Collagen XIV is important for growth and structural integrity of the myocardium.

Collagen XIV is a fibril-associated collagen with an interrupted triple helix (FACIT). Previous studies have shown that this collagen type regulates early stages of fibrillogenesis in connective tissues of high mechanical demand. Mice null for Collagen XIV are viable, however formation of the interstitial collagen network is defective in tendons and skin leading to reduced biomechanical function.

Mmp15 is a direct target of Snai1 during endothelial to mesenchymal transformation and endocardial cushion development.

Cardiac valves originate from endocardial cushions (EC) formed by endothelial-to-mesenchymal transformation (EMT) during embryogenesis. The zinc-finger transcription factor Snai1 has previously been reported to be important for EMT during organogenesis, yet its role in early valve development has not been directly examined. In this study we show that Snai1 is highly expressed in endothelial, and newly transformed mesenchyme cells during EC development.

Reduced sox9 function promotes heart valve calcification phenotypes in vivo.

Rationale: Calcification of heart valve structures is the most common form of valvular disease and is characterized by the appearance of bone-like phenotypes within affected structures. Despite the clinical significance, the underlying etiology of disease onset and progression is largely unknown and valve replacement remains the most effective treatment. The SRY-related transcription factor Sox9 is expressed in developing and mature heart valves, and its function is required for expression of cartilage-associated proteins, similar to its role in chondrogenesis.

Scleraxis is required for cell lineage differentiation and extracellular matrix remodeling during murine heart valve formation in vivo.

Heart valve structures, derived from mesenchyme precursor cells, are composed of differentiated cell types and extracellular matrix arranged to facilitate valve function. Scleraxis (scx) is a transcription factor required for tendon cell differentiation and matrix organization. This study identified high levels of scx expression in remodeling heart valve structures at embryonic day 15.