Proteoglycan 4

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AliasesPRG4, CACP, HAPO, JCAP, MSF, SZP, bG174L6.2, proteoglycan 4
External IDsOMIM: 604283 HomoloGene: 130465 GeneCards: PRG4
RefSeq (mRNA)



RefSeq (protein)



Location (UCSC)Chr 1: 186.3 – 186.31 Mbn/a
PubMed search[2]n/a
View/Edit Human

Proteoglycan 4 or lubricin is a proteoglycan that in humans is encoded by the PRG4 gene.[3][4][5] It acts as a joint/boundary lubricant.[5]


Lubricin is present in synovial fluid and on the surface (superficial layer) of articular cartilage and therefore plays an important role in joint lubrication and synovial homeostasis. When first isolated, cartilage lubricin was called "superficial zone protein" (SZP). [6][7] Due to the discovery that the 32-kDa amino terminal fragment of lubricin could stimulate in-vitro megakaryocyte growth, the gene responsible for the expression of lubricin was initially called "megakaryocyte-stimulating factor" (MSF).[8] However, Lubricin, MSF, and SZP are now collectively known as Proteoglycan 4 (hence PRG4 for the gene nomenclature). The evidence that lubricin is actually a proteoglycan is not solid.[9] The expression of lubricin has also been detected and the protein localized in tendon,[10] meniscus,[11] lung, liver, heart, bone,[12] ligament, muscle, and skin.[13] It is present in human plasma, where it binds to neutrophils via L-selectin.[14]

The adhesion of Lubricin's N- (blue) and C- (red) termini to two opposing cartilage surfaces undergoing shear stress (𝜏) and normal forces (𝐹_𝑁). Steric repulsion between mucin domains and hydration forces of the trapped solvent layer are thought to give lubricin its characteristic lubrication ability. Two glycoprotein monomers are linked by a disulfide bond in yellow to form a dimer.

Lubricin shares many properties with other members of the mucin family and similarly plays important roles in protecting cartilage surface from protein deposition and cell adhesion, in inhibiting synovial cell overgrowth, and in preventing cartilage-cartilage adhesion.[15][16]

Early work on lubricin showed that it was able to lubricate non cartilaginous surfaces as effectively as whole synovial fluid, confirming its important biological lubrication role.[17] Understanding lubricin is key to understanding joint mechanics and friction-based diseases. [18]


The protein encoded by this gene is a approximately 345 kDa[19] specifically synthesized by chondrocytes located at the surface of articular cartilage, and also by synovial lining cells. The cDNA encodes a protein of 1,404 amino acids (human A isoform) with a somatomedin B homology domain, heparin-binding domains, multiple mucin-like repeats, a hemopexin domain, and an aggregation domain. There are 3 consensus sequences for N-glycosylation[5] and more than 168 sites for O-linked glycosylation.[20]

Lubricin is a large glycoprotein that consists of approximately equal proportions of protein and oligosaccharides. The oligosaccharides are O-linked both with and without sialic acid.[14][20] Electron microscope measurements show that the lubricin molecule is a partially extended flexible rod and, in solution, occupies a smaller spatial domain than would be expected from structural predictions.[21] The large glycosylated region (i. e mucin domain) of lubricin makes it a water-soluble synovial fluid protein. In synovial fluid it interacts with Galectin-3 that improves its lubricating property.[22][23] Lubricin's unglycosylated regions can interact with cartilage proteins.[24][25] This characteristic may aid in the molecule's boundary lubricating ability.

Lubricin is a close analog to vitronectin, as both of these proteins contain a somatomedin B-like (SMB) domain and a hemopexin-like chain. These domains play a unique role in cell-cell and cell-extracellular matrix interactions. [26] However, unlike vitronectin, lubricin carries a central mucin-like domain with a large number of repeating KEPAPTT motifs.[27]

In total, lubricin is approximately 200nm +/- 50 nm in length and has a diameter of a few nanometers. The glycoprotein consists of >5% serine and >20% threonine residues, which give rise to a large number of O-glycosylations. These are thought to contain short polar (Galβ1-3GalNAcα1-Ser/Thr) and negatively charged (NeuAcα2-3Galβ1-3GalNAcα1α1-Ser/Thr) sugar groups. About two thirds of these sugar groups are capped with sialic acid, and the end domains of the glycoprotein are thought to be globular, due to the nature of their protein-like domains. The N-terminus of lubricin is associated with its SMB-like domains, [28] whereas the C-terminus is associated with the hemopexin-like domain.[29] Due to the protein's overall slight negative charge and the fact that the center of the protein carries negatively charged sugar groups, the two end domains are thought to carry much of the protein's positive charge. [16][21][30][31]

