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.