《國際發(fā)育生物學(xué)雜志》10月刊以封面文章發(fā)表了中科院水生所關(guān)于“銀鯽cagMdkb基因在胚胎發(fā)育過程中發(fā)育表達(dá)”的研究成果(The International Journal of Developmental Biology, 2007, 51: 761-769),。該論文是在桂建芳研究員指導(dǎo)下由博士研究生尹雋等人共同完成。封面圖片顯示的是過量注射野生型CagMdkb RNAs 造成的銀鯽胚胎前腦組組織和眼睛發(fā)育受到抑制等嚴(yán)重缺陷,。
Mdk是一種分泌型蛋白，在神經(jīng)發(fā)育中有重要作用，并參與人類腫瘤的形成,。但是,，在不同種類的脊椎動(dòng)物中，Mdk基因的表達(dá)模式卻大相徑庭,。該文報(bào)道了從銀鯽10體節(jié)胚胎的SMART cDNA文庫中克隆的銀鯽Mdkb基因的特征,、表達(dá)圖式及功能。在銀鯽胚胎發(fā)育過程中,，CagMdkb基因在原腸期開始表達(dá),，在10體節(jié)期時(shí)表達(dá)量上升到最高，此后表達(dá)量保持穩(wěn)定,。Western印跡顯示胚胎早期有一條19kDa的母源CagMdkb蛋白帶,，合子CagMdkb蛋白從原腸期開始產(chǎn)生。大約在10體節(jié)時(shí),，19kDa的CagMdkb蛋白剪掉了信號(hào)肽,，變成17kDa的成熟蛋白。在胚胎發(fā)育早期,，母源的CagMdkb蛋白在所有卵裂球的細(xì)胞質(zhì)中被檢測(cè)到,。當(dāng)胚胎發(fā)育到18體節(jié)期時(shí)，新合成蛋白的信號(hào)出現(xiàn)在后腦的一對(duì)巨大神經(jīng)元中,。此后,，新合成的CagMdkb蛋白延伸到前腦、中腦,、后腦的神經(jīng)元和脊髓的神經(jīng)纖維中,。3A10抗體共定位表明這對(duì)巨大的神經(jīng)元是Mauthner神經(jīng)元。在銀鯽和斑馬魚受精卵中進(jìn)行的基因轉(zhuǎn)移實(shí)驗(yàn)發(fā)現(xiàn)，野生型CagMdkb RNAs的過量表達(dá)造成了胚胎前腦組織和眼睛發(fā)育受到抑制等嚴(yán)重缺陷,，并發(fā)現(xiàn)其功能的發(fā)揮還依賴于它的分泌特性,。上述結(jié)果表明，CagMdkb在魚類神經(jīng)系統(tǒng)的早期發(fā)育中起著重要作用,。
該研究是在國家973計(jì)劃項(xiàng)目和國家自然科學(xué)基金項(xiàng)目的支持下完成的,。（水生生物研究所）
原始出處:
Int. J. Dev. Biol. 51: 761 - 769 (2007)
doi: 10.1387/ijdb.072346jy
Developmental expression of CagMdkb during gibel carp embryogenesis
Jun Yin, Jian-Hong Xia, Xin-Zheng Du, Jun Liu, Li Zhou, Yun-Han Hong and Jian-Fang Gui*
State Key Laboratory of Freshwater Ecology and Biotechnology, Wuhan Center for Developmental Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, Wuhan, China
ABSTRACT Midkine (Mdk) genes have been revealed to have different expression patterns in vertebrates and therefore, additional studies on Mdk expression patterns are required in more species. In this study, CagMdkb has been cloned and characterized from a SMART cDNA library of 10-somite stage embryos of Carassius auratus gibelio. Its full length cDNA is 1091 bp and encodes a sequence of 147 amino acids, which shows 97.3% identity to zebrafish Mdkb on the amino acid level. RT-PCR analysis reveals that CagMdkb is first transcribed in gastrula embryos and maintains a relatively stable expression level during subsequent embryogenesis. Western blot analysis reveals a 19 kDa maternal CagMdkb protein band and the zygotic CagMdkb protein is expressed from gastrula stage. At around 10 somite stage, the 19 kDa CagMdkb is processed to another protein band of about 17 kDa, which might be the secreted form with the 21-residue signal peptide removed. With immunofluorescence analysis, maternal CagMdkb protein was found to be localized in each blastamere cell of early embryos. The zygotic CagMdkb positive fluorescence signal was detected from a pair of large neurons at 18-somite stage. At the later stages, CagMdkb protein was also extended to numerous small neurons in the forebrain, midbrain and hindbrain, as well as to nerve fibers in the spinal cord. Co-localization with 3A10 antibody revealed CagMdkb immunoreactivity on developing Mauthner neurons, a member of reticulospinal neurons. In addition, ectopic expression of CagMdkb in early embryos of gibel carp and zebrafish suppressed head formation and CagMdkb function was found to depend on secretory activity. All these findings indicate that CagMdkb plays an important role in neural development during gibel carp embryogenesis and there is functional conservation of Mdkb in fish head formation.
Key words: Mdkb, embryogenesis, Mauthner cell, nerve development, gibel carp
*Corresponding author e-mail: [email protected]
