Radomska Katarzyna J, Sager Jonathan, Farnsworth Bryn, Tellgren-Roth Åsa, Tuveri Giulia, Peuckert Christiane, Kettunen Petronella, Jazin Elena, Emilsson Lina S
Department of Evolution and Development, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden.
Department of Neuroscience, Uppsala Biomedical Centre, Uppsala University, Uppsala, Sweden.
PLoS One. 2016 Jan 4;11(1):e0146155. doi: 10.1371/journal.pone.0146155. eCollection 2016.
Quaking (QKI) is an RNA-binding protein involved in post-transcriptional mRNA processing. This gene is found to be associated with several human neurological disorders. Early expression of QKI proteins in the developing mouse neuroepithelium, together with neural tube defects in Qk mouse mutants, suggest the functional requirement of Qk for the establishment of the nervous system. As a knockout of Qk is embryonic lethal in mice, other model systems like the zebrafish could serve as a tool to study the developmental functions of qki. In the present study we sought to characterize the evolutionary relationship and spatiotemporal expression of qkia, qki2, and qkib; zebrafish homologs of human QKI. We found that qkia is an ancestral paralog of the single tetrapod Qk gene that was likely lost during the fin-to-limb transition. Conversely, qkib and qki2 are orthologs, emerging at the root of the vertebrate and teleost lineage, respectively. Both qki2 and qkib, but not qkia, were expressed in the progenitor domains of the central nervous system, similar to expression of the single gene in mice. Despite having partially overlapping expression domains, each gene has a unique expression pattern, suggesting that these genes have undergone subfunctionalization following duplication. Therefore, we suggest the zebrafish could be used to study the separate functions of qki genes during embryonic development.
震颤蛋白（QKI）是一种参与转录后mRNA加工的RNA结合蛋白。该基因被发现与多种人类神经疾病有关。QKI蛋白在发育中的小鼠神经上皮中的早期表达，以及Qk基因敲除小鼠中的神经管缺陷，表明Qk对神经系统的建立具有功能需求。由于Qk基因敲除在小鼠中是胚胎致死的，其他模型系统如斑马鱼可作为研究qki发育功能的工具。在本研究中，我们试图表征qkia、qki2和qkib（人类QKI的斑马鱼同源物）的进化关系和时空表达。我们发现qkia是单拷贝四足动物Qk基因的祖先旁系同源物，可能在鳍到肢体的转变过程中丢失。相反，qkib和qki2是直系同源物，分别出现在脊椎动物和硬骨鱼谱系的根部。与小鼠中单一基因的表达相似，qki2和qkib都在中枢神经系统的祖细胞区域表达，但qkia不表达。尽管表达域部分重叠，但每个基因都有独特的表达模式，表明这些基因在复制后经历了亚功能化。因此，我们建议斑马鱼可用于研究胚胎发育过程中qki基因的不同功能。
