Protocol Development for CRISPR/Cas9 Knockout of the Anti-inflammatory Protein TNIP1 in HaCaT Keratinocytes

Gene editing in cultured cells, including the intent of sequence disruption to achieve a functional knockout of the targeted gene, has been greatly facilitated with the advent of Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR)/CRISPR-associated protein 9 (CRISPR/Cas9) technology. Primary cell strains and immortalized cell lines from diverse tissue types have been successfully targeted both for basic research examining the effects of loss of the correlating protein and for modeling select loss-of-function disorders. Such accomplishments have extended to cutaneous cells, especially epidermal keratinocytes given their key structural and functional role in barrier formation and surveillance of and response to surface events such as triggering and processing inflammatory responses. Here we describe disruption of the Tumor Necrosis factor-induced protein 3-Interacting Protein 1 (TNIP1) gene in human HaCaT keratinocytes to generate an ongoing loss of expression as a parallel system to transient knockdown we had previously achieved with siRNA transfection. The TNIP1 protein restricts cytoplasmic progression of inflammatory signals. We cover our CRISPR/Cas9 vector choice, enrichment of transfected cells via positive selection for puromycin resistance, their subsequent cloning, and gene disruption and expression analysis. We also emphasize prior keratinocyte-CRISPR/Cas9 literature as a springboard for other investigators and to illustrate the widespread relevance of such editing to the diverse, yet highly consequentially different, genes expressed in keratinocytes.