A rad50 germline mutation induces tumorigenesis and ataxia-telangiectasia phenotype in a transparent medaka model

The MRE11A-RAD50-NBS1 complex activates the ataxia-telangiectasia mutated (ATM) pathway and plays a central role in genome homeostasis. The association of RAD50 mutations with disease remains unclear; hence, we adopted a medaka rad50 mutant to demonstrate the significance of RAD50 mutation in pathogenesis using the medaka as an experimental animal. A 2-base pair deletion in the rad50 gene was introduced into transparent STIII medaka using the CRISPR/Cas9 system. The mutant was analyzed histologically for tumorigenicity and hindbrain quality, as well as for swimming behavior, to compare with existing ATM-, MRE11A-, and NBS1-mutation-related pathology. Our results revealed that the medaka rad50 mutation concurrently reproduced tumorigenesis (8 out of 10 rad50(Delta 2/+) medaka), had a decrease in median survival time (65.7 +/- 1.1 weeks in control vs. 54.2 +/- 2.6 weeks in rad50(Delta 2/+) medaka, p = 0.001, Welch's t-test), exhibited semi-lethality in rad50(Delta 2/Delta 2) medaka and most of the major ataxia-telangiectasia phenotypes, including ataxia (rheotaxis ability was lower in rad50(Delta 2/+) medaka than in the control, Mann-Whitney U test, p < 0.05), and telangiectasia (6 out of 10 rad50(Delta 2/+) medaka). The fish model may aid in further understanding the tumorigenesis and phenotype of ataxia-telangiectasia-related RAD50 germline mutations and in developing novel therapeutic strategies against RAD50 molecular disorders.

Automated summary

The MRE11A-RAD50-NBS1 complex is important for genome homeostasis and its association with diseases, especially RAD50 mutations, is not clear. In this study, we used medaka as an experimental animal to investigate the significance of RAD50 mutation in pathogenesis. A 2-base pair deletion in the rad50 gene was introduced into medaka using the CRISPR/Cas9 system, and the mutant exhibited tumorigenesis and ataxia-telangiectasia phenotypes. This fish model provides a valuable tool for studying and developing therapies for RAD50-related molecular disorders.