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エンハンサートラップ法を用いたDrosophila melanogasterにおける遺伝子発現パターンの解析

By  Etsuko MACHIYAMA and  Akira KOMATSU


キイロショウジョウバエDrosophila melanogasterのゲノムに,jump-start法を用いて,レポーター遺伝子として大腸菌のβ-galactosidase遺伝子(lac-Z)を組み込んだP因子(P-lwB)挿入系統で,エンハンサーによる遺伝子発現を観察した.101の妊性系統を用い,3令幼虫の主要な22の器官と組織における遺伝子発現を,β-galactosidaseの活性を組織化学的に検出して(X-gal法)解析した.lac-Z の発現は器官や組織によって,また,系統によって多様な発現パターンを示した.lac-Zの発現頻度は,中枢神経系で最も高く(脳で91%,胸腹部神経節で75%),成虫原基(30~65%)や消化管(30~50%)は中程度で,筋肉(13%)とエノサイト(11%)では低値を示した.中枢神経系での発現率が高いのは,中枢神経系を構成する細胞の種類が多いことによるものと考えられる.また,3令幼虫の後期はホルモン分泌や蛋白合成の盛んな発生過程にあり,中枢神経系とともに成虫原基での発現率が高いのは,これらの器官でダイナミックな組織再編成が生じていることを反映しているものと考えられる.複数器官での同時発現率を調べると,少数の器官で特異的に発現するものから多数同時発現を示すものと多様であり,その平均値は雌雄とも4.4であった.また,2つの器官で同時に発現する頻度は,両者の発現率の積よりも,ほとんど全部の組み合わせで高い値を示した.このことは,多くの器官に共通する細胞過程に必要な遺伝子,あるいは,ハウスキーピング遺伝子のような細胞の基本過程に共通して必要な遺伝子の存在を示唆する.Patterns of expression of the reporter gene, lac-Z, were analyzed in 22 major organs of third instar larvae from a total of 101 independent enhancer trapped strains of the fruit fly, Drosophila melanogaster. The lac-Z gene expression showed diverse patterns among different organs and among different strains. Of the organs examined, the CNS showed the highest lac-Z expression (91% in the brain, 75% in the thoracico-abdominal ganglia), followed by imaginal discs (30% to 65%) and the digestive duct (30% to 50%), while muscles and oenocytes showed the lowest frequencies of lac-Z expression, at 13% and 11% respectively. Organs with high frequencies of gene expression may reflect a much more complex organ, consisting of many different cell types, such as the CNS, or it may reflect a dynamic developmental process under hormonal control in the morphogenesis of imaginal discs and in CNS reorganization. Many genes were expressed simultaneously in many different organs. The frequency of simultaneous gene expressions in different organs was spread over a wide range, from a few organs to almost all organs examined, and the average number of organs showing simultaneous gene expression was 4.4 both in the male and female. Simultaneous gene expression in a certain combination of organs was, in almost all combinations, higher than the simple product of the expression percentages of individual organs. These results indicate the presence of genes necessary for cellular processes shared by many organs, or necessary for basic cellular processes, such as housekeeping genes

Publisher: 東京女子医科大学学会
Year: 1996
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