Structure of lubricin
The basic "bottle brush" structure of lubricin, including its mucin, hemopexin-like and somatomedin B (SMB)-like domains. Figure created with[32]

Lubricin's complex protein structure is termed "bottle brush," which refers to the large number of densely packed glycosylations on lubricin's backbone. Overall, lubricin's structure is similar to other mucin proteins and bottle brush polymers. This structure is key to its lubricating ability, which is ascribed to interchain repulsion. This leads to trapping of large quantities of solvent and the stabilization of a fluid-like cushioning layer, which enables bottle brush polymers to lower the friction between joints when external pressure is applied.[33][34]

Furthermore, lubricin's N-terminus is thought to create disulfide bonds between two lubricin monomers. The glycoprotein thus exists as both a monomer and a dimer. [28] The adsorption of lubricin to cartilage surfaces occurs through interactions on its N- and C- terminus, where its bottle brush structure plays a role in both coating and repelling similarly coated cartilage surfaces due to steric repulsion. [35][36] [37] Lubricin's high degree of hydration is also thought to be involved in repulsion forces generated by lubricin between opposing cartilage surfaces. [38]

Shear studies of lubricin adsorbed between various hydrophilic and hydrophobic surfaces have confirmed the importance of the glycoprotein in boundary lubrication and wear protection in articular joints. [16] Lubricin's bottle brush structure is common among a number of human lubricating glycoproteins, and a number of studies have been conducted to mimic this. [39] Researchers have successfully designed low-friction polymers imitating lubricin's bottle-brush-like structure, further supporting the notion that it is lubricin's architecture which plays an important role in reducing friction. [40] Similarly, another study on zwitterionic polymer brushes, which intended to mimic the structure of bottle-brush polymers present in cartilage, found that the brushes produced super low fouling surfaces and super low friction surfaces.[41]

Clinical significance

Lubricin, as MSF, was detected in the urine of patients undergoing bone marrow transplantation during a period of acute thrombocytopenia.[42] Depletion of lubricin function has also been associated with camptodactyly-arthropathy-coxa vara-pericarditis syndrome (CACP), an arthritis-like autosomal recessive disorder.[3]

The locus for autosomal recessive camptodactyly-arthropathy-coxa vara-pericarditis syndrome maps to chromosome 1q25-q31 where the PRG4 gene is located. Cell overgrowth may be primary to the pathogenesis of this protein.[5]

Lubricin’s role in improving tendon gliding has also been studied. While adding lubricin alone fails to affect the tendon gliding resistance, the addition of cd-gelatin plus lubricin significantly lowered the gliding resistance of the tendons. This research can aid in improving the gliding ability of tendon grafts done clinically.[43] Extracorporeal shockwave therapy application has been shown to induce an increased lubricin expression in tendons and septa of rat hindlimbs, which might suggest a beneficial lubricating effect for joints and tissues prone to wear and tear degradation.[44]

Furthermore, the synovial fluid of patients with rheumatoid arthritis and osteoarthritis has been shown to exhibit reduced levels of lubricin when compared to healthy patients. [45] <span Researchers are currently exploring potential applications of lubricin for treating these and other related diseases.[46] Thus far, adding supplement lubricin has been shown to restore the lubricating ability of synovial fluid from patients with established osteoarthritis.[47] Lubricin has been shown to also play a role in anti-inflammation for osteoarthritis patients. Additionally, reduced lubricin levels have also been observed in the synovial fluid of patients with ACL injuries, and decreased lubricating ability has been found in patients with traumatic synovitis.[48][49]

Lubricin, which is naturally present in human cornea-eyelid interface, has also been shown to play a key role in reducing friction between the cornea and conjunctiva of the eye. [50] Clinical trials of the use of recombinant lubricin eye drops for treatment of dry eye disease have thus far been relatively successful. [51]


