Fig. 1: MommeD43 is a Smchd1 mutant with increased transgene array silencing activity.

a Diagram of ENU screen experiment (left) and results (right). Erythrocytes from mice with an 11-unit GFP transgene repeat array carrying heterozygous or homozygous MommeD43 mutations and wild-type littermate controls were analyzed by FACS to measure GFP transgene expression levels. b Schematic representation of murine SMCHD1 (resolved ATPase and hinge domains linked by flexible still unresolved domain) and the location of the MommeD43 mutation in its structure (orange). c Western blot of SMCHD1 in Smchd1^{MommeD43/MommeD43}, Smchd1^MommeD43/+, and Smchd1^+/+ cells showing no noticeable change in SMCHD1 levels (representative image of two independent experiments). d ChIP-seq genome browser tracks of the Hoxb cluster locus showing GFP ChIP in primary NSCs with endogenous SMCHD1-GFP fusion protein, compared to the whole cell extract (WCE) input control. This region is heavily marked by SMCHD1 and MommeD43 does not alter localization. On top are indicated a few genes in the locus for reference. e Scatter plot of log2-transformed normalized GFP ChIP-seq counts in Smchd1^GFP/GFP and Smchd1^{MommeD4-GFP3/MommeD43-GFP} NSCs around (±5 kb) previously published peaks¹⁴. The Pearson coefficient indicates very high positive correlation showing no noticeable changes in SMCHD1 DNA binding sites, two-tailed p value. f ATPase assay using recombinant purified wild-type murine SMCHD1 extended ATPase domain (grayscale) compared with the MommeD43 mutant equivalent (blue). Mean ± SD, N = 3 per concentration per protein. MommeD43 abbreviated to MD43.