Isolation and characterization of a genomic clone encoding chick alpha 1 type III collagen

We have isolated a cloned segment of the chick alpha 1 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 alpha 1 type I collagen. This genomic clone was identified as coding for alpha 1 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 alpha 1 type III collagen in crop but not in calvaria. The deduced amino acid sequences reveal characteristic features for alpha 1 type III collagen and are in good agreement with the known protein sequences of calf and human alpha 1 type III collagen. The size of alpha 1 type III mRNA is about 6 kilobases, slightly larger than the mRNA for alpha 1 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 alpha 1 type III collagen gene.