MAP3K1 and teratoma: The defect in spatial restriction of progenitor differentiation following map3k1 RNAi can lead to dramatic tissue patterning defects, including the differentiation of ectopic isolated cells that normally only appear in groups (e.g., isolated photoreceptor neurons), the emergence of ectopic organs, differentiated cells from one tissue type being present within an incorrect organ, and teratoma formation (Figure 8B).