Expanding the CRISPR toolbox for Chinese hamster ovary cells with comprehensive tools for Mad7 genome editing.

The production of high-value biopharmaceuticals is dominated by mammalian production cells, particularly Chinese hamster ovary (CHO) cells, which have been widely used and preferred in manufacturing processes. The discovery of CRISPR-Cas9 significantly accelerated cell line engineering advances, allowing for production yield and quality improvements. Since then, several other CRISPR systems have become appealing genome editing tools, such as the Cas12a nucleases, which provide broad editing capabilities while utilizing short guide RNAs (gRNAs) that reduce the complexity of the editing systems. One of these is the Mad7 nuclease, which has been shown to efficiently convey targeted gene disruption and insertions in several different organisms. In this study, we demonstrate that Mad7 can generate indels for gene knockout of host cell proteins in CHO cells. We found that the efficiency of Mad7 depends on the addition of protein nuclear localization signals and the gRNAs employed for genome targeting. Moreover, we provide computational tools to design Mad7 gRNAs against any genome of choice and for automated indel detection analysis from next-generation sequencing data. In summary, this paper establishes the application of Mad7 in CHO cells, thereby improving the CRISPR toolbox versatility for research and cell line engineering.

Enhancement in production of recombinant two-chain Insulin Glargine by over-expression of Kex2 protease in Pichia pastoris.

Glargine is an analog of Insulin currently being produced by recombinant DNA technology using two different hosts namely Escherichia coli and Pichia pastoris. Production from E. coli involves the steps of extraction of inclusion bodies by cell lysis, refolding, proteolytic cleavage and purification. In P. pastoris, a single-chain precursor with appropriate disulfide bonding is secreted to the medium. Downstream processing currently involves use of trypsin which converts the precursor into two-chain final product. The use of trypsin in the process generates additional impurities due to presence of Lys and Arg residues in the Glargine molecule. In this study, we describe an alternate approach involving over-expression of endogenous Kex2 proprotein convertase, taking advantage of dibasic amino acid sequence (Arg-Arg) at the end of B-chain of Glargine. KEX2 gene over-expression in Pichia was accomplished by using promoters of varying strengths to ensure production of greater levels of fully functional two-chain Glargine product, confirmed by HPLC and mass analysis. In conclusion, this new production process involving Kex2 protease over-expression improves the downstream process efficiency, reduces the levels of impurities generated and decreases the use of raw materials.