Pericellular processing of procollagen. The conversion of a pulse of [3H]-procollagen to collagen was followed over 5 days (d0-d5). The pulse chase analyses are shown for a control sample, P1, P4, and a patient with EDS arthrochalasis type due to an exon 6 skip in COL1A2 (EDS VIIB). In the control sample a clear decrease of the bands representing the pNα2(I) chain and increase of bands representing the mature α2(I) chains is observed over 5 days. Processing of the N-propeptide of type I collagen is delayed in both P1, P4 and in the patient with EDS VIIB. This is best seen by the accumulation of the bands representing pNα2(I) chains and a slower increase of mature α2(I) chains by day 5, compared to control.