Type XII collagen: distinct extracellular matrix component discovered by cDNA cloning

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• Collagenous proteins are crucial structural components in various tissues.
• Understanding collagen diversity is essential for comprehending tissue development and function.
• Previous research has identified several types of collagen, each with specific roles.

Purpose of the Study:

• To identify and characterize novel collagenous coding sequences from tendon fibroblast mRNA.
• To determine the structural and genetic relationship of a newly identified collagen to known types.
• To investigate the tissue-specific expression patterns of this novel collagen.

Main Methods:

• Screening of a cDNA library derived from tendon fibroblast mRNA.
• Nucleotide sequence analysis of isolated cDNA clones.
• Ribonuclease protection assays to determine mRNA expression.
• Isolation and partial nucleotide sequence analysis of the corresponding genomic DNA.

Main Results:

• A novel collagenous coding sequence, designated alpha 1(XII), was identified.
• The deduced polypeptide sequence of alpha 1(XII) is homologous but distinct from type IX short-chain collagen.
• Alpha 1(XII) mRNA is expressed in various embryonic chicken tissues, including calvaria, tendon, sternal cartilage, and cornea.
• The gene structure of alpha 1(XII) shows homology to type IX collagen genes.
• Types IX and XII collagens represent a homologous family distinct from fibrillar collagens.

Conclusions:

• Type XII collagen represents a novel collagenous protein family.
• The type IX and XII collagen family is characterized by homologous structures and tissue-specific expression.
• This collagen family is structurally and genetically distinct from fibrillar collagens.