The VISION Project The VISION project conducted a ValIdated Systematic IntegratiON of epigenetic datasets across progenitor and differentiated blood cell types in mouse and human (Heuston et al. 2018, Xiang et al. 2020, Xiang et al. 2024). The project was carried out by an international group of scientists funded by the National Institute of Diabetes, Digestive, and Kidney Diseases of the National Institutes of Health (grant R24DK106766) and with intramural support from the National Human Genome Research Institute. Key products and results of the project can be visualized on the UCSC Genome Browser using this track hub. The project website provides other servers, databases, and data downloads.
Sonication During the VISION project, a study by Keller et al. (2021) showed that the level of sonication of cross-linked chromatin had a pronounced impact on the quality of ChIP-seq signals. Over-sonication consistently reduced quality, while the impact of under-sonication differed among transcription factors, with no impact on sites bound by CTCF but frequently leading to the loss of sites occupied by TAL1 or bound by POL2. The bound sites not observed in low-quality datasets were inferred to be a mix of both direct and indirect binding. Our observation that the amount of chromatin sonication is a key variable in success of ChIP-seq experiments indicates that monitoring the level of sonication can improve ChIP-seq quality and reproducibility and facilitate ChIP-seq in rare cell types.
This composite track allows visualization of the signals and peak calls for the ChIP-seq experiments conducted by varying the amount of sonication and number of cells for the input chromatin.
The ChIP-seq experiments were conducted in the cell line G1E-ER4 treated with estradiol (G1E-ER4+E2). The G1E cells are an immortalized, GATA1-null cell line derived from mouse embryonic stem cells by gene targeting; these cells proliferate in culture as immature erythroid progenitor cells (Weiss, Yu, Orkin 1997). A stable subline of these cells, called G1E-ER4, undergoes terminal erythroid maturation when GATA1 function is restored as an activatable fusion of GATA1 to the ligand-binding domain of the estrogen receptor (ER). Untreated G1E-ER4 cells, carrying the inactive GATA1-ER, proliferate without differentiation, but treatment with estradiol (E2) activates the hybrid protein, effectively complementing the GATA1 loss-of-function and allowing synchronous erythroid differentiation and maturation (Gregory et al. 1999).
The signals (wiggle tracks) and peak calls (via MACS 1.3.7.1) are provided for each experiment. The track names include the antigen that was the target of the antibody used for ChIP-seq (CTCF or TAL1), the cell line (G1E-ER4+E2), the number of cycles of sonication, and the number of cells used (in millions, M).
Detailed methods for the sonication and ChIP-seq experiments are given in Keller et al. (2021).
Belinda Giardine generated the tracks displayed and developed the track hub.
Gregory T, Yu C, Ma A, Orkin SH, Blobel GA, Weiss MJ. GATA-1 and erythropoietin cooperate to promote erythroid cell survival by regulating bcl-xL expression. Blood. 1999; 94:87-96. PMID: 10381501.
Keller CA, Wixom AQ, Heuston EF, Giardine B, Hsiung CC, Long MR, Miller A, Anderson SM, Cockburn A, Blobel GA, Bodine DM, Hardison RC. Effects of sheared chromatin length on ChIP-seq quality and sensitivity. G3 (Bethesda). 2021 Jun 17;11(6):jkab101. doi: 10.1093/g3journal/jkab101. PMID: 33788948; PMCID: PMC8495733.
Weiss MJ, Yu C, Orkin SH. Erythroid-cell-specific properties of transcription factor GATA-1 revealed by phenotypic rescue of a gene-targeted cell line. Mol Cell Biol. 1997; 17:1642-1651. PMID: 9032291; PMCID: PMC231889.
These data are available for use without restrictions.
Ross Hardison rch8@psu.edu