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Ahmed S, Rogers AV, Nowlan NC. Mechanical loading due to muscle movement regulates establishment of the collagen network in the developing murine skeleton. R Soc Open Sci 2023; 10:231023. [PMID: 37859832 PMCID: PMC10582611 DOI: 10.1098/rsos.231023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Accepted: 09/14/2023] [Indexed: 10/21/2023]
Abstract
Mechanical loading is critical for collagen network maintenance and remodelling in adult skeletal tissues, but the role of loading in collagen network formation during development is poorly understood. We test the hypothesis that mechanical loading is necessary for the onset and maturation of spatial localization and structure of collagens in prenatal cartilage and bone, using in vivo and in vitro mouse models of altered loading. The majority of collagens studied was aberrant in structure or localization, or both, when skeletal muscle was absent in vivo. Using in vitro bioreactor culture system, we demonstrate that mechanical loading directly modulates the spatial localization and structure of collagens II and X. Furthermore, we show that mechanical loading in vitro rescues aspects of the development of collagens II and X from the effects of fetal immobility. In conclusion, our findings show that mechanical loading is a critical determinant of collagen network establishment during prenatal skeletal development.
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Affiliation(s)
- Saima Ahmed
- Department of Bioengineering, Imperial College London, London, UK
| | | | - Niamh C. Nowlan
- Department of Bioengineering, Imperial College London, London, UK
- School of Mechanical and Materials Engineering, University College Dublin, Dublin, Ireland
- UCD Conway Institute, University College Dublin, Dublin, Ireland
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2
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Jacobson A, Besirli CG, Bohnsack BL. Characteristics of a Three-Generation Family with Stickler Syndrome Type I Carrying Two Different COL2A1 Mutations. Genes (Basel) 2023; 14:genes14040847. [PMID: 37107605 PMCID: PMC10138194 DOI: 10.3390/genes14040847] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2022] [Revised: 02/18/2023] [Accepted: 03/29/2023] [Indexed: 04/03/2023] Open
Abstract
Stickler Syndrome is typically characterized by ophthalmic manifestations including vitreous degeneration and axial lengthening that predispose to retinal detachment. Systemic findings consist of micrognathia, cleft palate, sensorineural hearing loss, and joint abnormalities. COL2A1 mutations are the most common, however, there is a lack of genotype-phenotype correlations. Retrospective, single-center case series of a three-generation family. Clinical features, surgical requirements, systemic manifestations, and genetic evaluations were collected. Eight individuals clinically displayed Stickler Syndrome, seven of whom had genetic confirmation, and two different COL2A1 mutations (c.3641delC and c.3853G>T) were identified. Both mutations affect exon 51, but display distinct phenotypes. The c.3641delC frameshift mutation resulted in high myopia and associated vitreous and retinal findings. Individuals with the c.3853G>T missense mutation exhibited joint abnormalities, but mild ocular manifestations. One individual in the third generation was biallelic heterozygous for both COL2A1 mutations and showed ocular and joint findings in addition to autism and severe developmental delay. These COL2A1 mutations exhibited distinct eye vs. joint manifestations. The molecular basis for these phenotypic differences remains unknown and demonstrates the need for deep phenotyping in patients with Stickler syndrome to correlate COL2A1 gene function and expression with ocular and systemic findings.
