Journal: bioRxiv

Article Title: Abnormal ventricular wall patterning precedes and drives MYBPC3 hypertrophic cardiomyopathy

doi: 10.64898/2026.03.25.714341

Figure Lengend Snippet: ( A ) Gene set enrichment analysis (GSEA) analysis of ventricular RNA-seq datasets at E15.5, P1, P7 and adulthood comparing homozygous Mybpc3 p.Pro109Serfs*12 and Mybpc3 +/+ ventricular transcriptome against Hallmark and Reactome gene sets. The first 4 columns show comparisons between mutant and control samples at E15.5, P1, P7 and adult stages. Most significant processes seem to occur at P1 and P7. The mutation causes similar direction changes at P1 and P7 on cell cycle terms (increased in the mutants), but opposite changes in metabolism, NMD and metabolism/proteostasis terms (oxphos, translation) which are decreased at P1 mutants compared to control but increased in the mutants at P7. The last two columns represent the longitudinal comparisons between P1 and P7 in both control and mutant samples. The WT (control) P7-P1 column indicates the developmental change in the transition from P1 to P7 (red, up in P7). NMD and proteostasis (translation etc.) terms are decreased in the controls at P7, but in the mutants, these same processes are increased. Cell cycle terms maintain the same enrichment direction in the mutants but seem to be even more exacerbated at P7. ( B ) Left, bubble plot of differentially expressed genes at P7 in homozygous Mybpc3 p.Pro109Serfs*12 and Mybpc3+/+ hearts highlights upregulation of several genes and downregulation of Prdm16 within a hypertrophy-associated gene signature. Right, ISH for Nppa and Ankrd1 in control and homozygous Mybpc3 p.Pro109Serfs*12 P7 hearts. 250 μm. lv, left ventricle; rv, right ventricle. (( C ) Bar plot summarizing the normalized enrichment score (NES) and –log(padj) values for Mybpc3 P109Sfs*12 mutant vs. WT comparisons at E15.5, P1, P7, and Adult. Dotted line: p-value = 0.25. Dashed line: p -value = 0.01. D ) Bar plot summarizing the NES and –log(padj) values for P7 vs. P1 comparisons in control (WT) and Mybpc3 p.Pro109Serfs*12 (P109S) mutant. Dotted line: p -value = 0.25. Dashed line: p-value = 0.01. The NES represents the enrichment score after normalization, with higher scores (red) indicating positive enrichment and lower scores (blue) indicating negative enrichment. The adjusted p-value (padj) corresponds to p-values corrected for multiple testing using the Benjamini–Hochberg procedure, which controls the false discovery rate. ( E-F’’ ) IF for Prdm16 (green), Endomucin (red), and DAPI (blue) in in ventricular sections of E18.5 wild type ( E-E ’’) and homozygous Prdm16 Δ8 mutant hearts. Arrowheads in E’’ point to nuclear Prdm16 expression in trabecular cardiomyocytes. Scale bar 250 μm. Magnified views are shown in ( ’ ). Scale bar 50 μm. ( G-J’ ) IF for Prdm16 in ventricular sections at E16.5 ( G-H’ ) and P7 ( I-J’ ) reveals expanded Prdm16 signal in E16.5 Mybpc3 p.Pro109Serfs*12 mutant trabeculae (arrowheads, H’ , inset), and reduced Prdm16 expression at P7 in subendocardial myocardium of mutants ( J’ ). Scale bar, 250 μm. ( K ) Quantification of the ratio of trabecular (TM) to compact myocardium (CM) Prdm16 expression in E16.5 hearts (n=3, ≥3 sections per heart), and the ratio of inner myocardium (IM) to outter myocardium (OM) in P7 hearts. (n=4 control and n=3 Mybpc3 p.Pro109Serfs*12, ≥3 sections per heart). Data are represented as means ± SD. Statistical significance was determined by unpaired Student’s t-test (* p -value < 0.05).

Article Snippet: A full-length mouse Prdm16 cDNA cloned into pcDNA3.1 was obtained from addgene (#15503).

