EXCLUSIVE EXPRESSION OF THE RECEPTOR TYROSINE KINASE MDK4 IN SKELETAL-MUSCLE AND THE DECIDUA

Mouse developmental kinase 4 (MDK4), a novel receptor tyrosine kinase (RTK), was identified via degenerate primer screening of mouse embryo cDNA. The mRNA encoding this RTK was found only in skeletal muscle of mouse embryos and the maternal decidua. Northern blot analysis predict ed an mRNA transcript size of 6.1 kb. The amino acid sequence is most closely related to Torpedo RTK. Analysis of mRNA and protein content o f C2C12 cells at different stages of the differentiation process revea led increasing levels of MDK4 during this process. Immunofluorescence data indicated that MDK4 protein production begins with myoblasts elon gation and is maintained throughout myotube formation. MDK4 transcript s were furthermore detected in the decidua tissue surrounding young em bryos. Since decidua cells also form syncytia, it is possible that MDK 4 is involved in the formation, regulation, and/or maintenance of the polynucleated state.