  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000116690 - Ensembl, May 2017
  2. ^ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  3. ^ a b Marcelino J, Carpten JD, Suwairi WM, Gutierrez OM, Schwartz S, Robbins C, et al. (November 1999). "CACP, encoding a secreted proteoglycan, is mutated in camptodactyly-arthropathy-coxa vara-pericarditis syndrome". Nature Genetics. 23 (3): 319–22. doi:10.1038/15496. PMID 10545950. S2CID 32556762.
  4. ^ Flannery CR, Hughes CE, Schumacher BL, Tudor D, Aydelotte MB, Kuettner KE, Caterson B (January 1999). "Articular cartilage superficial zone protein (SZP) is homologous to megakaryocyte stimulating factor precursor and Is a multifunctional proteoglycan with potential growth-promoting, cytoprotective, and lubricating properties in cartilage metabolism". Biochemical and Biophysical Research Communications. 254 (3): 535–41. doi:10.1006/bbrc.1998.0104. PMID 9920774.
  5. ^ a b c d "Entrez Gene: PRG4 proteoglycan 4".
  6. ^ Schumacher BL, Block JA, Schmid TM, Aydelotte MB, Kuettner KE (May 1994). "A novel proteoglycan synthesized and secreted by chondrocytes of the superficial zone of articular cartilage". Archives of Biochemistry and Biophysics. 311 (1): 144–52. doi:10.1006/abbi.1994.1219. PMID 8185311.
  7. ^ Jay GD, Britt DE, Cha CJ (March 2000). "Lubricin is a product of megakaryocyte stimulating factor gene expression by human synovial fibroblasts". The Journal of Rheumatology. 27 (3): 594–600. PMID 10743795.
  8. ^ Preissner KT (1993). Biology of vitronectins and their receptors : proceedings of the First International Vitronectin Workshop, Rauischholzhausen Castle, Marburg, Germany, 25-28 August, 1993. Elsevier. pp. 45–52. ISBN 0-444-81680-1. OCLC 246493326.{{cite book}}: CS1 maint: date and year (link)
  9. ^ Lord MS, Estrella RP, Chuang CY, Youssef P, Karlsson NG, Flannery CR, Whitelock JM (2012). "Not all lubricin isoforms are substituted with a glycosaminoglycan chain". Connective Tissue Research. 53 (2): 132–41. doi:10.3109/03008207.2011.614364. PMID 21966936. S2CID 7344867.
  10. ^ Rees SG, Davies JR, Tudor D, Flannery CR, Hughes CE, Dent CM, Caterson B (November 2002). "Immunolocalisation and expression of proteoglycan 4 (cartilage superficial zone proteoglycan) in tendon". Matrix Biology. 21 (7): 593–602. doi:10.1016/S0945-053X(02)00056-2. PMID 12475643.
  11. ^ Schumacher BL, Schmidt TA, Voegtline MS, Chen AC, Sah RL (May 2005). "Proteoglycan 4 (PRG4) synthesis and immunolocalization in bovine meniscus". Journal of Orthopaedic Research. 23 (3): 562–8. doi:10.1016/j.orthres.2004.11.011. PMID 15885476. S2CID 1011398..
  12. ^ Ikegawa S, Sano M, Koshizuka Y, Nakamura Y (2000). "Isolation, characterization and mapping of the mouse and human PRG4 (proteoglycan 4) genes". Cytogenetics and Cell Genetics. 90 (3–4): 291–7. doi:10.1159/000056791. PMID 11124536. S2CID 39376563.
  13. ^ Sun Y, Berger EJ, Zhao C, An KN, Amadio PC, Jay G (2006). "Mapping lubricin in canine musculoskeletal tissues". Connective Tissue Research. 47 (4): 215–21. doi:10.1080/03008200600846754. PMID 16987753. S2CID 46582604..
  14. ^ a b Jin C, Ekwall AK, Bylund J, Björkman L, Estrella RP, Whitelock JM, et al. (October 2012). "Human synovial lubricin expresses sialyl Lewis x determinant and has L-selectin ligand activity". The Journal of Biological Chemistry. 287 (43): 35922–33. doi:10.1074/jbc.M112.363119. PMC 3476260. PMID 22930755.
