染色体10q24微重复引起先天性手足分裂畸形的分子机制

最新研究表明，染色体构象改变可造成人类疾病。10q24微重复导致先天性手足分裂畸形（SHFM），其分子机制不明。在一个SHFM家系中，我们发现10q24区域500kb微重复导致额外FBXW4-LBX1杂合基因产生。染色体构象图谱显示，FBXW4与相邻肢体发育关键基因FGF8共同构成一个染色体拓扑关联域（TAD），调控FGF8在胚胎肢芽的表达。据此，我们提出假说：10q24微重复产生的FBXW4-LBX1杂合基因通过形成新TAD导致SHFM。为验证该假说，本课题将利用靶向减数分裂重组技术建立基因组微重复疾病小鼠模型；用染色体构象靶向捕获Hi-C及4C-Seq方法研究疾病小鼠是否产生新TAD；研究新TAD是否造成LBX1在胚胎肢芽异位表达进而干扰正常肢体发育。最后，我们将在病人组织样本中验证这一机制。研究将首次揭示染色体构象变化引起先天性手足分裂畸形的关键机制。

The latest studies indicated that changes of chromatin structure can cause hunman diseases. Microduplication of human 10q24 genomic region has been associated with congenital split-hand/foot malformation (SHFM), but the molecular mechanism is unknown. In a pedigree with SHFM, we found that a 500kb microduplication in 10q24 region cause the formation of an extra FBXW4-LBX1 hybrid gene. The 3D map of the human genome indicated that FBXW4 and nearby FGF8, the key regulator of limb morphogenesis, comprise a topologically associating domain (TAD), which determines the spatio-temporal expression of FGF8 in developing limb bud. We propose that the FBXW4-LBX1 hybrid gene forms a new TAD and causes SHFM. To prove this hypothesis, a genomic duplication SHFM mouse model will be established by targeted meiotic recombination. The capture-HiC and 4C-Seq experiments will be performed to examine the formation of new TAD in the mouse model. Then we will investigate whether the new TAD drives the ectopic expression of LBX1 in developing limb bud and by what mechanism LBX1 impairs the limb bud development and causes SHFM. Finally, we will validate this mechanism in patient-derived specimens. This study will reveal for the first time that the chromatin conformation change can cause human congenital SHFM.