Position effects in the 3D genome as the cause of neurodevelopmental disorders

拓扑关联结构域（TADs）的发现和我们对长程调控的理解使我们能够更好地理解“位置效应”的潜在机制。结构变异体（SV）有可能破坏更高级的染色质组织，从而重新连接基因座的复杂三维染色质组织。破坏细胞边界和启动子-增强子相互作用的SV在骨骼畸形和某些肿瘤中相对常见。然而，SV改变3D基因组结构在神经发育障碍（NDD）中的作用尚不清楚。在第一个资助期内，我们成功地证明了SV在NDD的3D基因组中引起位置效应，并且HiC可以有效地用于识别患者细胞中的SV。在第二个资助期内，我们现在的目标是在功能上表征Zfp 608/Lmnb 1基因座的特定缺失和Sox 3基因座的插入，以破译导致NDD的位置效应的分子驱动因素。在目标1中，我们将破译与常染色体显性脱髓鞘性脑白质营养不良（ADLD）相关的Zfp 608/Lmnb 1基因座的3D位置效应的分子驱动因素。在目标2中，我们将剖析与痉挛性截瘫和降低SOX 3表达相关的SOX 3位点插入的分子机制。最后，在目标3中，我们将以单细胞分辨率绘制位于Zfp 608/Lmnb 1体内调控景观中的增强子元件的细胞类型特异性活性。我们的数据将有助于更好地了解NDD患者的位置效应的分子生物学。

The discovery of topologically associating domains (TADs) and our increased understanding of long-range regulation have allowed us to better understand the mechanisms underlying “position effects. Structural variants (SVs) have the potential to disrupt higher order chromatin organization thereby rewiring the complex three-dimensional chromatin organization of the locus. SVs that disrupt TAD boundaries and promoter-enhancer interactions are relatively common in skeletal malformations and certain tumors. However, the role of SVs changing the 3D genome architecture in neurodevelopmental disorders (NDDs) is less understood. In the first funding period we have successfully shown that SVs cause position effects in the 3D genome in NDDs and that HiC can effectively be used to identify SVs in patient cells. In the second funding period we now aim to functionally characterize specific deletions at the Zfp608/Lmnb1 locus and an insertion at the Sox3 locus to decipher the molecular drivers of position effects causing NDDs. In Aim 1 we will decipher the molecular drivers of 3D position effects at the Zfp608/Lmnb1 locus associated with autosomal dominant demyelinating leukodystrophy (ADLD). In Aim 2 we will dissect the molecular mechanism of an insertion at the SOX3 locus associated with spastic paraplegia and reduced SOX3 expression. And finally in Aim 3 we will map the cell type specific activity of enhancer elements located in the regulatory landscapes of Zfp608/Lmnb1 in vivo at single-cell resolution. Our data will contribute to a better understanding of the molecular biology of position effects in patients with NDDs.