Type X collagen is well known to be associated with hypertrophic chondrocytes during the process of endochondral ossification (EO). Intramembraneous bone formation does not follow the same developmental/histological sequence of events as seen in EO. One intramembraneous ossification event, however, has been described, in the literature, to be associated with “large, stacking fibroblasts.” The ossification takes place in the turkey gastrocnemius tendon, as well as other turkey tendons. This description has led us to wonder whether or not these “hypertrophic cells” might produce collagen type X. Objectives: The purpose of this study was to isolate cDNA clones encoding type X collagen from turkey gastrocnemius tendon RNA. Methods: Turkey gastrocnemius tendons were isolated from freshly sacrificed animals, and then placed into RNALater®. The samples were frozen in liquid N2, ground, and RNA isolated using the Ultraspec® RNA isolation system and reverse transcribed. This first strand cDNA was used as the template DNA for PCR. The primer pairs were based on published chicken type X cDNA sequence. The resulting cDNA was subcloned and plated. Colonies were picked, grown in small scale and mini-prepped to isolate plasmid DNA. Several clones from each group were sent for automated sequencing and the sequences compared to the DNA database. Results: The PCR reactions yielded products of the expected sizes. The sequences of these clones from the 5' and 3' regions of the type X molecule showed 95% and 98% homologies to chicken sequence, respectively. Conclusion: These clones contain turkey type X collagen cDNA. This study was supported by the Baylor Oral Health Foundation and NIH T35 DEO.

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