Recently, several pedigree-based studies have shown that abnormal replication of an enhancer element regulatory region in the downstream of the bone morphogenetic protein 2 (BMP2) gene is the cause of brachydactyly type A2 (BDA2). However, the exact molecular function of this regulatory region is unclear, and even conflicting results have emerged. In this study, based on bioinformatics analysis, we amplified target fragments of different lengths in this regulatory region by PCR technology, including a highly conserved 2.1 kb core sequence and 3 fragments that can completely cover the core 2.1 kb fragment. Then, the gene recombination vectors were constructed, and the biological function of these fragments was analyzed by the dual-luciferase reporter gene technology system. We found that the highly conserved 2.1 kb fragment did not have enhancer activity, while all of three truncated fragments showed strong enhancer activity. The results suggest that the expression regulation mode of the BMP2 gene is very complex. For the downstream regulatory region, selecting fragments of different lengths may have different effects on the regulation of BMP2 expression, which may due to the fragments with different lengths carrying different regulatory elements in the number of types. In summary, this study revealed the complexity of BMP2 gene regulatory elements, and provided new clues and directions for the subsequent in-depth exploration of the molecular pathogenic mechanism of BDA2.
近年来数项基于遗传家系的研究表明，骨形态发生蛋白2(bone morphogenetic protein 2, BMP2)基因下游的远端增强子元件调控区域的异常重复是A2型短指(趾)症(brachydactyly type A2, BDA2)的致病原因，但是这段调控区域的确切分子功能尚不明确，甚至出现有相互矛盾的结果。本研究在生物信息学分析的基础上，通过PCR技术扩增了该调控区域的不同长度的目的片段，包括高度保守的2.1 kb核心序列和3个能够完全覆盖该2.1 kb片段的不同长度的截短体片段，进而构建基因重组载体，采用双荧光素酶报告基因检测方法对这些片段的生物学功能进行分析。结果发现，高度保守的2.1 kb片段并不具有增强子活性，而3个截短体片段均表现出强烈的增强子活性。这表明BMP2基因的表达调控模式非常复杂，对其下游的这段调控区域而言，选取不同长度的片段，其对BMP2表达调控的效果可能并不一致，这很可能是由于不同长度的片段所携带的调控元件数量或种类不同所致。此项研究初步揭示了BMP2基因调控元件的复杂性，为后续深入探究BDA2的分子致病机制提供了新的线索和方向。.
Keywords: BMP2; brachydactyly type A2; enhancer; regulation; replication.