Similarities and differences in tissue distribution of DLK1 and DLK2 during E16.5 mouse embryogenesis.

DLK1 and DLK2 are transmembrane proteins belonging to the EGF-like repeat-containing family that function as non-canonical NOTCH inhibitory ligands. DLK1 is usually downregulated after embryo development and its distribution in some adult and embryonic tissues has been described. However, the expression and role of DLK2 in embryo and adult tissues remains unclear. To better understand the relevance of both proteins during embryo development, we analyzed the expression pattern of DLK1 and DLK2 in 16.5-day-old mouse embryos (E16.5) and evaluated the possible relationship between these two proteins in embryo tissues and cell types. We found that DLK1 and DLK2 proteins exhibited a broad distribution pattern, which was detected in developing mouse organs from each of the three germ layers: ectoderm (brain, salivary glands), mesoderm (skeletal muscle, vertebral column, kidney, cartilage), and endoderm (thymus, lung, pancreas, intestine, liver). The expression pattern of DLK1 and DLK2 indicates that both proteins could play a synergistic role during cell differentiation. This study provides additional information for understanding temporal and site-specific effects of DLK1 and DLK2 during embryo morphogenesis and cell differentiation.