  15. ^ Rhee DK, Marcelino J, Baker M, Gong Y, Smits P, Lefebvre V, et al. (March 2005). "The secreted glycoprotein lubricin protects cartilage surfaces and inhibits synovial cell overgrowth". The Journal of Clinical Investigation. 115 (3): 622–31. doi:10.1172/JCI22263. PMC 548698. PMID 15719068.
  16. ^ a b c Zappone B, Ruths M, Greene GW, Jay GD, Israelachvili JN (March 2007). "Adsorption, lubrication, and wear of lubricin on model surfaces: polymer brush-like behavior of a glycoprotein". Biophysical Journal. 92 (5): 1693–708. Bibcode:2007BpJ....92.1693Z. doi:10.1529/biophysj.106.088799. PMC 1796837. PMID 17142292.
  17. ^ Jay GD, Lane BP, Sokoloff L (January 1992). "Characterization of a bovine synovial fluid lubricating factor. III. The interaction with hyaluronic acid". Connective Tissue Research. 28 (4): 245–55. doi:10.3109/03008209209016818. PMID 1304440.
  18. ^ Jay GD, Waller KA (October 2014). "The biology of lubricin: near frictionless joint motion". Matrix Biology. 39: 17–24. doi:10.1016/j.matbio.2014.08.008. PMID 25172828.
  19. ^ Su JL, Schumacher BL, Lindley KM, Soloveychik V, Burkhart W, Triantafillou JA, et al. (June 2001). "Detection of superficial zone protein in human and animal body fluids by cross-species monoclonal antibodies specific to superficial zone protein". Hybridoma. 20 (3): 149–57. doi:10.1089/027245701750293475. PMID 11461663.
  20. ^ a b Ali L, Flowers SA, Jin C, Bennet EP, Ekwall AK, Karlsson NG (December 2014). "The O-glycomap of lubricin, a novel mucin responsible for joint lubrication, identified by site-specific glycopeptide analysis". Molecular & Cellular Proteomics. 13 (12): 3396–409. doi:10.1074/mcp.M114.040865. PMC 4256492. PMID 25187573.
  21. ^ a b Swann DA, Slayter HS, Silver FH (June 1981). "The molecular structure of lubricating glycoprotein-I, the boundary lubricant for articular cartilage". The Journal of Biological Chemistry. 256 (11): 5921–5. doi:10.1016/S0021-9258(19)69297-5. PMID 7240180.
  22. ^ Reesink HL, Bonnevie ED, Liu S, Shurer CR, Hollander MJ, Bonassar LJ, Nixon AJ (May 2016). "Galectin-3 Binds to Lubricin and Reinforces the Lubricating Boundary Layer of Articular Cartilage". Scientific Reports. 6: 25463. Bibcode:2016NatSR...625463R. doi:10.1038/srep25463. PMC 4860590. PMID 27157803.
  23. ^ Flowers SA, Thomsson KA, Ali L, Huang S, Mthembu Y, Regmi SC, et al. (November 2020). "Decrease of core 2 O-glycans on synovial lubricin in osteoarthritis reduces galectin-3 mediated crosslinking". The Journal of Biological Chemistry. 295 (47): 16023–16036. doi:10.1074/jbc.RA120.012882. PMC 7681006. PMID 32928962.
  24. ^ Flowers SA, Kalamajski S, Ali L, Björkman LI, Raj JR, Aspberg A, et al. (September 2017). "Cartilage oligomeric matrix protein forms protein complexes with synovial lubricin via non-covalent and covalent interactions". Osteoarthritis and Cartilage. 25 (9): 1496–1504. doi:10.1016/j.joca.2017.03.016. PMID 28373131.
  25. ^ Raj A, Wang M, Liu C, Ali L, Karlsson NG, Claesson PM, Dėdinaitė A (June 2017). "Molecular synergy in biolubrication: The role of cartilage oligomeric matrix protein (COMP) in surface-structuring of lubricin". Journal of Colloid and Interface Science. 495: 200–206. Bibcode:2017JCIS..495..200R. doi:10.1016/j.jcis.2017.02.007. PMID 28208081.
  26. ^ Jay GD (October 2004). "Lubricin and surfacing of articular joints". Current Opinion in Orthopaedics. 15 (5): 355–359. doi:10.1097/01.bco.0000136127.00043.a8.
