title: Unexpected Cartilage Phenotype in CD4-Cre-Conditional SOS-Deficient Mice.
abstract: RAS signaling is central to many cellular processes and SOS proteins promote RAS activation. To investigate the role of SOS proteins in T cell biology, we crossedSos1f/fSos2-/-mice to CD4-Cre transgenic mice. We previously reported an effect of these mutations on T cell signaling and T cell migration. Unexpectedly, we observed nodules on the joints of greater than 90% of these mutant mice at 5 months of age, especially on the carpal joints. As the mice aged further, some also displayed joint stiffness, hind limb paralysis, and lameness. Histological analysis indicated that the abnormal growth in joints originated from dysplastic chondrocytes. Second harmonic generation imaging of the carpal nodules revealed that nodules were encased by rich collagen fibrous networks. Nodules formed in mice also deficient in RAG2, indicating that conventional T cells, which undergo rearrangement of the T cell antigen receptor, are not required for this phenotype. CD4-Cre expression in a subset of cells, either immune lineage cells (e.g., non-conventional T cells) or non-immune lineage cells (e.g., chondrocytes) likely mediates the dramatic phenotype observed in this study. Disruptions of genes in the RAS signaling pathway are especially likely to cause this phenotype. These results also serve as a cautionary tale to those intending to use CD4-Cre transgenic mice to specifically delete genes in conventional T cells.
authors.affiliation: Laboratory of Cellular and Molecular Biology, CCR, NCI, NIH , Bethesda, MD , USA.
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Guittard
authors.affiliation: Laboratory Animal Sciences Program, Leidos Biomedical Research, NCI, NIH , Bethesda, MD , USA.
authors.forename: Devorah L
authors.initials: DL
authors.lastname: Gallardo
authors.affiliation: Laboratory of Cellular and Molecular Biology, CCR, NCI, NIH , Bethesda, MD , USA.
authors.forename: Wenmei
authors.initials: W
authors.lastname: Li
authors.affiliation: Laboratory of Cellular and Molecular Biology, CCR, NCI, NIH , Bethesda, MD , USA.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Melis
authors.affiliation: Section on Growth and Development, NICHD, NIH , Bethesda, MD , USA.
authors.forename: Julian C
authors.initials: JC
authors.lastname: Lui
authors.affiliation: Department of Pharmacology, Uniformed Services University of the Health Sciences , Bethesda, MD , USA.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Kortum
authors.affiliation: Laboratory of Cellular and Molecular Biology, CCR, NCI, NIH , Bethesda, MD , USA.
authors.forename: Nicholas G
authors.initials: NG
authors.lastname: Shakarishvili
authors.affiliation: Laboratory of Cellular and Molecular Biology, CCR, NCI, NIH , Bethesda, MD , USA.
authors.forename: Sunmee
authors.initials: S
authors.lastname: Huh
authors.affiliation: Section on Growth and Development, NICHD, NIH , Bethesda, MD , USA.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Baron
authors.affiliation: Laboratory of Cellular and Molecular Biology, CCR, NCI, NIH , Bethesda, MD , USA.
authors.forename: Roberto
authors.initials: R
authors.lastname: Weigert
authors.affiliation: Laboratory Animal Sciences Program, Leidos Biomedical Research, NCI, NIH , Bethesda, MD , USA.
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Kramer
authors.affiliation: Laboratory of Cellular and Molecular Biology, CCR, NCI, NIH , Bethesda, MD , USA.
authors.forename: Lawrence E
authors.initials: LE
authors.lastname: Samelson
authors.affiliation: Laboratory of Cellular and Molecular Biology, CCR, NCI, NIH , Bethesda, MD , USA.
authors.forename: Connie L
authors.initials: CL
authors.lastname: Sommers
keywords: RAS; SOS; T cell signaling; cartilage homeostasis; chondrocyte dysplasia; proliferation