Nanos genes encode essential RNA-binding proteins involved in germline determination and germline stem cell maintenance. When examining diverse classes of echinoderms, typically three, sometimes four, nanos genes are present. In this analysis, we identify and annotate nine nanos orthologs in the green sea urchin, Lytechinus variegatus (Lv). All nine genes are transcribed and grouped into three distinct classes. Class one includes the germline Nanos, with one member: Nanos2. Class two includes Nanos3-like genes, with significant sequence similarity to Nanos3 in the purple sea urchin, Strongylocentrotus purpuratus (Sp), but with wildly variable expression patterns. The third class includes several previously undescribed nanos zinc-finger genes that may be the result of duplications of Nanos2. All nine nanos transcripts occupy unique genomic loci and are expressed with unique temporal profiles during development. Importantly, here we describe and characterize the unique genomic location, conservation, and phylogeny of the Lv ortholog of the well-studied Sp Nanos2. However, in addition to the conserved germline functioning Nanos2, the green sea urchin appears to be an outlier in the echinoderm phyla with eight additional nanos genes. We hypothesize that this expansion of nanos gene members may be the result of a previously uncharacterized L1-class transposon encoded on the opposite strand of a nanos2 pseudogene present on chromosome 12 in this species. The expansion of nanos genes described here represents intriguing insights into germline specification and nanos evolution in this species of sea urchin.

中文翻译：

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绿海胆 Lytechinus variegatus 中大量扩展的纳米库的功能注释

Nanos 基因编码参与种系测定和种系干细胞维持的必需 RNA 结合蛋白。在检查不同类别的棘皮动物时，通常存在三个（有时是四个）纳米基因。在此分析中，我们识别并注释了绿海胆Lytechinus variegatus (Lv) 中的九个纳米直系同源物。所有九个基因都被转录并分为三个不同的类别。第一类包括种系 Nanos，其中一个成员是：Nanos2。第二类包括 Nanos3 样基因，与紫色海胆Strongylocentrotus purpuratus中的 Nanos3 具有显着序列相似性(Sp)，但表达模式变化很大。第三类包括几个以前未描述的 nanos 锌指基因，它们可能是 Nanos2 重复的结果。所有 9 个 nanos 转录本都占据独特的基因组位点，并在发育过程中以独特的时间特征表达。重要的是，我们在这里描述和描述了经过充分研究的 Sp Nanos2 的 Lv 直向同源基因的独特基因组位置、保护和系统发育。然而，除了保守的种系功能 Nanos2 之外，绿海胆似乎是棘皮动物门中的异常值，具有八个额外的 nanos 基因。我们假设 nanos 基因成员的这种扩展可能是先​​前未表征的 L1 类转座子的结果，该转座子编码在该物种 12 号染色体上存在的 nanos2 假基因的相反链上。