CRISPR-Cas9 Mediated Generation of a Conditional Poly(a) Binding Protein Nuclear 1 (pabpn1) Mouse Model Reveals an Essential Role for Hematopoietic Stem Cells

Poly(A) binding protein nuclear 1 (PABPN1) is known for its role in poly(A) tail addition and regulation of poly(A) tail length. In addition, it has been shown to be involved in alternative polyadenylation (APA). APA is a process regulating differential selection of polyadenylation sites, thereby influencing protein isoform expression and 3ʹ-UTR make-up. In this study, we generated an inducible Pabpn1flox/flox mouse model using crRNA-tracrRNA:Cas9 complexes targeting upstream and downstream genomic regions, respectively, in combination with a long single-stranded DNA (ssDNA) template. We performed extensive in vitro testing of various guide RNAs (gRNAs) to optimize recombination efficiency for in vivo application. Pabpn1flox/flox mice were generated and crossed to MxCre mice for validation experiments, allowing the induction of Cre expression in the bone marrow (BM) by poly(I:C) (pIC) injections. Validation experiments revealed successful deletion of Pabpn1 and absence of PABPN1 protein. Functionally, knockout (KO) of Pabpn1 led to a rapid and robust depletion of hematopoietic stem and progenitor cells (HSPCs) as well as myeloid cells, suggesting an essential role of Pabpn1 in the hematopoietic lineage. Overall, the mouse model allows an inducible in-depth in vivo analysis of the role of PABPN1 and APA regulation in different tissues and disease settings.