Anne Heikkinen

Background: Collagen XIII is a transmembrane collagen associated with neuromuscular junction development, and in humans its deficiency results in congenital myasthenic syndrome type 19 (CMS19), which leads to breathing difficulties. CMS19 patients usually have restricted lung capacity and one patient developed chronic lung disease. In single-cell RNA sequencing studies, collagen XIII has been identified as a marker for pulmonary lipofibroblasts, which have been implicated in the resolution of pulmonary fibrosis.Methods: We investigated the location and function of collagen XIII in the lung to understand the origin of pulmonary symptoms in human CMS19 patients. Additionally, we performed immunostainings on idiopathic pulmonary fibrosis (IPF) samples (N=5) and both normal and fibrotic mouse lung. To study whether the lack of collagen XIII predisposes to restrictive lung disease, we exposedCol13a1-modified mice to bleomycin-induced pulmonary fibrosis.Results: Apparently normal alveolar septum sections of IPF patients′ lungs stained faintly for collagen XIII, and its expression was pinpointed to the septal fibroblasts in the mouse lung. Lung capacity was increased in mice lacking collagen XIII by over 10%. In IPF samples, collagen XIII was expressed by basal epithelial cells, hyperplastic alveolar epithelial cells and stromal cells in fibrotic areas, but the development of pulmonary fibrosis was unaffected in collagen XIII-deficient mice.Conclusions: Changes in mouse lung function appear to represent a myasthenic manifestation of collagen XIII deficiency. We suggest that respiratory muscle myasthenia is the primary cause of the breathing problems suffered by CMS19 patients in addition to skeletal deformities. Induction of collagen XIII expression in the IPF patients′ lungs warrants further studies to reveal collagen XIII-dependent disease mechanisms.

Visualization of basal cell surface of ANGPT2-GFP HUVECs during cell spreading.

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Supplementary Figure S1: Amino acid sequence of ANGPT2, ANGPT2443 and ANGTPT2DAP. Supplementary Figure S2: Competitive inhibition of ANGPT4-induced TIE2 phosphorylation by ANGPT2 isoforms. Supplementary Figure S3. TIE2 phosphorylation by ANGPT2 isoforms at the retracting cell edges. Supplementary Figure S4. Generation of Angpt2443 allele and the effects of Angpt2443 expression on the retina. Supplementary Figure S5. MMTV-PyMT mammary gland tumor model. Supplementary Figure S6. ANGPT2 at the Weibel-Palade bodies and the subendothelial space. Supplementary Figure S7. B16F10 melanoma lung colonization model. Supplementary Figure S8. E0771 breast cancer cell transplantation model.

Supplementary Materials and Methods

Visualization of basal cell surface of GFP-HUVECs

Visualization of basal cell surface of GFP-HUVECs

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