Fig 2: Summary of physiopathological functions of YY2. YY2 is involved in several physiopathological events. Low level of YY2 is crucial for maintaining the pluripotency of embryonic stem cells, and overexpression of YY2 drives cells toward differentiation. YY2 is also involved in the development of organs such as heart and neurons, as well as immune response. Furthermore, it acts as a tumour suppressor gene by suppressing tumour cells proliferation, tumour metabolism, and tumour metastasis

Fig 3: Generation of inducible YY2 transgenic mice. (A) A schematic diagram showing the inducible YY2 construct that contains HA-tagged human YY2 (HA-hYY2). (B) Two independent transgenic mouse lines, #1758 and #1770, were identified. Western blot analysis was performed with heart lysates as described in Figure 1. Upper panel: immunoblotting with HA-HRP; lower panel: immunoblotting with GAPDH-HRP (loading control). (C) Western blot analysis shows that the cardiac expression levels of the HA-YY2 transgene and endogenous YY2 in mouse line #1758 and line #1770 (n = 3 per group). *p < 0.05 vs. cont. (D) Partial embryonic death was observed in mouse embryos overexpressing YY2. Timed mating was performed between pCAG-YY2-Tg+and MHC-Cre+mice; the P1 frequency of double Tg (dTg; pCAG-YY2-Tg+/MHC-Cre+) mice from either of the pCAG-YY2 Tg mouse lines was significantly lower than the expected Mendelian rate. ** p < 0.01 vs. WT.

Fig 4: Multi-stages regulation of YY2 expression. A, Epigenetic regulation of YY2 gene. Human YY2 gene transcription is inhibited by DNA methylation. B, Post-transcriptional regulation of YY2 mRNA. Posttranscriptional regulation of YY2 expression occurs by two steps: (i) PTBP1 suppresses the splicing of the YY2 5’-UTR, leading to the generation of YY2 splicing variant with higher intron retention; and (ii) 4E-BP1/2 suppresses the translation of the YY2 mRNA with the suppression effect depends on the intron retention degree. C, Post-translational modification of YY2 protein. YY2 protein is methylated by SET7/9 and demethylated by LSD1. Methylation of YY2 increases its binding affinity to the promoters of its target genes

Fig 5: Adult cardiomyopathy resulting from the targeted activation of YY2 in mice.(A) The mortality rate in each genotype group within 1 year after birth is shown. The mortality rate was determined by calculating the number of deceased mice divided by the total number of mice analyzed in each group. For mouse line #1758 (n = 70), the following groups were analyzed: wild-type (WT) (n = 12), pCAG-YY2-Tg+(n = 20), MHC-cre+(n = 29), and dTg (n = 9). For mouse line #1770 (n = 87), the following groups were analyzed: WT (n = 31), pCAG-YY2-Tg+, (n = 23), MHC-cre+(n = 19), and dTg (n = 14). (B) Gross images of age-matched control and double transgenic (dTg) hearts from living mice euthanized at P120 and of a dTg heart from a mouse dead at P85. (C) Hematoxylin and eosin staining showed increased spaces between cardiomyocytes in dTg mouse hearts that were not observed in control hearts. The lower two panels represent magnified images of the respective boxed areas in the upper panels. Scale bar, 10 µm. Magnifications (10× and 40×) are indicated on the left side. (D) Masson’s trichrome staining showing increased fibrosis in dTg mouse hearts compared with control hearts. Heart sections were prepared from the mouse hearts shown in (C). Two mouse hearts from each group are shown. Magnification, 40×; scale bar, 10 µm.