Krüppel-like factor gene function in the ctenophore Mnemiopsis leidyi assessed by CRISPR/Cas9-mediated genome editing

The Krüppel-like factor (Klf) gene family encodes for transcription factors that play an important role in the regulation of stem cell proliferation, cell differentiation, and development in bilaterians. While Klf genes have been shown to be expressed in various cell types in non-bilaterian animals, their functional role in early diverging animal lineages has not been assessed. Thus, the ancestral activity of these transcription factors in animal development is not well understood. The ctenophore Mnemiopsis leidyi has emerged as an important non-bilaterian model system for understanding early animal evolution. Here we characterize the expression and functional role of Klf genes during M. leidyi embryogenesis. Zygotic Klf gene function was assessed with both CRISPR/Cas9-mediated genome editing knockout and splice-blocking morpholino oligonucleotide knockdown approaches. Abrogation of zygotic Klf expression during M. leidyi embryogenesis results in the irregular development of several organs including the pharynx, tentacle bulbs, and apical organ. Our data suggest an ancient role for Klf genes in regulating endodermal patterning.Summary StatementUsing morpholino oligonucleotide knockdown and CRISPR/Cas9 genome editing, this study shows that in the ctenophore Mnemiopsis leidyi, tissues derived from the endoderm are dependent upon Klf5 ortholog expression for proper development and patterning.