Germain Noelle D, Chen Pin-Fang, Plocik Alex M, Glatt-Deeley Heather, Brown Judith, Fink James J, Bolduc Kaitlyn A, Robinson Tiwanna M, Levine Eric S, Reiter Lawrence T, Graveley Brenton R, Lalande Marc, Chamberlain Stormy J
Department of Genetics and Developmental Biology, University of Connecticut Health Center, 400 Farmington Avenue, Farmington, CT 06032, USA.
Chromosome Core, Department of Molecular and Cell Biology and Department of Allied Health Sciences, University of Connecticut, 354 Mansfield Road, Storrs, CT 06269, USA.
Mol Autism. 2014 Aug 20;5:44. doi: 10.1186/2040-2392-5-44. eCollection 2014.
Duplications of the chromosome 15q11-q13.1 region are associated with an estimated 1 to 3% of all autism cases, making this copy number variation (CNV) one of the most frequent chromosome abnormalities associated with autism spectrum disorder (ASD). Several genes located within the 15q11-q13.1 duplication region including ubiquitin protein ligase E3A (UBE3A), the gene disrupted in Angelman syndrome (AS), are involved in neural function and may play important roles in the neurobehavioral phenotypes associated with chromosome 15q11-q13.1 duplication (Dup15q) syndrome.
We have generated induced pluripotent stem cell (iPSC) lines from five different individuals containing CNVs of 15q11-q13.1. The iPSC lines were differentiated into mature, functional neurons. Gene expression across the 15q11-q13.1 locus was compared among the five iPSC lines and corresponding iPSC-derived neurons using quantitative reverse transcription PCR (qRT-PCR). Genome-wide gene expression was compared between neurons derived from three iPSC lines using mRNA-Seq.
Analysis of 15q11-q13.1 gene expression in neurons derived from Dup15q iPSCs reveals that gene copy number does not consistently predict expression levels in cells with interstitial duplications of 15q11-q13.1. mRNA-Seq experiments show that there is substantial overlap in the genes differentially expressed between 15q11-q13.1 deletion and duplication neurons, Finally, we demonstrate that UBE3A transcripts can be pharmacologically rescued to normal levels in iPSC-derived neurons with a 15q11-q13.1 duplication.
Chromatin structure may influence gene expression across the 15q11-q13.1 region in neurons. Genome-wide analyses suggest that common neuronal pathways may be disrupted in both the Angelman and Dup15q syndromes. These data demonstrate that our disease-specific stem cell models provide a new tool to decipher the underlying cellular and genetic disease mechanisms of ASD and may also offer a pathway to novel therapeutic intervention in Dup15q syndrome.
15号染色体q11-q13.1区域的重复与所有自闭症病例的1%至3%相关，使得这种拷贝数变异（CNV）成为与自闭症谱系障碍（ASD）相关的最常见染色体异常之一。位于15q11-q13.1重复区域内的几个基因，包括泛素蛋白连接酶E3A（UBE3A），该基因在天使综合征（AS）中发生突变，参与神经功能，可能在与15号染色体q11-q13.1重复（Dup15q）综合征相关的神经行为表型中起重要作用。
我们从五个含有15q11-q13.1 CNV的不同个体中生成了诱导多能干细胞（iPSC）系。将iPSC系分化为成熟的功能性神经元。使用定量逆转录PCR（qRT-PCR）比较五个iPSC系和相应的iPSC衍生神经元中15q11-q13.1位点的基因表达。使用mRNA-Seq比较来自三个iPSC系的神经元之间的全基因组基因表达。
对Dup15q iPSC衍生神经元中15q11-q13.1基因表达的分析表明，基因拷贝数并不能始终如一地预测15q11-q13.1间质性重复细胞中的表达水平。mRNA-Seq实验表明，15q11-q13.1缺失和重复神经元之间差异表达的基因存在大量重叠。最后，我们证明在具有15q11-q13.1重复的iPSC衍生神经元中，UBE3A转录本可以通过药物恢复到正常水平。
染色质结构可能影响神经元中15q11-q13.1区域的基因表达。全基因组分析表明，天使综合征和Dup15q综合征中常见的神经通路可能受到破坏。这些数据表明，我们的疾病特异性干细胞模型为破译ASD潜在的细胞和遗传疾病机制提供了一种新工具，也可能为Dup15q综合征的新型治疗干预提供一条途径。