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Affiliation(s)
- Adam Jacobson
- Kellogg Eye Center, Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI 48105, USA
| | - Cagri G. Besirli
- Kellogg Eye Center, Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI 48105, USA
| | - Brenda L. Bohnsack
- Division of Ophthalmology, Ann & Robert H. Lurie Children’s Hospital of Chicago, Chicago, IL 60611, USA
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60208, USA
- Correspondence:
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Rekad Z, Izzi V, Lamba R, Ciais D, Van Obberghen-Schilling E. The Alternative Matrisome: alternative splicing of ECM proteins in development, homeostasis and tumor progression. Matrix Biol 2022; 111:26-52. [DOI: 10.1016/j.matbio.2022.05.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2022] [Revised: 04/19/2022] [Accepted: 05/04/2022] [Indexed: 12/14/2022]
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Demal TJ, Scholz T, Schüler H, Olfe J, Fröhlich A, Speth F, von Kodolitsch Y, Mir TS, Reichenspurner H, Kubisch C, Hempel M, Rosenberger G. Expanding the clinical spectrum of COL2A1 related disorders by a mass like phenotype. Sci Rep 2022; 12:4489. [PMID: 35296718 DOI: 10.1038/s41598-022-08476-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 03/04/2022] [Indexed: 11/16/2022] Open
Abstract
MASS phenotype is a connective tissue disorder clinically overlapping with Marfan syndrome and caused by pathogenic variants in FBN1. We report four patients from three families presenting with a MASS-like phenotype consisting of tall stature, arachnodactyly, spinal deformations, dural ectasia, pectus and/or feet deformations, osteoarthritis, and/or high arched palate. Gene panel sequencing was negative for FBN1 variants. However, it revealed likely pathogenic missense variants in three individuals [c.3936G > T p.(Lys1312Asn), c.193G > A p.(Asp65Asn)] and a missense variant of unknown significance in the fourth patient [c.4013G > A p.(Ser1338Asn)] in propeptide coding regions of COL2A1. Pathogenic COL2A1 variants are associated with type II collagenopathies comprising a remarkable clinical variablility. Main features include skeletal dysplasia, ocular anomalies, and auditory defects. A MASS-like phenotype has not been associated with COL2A1 variants before. Thus, the identification of likely pathogenic COL2A1 variants in our patients expands the phenotypic spectrum of type II collagenopathies and suggests that a MASS-like phenotype can be assigned to various hereditary disorders of connective tissue. We compare the phenotypes of our patients with related disorders of connective tissue and discuss possible pathomechanisms and genotype–phenotype correlations for the identified COL2A1 variants. Our data recommend COL2A1 sequencing in FBN1-negative patients suggestive for MASS/Marfan-like phenotype (without aortopathy).
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Zubillaga V, Alonso-Varona A, Fernandes SCM, Salaberria AM, Palomares T. Adipose-Derived Mesenchymal Stem Cell Chondrospheroids Cultured in Hypoxia and a 3D Porous Chitosan/Chitin Nanocrystal Scaffold as a Platform for Cartilage Tissue Engineering. Int J Mol Sci 2020; 21:E1004. [PMID: 32028724 PMCID: PMC7037297 DOI: 10.3390/ijms21031004] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 01/30/2020] [Accepted: 01/31/2020] [Indexed: 01/06/2023] Open
Abstract
Articular cartilage degeneration is one of the most common causes of pain and disability in middle-aged and older people. Tissue engineering (TE) has shown great therapeutic promise for this condition. The design of cartilage regeneration constructs must take into account the specific characteristics of the cartilaginous matrix, as well as the avascular nature of cartilage and its cells' peculiar arrangement in isogenic groups. Keeping these factors in mind, we have designed a 3D porous scaffold based on genipin-crosslinked chitosan/chitin nanocrystals for spheroid chondral differentiation of human adipose tissue-derived mesenchymal stem cells (hASCs) induced in hypoxic conditions. First, we demonstrated that, under low oxygen conditions, the chondrospheroids obtained express cartilage-specific markers including collagen type II (COL2A1) and aggrecan, lacking expression of osteogenic differentiation marker collagen type I (COL1A2). These results were associated with an increased expression of hypoxia-inducible factor 1α, which positively directs COL2A1 and aggrecan expression. Finally, we determined the most suitable chondrogenic differentiation pattern when hASC spheroids were seeded in the 3D porous scaffold under hypoxia and obtained a chondral extracellular matrix with a high sulphated glycosaminoglycan content, which is characteristic of articular cartilage. These findings highlight the potential use of such templates in cartilage tissue engineering.
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Affiliation(s)
- Veronica Zubillaga
- Department of Cell Biology and Histology, Faculty of Medicine and Nursey, University of the Basque Country (UPV/EHU), B Sarriena s/n, 48940 Leioa, Spain;
| | - Ana Alonso-Varona
- Department of Cell Biology and Histology, Faculty of Medicine and Nursey, University of the Basque Country (UPV/EHU), B Sarriena s/n, 48940 Leioa, Spain;
| | - Susana C. M. Fernandes
- Institute of Analytical Sciences and Physico-chemistry for the Environment and Materials, University of Pau and Pays Adour, E2S UPPA, CNRS, 64600 Anglet, France;
| | - Asier M. Salaberria
- Biorefinery Processes Research Group, Department of Chemical and Environmental Engineering, Polytechnic School, University of the Basque Country (UPV/EHU), Pza. Europa 1, 20018 Donostia-San Sebastian, Spain;
| | - Teodoro Palomares
- Department of Surgery, Radiology and Physic Medicine, Faculty of Medicine, University of the Basque Country (UPV/EHU), B Sarriena, s/n, 48940 Leioa, Spain
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Zhang B, Zhang Y, Wu N, Li J, Liu H, Wang J. Integrated analysis of COL2A1 variant data and classification of type II collagenopathies. Clin Genet 2019; 97:383-395. [PMID: 31758797 DOI: 10.1111/cge.13680] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 11/18/2019] [Accepted: 11/20/2019] [Indexed: 11/29/2022]
Abstract
The COL2A1 gene encodes the alpha-1 chain of type II procollagen. Type II collagen, comprised of three identical alpha-1 chains, is the major component of cartilage. COL2A1 gene variants are the etiologies of genetic diseases, termed type II collagenopathies, with a wide spectrum of clinical presentations. To date, at least 460 distinct COL2A1 mutations, identified in 663 independent probands, and 21 definite disorders have been reported. Nevertheless, a well-defined genotype-phenotype correlation has not been established, and few hot spots of mutation have been reported. In this study, we analyzed data of COL2A1 variants and clinical information of patients obtained from the Leiden Open Variation Database 3.0, as well as the currently available relevant literature. We determined the characteristics of the COL2A1 variants and distributions of the clinical manifestations in patients, and identified four likely genotype-phenotype correlations. Moreover, we classified 21 COL2A1-related disorders into five categories, which may assist clinicians in understanding the essence of these complex phenotypes and prompt genetic screening in clinical practice.
