Andersen Øivind, Johnsen Hanne, De Rosa Maria Cristina, Præbel Kim, Stjelja Suzana, Kirubakaran Tina Graceline, Pirolli Davide, Jentoft Sissel, Fevolden Svein-Erik
Nofima, P.O. Box 5010, N-1430 Ås, Norway; Department of Animal and Aquaculture Sciences, University of Life Sciences, P.O. Box 5003, N-1430 Ås, Norway.
Nofima, Muninbakken 9-13, N-9291 Tromsø, Norway.
Mar Genomics. 2015 Aug;22:45-54. doi: 10.1016/j.margen.2015.03.009. Epub 2015 Mar 31.
The synaptophysin (SYP) family comprises integral membrane proteins involved in vesicle-trafficking events, but the physiological function of several members has been enigmatic for decades. The presynaptic SYP protein controls neurotransmitter release, while SYP-like 2 (SYPL2) contributes to maintain normal Ca(2+)-signaling in the skeletal muscles. The polymorphic pantophysin (Pan I) of Atlantic cod shows strong genetic divergence between stationary and migratory populations, which seem to be adapted to local environmental conditions. We have investigated the functional involvement of Pan I in the different ecotypes by analyzing the 1) phylogeny, 2) spatio-temporal gene expression, 3) structure-function relationship of the Pan I(A) and I(B) protein variants, and 4) linkage to rhodopsin (rho) recently proposed to be associated with different light sensitivities in Icelandic populations of Atlantic cod. We searched for SYP family genes in phylogenetic key species and identified a single syp-related gene in three invertebrate chordates, while four members, Syp, Sypl1, Sypl2 and synaptoporin (Synpr), were found in tetrapods, Comoran coelacanth and spotted gar. Teleost fish were shown to possess duplicated syp, sypl2 and synpr genes of which the sypl2b paralog is identical to Pan I. The ubiquitously expressed cod Pan I codes for a tetra-spanning membrane protein possessing five amino acid substitutions in the first intravesicular loop, but only minor structural differences were shown between the allelic variants. Despite sizable genomic distance (>2.5 Mb) between Pan I and rho, highly significant linkage disequilibrium was found by genotyping shallow and deep water juvenile settlers predominated by the Pan I(A)-rho(A) and Pan I(B)-rho(B) haplotypes, respectively. However, the predicted rhodopsin protein showed no amino acid changes, while multiple polymorphic sites in the upstream region might affect the gene expression and pigment levels in stationary and migratory cod. Alternatively, other strongly linked genes might be responsible for the sharp settling stratification of juveniles and the different vertical behavior patterns of adult Atlantic cod.
突触素（SYP）家族由参与囊泡运输事件的整合膜蛋白组成，但几十年来，几个成员的生理功能一直成谜。突触前SYP蛋白控制神经递质释放，而类突触素2（SYPL2）有助于维持骨骼肌中正常的Ca（2+）信号传导。大西洋鳕鱼的多态泛突触素（Pan I）在定居和洄游种群之间表现出强烈的遗传差异，这两种种群似乎都适应了当地的环境条件。我们通过分析以下方面研究了Pan I在不同生态型中的功能参与情况：1）系统发育，2）时空基因表达，3）Pan I（A）和I（B）蛋白变体的结构-功能关系，以及4）与最近提出的在冰岛大西洋鳕鱼种群中与不同光敏感性相关的视紫红质（rho）的连锁关系。我们在系统发育关键物种中搜索SYP家族基因，在三种无脊椎脊索动物中鉴定出一个与syp相关的基因，而在四足动物、科莫罗腔棘鱼和斑点雀鳝中发现了四个成员，即Syp、Sypl1、Sypl2和突触孔蛋白（Synpr）。硬骨鱼被证明拥有重复的syp、sypl2和synpr基因，其中sypl2b旁系同源物与Pan I相同。在所有组织中均有表达的鳕鱼Pan I编码一种四跨膜蛋白，其第一个囊泡内环中有五个氨基酸替换，但等位基因变体之间仅显示出微小的结构差异。尽管Pan I和rho之间存在相当大的基因组距离（>2.5 Mb），但通过对分别以Pan I（A）-rho（A）和Pan I（B）-rho（B）单倍型为主的浅水和深水幼体定居者进行基因分型，发现了高度显著的连锁不平衡。然而，预测的视紫红质蛋白没有氨基酸变化，而上游区域的多个多态性位点可能会影响定居和洄游鳕鱼的基因表达和色素水平。或者，其他紧密连锁的基因可能是导致幼鱼急剧的定居分层和成年大西洋鳕鱼不同垂直行为模式的原因。
