When considering relationships between genotype and phenotype we frequently ignore the fact that the genome of a typical animal, notably including that of a fish and a human, harbors a huge amount of foreign DNA. Such DNA, in the form of transposable elements, can affect genome function in a major way, and transgene biology needs to be included in our understanding of the genome. Here we examine an unexpected phenotypic effect of the chromosomally integrated transgene fli1a-F-hsp70l:Gal4VP16, that serves as a model for transgene function generally. We examine larval fras1 mutant zebrafish (Danio rerio). Gal4VP16 is a potent transcriptional activator, and already well known for toxicity and mediating unusual transcriptional effects. In the presence of the transgene, phenotypes in the neural crest-derived craniofacial skeleton, notably fusions and shape changes associated with loss of function fras1 mutations, are made more severe, as we quantify by scoring phenotypic penetrance, the fraction of mutants expressing the trait. A very interesting feature is that the enhancements are highly specific for fras1 mutant phenotypes - occurring in the apparent absence of more wide-spread changes. Except for the features due to the fras1 mutation, the transgene-bearing larvae appear generally healthy and to be developing normally. The transgene behaves as a genetic partial dominant: A single copy is sufficient for the enhancements, yet, for some traits, two copies may exert a stronger effect. We made new strains bearing independent insertions of the fli1a-F-hsp70l:Gal4VP16 transgene, in new locations in the genome, and observed increased severities of the same phenotypes as observed for the original insertion. This finding suggests that sequences within the transgene, e.g. Gal4VP16, are responsible for the enhancements, rather than effect on neighboring host sequences (such as an insertional mutation). The specificity, and biological action underlying the traits, are subjects of considerable interest for further investigation, as we discuss. Our findings show that work with transgenes needs to be undertaken with caution and attention to detail. This article is protected by copyright. All rights reserved.

中文翻译：

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转基因介导的斑马鱼骨骼表型变异


在考虑基因型和表型之间的关系时，我们经常忽略这样一个事实：典型动物的基因组（尤其是鱼类和人类的基因组）含有大量外源 DNA。这种转座元件形式的 DNA 可以在很大程度上影响基因组功能，转基因生物学需要纳入我们对基因组的理解中。在这里，我们检查了染色体整合转基因 fli1a-F-hsp70l:Gal4VP16 的意外表型效应，该基因通常作为转基因功能的模型。我们检查了 fras1 突变斑马鱼 (Danio rerio) 的幼虫。 Gal4VP16 是一种有效的转录激活剂，因其毒性和介导异常转录效应而闻名。在转基因存在的情况下，神经嵴衍生的颅面骨骼中的表型，特别是与 fras1 功能丧失突变相关的融合和形状变化，变得更加严重，正如我们通过对表型外显率（表达该性状的突变体的比例）进行评分来量化的那样。一个非常有趣的特征是，这些增强对于 fras1 突变表型具有高度特异性 - 发生在明显没有更广泛的变化的情况下。除了 fras1 突变造成的特征外，携带转基因的幼虫看起来总体健康并且发育正常。转基因表现为遗传部分显性：单个拷贝足以增强效果，但对于某些性状，两个拷贝可能会产生更强的效果。我们在基因组的新位置制作了带有独立插入的 fli1a-F-hsp70l:Gal4VP16 转基因的新菌株，并观察到与原始插入所观察到的相同表型的严重程度增加。这一发现表明转基因内的序列，例如 Gal4VP16 负责增强，而不是影响邻近的宿主序列（例如插入突变）。正如我们所讨论的，这些性状背后的特异性和生物作用是进一步研究的重要课题。我们的研究结果表明，转基因工作需要谨慎进行并注重细节。本文受版权保护。版权所有。