Osteopontin expression in the brain triggers localized inflammation and cell death when immune cells are activated by pertussis toxin.

Upregulation of osteopontin (OPN) is a characteristic of central nervous system pathologies. However, the role of OPN in inflammation is still controversial, since it can both prevent cell death and induce the migration of potentially damaging inflammatory cells. To understand the role of OPN in inflammation and cell survival, we expressed OPN, utilizing an adenoviral vector, in the caudoputamen of mice deficient in OPN, using beta-galactosidase- (ß-gal-) expressing vector as control. The tissue pathology and the expression of proinflammatory genes were compared in both treatments. Interestingly, inflammatory infiltrate was only found when the OPN-vector was combined with a peripheral treatment with pertussis toxin (Ptx), which activated peripheral cells to express the OPN receptor CD44v6. Relative to ß-gal, OPN increased the levels of inflammatory markers, including IL13Rα1, CXCR3, and CD40L. In Ptx-treated OPN KOs, apoptotic TUNEL+ cells surrounding the OPN expression site increased, compared to ß-gal. Together, these results show that local OPN expression combined with a peripheral inflammatory stimulus, such as Ptx, may be implicated in the development of brain inflammation and induction of cell death, by driving a molecular pattern characteristic of cytotoxicity. These are characteristics of inflammatory pathologies of the CNS in which OPN upregulation is a hallmark.

A Gja8 (Cx50) point mutation causes an alteration of alpha 3 connexin (Cx46) in semi-dominant cataracts of Lop10 mice.

Mutations of connexin alpha 8 (GJA8 or Cx50) and connexin alpha 3 (GJA3 or Cx46) in humans have been reported to cause cataracts with semi-dominant inheritance patterns. Targeted null mutations in Gja8 and Gja3 in mice cause cataracts with recessive inheritance. The molecular bases for these differences in inheritance patterns and the mechanism for cataractogenesis in these mutants are poorly understood. We recently mapped an autosomal semi-dominant cataract [lens opacity 10 (Lop10)] mutation to mouse chromosome 3 and identified a missense mutation (G-->C) in the Gja8 gene, which causes glycine at codon 22 to be replaced with arginine (G22R). Moreover, we demonstrated that the alpha 8 G22R isoform is a loss-of-function mutant for alpha 8, as well as a dominant mutation for reducing the phosphorylated forms of alpha 3 connexin in vivo. To test the hypothesis that the alteration of endogenous alpha 3 connexin in Lop10 mice led to a unique lens phenotype, we generated double mutant offspring between Lop10 and the Gja3(tm1) (alpha 3(-/-)) mice. The double homozygous mutant mice (Lop10/Lop10 alpha 3(-/-)) showed relatively normal lens cortical fibers compared to the Lop10 mice. A functional impairment of endogenous alpha 3 connexin is therefore partly responsible for cellular phenotypes in the Lop10 mice. This study has provided some novel molecular insights into mouse and human cataractogenesis caused by alpha 8 and alpha 3 mutations. These mouse models will be useful for investigating the mechanistic relationship between gap junction impairment and cataract formation.