Kawakami Group / Laboratory of Molecular and Developmental Biology 

Production of multi-subunit proteins in CHO cells by transposase-mediated integration of subunit-splitting vectors.

Keina Yamaguchi, Risa Ogawa, Masayoshi Tsukahara and Koichi Kawakami

Scientific reports (2025) 15, 18512 DOI:10.1038/s41598-025-03301-3

Chinese Hamster Ovary (CHO) cells are widely used for therapeutic protein production. We previously developed a method using the Tol2 transposon system to efficiently establish protein-producing cell lines via multiple genomic integrations of the gene of interest. In this study, we introduced two separate vectors—one carrying the light chain　(LC) gene and the other the heavy chain (HC) gene—into CHO cells, rather than a single vector with both genes. As a result, we obtained cell lines that stably produced monoclonal antibodies for up to 12 weeks and showed high productivity in fed-batch culture. Each cell line exhibited variable copy numbers of integrated LC and HC vectors, depending on the antibody type. High-producing lines had optimal ratios of LC and HC gene copies. Notably, optimization was achieved even when the drug resistance gene was present only in the HC vector. These findings highlight the potential of the Tol2 system for efficient production of monoclonal antibodies and other multi-subunit proteins.

Figure: Overview of the method.
Separate transposon vectors carrying the heavy chain (HC) and light chain (LC) genes are co-transfected into CHO cells. The drug resistance gene (cycloheximide resistance) is present only in the LC vector. In the transfected cells, the HC and LC vectors are integrated into the host genome in varying copy numbers. Cell lines carrying optimal copy numbers of both HC and LC vectors can be selected as cell lines that efficiently produce monoclonal antibodies.

Miyagishima Group / Symbiosis and Cell Evolution Laboratory

Costs of photosynthesis and cellular remodeling in trophic transitions of the unicellular red alga Galdieria partita

Shota Yamashita, Shunsuke Hirooka, Takayuki Fujiwara, Baifeng Zhou, Fumi Yagisawa, Kei Tamashiro, Hiroki Murakami, Koichiro Awai, and Shin-ya Miyagishima

Communications Biology (2025) 8, 891 DOI:10.1038/s42003-025-08284-5

As in plastid differentiation in land plants, some unicellular algae reversibly remodel photosynthetic plastids into a colorless heterotrophic state (bleaching) in the presence of organic carbon sources. To understand these mechanisms and their significance, we performed comparative omics analyses on the photoautotrophic and heterotrophic states and their transitions in the genetically tractable red alga Galdieria partita. Photoautotrophic cells require 1.5, 1.3 and 1.7 times more nitrogen, protein, and fatty acids than heterotrophic cells. In the photoautotrophic cells, plastid- and nucleus-encoded proteins for photosynthesis are highly synthesized, while in the heterotrophic state, cytoplasmic and mitochondrial proteins are more abundant, enabling 1.6 times faster growth. Changes in non-plastid metabolic enzymes are limited, with some upregulated in the photoautotrophic state to support fatty acid and glycolipid synthesis in the plastid for thylakoid membranes. In contrast, solute transporters show broader changes. Bleaching occurs upon adding certain sugars or sugar alcohols, regardless of light, not by active digestion of photosynthetic machinery, but by dilution due to suppressed synthesis at the transcriptional level and faster cell growth. Thus, when assimilable organic carbon is available, the cells repress the synthesis of proteins, lipids, and pigments for photosynthesis, reallocating resources to promote faster growth.

This study was supported by JSPS KAKENHI (22K15166, 24KJ0224, 24H00579), and JST-MIRAI Program (JPMJMI22E1).

Figure: Liquid culture (left) and micrographs of cells (right) of Galdieria partita grown under light or dark conditions with or without exogenous glucose. Modified from Fig. 1A and B of the paper.