Ttc22 knockout mice show no developmental or tumor phenotypes

Deleting the Ttc22 gene in mice does not appear to disrupt development, fertility, or spontaneous tumor formation, according to a study in which researchers inactivated the gene in C57BL/6N mice and monitored the animals over the long term. The finding is notable because TTC22, the human counterpart of the gene, had previously been implicated in promoting metastasis in human colon adenocarcinoma, raising expectations that its loss might protect mice from colorectal cancer.

TTC22 encodes a protein built around seven tetratricopeptide repeats, structural motifs that mediate protein-protein interactions and often function as chaperones. Earlier work by the same team had shown that transcript variant 1 of TTC22 was downregulated in human colon adenocarcinoma, while the protein upregulated m6A-mediated expression of WTAP and SNAI1 through an interaction with RPL4, ultimately promoting metastatic behavior in that cancer. To test whether the gene matters for disease in a living organism, the researchers turned to a commercially available mouse line in which exons 2 and 3, encoding the TPR4 domain corresponding to human TTC22 TPR3, had been removed using CRISPR-Cas9.

Because the deletion removes only part of the protein, the team first verified the model at the molecular level. They generated a rabbit polyclonal antibody against mouse Ttc22 and confirmed by Western blot that it bound both wild-type Ttc22 and the TPR4-deleted variant when the proteins were overexpressed in HEK293T cells. Using this antibody, they detected Ttc22 protein in colon tissue from wild-type mice and from hemizygous Ttc22+/- animals, but not from fully knockout Ttc22-/- mice, confirming that the engineered line abolished detectable protein in homozygous animals.

Long-term observation, however, showed no consequences of losing the gene. Neither heterozygous nor homozygous knockout mice of either sex differed from controls in body weight, general development, fertility, or the incidence of spontaneous tumors. When the researchers induced colorectal cancer with the standard AOM/DSS chemical regimen, tumor incidence was also indistinguishable between the groups, despite the earlier evidence linking TTC22 to metastatic pathways in human colon cancer cells.

One molecular change did emerge: deleting Ttc22 partially upregulated genes involved in the host adaptive immune response to inflammation in the colon mucosa. That transcriptional shift did not translate into any measurable disease phenotype in the model. The authors conclude that Ttc22 inactivation in C57BL/6N mice induces no phenotypes, a negative result that cautions against extrapolating the gene’s pro-metastatic role in human tumor cells to intact animal physiology and suggests that TTC22’s contribution to colorectal cancer, if any, depends on contexts not reproduced in this knockout model.

Subject of Research: Phenotypic analysis of Ttc22 knockout mice and colorectal cancer susceptibility

Article Title: No phenotypes in Ttc22 knockout mice

Article References: Liu, J., Gu, L., You, A., Yuan, H., Zhou, J., Tian, W., & Deng, D. (2026). No phenotypes in Ttc22 knockout mice. PLOS One, 21(10), e0361340. https://doi.org/10.1371/journal.pone.0361340

Image Credits: AI Generated

DOI: 10.1371/journal.pone.0361340

Keywords: Ttc22, knockout mice, colorectal cancer, tetratricopeptide repeats, CRISPR-Cas9, C57BL/6N, AOM/DSS model, colon adenocarcinoma, metastasis, gene function, phenotypes, knockout