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 predicted 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 of C2C12 cells at different stages of the differentiation process revealed increasing levels of MDK4 during this process. Immunofluorescence data indicated that MDK4 protein production begins with myoblasts elongation and is maintained throughout myotube formation. MDK4 transcripts were furthermore detected in the decidua tissue surrounding young embryos. Since decidua cells also form syncytia, it is possible that MDK4 is involved in the formation, regulation, and/or maintenance of the polynucleated state.