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Isolation, characterization and mapping of the mouse and human PRG4 (proteoglycan 4) genes
S Ikegawa1, M Sano, Y Koshizuka
1Laboratory of Genome Medicine, Human Genome Center, Institute of Medical Science, The University of Tokyo, Tokyo, Japan. sikegawa@ims.u-tokyo.ac.jp
Abstract:
PRG4 (proteoglycan 4) has been identified as megakaryocyte stimulating factor and articular superficial zone protein. PRG4 has characteristic motifs including somatomedin B and hemopexin domains, a chondroitin sulfate-attachment site and mucin-like repeats. During a screen of genes implicated in ectopic ossification, we found a novel mouse gene highly homologous to human and bovine PRG4 genes. Here, we report isolation, characterization and mapping of the gene, Prg4 together with characterization of its human orthologue. Prg4 cDNA was 3,320 bp long, encoding a 1,054 amino-acid protein. Human and mouse PRG4 genes each consisting of 12 exons spanned 18 and 16 kb, respectively. Characteristic motifs were conserved across species; however, the mucin-like repeat regions were highly diverse in length between species with a tendency that larger animals had longer repeats. Expression of human and mouse PRG4 genes was similar and found not only in cartilage, but also in liver, heart, lung, and bone. Expression of the mouse gene increased with progression of ectopic ossification. Multiple tissue-specific splicing variants lacking some of the motifs were found in both human and mouse. Although a specific role in the articular joint has previously been reported, the presence of multi-functional motifs as well as unique expression and alternative splicing patterns suggest that PRG4 functions in several distinctive biological process including regulation of ossification.
Insights
Proteoglycan 4 (PRG4) is a novel gene involved in ectopic ossification. This study characterizes the PRG4 gene in mice and humans, revealing its diverse functions beyond joint health.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Proteoglycan 4 (PRG4) is known as a megakaryocyte stimulating factor and articular superficial zone protein.
- PRG4 possesses characteristic motifs including somatomedin B and hemopexin domains, a chondroitin sulfate-attachment site, and mucin-like repeats.
Purpose of the Study:
- To isolate, characterize, and map the novel mouse Prg4 gene.
- To characterize its human orthologue.
- To investigate the expression patterns and alternative splicing of PRG4 in different species and tissues.
Main Methods:
- Gene isolation and characterization (cDNA sequencing, gene mapping).
- Bioinformatic analysis of conserved motifs and repeat regions.
- Gene expression analysis in various tissues and during ectopic ossification.
- Identification of tissue-specific splicing variants.
Main Results:
- A novel mouse PRG4 gene, homologous to human and bovine PRG4, was identified and characterized.
- Prg4 cDNA is 3,320 bp, encoding a 1,054 amino-acid protein; human and mouse PRG4 genes have 12 exons.
- Conserved motifs were observed, but mucin-like repeat lengths varied significantly between species, correlating with animal size.
- PRG4 expression was detected in cartilage, liver, heart, lung, and bone, increasing during ectopic ossification.
- Multiple tissue-specific splicing variants were found in both human and mouse PRG4.
Conclusions:
- PRG4 exhibits conserved structural motifs but diverse repeat lengths across species.
- PRG4 is expressed in multiple tissues beyond cartilage and its expression is linked to ossification.
- Alternative splicing of PRG4 generates tissue-specific variants.
- These findings suggest PRG4 has broader biological functions, including the regulation of ossification, in addition to its role in articular joints.