Journal: Nature structural & molecular biology

Article Title: Spatiotemporal allele organization by allele-specific CRISPR live-cell imaging: SNP-CLING

doi: 10.1038/s41594-017-0015-3

Figure Lengend Snippet: (a) sgRNAs harboring internal protein-binding RNA-motifs (MS2, or PP7, or Puf1) direct non-catalytic dCas9 to each targeted locus. The corresponding RNA-binding proteins (RBP) MS2, or PP7, or PUM1, are fused to mVenus, or mCherry, or iRFP670, and fluorescently label up to three different loci. For allele-specific labelling, either the 2 nd or 3 rd nucleotide in the dCas9 PAM-motif 5′-NRG-3′ was substituted by a heterozygous SNP to a non-specific dCas9-motif (IUPAC code: ‘Y’ = ‘C’ or ‘T’; ‘H’ = ‘A’, ‘C’ or ‘T’), thereby preventing dCas9-binding to either the 129S1 or CAST alleles in mouse hybrid cells. Sanger sequencing of selected SNPs confirmed heterozygosity. (b) Allele-specific visualization of 129S1- Ypel4 (yellow = MS2-mVenus) and CAST- Ypel4 (red = PP7-mCherry) in male 129S1/CAST mESCs (scale bar = 5 μm, n = 4, 35 nuclei, dashed line = mESC nucleus, arrowheads = SNP-CLING foci of maternal and paternal Ypel4 alleles). (c) Three sgRNAs in MS2 and another set of three sgRNAs in PP7 targeted the CISTR-ACT locus (sgRNA-pool 1 and 2) in RPE-1 cells to elucidate specificity. (d) All measurable foci exhibited two-color co-localization indicating locus-specificity in female RPE-1 cells (edges of foci: < 1 voxel distance = < 50 nm 3 , scale bar = 500 nm, n = 4, 35 nuclei, arrowheads = CLING foci of CISTR-ACT ). (e) To address resolution, two sgRNAs pools targeted XIST (yellow = MS2-mVenus) and TSIX (red = PP7-mCherry), separated by a topological associated domain (TAD) boundary; genomic linear distance ~69 kb. (f) Distinct, non-co-localized signals occurred in 6 out of 10 cells between XIST and TSIX , with spatial displacements of ∼163-638 nm in all three dimensions in RPE-1 cells (scale bar = 100 nm, arrowheads = CLING foci of XIST and TSIX ).

Article Snippet: Flanking BbsI restriction sites were used to ligate sgRNAs with a backbone expressing either three MS2, or three PP7, or six Puf1 motifs (Addgene #68426, #68424), . mCherry or mVenus fluorescent proteins were expressed as fusion proteins with either MS2 or PP7 binding proteins (Addgene #68420), independent of dCas9 (Addgene #68416).

Techniques: Protein Binding, RNA Binding Assay, Binding Assay, Sequencing

Journal: Nature structural & molecular biology

Article Title: Spatiotemporal allele organization by allele-specific CRISPR live-cell imaging: SNP-CLING

doi: 10.1038/s41594-017-0015-3

Figure Lengend Snippet: (a) Inter -allelic distances of Hdac4 [CI = 2.31-3.59] on largest chromosome 1 compared to a locus on small chromosome 18 (44.21 Mb, [CI = 2.14-3.19 μm]) in female 129S1/CAST MEFs were similar (each 80 nuclei, scale bars = 5 μm, arrowheads = SNP-CLING foci of maternal and paternal Hdac4 alleles). (b) Inter -allelic distances between 129S1 and CAST alleles of loci on gene dense chromosomes (chr.7:99.55 Mb [CI = 2.48-3.96 μm], chr. 11 – Sox9 [CI = 1.82-2.75 μm]) or gene-poor chromosome 15 ( Cistr-act [CI = 2.05-3.03 μm]). Chr. 11 distances were different to chr. 7 (two-tailed Mann Whitney rank sum test, * p = 0.02, each 80 nuclei, arrowheads = SNP-CLING foci of maternal and paternal Sox9 alleles). (c) Inter -allelic distances of the SNP-CLING-labeled alleles on chr.7 (arrowheads: yellow = paternal MS2-mVenus, red = maternal PP7-mCherry) relative to inter -genic distances of a CLING-labeled locus (non-allele-specific) on chr.18 (arrowheads: purple = Puf1-PUM1-iRFP670, Pearson's r 2 = 0.71, significance of Pearson's: *** p < 0.0001, 80 nuclei).

Article Snippet: Flanking BbsI restriction sites were used to ligate sgRNAs with a backbone expressing either three MS2, or three PP7, or six Puf1 motifs (Addgene #68426, #68424), . mCherry or mVenus fluorescent proteins were expressed as fusion proteins with either MS2 or PP7 binding proteins (Addgene #68420), independent of dCas9 (Addgene #68416).

Techniques: Two Tailed Test, MANN-WHITNEY, Labeling