哈佛大学新研究揭示海绵基因组传达遗传复杂性的出现
哈佛大学更近研究了四个纲(Hexactinellida, Demospongiae, Homoscleromorpha and Calcarea)八个种海绵的转录组，专门寻找与动物复杂性相关的基因和途径，成果发表在Mol Biol Evol上。
海绵(多孔动物)是更早进化的动物，它滤食性身体计划是由复杂的含水系统组成的环细胞室组成的，在后生动物中非常独特。它表示海绵与其他动物在肌肉和神经功能进化之前早有分歧，或表示海绵已失去这些特征。Amphimedon和Oscarella基因组的分析支持这一观点——许多后生动物的关键基因在所研究的海绵中的是不存在的，但其他海绵中这些基因的存在是未知的。哈佛大学更近研究了四个纲(Hexactinellida, Demospongiae, Homoscleromorpha and Calcarea)八个种海绵的转录组，专门寻找与动物复杂性相关的基因和途径，成果发表在Mol Biol Evol上。
他们在三种单细胞后鞭毛生物和两种两侧对称动物类群的转录组和基因组中寻找这些基因作为参考。他们的分析表明，所有海绵纲与其他后生动物共享补充基因。该团队发现Hexactinellid, Calcareous and Homoscleromorph三种海绵与非两侧对称动物相比共享给两侧对称动物更多的基因(由联川生物提供poly(A)RNA测序服务)。
他们还发现大多数分子代表参与细胞与细胞间的通信，发出信号，活跃在复杂的上皮细胞中，免疫识别和生殖系/性别，只有少数潜在的关键分子没有参与。一个值得注意的发现是，所有寻常海绵纲(转录组和Amphimedon基因组)某些重要基因的缺失可能反映了主干谱系包括Hexactinellid, Calcareous and Homoscleromorph的分歧。
其结果表明，遗传复杂性产生于进化初，这些基因在大多数动物细胞系是存在的。这表明海绵要么具有隐蔽生理和形态的复杂性，要么失去祖细胞类型或生理过程。
原文摘要：
The analysis of eight transcriptomes from all Porifera classes reveals surprising genetic complexity in sponges
Ana Riesgo, Nathan Farrar, Pamela J Windsor, Gonzalo Giribet and Sally P Leys
Sponges (Porifera) are among the earliest evolving metazoans. Their filter-feeding body plan based on choanocyte chambers organized into a complex aquiferous system is so unique among metazoans that it either reflects an early divergence from other animals prior to the evolution of features such as muscles and nerves, or that sponges lost these characters. Analyses of the Amphimedon and Oscarella genomes support this view of uniqueness – many key metazoan genes are absent in these sponges – but whether this is generally true of other sponges remains unknown. We studied the transcriptomes of eight sponge species in four classes (Hexactinellida, Demospongiae, Homoscleromorpha and Calcarea) specifically seeking genes and pathways considered to be involved in animal complexity. For reference, we also sought these genes in transcriptomes and genomes of three unicellular opisthokonts and two bilaterian taxa. Our analyses showed that all sponge classes share an unexpectedly large complement of genes with other metazoans. Interestingly, hexactinellid, calcareous and homoscleromorph sponges share more genes with bilaterians than with non-bilaterian metazoans. We were surprised to find representatives of most molecules involved in cell-cell communication, signaling, complex epithelia, immune recognition and germ-lineage/sex, with only a few, but potentially key, absences. A noteworthy finding was that some important genes were absent from all demosponges (transcriptomes and the Amphimedongenome), which might reflect divergence from main-stem lineages including hexactinellids, calcareous sponges, and homoscleromorphs. Our results suggest that genetic complexity arose early in evolution as shown by the presence of these genes in most of the animal lineages, which suggests sponges either possess cryptic physiological and morphological complexity and/or have lost ancestral cell types or physiological processes.
