Webster Timothy H, Vannan Annika, Pinto Brendan J, Denbrock Grant, Morales Matheo, Dolby Greer A, Fiddes Ian T, DeNardo Dale F, Wilson Melissa A
Department of Anthropology, University of Utah, Salt Lake City, UT.
School of Life Sciences, Arizona State University, Tempe, AZ.
bioRxiv. 2023 Apr 28:2023.04.26.538436. doi: 10.1101/2023.04.26.538436.
Reptiles exhibit a variety of modes of sex determination, including both temperature-dependent and genetic mechanisms. Among those species with genetic sex determination, sex chromosomes of varying heterogamety (XX/XY and ZZ/ZW) have been observed with different degrees of differentiation. Karyotype studies have demonstrated that Gila monsters () have ZZ/ZW sex determination and this system is likely homologous to the ZZ/ZW system in the Komodo dragon (), but little else is known about their sex chromosomes. Here, we report the assembly and analysis of the Gila monster genome. We generated a draft genome assembly for a male using 10X Genomics technology. We further generated and analyzed short-read whole genome sequencing and whole transcriptome sequencing data for three males and three females. By comparing female and male genomic data, we identified four putative Z-chromosome scaffolds. These putative Z-chromosome scaffolds are homologous to Z-linked scaffolds identified in the Komodo dragon. Further, by analyzing RNAseq data, we observed evidence of incomplete dosage compensation between the Gila monster Z chromosome and autosomes and a lack of balance in Z-linked expression between the sexes. In particular, we observe lower expression of the Z in females (ZW) than males (ZZ) on a global basis, though we find evidence suggesting local gene-by-gene compensation. This pattern has been observed in most other ZZ/ZW systems studied to date and may represent a general pattern for female heterogamety in vertebrates.
爬行动物表现出多种性别决定模式，包括温度依赖型和遗传机制。在那些具有遗传性别决定的物种中，已观察到具有不同异配性的性染色体（XX/XY和ZZ/ZW），且分化程度不同。核型研究表明，吉拉毒蜥具有ZZ/ZW性别决定，该系统可能与科莫多龙的ZZ/ZW系统同源，但对其性染色体了解甚少。在此，我们报告了吉拉毒蜥基因组的组装和分析。我们使用10X基因组技术为一只雄性吉拉毒蜥生成了一个草图基因组组装。我们进一步生成并分析了三只雄性和三只雌性的短读长全基因组测序和全转录组测序数据。通过比较雌性和雄性基因组数据，我们鉴定出四个假定的Z染色体支架。这些假定的Z染色体支架与在科莫多龙中鉴定出的Z连锁支架同源。此外，通过分析RNAseq数据，我们观察到吉拉毒蜥Z染色体与常染色体之间存在不完全剂量补偿的证据，以及两性之间Z连锁表达缺乏平衡。特别是，我们观察到雌性（ZW）的Z染色体在整体上比雄性（ZZ）表达更低，尽管我们发现有证据表明存在局部基因对基因的补偿。这种模式在迄今为止研究的大多数其他ZZ/ZW系统中都有观察到，可能代表了脊椎动物雌性异配性的一种普遍模式。