  27. ^ Jay GD, Harris DA, Cha CJ (October 2001). "Boundary lubrication by lubricin is mediated by O-linked beta(1-3)Gal-GalNAc oligosaccharides". Glycoconjugate Journal. 18 (10): 807–15. doi:10.1023/a:1021159619373. PMID 12441670. S2CID 23192748.
  28. ^ a b Schmidt TA, Plaas AH, Sandy JD (May 2009). "Disulfide-bonded multimers of proteoglycan 4 PRG4 are present in normal synovial fluids". Biochimica et Biophysica Acta (BBA) - General Subjects. 1790 (5): 375–84. doi:10.1016/j.bbagen.2009.03.016. PMID 19332105.
  29. ^ Rhee DK, Marcelino J, Al-Mayouf S, Schelling DK, Bartels CF, Cui Y, et al. (September 2005). "Consequences of disease-causing mutations on lubricin protein synthesis, secretion, and post-translational processing". The Journal of Biological Chemistry. 280 (35): 31325–32. doi:10.1074/jbc.M505401200. PMID 16000300.
  30. ^ Radin EL, Swann DA, Weisser PA (October 1970). "Separation of a hyaluronate-free lubricating fraction from synovial fluid". Nature. 228 (5269): 377–8. Bibcode:1970Natur.228..377R. doi:10.1038/228377a0. PMID 5473985. S2CID 1832467.
  31. ^ Ali L, Flowers SA, Jin C, Bennet EP, Ekwall AK, Karlsson NG (December 2014). "The O-glycomap of lubricin, a novel mucin responsible for joint lubrication, identified by site-specific glycopeptide analysis". Molecular & Cellular Proteomics. 13 (12): 3396–409. doi:10.1074/mcp.M114.040865. PMC 4256492. PMID 25187573.
  32. ^ Created with "Biorender".
  33. ^ Lee S, Spencer ND (February 2008). "Materials science. Sweet, hairy, soft, and slippery". Science. 319 (5863): 575–6. doi:10.1126/science.1153273. PMID 18239111. S2CID 206510494.
  34. ^ de Gennes PG (September 1980). "Conformations of Polymers Attached to an Interface". Macromolecules. 13 (5): 1069–1075. Bibcode:1980MaMol..13.1069D. doi:10.1021/ma60077a009.
  35. ^ Zappone B, Greene GW, Oroudjev E, Jay GD, Israelachvili JN (February 2008). "Molecular aspects of boundary lubrication by human lubricin: effect of disulfide bonds and enzymatic digestion". Langmuir. 24 (4): 1495–508. doi:10.1021/la702383n. PMID 18067335.
  36. ^ Flowers SA, Zieba A, Örnros J, Jin C, Rolfson O, Björkman LI, et al. (October 2017). "Lubricin binds cartilage proteins, cartilage oligomeric matrix protein, fibronectin and collagen II at the cartilage surface". Scientific Reports. 7 (1): 13149. Bibcode:2017NatSR...713149F. doi:10.1038/s41598-017-13558-y. PMC 5640667. PMID 29030641.
  37. ^ Flowers SA, Kalamajski S, Ali L, Björkman LI, Raj JR, Aspberg A, et al. (September 2017). "Cartilage oligomeric matrix protein forms protein complexes with synovial lubricin via non-covalent and covalent interactions". Osteoarthritis and Cartilage. 25 (9): 1496–1504. doi:10.1016/j.joca.2017.03.016. PMID 28373131.
  38. ^ Briscoe WH, Titmuss S, Tiberg F, Thomas RK, McGillivray DJ, Klein J (November 2006). "Boundary lubrication under water". Nature. 444 (7116): 191–4. Bibcode:2006Natur.444..191B. doi:10.1038/nature05196. PMID 17093447. S2CID 4325718.
  39. ^ Lee Y, Choi J, Hwang NS (2018-03-16). "Regulation of lubricin for functional cartilage tissue regeneration: a review". Biomaterials Research. 22: 9. doi:10.1186/s40824-018-0118-x. PMC 5857089. PMID 29568558.
  40. ^ Banquy X, Burdyńska J, Lee DW, Matyjaszewski K, Israelachvili J (April 2014). "Bioinspired bottle-brush polymer exhibits low friction and Amontons-like behavior". Journal of the American Chemical Society. 136 (17): 6199–202. doi:10.1021/ja501770y. PMID 24716507.
