TY - JOUR
T1 - Analysis of dermal elastic fibers in the absence of fibulin-5 reveals potential roles for fibulin-5 in elastic fiber assembly
AU - Choi, Jiwon
AU - Bergdahl, Andreas
AU - Zheng, Qian
AU - Starcher, Barry
AU - Yanagisawa, Hiromi
AU - Davis, Elaine C.
N1 - Funding Information:
The authors thank Dr. Robert P. Mecham (Washington University School of Medicine, St. Louis, MO) for critical review of the manuscript and for the mouse tropoelastin antibody, and Dr. Tiansan Li (Harvard University Medical School, Boston, MA) for antibodies to LOXL-1. We also thank Jeannie Mui, Lee-Anne Monaghan and Kelly Sears for EM support, Rujuan Huo, Ailian Li and Shaozhen Fang for histology preparation, and Rachel Bissonnette and Shelby Chapman for animal care. This work was supported by the National Institutes of Health grant HL71157 (HY, with consortium funds to ECD), Canadian Institutes of Health grants MOP57663 and MOP86713 (ECD), Natural Sciences and Engineering Research Council of Canada grant RGPIN 35710-08 (ECD) and a Swedish Heart–Lung Foundation Fellowship (AB). ECD is a Canada Research Chair.
PY - 2009/5
Y1 - 2009/5
N2 - Fibulin-5 is a 66 kDa modular, extracellular matrix protein that localizes to elastic fibers. Although in vitro protein-protein binding studies have shown that fibulin-5 binds many proteins involved in elastic fiber formation, the specific role of fibulin-5 in elastogenesis remains unclear. To provide a more detailed analysis of elastic fiber assembly in the absence of fibulin-5, the dermis of wild-type and fibulin-5 gene knockout (Fbln5-/-) mice was examined with electron microscopy (EM). Although light microscopy showed apparently normal elastic fibers near the hair follicles and the absence of elastic fibers in the intervening dermis of the Fbln5-/- mouse, EM revealed the presence of aberrantly assembled elastic fibers in both locales. Instead of the elastin being incorporated into the microfibrillar scaffold, the elastin appeared as globules juxtaposed to the microfibrils. Desmosine analysis showed significantly lower levels of mature cross-linked elastin in the Fbln5-/- dermis, however, gene expression levels for tropoelastin and fibrillin-1, the major elastic fiber components, were unaffected. Based on these results, the nature of tropoelastin cross-linking was investigated using domain specific antibodies to lysyl oxidase like-1 (LOXL-1). Immunolocalization with an antibody to the N-terminal pro-peptide, which is cleaved to generate the active enzyme, revealed abundant staining in the Fbln5-/- dermis and no staining in the wild-type dermis. Overall, these results suggest two previously unrecognized functions for fibulin-5 in elastogenesis; first, to limit the extent of aggregation of tropoelastin monomers and/or coacervates and aid in the incorporation of elastin into the microfibril bundles, and second, to potentially assist in the activation of LOXL-1.
AB - Fibulin-5 is a 66 kDa modular, extracellular matrix protein that localizes to elastic fibers. Although in vitro protein-protein binding studies have shown that fibulin-5 binds many proteins involved in elastic fiber formation, the specific role of fibulin-5 in elastogenesis remains unclear. To provide a more detailed analysis of elastic fiber assembly in the absence of fibulin-5, the dermis of wild-type and fibulin-5 gene knockout (Fbln5-/-) mice was examined with electron microscopy (EM). Although light microscopy showed apparently normal elastic fibers near the hair follicles and the absence of elastic fibers in the intervening dermis of the Fbln5-/- mouse, EM revealed the presence of aberrantly assembled elastic fibers in both locales. Instead of the elastin being incorporated into the microfibrillar scaffold, the elastin appeared as globules juxtaposed to the microfibrils. Desmosine analysis showed significantly lower levels of mature cross-linked elastin in the Fbln5-/- dermis, however, gene expression levels for tropoelastin and fibrillin-1, the major elastic fiber components, were unaffected. Based on these results, the nature of tropoelastin cross-linking was investigated using domain specific antibodies to lysyl oxidase like-1 (LOXL-1). Immunolocalization with an antibody to the N-terminal pro-peptide, which is cleaved to generate the active enzyme, revealed abundant staining in the Fbln5-/- dermis and no staining in the wild-type dermis. Overall, these results suggest two previously unrecognized functions for fibulin-5 in elastogenesis; first, to limit the extent of aggregation of tropoelastin monomers and/or coacervates and aid in the incorporation of elastin into the microfibril bundles, and second, to potentially assist in the activation of LOXL-1.
KW - Elastic fibers
KW - Elastin
KW - Fibulin-5
KW - Lysyl oxidase like-1
KW - Skin
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U2 - 10.1016/j.matbio.2009.03.004
DO - 10.1016/j.matbio.2009.03.004
M3 - Article
C2 - 19321153
AN - SCOPUS:67349102260
SN - 0945-053X
VL - 28
SP - 211
EP - 220
JO - Matrix Biology
JF - Matrix Biology
IS - 4
ER -