小蝙蝠和某些鯨（包含海豚）各自獨立進化出回聲定位能力，關(guān)于它們回聲定位分子機制的研究一直是熱點，之前主要集中在耳蝸對高頻聲音的感知,。沈永義副研究員和博士生梁璐在張亞平院士的指導(dǎo)下，注意到回聲定位能力的形成,，不單單依賴耳蝸對超聲的感知,，還依賴大腦對聲音信號的處理，這才是比較完整的回聲定位通路,。
他們對耳蝸的Cadherin 23 (Cdh23) 基因和它的配體Protocadherin 15 (Pcdh15)基因,，以及神經(jīng)信號傳導(dǎo)的Otoferlin (Otof)基因進行分析，發(fā)現(xiàn)這三個基因在有回聲定位的物種里面都發(fā)生了顯著的趨同進化,，而且Cdh23和Pcdh15基因在有回聲定位的物種里發(fā)生了正選擇,。進一步對不同大腦皮層的Otof基因表達豐度分析表明，該基因的表達豐度在有回聲定位的蝙蝠的聽皮層里面最高,，遠遠高于其他皮層,，以及高于該種蝙蝠胚胎期的聽皮層和其他沒回聲定位蝙蝠的各種皮層。
因此,，該研究從聲音感知到神經(jīng)信號傳導(dǎo),，以及分子序列進化到基因表達豐度變化，受體和配體相互作用等方面比較系統(tǒng)地研究回聲定位的進化,，并第一次從分子水平揭示了大腦以及基因表達豐度的改變在回聲定位起源上的重要作用,。
該研究發(fā)表于國際知名學(xué)術(shù)期刊PLoS Genetics，并受到審稿人的好評,。（生物谷Bioon.com）
doi:10.1371/journal.pgen.1002788
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Parallel Evolution of Auditory Genes for Echolocation in Bats and Toothed Whales
Yong-Yi Shen1#, Lu Liang1,2#, Gui-Sheng Li1, Robert W. Murphy1,3, Ya-Ping Zhang1,4*
The ability of bats and toothed whales to echolocate is a remarkable case of convergent evolution. Previous genetic studies have documented parallel evolution of nucleotide sequences in Prestin and KCNQ4, both of which are associated with voltage motility during the cochlear amplification of signals. Echolocation involves complex mechanisms. The most important factors include cochlear amplification, nerve transmission, and signal re-coding. Herein, we screen three genes that play different roles in this auditory system. Cadherin 23 (Cdh23) and its ligand, protocadherin 15 (Pcdh15), are essential for bundling motility in the sensory hair. Otoferlin (Otof) responds to nerve signal transmission in the auditory inner hair cell. Signals of parallel evolution occur in all three genes in the three groups of echolocators—two groups of bats (Yangochiroptera and Rhinolophoidea) plus the dolphin. Significant signals of positive selection also occur in Cdh23 in the Rhinolophoidea and dolphin, and Pcdh15 in Yangochiroptera. In addition, adult echolocating bats have higher levels of Otof expression in the auditory cortex than do their embryos and non-echolocation bats. Cdh23 and Pcdh15 encode the upper and lower parts of tip-links, and both genes show signals of convergent evolution and positive selection in echolocators, implying that they may co-evolve to optimize cochlear amplification. Convergent evolution and expression patterns of Otof suggest the potential role of nerve and brain in echolocation. Our synthesis of gene sequence and gene expression analyses reveals that positive selection, parallel evolution, and perhaps co-evolution and gene expression affect multiple hearing genes that play different roles in audition, including voltage and bundle motility in cochlear amplification, nerve transmission, and brain function.
