Banerji Rajeswari, Skibbens Robert V, Iovine M Kathryn
Department of Biological Science, Lehigh University, Bethlehem, Pennsylvania 18015, USA.
Department of Biological Science, Lehigh University, Bethlehem, Pennsylvania 18015, USA
Biol Open. 2017 Dec 15;6(12):1802-1813. doi: 10.1242/bio.026013.
Robert syndrome (RBS) and Cornelia de Lange syndrome (CdLS) are human developmental disorders characterized by craniofacial deformities, limb malformation and mental retardation. These birth defects are collectively termed cohesinopathies as both arise from mutations in cohesion genes. CdLS arises due to autosomal dominant mutations or haploinsufficiencies in cohesin subunits (, and ) or cohesin auxiliary factors ( and ) that result in transcriptional dysregulation of developmental programs. RBS arises due to autosomal recessive mutations in cohesin auxiliary factor , the gene that encodes an N-acetyltransferase which targets the SMC3 subunit of the cohesin complex. The mechanism that underlies RBS, however, remains unknown. A popular model states that RBS arises due to mitotic failure and loss of progenitor stem cells through apoptosis. Previous findings in the zebrafish regenerating fin, however, suggest that Esco2knockdown results in transcription dysregulation, independent of apoptosis, similar to that observed in CdLS patients. Previously, we used the clinically relevant to demonstrate a transcriptional role for Esco2. is a gap junction gene conserved among all vertebrates that is required for direct cell-cell communication between adjacent cells such that mutations result in oculodentodigital dysplasia. Here, we show that morpholino-mediated knockdown of reduces expression and perturbs zebrafish bone and tissue regeneration similar to those previously reported for knockdown. Also similar to Esco2-dependent phenotypes, Smc3-dependent bone and tissue regeneration defects are rescued by transgenic Cx43 overexpression, suggesting that Smc3 and Esco2 cooperatively act to regulate cx43 transcription. In support of this model, chromatin immunoprecipitation assays reveal that Smc3 binds to a discrete region of the promoter, suggesting that Esco2 exerts transcriptional regulation of through modification of Smc3 bound to the promoter. These findings have the potential to unify RBS and CdLS as transcription-based mechanisms.
罗伯特综合征（RBS）和科妮莉亚·德朗热综合征（CdLS）是人类发育障碍疾病，其特征为颅面畸形、肢体畸形和智力发育迟缓。这些出生缺陷统称为黏连蛋白病，因为二者均由黏连蛋白基因的突变引起。CdLS是由于黏连蛋白亚基（SMC1A、SMC3和RAD21）或黏连蛋白辅助因子（NIPBL和MAU2）的常染色体显性突变或单倍剂量不足导致发育程序的转录失调而引起的。RBS是由于黏连蛋白辅助因子ESCO2的常染色体隐性突变引起的，该基因编码一种靶向黏连蛋白复合物SMC3亚基的N - 乙酰转移酶。然而，RBS的潜在机制仍然未知。一个流行的模型认为，RBS是由于有丝分裂失败以及祖干细胞通过凋亡而丧失所导致的。然而，先前在斑马鱼再生鳍中的研究结果表明，ESCO2基因敲低会导致转录失调，且与凋亡无关，这与在CdLS患者中观察到的情况类似。此前，我们使用临床相关的Cx43来证明ESCO2的转录作用。Cx43是所有脊椎动物中保守的间隙连接基因，相邻细胞之间的直接细胞 - 细胞通讯需要该基因，因此Cx43突变会导致眼齿指发育不良。在这里，我们表明吗啉代介导的Cx43基因敲低会降低其表达，并扰乱斑马鱼骨骼和组织再生，这与先前报道的ESCO2基因敲低的情况相似。同样与ESCO2依赖性表型相似，转基因Cx43过表达可挽救SMC3依赖性骨骼和组织再生缺陷，这表明SMC3和ESCO2协同作用来调节Cx43转录。支持该模型的是，染色质免疫沉淀分析表明，SMC3与Cx43启动子的一个离散区域结合，这表明ESCO2通过修饰与Cx43启动子结合的SMC3来对其进行转录调控。这些发现有可能将RBS和CdLS统一为基于转录的机制。