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Affiliation(s)
- Boyan Zhang
- Orthopedic Medical Center, The Second Hospital of Jilin University, Changchun, China
| | - Yue Zhang
- Department of Radiation Oncology, First Bethune Hospital of Jilin University, Changchun, China
| | - Naichao Wu
- Orthopedic Medical Center, The Second Hospital of Jilin University, Changchun, China
| | - Jianing Li
- Jilin Provincial Key Laboratory of Animal Embryo Engineering, College of Animal Sciences, Jilin University, Changchun, China
| | - He Liu
- Orthopedic Medical Center, The Second Hospital of Jilin University, Changchun, China
| | - Jincheng Wang
- Orthopedic Medical Center, The Second Hospital of Jilin University, Changchun, China
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Wang T, Nimkingratana P, Smith CA, Cheng A, Hardingham TE, Kimber SJ. Enhanced chondrogenesis from human embryonic stem cells. Stem Cell Res 2019; 39:101497. [PMID: 31326745 PMCID: PMC6745516 DOI: 10.1016/j.scr.2019.101497] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 05/17/2019] [Accepted: 07/08/2019] [Indexed: 02/06/2023] Open
Abstract
Human embryonic stem cells (hESCs) have great potential for the repair of damaged articular cartilage. We developed a serum-free 14-day protocol for hESC differentiation into chondrocyte progenitors, which surprisingly lacked strong cartilage matrix production in in vitro tests. In order to direct these progenitors to a more mature phenotype, we investigated substituting different members of the TGFβ family in the protocol. Initially, we supplemented, or substituted GDF5 (day 11-14), with combinations of BMP7 and TGFβ-1, or -3, but these modifications yielded no improvement in matrix gene expression. However, replacing BMP4 with BMP2 (days 3-10 of the protocol) resulted in a more rapid increase in SOX9 gene expression and increased expression of chondrogenic genes SOX5, ACAN and COL2A1. The replacement of BMP4 with BMP2 also enhanced the formation of chondrogenic cell aggregates, with greater deposition of type II collagen. This change was not accompanied by hypertrophic chondrocyte marker COL10A1 expression. The results demonstrate that BMP2 has greater specificity for the generation of chondrogenic cells from hESCs than BMP4 and this was consistent in two hESC lines (HUES1 and MAN7). hESC-chondrogenic cells derived with either BMP2 or BMP4 were tested in vivo by implanting them in fibrin into osteochondral defects in the femur of RNU rats. Repaired cartilage tissue, positive for Safranin O and type II collagen was detected at 6 and 12 weeks with both cell sources, but the BMP2 cells scored higher for tissue quality (Pineda score). Therefore, BMP2 is more effective at driving chondrogenic differentiation from human pluripotent stem cells than BMP4 and the effect on the resulting chondroprogenitors is sustained in an in vivo setting.
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Affiliation(s)
- Tao Wang
- Faculty of Biology, Medicine and Health, University of Manchester, UK
| | | | | | - Aixin Cheng
- Faculty of Biology, Medicine and Health, University of Manchester, UK
| | - Timothy E Hardingham
- Wellcome Centre for Cell-Matrix Research, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Susan J Kimber
- Faculty of Biology, Medicine and Health, University of Manchester, UK.
