Proteins that emerge de novo from non-coding DNA contribute to the generation of evolutionary novelty. To study de novo genes in a heterologous context, we have expressed several different mouse de novo genes (Mdngs) in a human cell line from a defined genomic integration site. Each of the mouse de novo genes triggers a largely unique transcriptomic response, indicating specific, rather than generalized effects. Enrichment of different Gene Ontology terms associated with the transcriptomic response for each Mdng further supports their functional diversity.