A description of an abnormal segment-long-spacing crystallite (SLS) pattern has been reported for
type II collagen from patients with
diastrophic dysplasia (Stanescu et al., 1982 a), a disorder that is characterized by large
collagen fibrils in the cartilage matrix. The abnormal SLS consisted of an altered electron density between bands 42 and 45, which was interpreted as an abnormality in the
type II collagen molecule. It was suggested that the
type II collagen is abnormal in
diastrophic dysplasia. We have examined SLS of
type II collagen from two patients with
diastrophic dysplasia and found the SLS patterns to be identical with that of control type II SLS in almost all micrographs. In a few micrographs of diastrophic SLS, crystallites exhibiting the pattern reported by Stanescu et al. were seen. However, the abnormally patterned crystallites always consisted of dimers that were overlapped at the COOH ends in such a way that an electron dense band of one crystallite was positioned between bands 42 and 45 of the second crystallite, apparently creating the abnormal pattern. The abnormal SLS pattern seen in these cases of
diastrophic dysplasia appears to be the result of overlapping crystallites and may not be the result of an intrinsic abnormality of
type II collagen. We have constructed histograms of the
collagen fibril diameters in diastrophic cartilage. While they are larger than normal
collagen fibrils, this by itself does not indicate an abnormality of
type II collagen. We have shown that large fibrils such as these can be obtained from normal
type II collagen when the structure of the cartilage is disrupted by extraction with
guanidine.(ABSTRACT TRUNCATED AT 250 WORDS)