Promoter-associated noncoding RNAs (pancRNAs) are a class of long noncoding RNAs, transcribed from bidirectional promoters and thought to be involved in promoting expression of the gene transcribed from the opposite strand. Takuya Imamura and colleagues (p. 910) now set out to investigate the prevalence and potential functions of such pancRNAs during early mouse development. Focussing on the 2-cell stage, when the major wave of zygotic gene activation (ZGA) occurs, they use directional RNA-seq technology to identify several hundred pancRNAs upregulated in concert with their cognate coding RNA. To assess the potential functional relevance of this co-regulation, the authors analyse three candidates, including Il17d/pancIl17d. In each case, siRNA-mediated knockdown of the pancRNA impairs expression of the mRNA and also prevents the normal DNA demethylation associated with gene upregulation at the ZGA. They further find that depletion of pancIl17d leads to defects in blastocyst survival and in embryonic stem cell colony formation – phenotypes that can be rescued by the provision of recombinant IL17D. Although the mechanisms by which pancRNAs act remain poorly understood, these data provide evidence for an important physiological role for pancRNAs in promoting expression of their partner mRNAs during early development.