Dailey Simon C, Kozmikova Iryna, Somorjai Ildikó M L
University of St Andrews, Biomedical Sciences Research Complex, North Haugh, St Andrews, UK.
Int J Dev Biol. 2017;61(10-11-12):723-732. doi: 10.1387/ijdb.170205is.
A cluster of three Specificity Protein (Sp) genes (Sp1-4, Sp5 and Sp6-9) is thought to be ancestral in both chordates and the wider Eumetazoa. Sp5 and Sp6-9 gene groups are associated with embryonic growth zones, such as tailbuds, and are both Wnt/β-catenin signalling pathway members and targets. Currently, there are conflicting reports as to the number and identity of Sp genes in the cephalochordates, the sister group to the vertebrates and urochordates. We confirm the SP complement of Branchiostoma belcheri and Branchiostoma lanceolatum, as well as their genomic arrangement, protein domain structure and residue frequency. We assay Sp5 expression in B. lanceolatum embryos, and determine its response to pharmacologically increased β-catenin signalling. Branchiostoma possesses three Sp genes, located on the same genomic scaffold. Phylogenetic and domain structure analyses are consistent with their identification as SP1-4, SP5 and SP6-9, although SP1-4 contains a novel glutamine-rich N-terminal region. SP5 is expressed in axial mesoderm and neurectoderm, and marks the cerebral vesicle and presumptive pharynx. Early exposure to increased β-catenin caused ubiquitous SP5 expression in late gastrula, while later treatment at gastrula stages reduced SP5 expression in the posterior growth zone during axis elongation. Amphioxus possess a typical invertebrate eumetazoan SP complement, and SP5 expression in embryos is well conserved with vertebrate homologues. Its expression in the tailbud, a posterior growth zone, is consistent with expression seen in other bilaterians. Branchiostoma SP5 shows a dynamic response to Wnt/β-catenin signalling.
一组由三个特异性蛋白（Sp）基因（Sp1 - 4、Sp5和Sp6 - 9）组成的基因簇被认为在脊索动物和更广泛的真后生动物中是祖先基因。Sp5和Sp6 - 9基因簇与胚胎生长区域相关，如尾芽，它们既是Wnt/β - 连环蛋白信号通路的成员，也是该信号通路的靶标。目前，关于头索动物（脊椎动物和尾索动物的姐妹群）中Sp基因的数量和身份存在相互矛盾的报道。我们确定了文昌鱼和 lanceolatum文昌鱼的SP基因组成，以及它们的基因组排列、蛋白质结构域结构和残基频率。我们检测了lanceolatum文昌鱼胚胎中Sp5的表达，并确定了其对药理学上增加的β - 连环蛋白信号的反应。文昌鱼拥有三个Sp基因，位于同一基因组支架上。系统发育和结构域结构分析与它们被鉴定为SP1 - 4、SP5和SP6 - 9一致，尽管SP1 - 4包含一个新的富含谷氨酰胺的N端区域。SP5在轴中胚层和神经外胚层中表达，并标记脑泡和假定的咽部。早期暴露于增加的β - 连环蛋白会导致原肠后期SP5在全身表达，而在原肠期后期进行处理会在轴伸长过程中降低后生长区的SP5表达。文昌鱼拥有典型的无脊椎动物真后生动物SP基因组成，并且胚胎中的SP5表达与脊椎动物同源物高度保守。它在尾芽（一个后生长区）中的表达与其他两侧对称动物中的表达一致。文昌鱼SP5对Wnt/β - 连环蛋白信号表现出动态反应。
