An alternative spliced transcript of ADAMTS4 is present in human synovium from OA patients

Area of Science:

• Biochemistry
• Molecular Biology
• Rheumatology

Background:

• Aggrecan is a major proteoglycan in articular cartilage.
• Aggrecan serves as a substrate for ADAMTS4 (a disintegrin and metalloproteinase with thrombospondin motifs 4).
• Osteoarthritis (OA) is a degenerative joint disease characterized by cartilage breakdown.

Purpose of the Study:

• To investigate the expression and potential alternative splicing of ADAMTS4 in human osteoarthritic synovial co-cultures.
• To identify any novel variants of ADAMTS4 that may be involved in OA pathogenesis.

Main Methods:

• Reverse transcription polymerase chain reaction (RT-PCR) was employed.
• Oligonucleotide primers were designed to amplify across the exon 8/9 junction of human ADAMTS4.
• Analysis of amplification products from OA synovial co-cultures.

Main Results:

• Two products were amplified: the expected full-length ADAMTS4 and a smaller product.
• The smaller product resulted from alternative splicing, with exon 8 joining a cryptic 3' splice site within exon 9.
• This alternative splicing event leads to a predicted protein with a novel C-terminal domain, differing from the standard ADAMTS4 spacer domain.

Conclusions:

• Alternative splicing of ADAMTS4 occurs in human osteoarthritic synovial co-cultures.
• The resulting ADAMTS4 variant protein possesses a modified C-terminal region.
• These C-terminal alterations in ADAMTS4 could potentially influence its substrate specificity and role in aggrecan degradation in OA.