Transcription factor ISL1 is essential for pacemaker development and function
Xingqun Liang, Qingquan Zhang, Paola Cattaneo, Shaowei Zhuang, Xiaohui Gong, Nathanael J. Spann, Cizhong Jiang, Xinkai Cao, Xiaodong Zhao, Xiaoli Zhang, Lei Bu, Gang Wang, H.S. Vincent Chen, Tao Zhuang, Jie Yan, Peng Geng, Lina Luo, Indroneal Banerjee, Yihan Chen, Christopher K. Glass, Alexander C. Zambon, Ju Chen, Yunfu Sun, Sylvia M. Evans
Xingqun Liang, Qingquan Zhang, Paola Cattaneo, Shaowei Zhuang, Xiaohui Gong, Nathanael J. Spann, Cizhong Jiang, Xinkai Cao, Xiaodong Zhao, Xiaoli Zhang, Lei Bu, Gang Wang, H.S. Vincent Chen, Tao Zhuang, Jie Yan, Peng Geng, Lina Luo, Indroneal Banerjee, Yihan Chen, Christopher K. Glass, Alexander C. Zambon, Ju Chen, Yunfu Sun, Sylvia M. Evans
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Research Article Cardiology Development

Transcription factor ISL1 is essential for pacemaker development and function

Abstract

The sinoatrial node (SAN) maintains a rhythmic heartbeat; therefore, a better understanding of factors that drive SAN development and function is crucial to generation of potential therapies, such as biological pacemakers, for sinus arrhythmias. Here, we determined that the LIM homeodomain transcription factor ISL1 plays a key role in survival, proliferation, and function of pacemaker cells throughout development. Analysis of several Isl1 mutant mouse lines, including animals harboring an SAN-specific Isl1 deletion, revealed that ISL1 within SAN is a requirement for early embryonic viability. RNA-sequencing (RNA-seq) analyses of FACS-purified cells from ISL1-deficient SANs revealed that a number of genes critical for SAN function, including those encoding transcription factors and ion channels, were downstream of ISL1. Chromatin immunoprecipitation assays performed with anti-ISL1 antibodies and chromatin extracts from FACS-purified SAN cells demonstrated that ISL1 directly binds genomic regions within several genes required for normal pacemaker function, including subunits of the L-type calcium channel, Ank2, and Tbx3. Other genes implicated in abnormal heart rhythm in humans were also direct ISL1 targets. Together, our results demonstrate that ISL1 regulates approximately one-third of SAN-specific genes, indicate that a combination of ISL1 and other SAN transcription factors could be utilized to generate pacemaker cells, and suggest ISL1 mutations may underlie sick sinus syndrome.

Authors

Xingqun Liang, Qingquan Zhang, Paola Cattaneo, Shaowei Zhuang, Xiaohui Gong, Nathanael J. Spann, Cizhong Jiang, Xinkai Cao, Xiaodong Zhao, Xiaoli Zhang, Lei Bu, Gang Wang, H.S. Vincent Chen, Tao Zhuang, Jie Yan, Peng Geng, Lina Luo, Indroneal Banerjee, Yihan Chen, Christopher K. Glass, Alexander C. Zambon, Ju Chen, Yunfu Sun, Sylvia M. Evans

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Figure 7

ISL1 directly regulates a number of genes required for normal pacemaker function in mice and humans.

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ISL1 directly regulates a number of genes required for normal pacemaker ...
(A) ChIP-seq ISL1-binding regions were mapped relative to their nearest TSS. Annotation includes whether a peak is in the TSS (defined as from –1 kb to +100 bp), transcription termination site (TTS; defined as from –100 bp to +1 kb), exon (coding), 5′ UTR, 3′ UTR, intronic, or intergenic. (B) Top motifs enriched in the vicinity of ISL1-binding sites. (C) GO functional clustering of genes associated with ISL1 ChIP-seq peaks (top 10 not redundant categories are shown). (D) Overlay of RNA-seq and ChIP-seq results correlates ISL1 binding with gene regulation in SAN cells. Scatterplot of RNA-Seq from Figure 6A with genes upregulated or downregulated 1.5-fold in Isl1 mutant SAN cells, colored in red and green, respectively. Up- and downregulated genes demonstrating vicinal ISL1 binding in SAN cells are black. (E) Overlay of RNA-seq and ChIP-seq results revealed 228 genes as potential direct targets of ISL1 in SAN cells. (F) GO functional clustering of these genes allowed for identification of cellular functions directly regulated by ISL1 (top 10 not redundant categories are shown). See also Supplemental Figure 4, Table 1, and Supplemental Tables 1, 2, 4, and 5.