Terencio Maria Leandra, Schneider Carlos Henrique, Gross Maria Claudia, Nogaroto Viviane, de Almeida Mara Cristina, Artoni Roberto Ferreira, Vicari Marcelo Ricardo, Feldberg Eliana
Laboratório de Genética Animal, Instituto Nacional de Pesquisas da Amazônia, Av. André Araújo, 2936, Petrópolis, Manaus, AM, 69011-970, Brazil.
Genetica. 2012 Dec;140(10-12):505-12. doi: 10.1007/s10709-013-9699-4. Epub 2013 Jan 17.
The possible origins and differentiation of a ZZ/ZW sex chromosome system in Semaprochilodus taeniurus, the only species of the family Prochilodontidae known to possess heteromorphic sex chromosomes, were examined by conventional (C-banding) and molecular (cross-species hybridization of W-specific WCP, Fluorescence in situ hybridization (FISH) with telomere (TTAGGG)n, and Rex1 probes) cytogenetic protocols. Several segments obtained by W-specific probe were cloned, and the sequences localized on the W chromosome were identified by DNA sequencing and search of nucleotide collections of the NCBI and GIRI using BLAST and CENSOR, respectively. Blocks of constitutive heterochromatin in chromosomes of S. taeniurus were observed in the centromere of all autosomal chromosomes and in the terminal, interstitial, and pericentromeric regions of the W chromosome, which did not demonstrate interstitial telomeric sites with FISH of the telomere probe. The Rex1 probe displayed a compartmentalized distribution pattern in some chromosomes and showed signs of invasion of the pericentromeric region in the W chromosome. Chromosomal painting with the W-specific WCP of S. taeniurus onto its own chromosomes showed complete staining of the W chromosome, centromeric sites, and the ends of the Z chromosome, as well as other autosomes. However, cross-species painting using this WCP on chromosomes of S. insignis, Prochilodus lineatus, and P. nigricans did not reveal a proto-W element, but instead demonstrated scattered positive signals of repetitive DNAs. Identification of the W-specific repetitive sequences showed high similarity to microsatellites and transposable elements. Classes of repetitive DNA identified in the W chromosome suggested that the genetic degeneration of this chromosome in S. taeniurus occurred through accumulation of these repetitive DNAs.
对半带半线脂鲤（Semaprochilodus taeniurus）中ZZ/ZW性染色体系统的可能起源和分化进行了研究，半带半线脂鲤是脂鲤科中唯一已知具有异形性染色体的物种，采用了传统的（C带）和分子（W特异性WCP的跨物种杂交、用端粒（TTAGGG）n和Rex1探针进行荧光原位杂交（FISH））细胞遗传学方法。克隆了通过W特异性探针获得的几个片段，并分别使用BLAST和CENSOR通过DNA测序以及搜索NCBI和GIRI的核苷酸文库来鉴定定位在W染色体上的序列。在半带半线脂鲤染色体中，组成型异染色质块出现在所有常染色体的着丝粒以及W染色体的末端、间质和着丝粒周围区域，用端粒探针进行FISH时未显示间质端粒位点。Rex1探针在一些染色体中呈现出分区分布模式，并显示出在W染色体着丝粒周围区域有侵入迹象。用半带半线脂鲤的W特异性WCP对其自身染色体进行染色体涂染，显示W染色体、着丝粒位点以及Z染色体末端和其他常染色体完全染色。然而，使用该WCP对半带半线脂鲤、条纹半线脂鲤（Prochilodus lineatus）和黑半线脂鲤（P. nigricans）的染色体进行跨物种涂染时，未发现原始W元件，而是显示出重复DNA的分散阳性信号。W特异性重复序列的鉴定显示与微卫星和转座元件高度相似。在W染色体中鉴定出的重复DNA类别表明，半带半线脂鲤中该染色体的遗传退化是通过这些重复DNA的积累发生的。
