Cox A A, Jezewski P A, Fang P-K, Payne-Ferreira T L
Department of Biology, University of Massachusetts, North Dartmouth, MA 02747, USA.
Gene Expr Patterns. 2010 Sep;10(6):251-8. doi: 10.1016/j.gep.2010.05.005. Epub 2010 May 24.
The Wnts are a highly conserved family of secreted glycoproteins involved in cell-cell signaling and pattern formation during early embryonic development. Teasing out the role of individual Wnt molecules through development is challenging. Gene duplications are one of the most important mechanisms for generating evolutionary variations. The current consensus suggests that most anatomical variation is generated by divergence of regulatory control regions rather than by coding sequence divergence. Thus phylogenetic comparisons of divergent gene expression patterns are essential to understanding ancestral morphogenetic patterns from which subsequent anatomy diversified in modern lineages. We previously demonstrated strongest expression of zebrafish wnt9b within its heart tube, limb bud and ventral/anterior ectoderm during oral and pharyngeal arch patterning. Our goal is to compare and contrast zwnt9b to its closest paralog, zwnt9a. Sequenced, fulllength zebrafish wnt9a and wnt9b cDNA clones were used for phylogenetic analysis, which suggests their derivation from a common pre-vertebrate archeolog by gene duplication and divergence. Here we demonstrate that zwnt9a expression is found within unique (CNS, pronephric ducts, sensory organs) and overlapping (pectoral fin buds) expression domains relative to zwnt9b. Apparently, Wnt9 paralogs differentially parsed common ancestral expression domains during their subsequent rounds of gene duplication, divergence and loss in different vertebrate lineages. This expression data suggests ancestral roles for Wnt9s in early patterning of neural/oral-pharyngeal ectoderm and mesendoderm derivatives.
Wnt 是一个高度保守的分泌型糖蛋白家族，参与早期胚胎发育过程中的细胞间信号传导和模式形成。在发育过程中梳理单个 Wnt 分子的作用具有挑战性。基因复制是产生进化变异的最重要机制之一。目前的共识表明，大多数解剖变异是由调控控制区域的分歧产生的，而不是由编码序列分歧产生的。因此，对不同基因表达模式进行系统发育比较对于理解现代谱系中后续解剖结构多样化所源自的祖先形态发生模式至关重要。我们之前证明，在口咽弓模式形成过程中，斑马鱼 wnt9b 在其心管、肢芽和腹侧/前外胚层中表达最强。我们的目标是比较和对比 zwnt9b 与其最接近的旁系同源基因 zwnt9a。对全长斑马鱼 wnt9a 和 wnt9b cDNA 克隆进行测序用于系统发育分析，这表明它们通过基因复制和分歧源自一个共同的脊椎动物前体。在这里，我们证明相对于 zwnt9b，zwnt9a 的表达存在于独特的（中枢神经系统、原肾管、感觉器官）和重叠的（胸鳍芽）表达域中。显然，Wnt9 旁系同源基因在不同脊椎动物谱系随后的基因复制、分歧和丢失过程中对共同的祖先表达域进行了不同的划分。该表达数据表明 Wnt9 在神经/口咽外胚层和中内胚层衍生物的早期模式形成中具有祖先作用。