  41. ^ Liu X, Dedinaite A, Rutland M, Thormann E, Visnevskij C, Makuska R, Claesson PM (November 2012). "Electrostatically anchored branched brush layers". Langmuir. 28 (44): 15537–47. doi:10.1021/la3028989. PMID 23046176.
  42. ^ Merberg DM et al. (1993) Comparison of vitronectin and megakaryocyte stimulating factor. In Biology of Vitronectins and their Receptors. (Preissner et al., eds) pp45-52 (Elsevier Science, Amsterdam).
  43. ^ Taguchi M, Sun YL, Zhao C, Zobitz ME, Cha CJ, Jay GD, et al. (January 2008). "Lubricin surface modification improves extrasynovial tendon gliding in a canine model in vitro". The Journal of Bone and Joint Surgery. American Volume. 90 (1): 129–35. doi:10.2106/JBJS.G.00045. PMID 18171967.
  44. ^ Zhang D, Kearney CJ, Cheriyan T, Schmid TM, Spector M (November 2011). "Extracorporeal shockwave-induced expression of lubricin in tendons and septa". Cell and Tissue Research. 346 (2): 255–62. doi:10.1007/s00441-011-1258-7. PMID 22009294. S2CID 12089961.
  45. ^ Kosinska MK, Ludwig TE, Liebisch G, Zhang R, Siebert HC, Wilhelm J, et al. (2015-05-01). Gualillo O (ed.). "Articular Joint Lubricants during Osteoarthritis and Rheumatoid Arthritis Display Altered Levels and Molecular Species". PLOS ONE. 10 (5): e0125192. Bibcode:2015PLoSO..1025192K. doi:10.1371/journal.pone.0125192. PMC 4416892. PMID 25933137.
  46. ^ Alquraini A, Garguilo S, D'Souza G, Zhang LX, Schmidt TA, Jay GD, Elsaid KA (December 2015). "The interaction of lubricin/proteoglycan 4 (PRG4) with toll-like receptors 2 and 4: an anti-inflammatory role of PRG4 in synovial fluid". Arthritis Research & Therapy. 17 (1): 353. doi:10.1186/s13075-015-0877-x. PMC 4672561. PMID 26643105.
  47. ^ Ludwig TE, McAllister JR, Lun V, Wiley JP, Schmidt TA (December 2012). "Diminished cartilage-lubricating ability of human osteoarthritic synovial fluid deficient in proteoglycan 4: Restoration through proteoglycan 4 supplementation". Arthritis and Rheumatism. 64 (12): 3963–71. doi:10.1002/art.34674. PMID 22933061.
  48. ^ Elsaid KA, Fleming BC, Oksendahl HL, Machan JT, Fadale PD, Hulstyn MJ, et al. (June 2008). "Decreased lubricin concentrations and markers of joint inflammation in the synovial fluid of patients with anterior cruciate ligament injury". Arthritis and Rheumatism. 58 (6): 1707–15. doi:10.1002/art.23495. PMC 2789974. PMID 18512776.
  49. ^ Jay GD, Zack J, Cha C (September 2001). "PA41 Traumatized knee joint synovial fluid fails to provide boundary lubrication among emergency department patients". Osteoarthritis and Cartilage. 9: S32. doi:10.1016/s1063-4584(01)80293-4.
  50. ^ Schmidt TA, Sullivan DA, Knop E, Richards SM, Knop N, Liu S, et al. (June 2013). "Transcription, translation, and function of lubricin, a boundary lubricant, at the ocular surface". JAMA Ophthalmology. 131 (6): 766–76. doi:10.1001/jamaophthalmol.2013.2385. PMC 3887468. PMID 23599181.
  51. ^ Lambiase A, Sullivan BD, Schmidt TA, Sullivan DA, Jay GD, Truitt ER, et al. (January 2017). "A Two-Week, Randomized, Double-masked Study to Evaluate Safety and Efficacy of Lubricin (150 μg/mL) Eye Drops Versus Sodium Hyaluronate (HA) 0.18% Eye Drops (Vismed®) in Patients with Moderate Dry Eye Disease". The Ocular Surface. 15 (1): 77–87. doi:10.1016/j.jtos.2016.08.004. PMID 27614318.

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