Fig. 1: Altered nuclear structure and differentiation following Matr3 loss.

a MATR3 expression was assessed in parental and Matr3 KO MEL cells by Western blot and immunohistochemistry. β-actin was used as a Western blot control. Scale bar, 5 μm. b May-Grunwald Giemsa staining was performed on uninduced and 5-day differentiated cells. During MEL cell differentiation, cell size is normally reduced (p = 0.002, by t test); the effect is more pronounced in Matr3 KO cells (p = 0.0004, by two-sided t test). The number of examined cells was n = 15, n = 23, n = 34, and n = 28, respectively. c β-globin mRNA expression was greater in Matr3 KO than normal MEL cells, indicative of enhanced cell differentiation (n = 3). Three independent Matr3 KO clones by CRISPR/Cas9 were examined. d mRNA encoding Slc4a1, an erythroid-specific gene, was also increased in Matr3 KO cells; expression of full-length Matr3 cDNA (Fig. S1c) lowered Slc4a1 expression to wild-type levels (n = 3). e Relative RNA levels based on z-score analysis demonstrated that expression of late erythroid genes was significantly higher in Matr3 KO than wild-type cells upon differentiation. P-values obtained from the two-sided t test between two groups at each day were 1.94e-01, 1.37e-02, and 3.65e-07, respectively. f Heterochromatin was visualized by immunohistochemistry using anti-HP1α antibody and super-resolution microscopy. Scale bar, 1 μm. g The number of distinct puncta per cell (p < 5.9e-11; n = 35, n = 32, respectively) and percentage of cells with at least one large puncta were quantified (5.7% and 59.4%, respectively). A large puncta was defined as having the longest diameter that is more than twice the average. Data were the result of 2–3 independent experiments and error bars represent mean ± 1 s.d. Source data are provided as a Source Data file.