Suzuki T, Srivastava A S, Kurokawa T
Metabolism Section, National Research Institute of Aquaculture, Fishery Agency, Nansei, Japan.
Int J Dev Biol. 1999 Jul;43(4):357-9.
Hox genes are expressed in domains with clear anterior borders exhibiting 3'-->5' hierarchy in hindbrain and in the pharyngeal area commonly in vertebrate embryos. Teleost embryos form seven pharyngeal arches, the mandibular arch, hyoid arch and the gill arches 1-5. We previously reported that, in Japanese flounder (Paralichthys olivaceus) embryos, Hoxd-4 is expressed from rhombomere 7 to the spinal cord in the central nervous system and at gill arches 2-5. At present, the hierarchy of Hox genes at gill arches 3-5 of teleost fish is unclear. Here, we investigated the expression domains of Hoxb-5 in the flounder embryo by whole-mount in situ hybridization to gain insight into the Hox code at gill arches. The initial signal indicating Hoxb-5 expression was identified in the spinal cord at hatching, corresponding with the prim-5 stage of zebrafish. Then, intense signals were detected from the anterior part of the spinal cord and from the posterior part of the pharyngeal area at 36 h after hatching. By serially sectioning the hybridized embryos, it was found that signal in the pharyngeal area came from the most posterior gill arch 5. Therefore, it is speculated that Hoxb-5 functions in regional identification of gill arch 5 in this teleost.
Hox基因在脊椎动物胚胎的后脑和咽区中，以前端边界清晰的区域表达，呈现出3'→5'的层级关系。硬骨鱼胚胎形成七个咽弓，即下颌弓、舌弓和第1 - 5鳃弓。我们之前报道过，在日本牙鲆（Paralichthys olivaceus）胚胎中，Hoxd - 4在中枢神经系统中从菱脑节7到脊髓以及在第2 - 5鳃弓中表达。目前，硬骨鱼第3 - 5鳃弓处Hox基因的层级关系尚不清楚。在此，我们通过整体原位杂交研究了牙鲆胚胎中Hoxb - 5的表达域，以深入了解鳃弓处的Hox编码。表明Hoxb - 5表达的初始信号在孵化时于脊髓中被识别，这与斑马鱼的prim - 5阶段相对应。然后，在孵化后36小时，从脊髓前部和咽区后部检测到强烈信号。通过对杂交胚胎进行连续切片，发现咽区的信号来自最靠后的第5鳃弓。因此，推测Hoxb - 5在这种硬骨鱼的第5鳃弓区域识别中发挥作用。
