Analysis of chromatin structure and gene function of chicken sex chromosomes

鸡的性染色体组成为雌性为ZW，雄性为ZZ。约2/3的W染色体和Z染色体的末端区域是异染色质的。两个W染色体特异的重复DNA序列，XhoI家族和EcoRI家族，是W异染色质的主要组成部分，但Z末端异染色质的性质尚不清楚。1）从雌性鸡基因组文库中获得了一个约13 kb的基因组克隆pCHZTH 8。荧光原位杂交（FISH）、Southern印迹杂交和核苷酸序列分析表明，该克隆序列是位于鸡Z-末端异染色质的大卫星DNA的一部分，且大部分为鸡属特有序列。2)虽然大约有20种表型被定位在Z染色体上，但分子水平的信息还没有得到。我们证明了cDNA克隆和FISH的ZOV 3（属于免疫球蛋白超家族的基因）和IREBP（铁反应元件结合蛋白的鸡同源物）位于Z染色体的不同臂。3)除上述两个重复家族外，W染色体特异性DNA序列尚不清楚。采用激光显微切割和随机PCR技术构建了W染色体特异性基因组文库。获得了两个含有W特异性非重复序列的克隆（CW 01和CW 50）。用CW 01和CW 50筛选雌性鸡基因组文库，获得了分别包含CW 01和CW 50序列的两个约25-kb的基因组区域的基因组克隆。

Constitution of chicken sex chromosomes is ZW for female and ZZ for male. About 2/3 of the W chromosome and a terminal region of the Z chromosome are heterochromatic. Two W-chromosome-specific repetitive DNA sequences, XhoI family and EcoRI family, are major constituents of the W heterochromatin, but nature of the Z-terminal heterochromatin is unknown. In this study, 1) a genomic clone pCHZTH8 containing about 13kb genomic fragment was obtained from the female chicken genomic library. Fluorescence in situ hybridization (FISH), Southern blot hybridization and nucleotide sequencing revealed that this cloned sequence was a part of the macrosatellite DNA localized in the Z-terminal heterochromatin and that most part of this sequence was specific to the genus Gallus. 2) Although about 20 phenotypes are mapped to the Z chromosome, molecular-level information has not been available. We demonstrated by cDNA cloning and FISH that ZOV3 (a gene belonging to the immunoglobulin superfamily) and IREBP (chicken homolog of iron responsive element binding protein) were localized on different arms of the Z chromosome. 3) Except for the above two repetitive families, W chromosome-specific DNA sequences are unknown. We constructed a W chromosome-specific genomic library by applying laser microdissection and random PCR amplification. Two clones containing W-specific non-repetitive sequences (CW01 and CW50) were obtained. A female chicken genomic library was screened with CW01 and CW50, and genomic clones convering two genomic regions of about 25-kb each, containing the CW01 and CW50 sequences, respectively, were obtained.