Genetic basis of brain size evolution in cetaceans: insights from adaptive evolution of seven primary microcephaly (MCPH) genes.
Genetic basis of brain size evolution in cetaceans: insights from adaptive evolution of seven primary microcephaly (MCPH) genes.
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鲸目动物大脑大小进化的遗传基础：七个原发性小头畸形（MCPH）基因的适应性进化的见解
DOI：
10.1186/s12862-017-1051-7
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发表时间：
2017-08-29
影响因子：
3.4
通讯作者：
Yang G
中科院分区：
文献类型：
--
作者：
Xu S;Sun X;Niu X;Zhang Z;Tian R;Ren W;Zhou K;Yang G
鲸目动物脑容量的扩大是哺乳动物进化过程中的一个谜，但其遗传基础仍未得到充分探索。本文研究了在脑发育过程中对大小调节起关键作用的7个初级小头畸形（MCPH）基因的所有外显子。MCPH2-7基因序列在鲸目动物中是完整的，但在MCPH1中发现了移码突变和终止密码子。在6个完整的MCPH基因中，有4个基因（WDR62、CDK5RAP2、CEP152和ASPM）存在广泛的阳性选择。特别的是，CDK5RAP2和ASPM的阳性选择在脑商（EQ）增加的齿螈谱系和EQ降低的神秘菌谱系中被检测到，而WDR62只在齿螈谱系中被检测到。有趣的是，CDK5RAP2和ASPM的进化速率（ω）和EQ之间存在正相关。此外，我们在鲸类动物中测试了钙调素（CaM）与ASPM IQ基序之间的结合亲和力，因为只有CaM与IQ结合，ASPM才能发挥决定脑大小的功能。初步功能分析显示，EQ升高的齿形菌的CaM和IQ基序的结合亲和性强于EQ降低的齿形菌。此外，ASPM和CDK5RAP2的进化率与平均群体规模（作为衡量社会复杂性的一种指标）显著相关。本研究探讨了鲸目动物脑大小进化的遗传基础。在CDK5RAP2和ASPM基因EQ升高和降低的谱系中发现了显著的正选择，这与鲸目动物复杂脑大小的进化非常吻合。CDK5RAP2和ASPM的进化速率与情商显著相关，提示这两个基因可能促进了鲸类动物情商的扩展。我们的初步功能测试进一步表明，ASPM可能主要与情商的进化增加有关。最引人注目的是，我们的结果表明，鲸类动物进化出了更大的大脑来管理复杂的社会系统，这与“社会大脑假说”相一致，因为ASPM和CDK5RAP2的进化速度与平均群体规模显著相关。本文的在线版本（doi:10.1186/s12862-017-1051-7）包含补充材料，可供授权用户使用。
Cetacean brain size expansion is an enigmatic event in mammalian evolution, yet its genetic basis remains poorly explored. Here, all exons of the seven primary microcephaly (MCPH) genes that play key roles in size regulation during brain development were investigated in representative cetacean lineages. Sequences of MCPH2–7 genes were intact in cetaceans but frameshift mutations and stop codons was identified in MCPH1. Extensive positive selection was identified in four of six intact MCPH genes: WDR62, CDK5RAP2, CEP152, and ASPM. Specially, positive selection at CDK5RAP2 and ASPM were examined along lineages of odontocetes with increased encephalization quotients (EQ) and mysticetes with reduced EQ but at WDR62 only found along odontocete lineages. Interestingly, a positive association between evolutionary rate (ω) and EQ was identified for CDK5RAP2 and ASPM. Furthermore, we tested the binding affinities between Calmodulin (CaM) and ASPM IQ motif in cetaceans because only CaM combined with IQ, can ASPM perform the function in determining brain size. Preliminary function assay showed binding affinities between CaM and IQ motif of the odontocetes with increased EQ was stronger than for the mysticetes with decreased EQ. In addition, evolution rate of ASPM and CDK5RAP2 were significantly related to mean group size (as one measure of social complexity). Our study investigated the genetic basis of cetacean brain size evolution. Significant positive selection was examined along lineages with both increased and decreased EQ at CDK5RAP2 and ASPM, which is well matched with cetacean complex brain size evolution. Evolutionary rate of CDK5RAP2 and ASPM were significantly related to EQ, suggesting that these two genes may have contributed to EQ expansion in cetaceans. This suggestion was further indicated by our preliminary function test that ASPM might be mainly linked to evolutionary increases in EQ. Most strikingly, our results suggested that cetaceans evolved large brains to manage complex social systems, consisting with the ‘social brain hypothesis’, as evolutionary rate of ASPM and CDK5RAP2 were significantly related to mean group size. The online version of this article (doi:10.1186/s12862-017-1051-7) contains supplementary material, which is available to authorized users.
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影响因子：
10.7
作者：
Anisimova, Maria;Yang, Ziheng
通讯作者：
Yang, Ziheng
影响因子：
6.6
作者：
Baselga, Andres;Orme, C. David L.
通讯作者：
Orme, C. David L.
DOI：
10.1098/rstb.2006.1997
发表时间：
2007-04-29
影响因子：
6.3
作者：
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通讯作者：
Connor, Richard C.
DOI：
10.1098/rstb.2006.2001
发表时间：
2007-04-29
影响因子：
6.3
作者：
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通讯作者：
Shultz, Susanne
影响因子：
3.3
作者：
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通讯作者：
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