Construction of a Human Proα1(III) Collagen cDNA Clone and Localization of Type III Collagen Expression in Human Fetal Tissues

Abstract A cDNA clone for human proα(III) collagen mRNA was isolated from a cDNA library constructed for human fetal skin RNA. The clone, pHFS3, was identified by restriction mapping and sequencing. Comparison with previously published human type III collagen sequences revealed some differences which may reflect individual variation. The clone was used to study the expression of type III collagen mRNA in various fetal tissues in comparison to the expression of type I collagen mRNAs. In 15-18-week fetal skin the ratio of α (I) to α (III) collagen mRNAs was 0.8. Diaphyseal and calvarial bone contained high amounts of type I collagen mRNA and low levels of type III collagen mRNA, resulting in high type I/type III ratios. In situ hybridization of sections of skeletal tissues was employed to identif y the cells containing the mRNAs for types I, II and III procollagens. The results revealed differential expression patterns for these three collagen types in various human fetal tissues. Lack of coordinate expression suggests that production of type I and type III collagens is under different regulatory mechanisms in developing skeletal tissues.