A long-range Shh enhancer regulates expression in the developing limb and fin and is associated with preaxial polydactyly
A long-range Shh enhancer regulates expression in the developing limb and fin and is associated with preaxial polydactyly
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DOI：
10.1093/hmg/ddg180
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发表时间：
2003-07-15
影响因子：
3.5
通讯作者：
de Graaff, E
中科院分区：
文献类型：
--
作者：
Lettice, LA;Heaney, SJH;de Graaff, E
由于调控元件的神秘性，很难明确鉴定基因的全部组成。众所周知，调控元件很难定位，并且可能位于离它们所作用的转录单位相当远的距离处，此外，还可能被掺入相邻基因的结构中。调节突变作为人类异常基础的重要性仍然不清楚。在这里，我们表明，染色体7q36相关的轴前多指（趾）畸形，经常观察到的先天性肢体畸形，结果从点突变的Shh调控元件。Shh通常在肢芽中的ZPA后部表达，在PPD小鼠模型中在前缘的额外异位部位表达。我们对异位Shh表达基础的研究确定了驱动ZPA中正常Shh表达的增强子元件。被命名为ZRS的调节子位于Lmbr 1基因的内含子5内，距离靶基因Shh 1 Mb。ZRS驱动四足动物肢体中的早期时空表达模式。尽管四肢和鳍之间存在形态差异，但在鱼类中发现了一种等效的调节元件。ZRS包含在四个不相关的PPD家族和Hx小鼠突变体中与多指（趾）畸形分离的点突变。因此，存在于长程调控元件中的点突变能够引起先天性异常，并且具有改变基因活性的能力，使得检测到新的异常范围。
Unequivocal identification of the full composition of a gene is made difficult by the cryptic nature of regulatory elements. Regulatory elements are notoriously difficult to locate and may reside at considerable distances from the transcription units on which they operate and, moreover, may be incorporated into the structure of neighbouring genes. The importance of regulatory mutations as the basis of human abnormalities remains obscure. Here, we show that the chromosome 7q36 associated preaxial polydactyly, a frequently observed congenital limb malformation, results from point mutations in a Shh regulatory element. Shh, normally expressed in the ZPA posteriorly in the limb bud, is expressed in an additional ectopic site at the anterior margin in mouse models of PPD. Our investigations into the basis of the ectopic Shh expression identified the enhancer element that drives normal Shh expression in the ZPA. The regulator, designated ZRS, lies within intron 5 of the Lmbr1 gene 1 Mb from the target gene Shh. The ZRS drives the early spatio-temporal expression pattern in the limb of tetrapods. Despite the morphological differences between limbs and fins, an equivalent regulatory element is found in fish. The ZRS contains point mutations that segregate with polydactyly in four unrelated families with PPD and in the Hx mouse mutant. Thus point mutations residing in long-range regulatory elements are capable of causing congenital abnormalities, and possess the capacity to modify gene activity such that a novel gamut of abnormalities is detected.