In this competing renewal of AR036794 (title updated to reflect the evolution in specific aims and scope), we focus on a newly discovered mechanism of regulation of collagen fibril diversity that is important for understanding skeletal tissue differentiation and pathobiology. We have evidence that 3-hydroxproline (3Hyp) residues play a fundamental role in directing the manner of fibrillar collagen supramolecular assembly. The first hint came from our demonstration by mass spectrometry that the single, fully occupied 3Hyp site (P986) near the C-terminus of collagen a1(I) and a1(II) chains fails to be hydroxylated in collagens of the crtap mouse and recessive forms of human osteogenesis imperfecta (O.I.) caused by CRTAP or LEPRE1 mutations. We now have evidence for three classes of 3Hyp site in fibril-forming collagens. For example, a second site in type II collagen is highly hydroxylated in vitreous, meniscus and intervertebral disc but not in hyaline cartilage. The sequence motif of this second site is reproduced at D-periodic intervals in a2(V), with 3Hyp present, and shows similarities to a 3Hyp motif in type IV collagen. Tendon collagen uniquely contains a third type of 3Hyp motif, which we believe is characteristic and functionally important in tendon, ligament and related highly tensile tissues. Under 4 aims, we intend to pursue this concept aggressively since it is central to understanding how different cell types regulate the diversity of heteropolymeric collagen assemblies between different cartilages, bone, tendon and other connective tissues. If correct, it also has concept- changing implications for the field of vertebrate collagen biology. The clinical significance is in providing a molecular basis for understanding processes that cause cartilages and other collagenous tissues of low turnover to degenerate in the adult musculoskeleton in osteoarthritis, disc degeneration and related disorders of collagen framework failure. In addition, a full understanding of the effects of disrupting prolyl 3-hydroxylation in recessive forms of osteogenesis imperfecta we believe will reveal a molecular mechanism for brittle bone common to all forms of O.I. Such findings will also be significant for understanding qualitative changes in bone matrix that add significant risk of osteoporotic fracture in the population as a whole and a potential for novel biomarkers and therapeutic targets.

Public Health Relevance

The goal is to understand molecular mechanisms that govern the diversity in properties of collagen, the protein that forms the structural framework of all major skeletal tissues in the body including bone, cartilages, tendons and ligaments. Specifically, we aim to define the biochemical pathways that equip bone collagen to mineralize, cartilage to last a lifetime as the bearing surfaces of joints and tendons and ligaments to transmit or restrain high mechanical loads without failing. With this knowledge new targets for therapy and prevention of genetic and acquired human disorders of bones and joints are predicted.

National Institute of Health (NIH)
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Research Project (R01)
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Skeletal Biology Development and Disease Study Section (SBDD)
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Tyree, Bernadette
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University of Washington
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Homan, Erica P; Lietman, Caressa; Grafe, Ingo et al. (2014) Differential effects of collagen prolyl 3-hydroxylation on skeletal tissues. PLoS Genet 10:e1004121
Hudson, David M; Werther, Rachel; Weis, MaryAnn et al. (2014) Evolutionary origins of C-terminal (GPP)n 3-hydroxyproline formation in vertebrate tendon collagen. PLoS One 9:e93467
Le Corre, St├ęphanie; Eyre, David; Drummond, Iain A (2014) Modulation of the secretory pathway rescues zebrafish polycystic kidney disease pathology. J Am Soc Nephrol 25:1749-59
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Gruenwald, Katrin; Castagnola, Patrizio; Besio, Roberta et al. (2014) Sc65 is a novel endoplasmic reticulum protein that regulates bone mass homeostasis. J Bone Miner Res 29:666-75
Kalamajski, Sebastian; Liu, Cuiping; Tillgren, Viveka et al. (2014) Increased C-telopeptide cross-linking of tendon type I collagen in fibromodulin-deficient mice. J Biol Chem 289:18873-9
Lietman, Caressa D; Rajagopal, Abbhirami; Homan, Erica P et al. (2014) Connective tissue alterations in Fkbp10-/- mice. Hum Mol Genet 23:4822-31
Jacobsen, Christina M; Barber, Lauren A; Ayturk, Ugur M et al. (2014) Targeting the LRP5 pathway improves bone properties in a mouse model of osteogenesis imperfecta. J Bone Miner Res 29:2297-306
Pingel, Jessica; Lu, Yinhui; Starborg, Tobias et al. (2014) 3-D ultrastructure and collagen composition of healthy and overloaded human tendon: evidence of tenocyte and matrix buckling. J Anat 224:548-55
Hudson, David M; Eyre, David R (2013) Collagen prolyl 3-hydroxylation: a major role for a minor post-translational modification? Connect Tissue Res 54:245-51

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