Convergent losses of SCPP genes and ganoid scales among non-teleost actinopterygians
Convergent losses of SCPP genes and ganoid scales among non-teleost actinopterygians
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DOI：
10.1016/j.gene.2021.146091
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发表时间：
2021-12-08
期刊：
影响因子：
3.5
通讯作者：
Kawasaki, Kazuhiko
中科院分区：
文献类型：
--
作者：
Mikami, Masato;Ineno, Toshinao;Kawasaki, Kazuhiko
在骨鱼（骨脊椎动物）的骨骼、牙齿和鳞片形成过程中，各种分泌性钙结合磷蛋白 (SCPP) 基因在皮肤和颌骨中表达。在这些矿化骨骼单元中，有类鳞片，在许多放线鱼化石中发现，但仅在现存分支中的多鳍鱼目（bichirs、芦鱼）和鳞鱼目（gars）中得到证实。在这里，我们检查了七种具有或不具有类鳞片的非硬骨鱼放线纲物种基因组中的 SCPP 基因。结果，在多鳍目和鳞鱼目中发现了 39-43 个 SCPP 基因，而在鲟形目（鲟鱼、白鲟）和弓形目（弓鳍鱼）中发现了 22-24 个 SCPP 基因。大多数这些基因在多翅目、鳞鱼目和伞形目的基因组中形成两个簇，并且这两个簇在鲟形目中重复。尽管系统发育关系较远，多翅目和鳞带目仍保留许多直系同源 SCPP 基因。这些结果表明，现存放线鱼的共同祖先拥有大量的 SCPP 基因，并且许多 SCPP 基因在鲟形目和阿米形目中独立丢失。值得注意的是，最初位于两个 SCPP 基因簇之一的大多数 SCPP 基因在多翅目和鳞鱼目中保留，但在鲟形目和Amiiformes 中继而丢失。在石带目中，这些丢失基因的直向同源物在皮肤中显示出高或可检测的表达水平，但在下巴中却没有。因此，我们假设位于该簇中的许多 SCPP 基因参与了多翅目和鳞石目中的类鳞甲鳞片的形成，并且它们的直系同源物和类鳞甲鳞片在鲟形目和阿米形目中逐渐丢失。
Various secretory calcium-binding phosphoprotein (SCPP) genes are expressed in the skin and jaw during the formation of bone, teeth, and scales in osteichthyans (bony vertebrates). Among these mineralized skeletal units is the ganoid scale, found in many fossil actinopterygians (ray-finned fish) but confirmed only in Polypteriformes (bichirs, reedfish) and Lepisosteiformes (gars) among extant clades. Here, we examined SCPP genes in the genome of seven non-teleost actinopterygian species that possess or do not possess ganoid scales. As a result, 39-43 SCPP genes were identified in Polypteriformes and Lepisosteiformes, whereas 22-24 SCPP genes were found in Acipenseriformes (sturgeons, paddlefish) and Amiiformes (bowfin). Most of these genes form two clusters in the genome of Polypteriformes, Lepisosteiformes, and Amiiformes, and these two clusters are duplicated in Acipenseriformes. Despite their distant phylogenetic relationship, Polypteriformes and Lepisosteiformes retain many orthologous SCPP genes. These results imply that common ancestors of extant actinopterygians possessed a large repertoire of SCPP genes, and that many SCPP genes were lost independently in Acipenseriformes and Amiiformes. Notably, most SCPP genes originally located in one of the two SCPP gene clusters are retained in Polypteriformes and Lepisosteiformes but were secondarily lost in Acipenseriformes and Amiiformes. In Lepisosteiformes, orthologs of these lost genes show high or detectable expression levels in the skin but not in the jaw. We thus hypothesize that many SCPP genes located in this cluster are involved in the formation of ganoid scales in Polypteriformes and Lepisosteiformes, and that their orthologs and ganoid scales were convergently lost in Acipenseriformes and Amiiformes.