DEVELOPMENTAL EXPRESSION OF PROTEIN-C AND PROTEIN-S IN THE RAT

In order to better understand the expression of the Protein C/Protein S anticoagulant system, we have isolated and characterized cDNAs codin g for rat Protein C and Protein S. These cDNAs were used in Northern a nalysis to determine tissue-specificity and developmental expression p atterns for mRNAs coding for Proteins C and S. In rats, Protein C mRNA is expressed almost exclusively in liver with a small amount of expre ssion in kidney, diaphragm, stomach, intestine, uterus and placenta. P rotein C mRNA was not expressed in brain, heart, lung, spleen, small i ntestine, large intestine, ovary, or urinary bladder. In liver, Protei n C mRNA is expressed at very low levels at prenatal day 18 and these levels increased to maximal levels by postnatal day 13. The size of th e mRNA coding for rat Protein C is approximately 1.9 kb. Rat Protein S mRNA was expressed in all tissues examined: brain, heart, lung, diaph ragm, liver, spleen, stomach, small intestine, large intestine, kidney , adrenal ovary, uterus, placenta, and urinary bladder. Interestingly, there were 4 bands hybridizing with the rat protein S cDNA that were evident in many of the tissues examined, corresponding to mRNA sizes o f approximately 3.5, 2.6, 1.8, and 0.3 kb. There was a difference in t issue-specificity of each mRNA. The 1.8 kb band is generally the most prominent autoradiographic band in any tissue. From these results, it is evident that the expression of Protein C mRNA is similar to that of other vitamin K-dependent proteins. The expression of Protein S mRNA, however, is surprisingly complex and may include alternative splicing of mRNA to generate the various sizes evident on Northern analysis.