Isolation and characterization of a genomic clone encoding chick α1 type III collagen

We have isolated a cloned segment of the chick α1 type III collagen gene from a genomic DNA library. This DNA clone was obtained by cross-hybridization with a cDNA clone containing sequences coding for a segment of the carboxy propeptide of chick α1 type I collagen. This genomic clone was identified as coding for α1 type III collagen by DNA sequence analysis of two segments of the gene and by its ability to hybridize to crop mRNA but not to calvaria mRNA in agreement with the presence of α1 type III collagen in crop but not in calvaria. The deduced amino acid sequences reveal characteristic features for α1 type III collagen and are in good agreement with the known protein sequences of calf and human α1 type III collagen. The size of α1 type III mRNA is about 6 kilobases, slightly larger than the mRNA for α1 type I. R-loop electron microscopic analysis indicates that at least 16 exons are interspersed in a 9-kilobase DNA segment that contains the third distal part of the α1 type III collagen gene.