Twenty-Fourth Annual Meeting and Symposium of the Desert Tortoise Council, March 5-8, 1999
Abstracts

In the course of our studies on the pathogenesis of cutaneous dyskeratosis, the numbers, sizes and relative concentrations of shell scute proteins from tortoises with cutaneous dyskeratosis were compared to shell scute proteins of ill and healthy tortoises with normal appearing shells. Gel electrophoresis of extracted scute protein samples on 10% Tris Tricin-SDS polyacrylamide gels revealed nine distinct protein bands, ranging from approximately 7 to 73 kilodaltons (KD) with the major protein component of about 14 KD molecular weight. This major protein component comprised up to 75% of the scute protein. Two-dimensional electrophoretic analysis of the 14 KD major protein component revealed three proteins, and amino acid composition analysis of the 14 KD proteins revealed an amino acid composition similar to that of chicken beta keratins. Moreover, immunoblot analysis revealed reactivity of several proteins, including the 14 KD major protein component, with antisera specific for chicken and alligator ß keratins.

This study showed no statistically significant differences (P < 0.05) in the relative concentration of scute proteins within each of the nine electrophoretic bands when comparing tortoises with cutaneous dyskeratosis to healthy tortoises. However, there were significant differences in the concentrations of the major 14 KD protein and of a low molecular weight protein found in normal appearing shells of ill tortoises relative to healthy tortoises. This suggests that systematic disease, such as mycoplasmosis, may affect composition of scute keratin proteins in desert tortoises. The exact cause of cutaneous dyskeratosis in desert tortoises remains to be elucidated. It may be that less concentrated scute protein components, such as matrix-associated proteins, or other components such as lipids or inorganic substances, play an important role in the disease. Also, a larger sample size may be required to detect differences in the relative concentrations of scute proteins found in tortoises with cutaneous dyskeratosis compared to healthy desert tortoises. Further studies, employing immunoblot analyses of scute proteins, are being conducted.