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Hao J, Wang W, Wen Y, Xiao X, He A, Wu C, Wang S, Guo X, Zhang F. Genome-wide association study identifies COL2A1 locus involved in the hand development failure of Kashin-Beck disease. Sci Rep 2017; 7:40020. [PMID: 28059113 DOI: 10.1038/srep40020] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 12/01/2016] [Indexed: 11/09/2022] Open
Abstract
Kashin-Beck disease (KBD) is a chronic osteochondropathy. The pathogenesis of growth and development failure of hand of KBD remains elusive now. In this study, we conducted a two-stage genome-wide association study (GWAS) of palmar length-width ratio (LWR) of KBD, totally including 493 study subjects. Affymetrix Genome Wide Human SNP Array 6.0 was applied for genome-wide SNP genotyping of 90 KBD patients. Association analysis was conducted by PLINK. Imputation analysis was performed by IMPUTE against the reference panel of the 1000 genome project. Two SNPs were selected for replication in an independent validation sample of 403 KBD patients. In the discovery GWAS, significant association was observed between palmar LWR and rs2071358 of COL2A1 gene (P value = 4.68 × 10−8). In addition, GWAS detected suggestive association signal at rs4760608 of COL2A1 gene (P value = 1.76 × 10−4). Imputation analysis of COL2A1 further identified 2 SNPs with association evidence for palmar LWR. Replication study observed significant association signals at both rs2071358 (P value = 0.017) and rs4760608 (P value = 0.002) of COL2A1 gene. Based on previous and our study results, we suggest that COL2A1 was a likely susceptibility gene involved in the hand development failure of KBD.
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Abstract
Fibrillar collagens (types I, II, III, V, XI, XXIV and XXVII) constitute a sub-group within the collagen family (of which there are 28 types in humans) whose functions are to provide three-dimensional frameworks for tissues and organs. These networks confer mechanical strength as well as signalling and organizing functions through binding to cellular receptors and other components of the extracellular matrix (ECM). Here we describe the structure and assembly of fibrillar collagens, and their procollagen precursors, from the molecular to the tissue level. We show how the structure of the collagen triple-helix is influenced by the amino acid sequence, hydrogen bonding and post-translational modifications, such as prolyl 4-hydroxylation. The numerous steps in the biosynthesis of the fibrillar collagens are reviewed with particular attention to the role of prolyl 3-hydroxylation, collagen chaperones, trimerization of procollagen chains and proteolytic maturation. The multiple steps controlling fibril assembly are then discussed with a focus on the cellular control of this process in vivo. Our current understanding of the molecular packing in collagen fibrils, from different tissues, is then summarized on the basis of data from X-ray diffraction and electron microscopy. These results provide structural insights into how collagen fibrils interact with cell receptors, other fibrillar and non-fibrillar collagens and other ECM components, as well as enzymes involved in cross-linking and degradation.
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Affiliation(s)
- Jordi Bella
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester, M13 9PT, UK.
| | - David J S Hulmes
- Tissue Biology and Therapeutic Engineering Unit (UMR5305), CNRS/Université Claude Bernard Lyon 1, Lyon, France
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Peffers MJ, Goljanek-Whysall K, Collins J, Fang Y, Rushton M, Loughlin J, Proctor C, Clegg PD. Decoding the Regulatory Landscape of Ageing in Musculoskeletal Engineered Tissues Using Genome-Wide DNA Methylation and RNASeq. PLoS One 2016; 11:e0160517. [PMID: 27533049 PMCID: PMC4988628 DOI: 10.1371/journal.pone.0160517] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 07/20/2016] [Indexed: 12/11/2022] Open
Abstract
Mesenchymal stem cells (MSC) are capable of multipotent differentiation into connective tissues and as such are an attractive source for autologous cell-based regenerative medicine and tissue engineering. Epigenetic mechanisms, like DNA methylation, contribute to the changes in gene expression in ageing. However there was a lack of sufficient knowledge of the role that differential methylation plays during chondrogenic, osteogenic and tenogenic differentiation from ageing MSCs. This study undertook genome level determination of the effects of DNA methylation on expression in engineered tissues from chronologically aged MSCs. We compiled unique DNA methylation signatures from chondrogenic, osteogenic, and tenogenic engineered tissues derived from young; n = 4 (21.8 years ± 2.4 SD) and old; n = 4 (65.5 years±8.3SD) human MSCs donors using the Illumina HumanMethylation 450 Beadchip arrays and compared these to gene expression by RNA sequencing. Unique and common signatures of global DNA methylation were identified. There were 201, 67 and 32 chondrogenic, osteogenic and tenogenic age-related DE protein-coding genes respectively. Findings inferred the nature of the transcript networks was predominantly for 'cell death and survival', 'cell morphology', and 'cell growth and proliferation'. Further studies are required to validate if this gene expression effect translates to cell events. Alternative splicing (AS) was dysregulated in ageing with 119, 21 and 9 differential splicing events identified in chondrogenic, osteogenic and tenogenic respectively, and enrichment in genes associated principally with metabolic processes. Gene ontology analysis of differentially methylated loci indicated age-related enrichment for all engineered tissue types in 'skeletal system morphogenesis', 'regulation of cell proliferation' and 'regulation of transcription' suggesting that dynamic epigenetic modifications may occur in genes associated with shared and distinct pathways dependent upon engineered tissue type. An altered phenotype in engineered tissues was observed with ageing at numerous levels. These changes represent novel insights into the ageing process, with implications for stem cell therapies in older patients. In addition we have identified a number of tissue-dependant pathways, which warrant further studies.
