School of Life Sciences, Arizona State University, Tempe, AZ, USA.
Center for Evolution and Medicine, Arizona State University, Tempe, AZ, USA.
J Hered. 2023 Aug 23;114(5):513-520. doi: 10.1093/jhered/esad016.
Genomic resources across squamate reptiles (lizards and snakes) have lagged behind other vertebrate systems and high-quality reference genomes remain scarce. Of the 23 chromosome-scale reference genomes across the order, only 12 of the ~60 squamate families are represented. Within geckos (infraorder Gekkota), a species-rich clade of lizards, chromosome-level genomes are exceptionally sparse representing only two of the seven extant families. Using the latest advances in genome sequencing and assembly methods, we generated one of the highest-quality squamate genomes to date for the leopard gecko, Eublepharis macularius (Eublepharidae). We compared this assembly to the previous, short-read only, E. macularius reference genome published in 2016 and examined potential factors within the assembly influencing contiguity of genome assemblies using PacBio HiFi data. Briefly, the read N50 of the PacBio HiFi reads generated for this study was equal to the contig N50 of the previous E. macularius reference genome at 20.4 kilobases. The HiFi reads were assembled into a total of 132 contigs, which was further scaffolded using HiC data into 75 total sequences representing all 19 chromosomes. We identified 9 of the 19 chromosomal scaffolds were assembled as a near-single contig, whereas the other 10 chromosomes were each scaffolded together from multiple contigs. We qualitatively identified that the percent repeat content within a chromosome broadly affects its assembly contiguity prior to scaffolding. This genome assembly signifies a new age for squamate genomics where high-quality reference genomes rivaling some of the best vertebrate genome assemblies can be generated for a fraction of previous cost estimates. This new E. macularius reference assembly is available on NCBI at JAOPLA010000000.
爬行动物(蜥蜴和蛇)的基因组资源落后于其他脊椎动物系统,高质量的参考基因组仍然稀缺。在 23 个染色体规模的蛇目参考基因组中,只有约 60 个蜥蜴科中的 12 个得到了代表。在壁虎(蜥蜴下目 Gekkota)中,蜥蜴的一个物种丰富的分支,染色体水平的基因组特别稀少,只代表了现存的七个科中的两个。利用基因组测序和组装方法的最新进展,我们为豹纹壁虎(Eublepharis macularius)生成了迄今为止质量最高的爬行动物基因组之一。我们将这个组装与 2016 年发表的以前的仅短读长的 E. macularius 参考基因组进行了比较,并使用 PacBio HiFi 数据检查了组装过程中影响基因组组装连续性的潜在因素。简而言之,本研究生成的 PacBio HiFi 读取的读取 N50 等于以前 E. macularius 参考基因组的 contig N50,均为 20.4 千碱基。HiFi 读取总共组装成 132 个 contig,然后使用 HiC 数据进一步支架组装成总共 75 个序列,代表所有 19 条染色体。我们发现 19 个染色体支架中有 9 个被组装成近单 contig,而其他 10 个染色体则分别由多个 contig 组装在一起。我们定性地发现,在支架之前,染色体内重复序列含量的百分比广泛影响其组装连续性。这个基因组组装标志着爬行动物基因组学的新时代,高质量的参考基因组可以以以前成本估算的一小部分为代价生成,与一些最好的脊椎动物基因组组装相媲美。这个新的 E. macularius 参考组装可在 NCBI 上获得,登录号为 JAOPLA010000000。
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