Techniques: RNA Sequencing, Mutagenesis, Control, Expressing

Journal: bioRxiv

Article Title: Abnormal ventricular wall patterning precedes and drives MYBPC3 hypertrophic cardiomyopathy

doi: 10.64898/2026.03.25.714341

Figure Lengend Snippet: ( A ) Whole-mount views of P7 control, Mybpc3 +/+ ;R26 Prdm16/+ ;Myh6 MerCreMer/+ , homozygous Mybpc3 p.Pro109Serfs*12 and Mybpc3 p.Pro109Serfs*12;R26 Prdm16/+ ;Myh6 MerCreMer/+ hearts. Right, Cre-mediated transgenic expression was induced upon Tamoxifen administration at P1. Scale bar, 250 μm. ( B ) Quantification of Heart weight/Body weight ratio (n=25 Mybpc3+/+, n=16 Mybpc3+/+;R26 Prdm16/+ ;Myh6 MerCreMer/+ , n=13 homozygous Mybpc3 p.Pro109Serfs*12 and n=14 Mybpc3 p.Pro109Serfs*12;R26 Prdm16/+ ;Myh6 MerCreMer/+ ), Septum thickness (μm), Left Ventricular Free Wall (LVFW) thickness (μm)(n=4 Mybpc3+/+, n=3 Mybpc3+/+;R26 Prdm16/+ ;Myh6 MerCreMer/+ , n=3 homozygous Mybpc3 p.Pro109Serfs*12 and n=5 Mybpc3 p.Pro109Serfs*12;R26 Prdm16/+ ;Myh6 MerCreMer ≥3 sections per heart), compact myocardium leght (CM) and trabecular myocardium leght (TM) (μm) (n=3 hearts per genotype, ≥3 sections per heart). Data are represented as means ± SD. Statistical significance was determined by unpaired Student’s t-test (ns, not significant; * p -value < 0.05; *** p -value < 0.001; **** p -value < 0.0001). ( C ) H&E images of representative hearts of the different genotypes. Scale bar, 250 μm. ( D ) ISH for Nppa in the different genotypes. Scale bar, 250 μm. ( E ) WGA (green) and DAPI (blue) fluorescence staining of P7 control, Mybpc3 +/+ ;R26 Prdm16/+ ;Myh6 MerCreMer/+ , Mybpc3 p.Pro109Serfs*12 and Mybpc3 p.Pro109Serfs*12;R26 Prdm16/+ ;Myh6 MerCreMer/+ heart sections. Scale bar, 10 μm. ( F ) Cardiomyocyte cross sectional area quantification of P7 hearts (n=3, ≥6 sections per heart). Data are represented as means ± SD. Statistical significance was determined by unpaired Student’s t-test (ns, not significant; * p -value < 0.05; ** p -value < 0.005). ( G ) Ventricular wall mispatterning drives MYBPC3-associated HCM that is attenuated by Prdm16 expression. Top, wild type: During late gestation (E18.5), compact (CM, Hey2⁺) and trabecular cardiomyocytes (TM, Hey2 - ) are spatially segregated and exhibit balanced proliferation, enabling ventricular compaction progression at birth (P1) and subsequent maturation. Postnatally, Prdm16 promotes cardiomyocyte maturation and restrains hypertrophy, resulting in normal ventricular architecture by P7. Middle, Mybpc3 P109Sfs*12 mutant. Mybpc3 loss disrupts ventricular wall patterning, leading to loss of compact–trabecular segregation, increased trabecular proliferation, and impaired compaction. This is accompanied by peak transcriptional dysregulation from P1 to P7. Abnormally reduced Prdm16 expression impairs maturation and contributes to pathological cardiomyocyte hypertrophy. Bottom, Mybpc3 P109Sfs*12; R26 Prdm16/+ ; Myh6 MerCreMer model. Tamoxifen-mediated Prdm16 expression at P1 attenuates hypertrophy despite persistent early patterning defects, promoting cardiomyocyte maturation and partially normalizing ventricular structure.

Article Snippet: A full-length mouse Prdm16 cDNA cloned into pcDNA3.1 was obtained from addgene (#15503).

Techniques: Control, Transgenic Assay, Expressing, Fluorescence, Staining, Mutagenesis