arising from Lü et al. Nature Genetics https://doi.org/10.1038/s41588-021-00836-9 (2020)

The eye migration that characterizes flatfish cranial development provides a unique opportunity to study the molecular mechanisms underlying anatomical asymmetry. In a paper in Nature Genetics, Lü et al.¹ (LEA) reported a comparative genomic assessment of flatfish asymmetry and claimed that the two major lineages (Pleuronectoidei and Psettodoidei) are polyphyletic, each evolving asymmetric bodies convergently from different symmetric ancestors (flatfish polyphyly (FP); Fig. 1b). Here we revisit this finding by analyzing three independent genome-scale datasets, including LEA’s, showing that support for FP results from a failure to accommodate lineage-specific variation in base composition. We also re-analyzed LEA’s genomic dataset to identify positively selected genes (PSGs) but using instead an inferred tree that groups flatfishes as monophyletic (FM), implying a single evolutionary origin of the asymmetric body plan (Fig. 1a). These results suggest a key evolutionary role of thyroid hormones (THs) and bone morphogenetic proteins (BMPs), bridging evidence from the fossil record² and single-species molecular assays³.

arising from Lü et al. Nature Genetics https://doi.org/10.1038/s41588-021-00836-9 (2020)

比目鱼颅骨发育特征的眼睛迁移为研究解剖不对称性的分子机制提供了独特的机会。在《自然遗传学》上的一篇论文中，Lü 等人。 ¹ （LEA）报告了比目鱼不对称性的比较基因组评估，并声称两个主要谱系（Pleuronectoidei和Psettodoidei）是多系的，每个谱系都从不同的对称祖先（比目鱼多系（FP）；图1b）汇聚进化出不对称体。在这里，我们通过分析三个独立的基因组规模数据集（包括 LEA）来重新审视这一发现，表明对 FP 的支持是由于未能适应碱基组成中谱系特异性的变化而导致的。我们还重新分析了 LEA 的基因组数据集，以识别正选基因 (PSG)，但使用了将比目鱼分组为单系群 (FM) 的推断树，这意味着不对称身体计划的单一进化起源（图 1a）。这些结果表明甲状腺激素 (TH) 和骨形态发生蛋白 (BMP) 的关键进化作用，连接了来自化石记录²和单物种分子测定³的证据。