Identification of gene mutations associated with the phenotype of short-limb mice emerging from a foundation colony of severely immunodeficient mice.

Here, we report the identification of causative genes for limb-shortening in individuals repeatedly found in a population of severely immunodeficient NOG mice maintained via sibling mating. First, we conducted a pedigree survey to determine whether limb-shortening was a recessive genetic trait and then identified it using a crossing test. Simultaneously, the symptoms were identified in detail using pathological analysis. Accordingly, a mouse strain exhibiting a recessive trait caused by a single gene trait and similar symptoms was identified, suggesting growth differentiation factor 5 (Gdf5) as a causative gene. Genome walking via PCR and sequence analysis of Gdf5 revealed a deletion of approximately 1.1 kb from the latter half of exon 2 of Gdf5. Furthermore, we established NOG-Gdf5bpJic by removing other modified genes and confirmed that the inheritance pattern was reconfirmed semi-dominant. In recent years, regenerative medicine research using immunodeficient mice has been actively conducted, and this murine strain is expected to contribute to niche stem cell analysis and transplantation research.