Exon-intron circRNA (EIciRNA) is a subclass of backsplicing-generated circRNAs featured with intron retention, among which some play roles in transcriptional regulation. We aim to characterize EIciRNAs by developing pipeline and investigate the factors involved in regulating EIciRNA biogenesis using CRISPR-Cas9 screen, as well as the physiology functions of EIciRNAs during neuronal differentiation. Overall design: To screen for potential regulators of EIciRNA biogenesis, two EIciGFP reporter cell lines were established. We performed genome-wide CRISPR knock-out screen using these two reporter cell lines.