Figure 4. MADM-induced uniparental chromosome disomy (UPD) results in paternal growth dominance in liver.

(A) MADM scheme for imprinted genes. G2-X MADM events generate differentially labeled cells with near-complete UPD (cells with two copies of either the maternal [matUPD] or the paternal [patUPD] chromosome). (Top) The GT MADM cassette is inherited from the mother (M, pink) and the TG MADM cassette from the father (P, blue), and green cells show patUPD (PP) and red cells matUPD (MM). In such a scenario, imprinted maternally expressed genes are expressed at twice the normal dose and paternally expressed genes are not expressed in cells with matUPD (red). In contrast, paternally expressed genes are overexpressed by factor two and maternally expressed genes are not expressed in cells with patUPD (green). (Bottom) Reverse scheme with GT MADM cassette inherited from father and TG MADM cassette inherited from mother. Here, cells with matUPD are labeled in green and cells with patUPD in red fluorescent color.

(B–U) Representative images of horizontal liver cryosections with MADM labeling (GFP, green; tdT, red) in MADM-1 (A) to MADM-19 (T and U) in combination with Hprt-Cre driver at P21. Higher resolution image (U) represents inset in (T) in left lateral lobe of liver in MADM-19.

(V) (Top) Representative images (left, middle) of liver in MADM-7^GT/TG;Hprt^Cre/+ with green GFP⁺ patUPD and red tdT⁺ matUPD (left) or red tdT⁺ patUPD and green GFP⁺ matUPD (middle) at P21; and quantification (right) of absolute (cells/mm³) and relative (PP/MM) numbers of MADM-labeled cells with UPD. (Middle) Representative images (left, middle) of liver in MADM-11^GT/TG;Hprt^Cre/+ with green GFP⁺ patUPD and red tdT⁺ matUPD (left) or red tdT⁺ patUPD and green GFP⁺ matUPD (middle) at P21; and quantification (right) of absolute (cells/mm³) and relative (PP/MM) numbers of MADM-labeled cells with UPD. (Bottom) Representative images (left, middle) of liver in MADM-17^GT/TG;Hprt^Cre/+ with green GFP⁺ patUPD and red tdT⁺ matUPD (left) or red tdT⁺ patUPD and green GFP⁺ matUPD (middle) at P21; and quantification (right) of absolute (cells/mm²) and relative (PP/MM) numbers of MADM-labeled cells with UPD. Nuclei were stained using DAPI. Bars represent mean ± SEM. Data show MADM-7^GT/TG;Hprt^Cre/+ n = 6, MADM-11^GT/TG;Hprt^Cre/+ n = 5, MADM-17^GT/TG;Hprt^Cre/+ n = 6 mice.

Scale bar: 200 mm.