Kobayashi M, Toyama R, Takeda H, Dawid I B, Kawakami K
Department of Biology, Jichi Medical School, Minamikawachi, Tochigi 329-0498, Japan.
Development. 1998 Aug;125(15):2973-82. doi: 10.1242/dev.125.15.2973.
The Drosophila homeobox gene sine oculis is expressed in the rostral region of the embryo in early development and is essential for eye and brain formation. Its murine homolog, Six3, is expressed in the anterior neural plate and eye anlage, and may have crucial functions in eye and brain development. In this study, we describe the cloning and expression of zebrafish six3, the apparent ortholog of the mouse Six3 gene. Zebrafish six3 transcripts are first seen in hypoblast cells in early gastrula embryos and are found in the anterior axial mesendoderm through gastrulation. six3 expression in the head ectoderm begins at late gastrula. Throughout the segmentation period, six3 is expressed in the rostral region of the prospective forebrain. Overexpression of six3 in zebrafish embryos induced enlargement of the rostral forebrain, enhanced expression of pax2 in the optic stalk and led to a general disorganization of the brain. Disruption of either the Six domain or the homeodomain abolish these effects, implying that these domains are essential for six3 gene function. Our results suggest that the vertebrate Six3 genes are involved in the formation of the rostral forebrain.
果蝇同源异型盒基因无眼在胚胎发育早期的头部区域表达，对眼睛和大脑的形成至关重要。其小鼠同源基因Six3在前神经板和眼原基中表达，可能在眼睛和大脑发育中具有关键作用。在本研究中，我们描述了斑马鱼six3的克隆和表达，它是小鼠Six3基因明显的直系同源基因。斑马鱼six3转录本最早在原肠胚早期的下胚层细胞中出现，并在整个原肠胚形成过程中在前轴中胚层中被发现。six3在头部外胚层的表达始于原肠胚后期。在整个体节期，six3在前脑原基的头部区域表达。在斑马鱼胚胎中过表达six3会导致前脑头部扩大、视柄中pax2表达增强，并导致大脑普遍紊乱。Six结构域或同源结构域的破坏会消除这些影响，这意味着这些结构域对six3基因功能至关重要。我们的结果表明，脊椎动物Six3基因参与前脑头部的形成。
