二噁英引起斑马鱼下颌短小及其与Sonic hedgehog基因的关联

Correlation Between Short Lower Jaw in Zebrafish Embryos Induced by 2,3,7,8-tetrachlo-rodibenzo-p-dioxin (TCDD) and Shh Gene

环境污染物二噁英中毒性最强的2,3,7,8-四氯二苯并对二噁英(2,3,7,8-tetrachlorodibenzo-p-dioxin,以下简称TCDD)经由芳烃基受体(arylhydrocarbonreceptor,Ahr)引起啮齿类口唇开裂,斑马鱼下颌短小等典型特征.本试验研究了TCDD引起的下颌短小与形态发育基因.Sonichedgehog(shh)的关系.用0—1.0μg/L的TCDD给受精后24h(24hpf)的斑马鱼胚染毒直至观察并进行形态学观察及原位杂交.结果观察到TCDD引起斑马鱼的下颌短小与其浓度相依存,同时观察到TCDD染毒群的Shh基因表达以及类似基因tiggy-winkleheagehog(twhh)的低下.观察Shh缺失的斑马鱼变异体Syu,或给正常斑马鱼染毒,添加Shh阻断药CycopamanCyclopamine,可以同样观察到斑马鱼的下颌短小.本试验表明TC-DD引起的下颌短小与shh和twhh表达是相关联的.同时也说明斑马鱼有可能作为二噁英类污染物的生物学毒性评价生物.

Dioxins including 2,3 ,7 ,8-tetrachlorodibenzo-p-dioxin (TCDD) are persistent, bioaccumulative toxicants that are widely distributed in the environment. TCDD induced cleft palate in the mice and short lower jaw in the zebrafish ( Danio rerio) by aryl hydrocarbon receptor ( AhR) which is most toxic in the Dioxins. In this experiment, we investigated the correlation between TCDD induced short lower jaw and Sonic hedgehog (Shh) a development gene in the zebrafish embryos during early development, it has many advantages as a vertebrate toxicological model. Embryos is exposed to TCDD (0-1 μg/L) at 24 h post fertilization (24 hpf) until the time of observation for studying by morphology and in situ hybridization. Embryos treated with TCDD showed marked short lower jaw and reduction of shh and twhh expression in lower developing jaw. This inhibitory effect was dependence on exposed concentration. TCDD concentrations 0.3, 0,5 and 1.0 g/L exerted significant effects that were first detected at 84, 72 , and 60 hpf, respectively. But 0. 1 μg/L TCDD did not have any effect until 120 hpf. Shh function defective mutant embryos (Syu) with relatively normal circulation around developing jaw showed marked retardation of jaw growth. When cyclopamine, an inhibitor for shh , was applied, lower jaw growth was significantly inhibited. It was found that TCDD affected chondrogenesis in the head in later stages of zebrafish development by alcian blue stain. TCDD shortened the length of Mechel's cartilage. Similarly, the short Mechel's cartilage was found in the syu embryos and cyclopamine treated embryos. These results indicate the close correlation between hedgehog expression and jaw growth retardation by TCDD in developing zebrafish embryos. It is also suggested zebrafish may become a bi-omarker of dioxin toxicity.