Powell B C, Walker S K, Bawden C S, Sivaprasad A V, Rogers G E
Department of Biochemistry, University of Adelaide, Australia.
Reprod Fertil Dev. 1994;6(5):615-23. doi: 10.1071/rd9940615.
Merino wool is the result of generations of selection, yet improvements in wool quality and performance are still being sought. Through gene manipulation, sheep transgenesis offers possibilities of understanding the relationship between wool keratin protein composition and fibre structure and properties and of introducing novel changes to fibre properties and growth rates. We have established an efficient sheep transgenesis programme with an overall transgenic rate of 2.1% of zygotes injected. However, by incorporating in vitro culture and assessment of injected zygotes, this equates to a transgenic rate of 13% from 516 lambs born. With the first keratin gene construct, a wool keratin type II intermediate filament gene, four live F0 transgenic sheep have been produced and all express the transgene. In one of them, the highest expressor, phenotypic and ultrastructural changes were evident in the fleece. To improve wool growth rate by increasing the supply of cysteine to the follicle, transgenic sheep are being produced carrying the two genes necessary for endogenous cysteine synthesis. Three promoters have been tested driving the cysteine synthesis genes: two general promoters, the Rous sarcoma virus long terminal repeat and mouse phosphoglycerate kinase promoter, and a rumen-specific promoter from the sheep small proline-rich protein gene. To date, one transgenic sheep (bearing the small proline-rich protein promoter constructs) has produced cysteine in the rumen, although the amount was low at 3 months of age and not detectable at 6 months.
美利奴羊毛是经过几代选育的成果，但人们仍在寻求羊毛质量和性能的改进。通过基因操作，绵羊转基因技术为理解羊毛角蛋白组成与纤维结构及性能之间的关系，以及对纤维性能和生长速度引入新的改变提供了可能性。我们已经建立了一个高效的绵羊转基因程序，注射受精卵的总体转基因率为2.1%。然而，通过结合体外培养和对注射受精卵的评估，这相当于从出生的516只羔羊中获得了13%的转基因率。利用第一个角蛋白基因构建体，即一种羊毛角蛋白II型中间丝基因，已经培育出了4只存活的F0转基因绵羊，且它们都表达了转基因。在其中表达量最高的一只绵羊身上，其羊毛在表型和超微结构上都有明显变化。为了通过增加毛囊中半胱氨酸的供应来提高羊毛生长速度，正在培育携带内源性半胱氨酸合成所需两个基因的转基因绵羊。已经测试了驱动半胱氨酸合成基因的三种启动子：两种通用启动子，即劳斯肉瘤病毒长末端重复序列和小鼠磷酸甘油酸激酶启动子，以及一种来自绵羊富含脯氨酸的小蛋白基因的瘤胃特异性启动子。迄今为止，一只转基因绵羊（携带富含脯氨酸的小蛋白启动子构建体）在瘤胃中产生了半胱氨酸，不过在3月龄时产量较低，6月龄时则检测不到。
