Nakayama I, Foresti F, Tewari R, Schartl M, Chourrout D
Institut National de la Recherche Agronomique, Laboratoire de Génétique des Poissons, Jouy en Josas, France.
Chromosoma. 1994 Mar;103(1):31-9. doi: 10.1007/BF00364723.
In order to study the divergence of teleost sex chromosomes, subtractive cloning was carried out between genomic DNA of males and females of the rainbow trout (XX/XY) and of Leporinus elongatus (ZW/ZZ). Inserts cloned in a plasmid vector were individually tested on Southern blots of DNA of males and females for sex specificity. No sex-specific insert was obtained from trout, but two out of ten inserts cloned from L. elongatus showed sex-specific patterns in this species: one corresponds to a sequence present on both Z and W chromosomes, while the other is W specific. Sequences of these two inserts show neither clear homology with other known sequences, nor an open reading frame. They cross-hybridize with the genomic DNA of Leporinus friderici, but without sex-specific patterns. Twenty-four L. elongatus adults were sexed by gonadal observation, chromosomed examination and Southern hybridization with one or the other insert. Ten males and 11 females had chromosomes and hybridization patterns typical of their sex. One ZW female was recognized as a male with the W-specific probe. This was also the case for two unusual ZW males, one having a male hybridization pattern with the other probe. These three atypical individuals may result from single genetic exchanges between four regions of the Z and the W, giving rise to three atypical W chromosomes. Finding males with such atypical heterochromosomes in a female heterogametic species may indicate that a gradual transition occurs between the heterogametic systems.
为了研究硬骨鱼性染色体的分歧，在虹鳟（XX/XY）和长身兔脂鲤（ZW/ZZ）的雄性和雌性基因组DNA之间进行了消减克隆。将克隆到质粒载体中的插入片段分别在雄性和雌性DNA的Southern印迹上进行性别特异性测试。虹鳟未获得性别特异性插入片段，但从长身兔脂鲤克隆的十个插入片段中有两个在该物种中显示出性别特异性模式：一个对应于Z和W染色体上都存在的序列，另一个是W特异性的。这两个插入片段的序列与其他已知序列既无明显同源性，也没有开放阅读框。它们与弗里德里克兔脂鲤的基因组DNA交叉杂交，但没有性别特异性模式。通过性腺观察、染色体检查以及与其中一个或另一个插入片段的Southern杂交对24只成年长身兔脂鲤进行性别鉴定。十只雄性和十一只雌性具有典型的性别染色体和杂交模式。一只ZW雌性用W特异性探针鉴定为雄性。两个不寻常的ZW雄性也是如此，其中一个与另一个探针具有雄性杂交模式。这三个非典型个体可能是由于Z和W的四个区域之间的单基因交换导致的，从而产生了三个非典型W染色体。在雌性异配物种中发现具有这种非典型异染色质的雄性可能表明在异配系统之间发生了逐渐转变。
