径能够非常迅速地进化。先前的细胞学研究表明，棘鱼科鱼类的近期分化物种具有不同的性染色体组成。在此，我们研究三刺鱼（Gasterosteus aculeatus）性别决定的遗传和染色体机制。
全基因组连锁图谱鉴定出位于连锁群（LG）19远端的单个染色体区域，该区域控制三刺鱼的雄性或雌性性发育。尽管在该物种中细胞遗传学上看不到性染色体，但几条证据表明LG 19是一个正在进化的性染色体系统，类似于许多其他物种中的XX雌性/XY雄性系统：（1）雄性在该区域的独特等位基因上始终是杂合的；（2）与性别决定区域连锁的基因座之间的重组在雄性减数分裂中相对于雌性减数分裂减少；（3）对来自性别决定区域的X和Y特异性细菌人工染色体（BAC）克隆的序列分析揭示了X和Y特异性克隆之间的许多序列差异；（4）Y染色体积累了转座元件和局部重复序列。
综上所述，我们的数据表明三刺鱼具有基于一条年龄小于1000万年的新生Y染色体的简单染色体性别决定机制。对三刺鱼系统的进一步分析将为脊椎动物性别决定途径和性染色体的进化提供一个令人兴奋的窗口。
