Extended Data Figure 5: Histopathology mitral valves.

Human posterior leaflets of control, Barlow’s with MVP, and DCHS1 p.R2330C were isolated, fixed and stained with Movat’s pentachrome. Leaflet thickening, elongation and myxomatous degeneration is observed in the Barlow’s and DCHS1 p.R2330C leaflets compared to controls. Expansion of the proteoglycan layer (blue) and disruption of the normal stratification of matrix boundaries is observed in the Barlow’s and DCHS1 p.R2330C leaflets. Blue, proteoglycan; yellow, collagen; black, elastin; red, fibrin or cardiac muscle. Scale bars, 0.5 cm.