Abstract
Fstl1, a secreted protein of the BMP antagonist class, has been implicated in the regulation of lung development and alveolar maturation. Here we generated a Fstl1-lacZ reporter mouse line as well as a Fstl1 knockout allele. We localized Fstl1 transcript in lung smooth muscle cells and identified Fstl1 as essential regulator of lung smooth muscle formation. Deletion of Fstl1 in mice led to postnatal death as a result of respiratory failure due to multiple defects in lung development. Analysis of the mutant phenotype showed impaired airway smooth muscle (SM) manifested as smaller SM line in trachea and discontinued SM surrounding bronchi, which were associated with decreased transcriptional factors myocardin/serum response factor (SRF) and impaired differentiation of SM cells. Fstl1 knockout mice also displayed abnormal vasculature SM manifested as hyperplasia SM in pulmonary artery. This study indicates a pivotal role for Fstl1 in early stage of lung airway smooth muscle development.
Highlights
Our lung is optimized for oxygen supply of organism
In addition to the reported defects in lung development [17], we showed that Follistain-like 1 (Fstl1) deficiency leads to a severe airway smooth muscle (SM) defect in Fstl1 null embryos
The wide distribution of smooth muscle in the body is matched by patterns of development that differ in different organs [35,36]
Summary
Our lung is optimized for oxygen supply of organism. The lung develops two highly branched and tree-like systems, the airways and the vasculature, to conduct air and blood supply. Both systems contain a intertwined component of smooth muscle (SM)—airway SM (ASM) controls the diameter of airway tubes, vascular SM (VSM), blood vessels. SM in the lung is thought to derive from the multipotent progenitors in developing lung mesoderm. The lung is a highly complex organ that develops from the ventral foregut via reciprocal interactions between foregut endoderm and surrounding mesoderm [2].
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