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Affiliation(s)
- Mandy Jayne Peffers
- Institute of Ageing and Chronic Disease, University of Liverpool, Leahurst, Chester High Road, Neston, Wirral, UK, CH64 7TE
| | - Katarzyna Goljanek-Whysall
- Institute of Ageing and Chronic Disease, University of Liverpool, Leahurst, Chester High Road, Neston, Wirral, UK, CH64 7TE
| | - John Collins
- Thurston Arthritis Research Centre, School Of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA, 27599
| | - Yongxiang Fang
- Centre for Genomic Research, Institute of Integrative Biology, Biosciences Building, Crown Street, University of Liverpool, Liverpool, UK, L69 7ZB
| | - Michael Rushton
- Musculoskeletal Research Group, Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, UK, NE2 4HH
| | - John Loughlin
- Musculoskeletal Research Group, Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, UK, NE2 4HH
| | - Carole Proctor
- Musculoskeletal Research Group, Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, UK, NE2 4HH
- Newcastle University Institute for Ageing, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, UK, NE4 5PL
| | - Peter David Clegg
- Institute of Ageing and Chronic Disease, University of Liverpool, Leahurst, Chester High Road, Neston, Wirral, UK, CH64 7TE
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Hering TM, Wirthlin L, Ravindran S, McAlinden A. Changes in type II procollagen isoform expression during chondrogenesis by disruption of an alternative 5' splice site within Col2a1 exon 2. Matrix Biol 2014; 36:51-63. [PMID: 24735995 DOI: 10.1016/j.matbio.2014.04.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 04/03/2014] [Accepted: 04/05/2014] [Indexed: 01/18/2023]
Abstract
This study describes a new mechanism controlling the production of alternatively spliced isoforms of type II procollagen (Col2a1) in vivo. During chondrogenesis, precursor chondrocytes predominantly produce isoforms containing alternatively spliced exon 2 (type IIA and IID) while Col2a1 mRNA devoid of exon 2 (type IIB) is the major isoform produced by differentiated chondrocytes. We previously identified an additional Col2a1 isoform containing a truncated exon 2 and premature termination codons in exon 6 (type IIC). This transcript is produced by utilization of another 5' splice site present in exon 2. To determine the role of this IIC splicing event in vivo, we generated transgenic mice containing silent knock-in mutations at the IIC 5' splice site (Col2a1-mIIC), thereby inhibiting production of IIC transcripts. Heterozygous and homozygous knock-in mice were viable and display no overt skeletal phenotype to date. However, RNA expression profiles revealed that chondrocytes in cartilage from an age range of Col2a1-mIIC mice produced higher levels of IIA and IID mRNAs and decreased levels of IIB mRNAs throughout pre-natal and post-natal development, when compared to chondrocytes from littermate control mice. Immunofluorescence analyses showed a clear increase in expression of embryonic type II collagen protein isoforms (i.e. containing the exon 2-encoded cysteine-rich (CR) protein domain) in cartilage extracellular matrix (ECM). Interestingly, at P14, P28 and P56, expression of embryonic Col2a1 isoforms in Col2a1-mIIC mice persisted in the pericellular domain of the ECM in articular and growth plate cartilage. We also show that persistent expression of the exon 2-encoded CR domain in the ECM of post-natal cartilage tissue may be due, in part, to the embryonic form of type XI collagen (the α3 chain of which is also encoded by the Col2a1 gene). In conclusion, expression of the Col2a1 IIC splice form may have a regulatory function in controlling alternative splicing of exon 2 to generate defined proportions of IIA, IID and IIB procollagen isoforms during cartilage development. Future studies will involve ultrastructural and biomechanical analysis of the collagen ECM to determine the effects of persistent mis-expression of embryonic collagen isoforms in mature cartilage tissue.
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