Fig. 4
Chromatin accessibility patterns between metaphase homologs are conserved between different cell types. A Human metaphase cells from T-lymphocyte (top row), bone marrow (center row) and fibroblast (bottom row) cells hybridized with scFISH probes PCK1_cen209-IVS6 (chr 20q13.3, left column), TPM1_tel3200 (chr 15q22, center column), and 3.3_1p36 (right column). Hybridized homologs are indicated with arrows on the metaphase cells and enlarged homologs. The differential hybridization intensity observed across all tissues at the PCK1_cen209-IVS6 (left) and TPM1_tel3200 (center) loci are characteristic of differential accessibility (DA). Equivalent hybridized probe intensities observed at locus 3.3_1p36, characteristic of equivalent accessibility (EA) are also conserved between all tissues. Probe 3.3_1p36 serves as a control as an EA locus. Chromosomes were counterstained with DAPI. Probes were labelled with digoxigenin-11-dUTP and detected with Cy3-digoxin antibody. Cells were imaged using Metasystems Axioimager Z.2 epifluorescence microscope system with Metafer4 (V3.8.12) and Isis package (V5.3) imaging software. Images presented in inverted gray scale. B Proportion of cells scored with DA (black) within lymphocytes, bone marrow cells, and fibroblasts are not significantly different from each other when hybridized with sc probes for XDH_IVS30-IVS27, DUOX1_IVS1-IVS3, PCK1_cen209-IVS6, TPM1_tel3200 and CTCFL_cen34302. Three of these DA probe targets (XDH, DUOX1, PCK1) are within genes and the other two (TPM1 and CTCFL) are within intergenic regions. Proportion of cells scored with EA (light grey) across tissue types did not significantly differ from each other when hybridized with EA probe, 3.3_1p36. Across the tissues examined for each DA or EA region, the accessibility between metaphase homologs remained the same. Sample size differs between each tissue and each probe (Additional file 4: Table S3). Significant differences were calculated using a Kruskal Wallis test (α = 0.05) comparing between tissues and proportion of cells scored as DA and EA