Pathologic and Phenotypic Alterations in a Mouse Expressing a Connexin47 Missense Mutation That Causes Pelizaeus-Merzbacher–Like Disease in Humans

Abstract

Gap junction channels are intercellular conduits that allow diffusional exchange of ions, second messengers, and metabolites. Human oligodendrocytes express the gap junction protein connexin47 (Cx47), which is encoded by the GJC2 gene. The autosomal recessive mutation hCx47M283T causes Pelizaeus-Merzbacher–like disease 1 (PMLD1), a progressive leukodystrophy characterized by hypomyelination, retarded motor development, nystagmus, and spasticity. We introduced the human missense mutation into the orthologous position of the mouse Gjc2 gene and inserted the mCx47M282T coding sequence into the mouse genome via homologous recombination in embryonic stem cells. Three-week-old homozygous Cx47M282T mice displayed impaired rotarod performance but unchanged open-field behavior. 10-15-day-old homozygous Cx47M282T and Cx47 null mice revealed a more than 80% reduction in the number of cells participating in glial networks after biocytin injections into oligodendrocytes in sections of corpus callosum. Homozygous expression of mCx47M282T resulted in reduced MBP expression and astrogliosis in the cerebellum of ten-day-old mice which could also be detected in Cx47 null mice of the same age. Three-month-old homozygous Cx47M282T mice exhibited neither altered open-field behavior nor impaired rotarod performance anymore. Adult mCx47M282T expressing mice did not show substantial myelin alterations, but homozygous Cx47M282T mice, additionally deprived of connexin32, which is also expressed in oligodendrocytes, died within six weeks after birth and displayed severe myelin defects accompanied by astrogliosis and activated microglia. These results strongly suggest that PMLD1 is caused by the loss of Cx47 channel function that results in impaired panglial coupling in white matter tissue.

Changes in Object Recognition and Anxiety-Like Behaviour in Mice Expressing a Cx47 Mutation That Causes Pelizaeus-Merzbacher-Like Disease

“…Two batches of experimentally naïve mice at ages of P23 (n = 9 Cx47 +/+ ; n = 12 Cx47 +/M282T ; n = 9 Cx47 M282T/M282T ) and 3 months (n = 14 Cx47 +/+ ; n = 18 Cx47 +/M282T ; n = 12 Cx47 M282T/M282T ) were used. The generation and genotyping of Cx47M282T mutant mice has been described previously [32]. Mutant mice were backcrossed with C57BL/6 mice to provide a >96% C57BL/6 genetic background.…”

“…We have generated a transgenic mouse model of PMLD that carries the Cx47M282T point mutation, the mouse ortholog of the corresponding human Cx47M283T mutation [32]. Homozygous Cx47M282T mice exhibited hypomyelination during the first weeks after birth accompanied by vacuolation of white matter tracts, astrogliosis and microglia activation.…”

“…Three-week-old mice homozygous for the Cx47M282T mutation showed impaired rotarod performance. No significant changes in myelin formation or rotarod performance were observed in 3-month-old Cx47M282T mice [32]. Here, we examined the effects of Cx47M282T expression in the juvenile and adult mouse on anxiety-like behaviour, neuromotor performance and on learning and memory.…”

The endocannabinoid system in normal and pathological brain ageing

“…In the brain of patients suffering from neurodegenerative diseases [138][139][140] and in animal models of these disorders [141][142][143][144], signs of massive neuroinflammation are detected. Importantly, the phenotype of both astrocytes and microglia changes in ageing.…”

The Role of Gap Junctions in Charcot-Marie-Tooth Disease

“…Oligodendrocytes, for example, coexpress Cx47, and at least in rodents, the loss of both Cx32 and Cx47 is far more deleterious than the loss of either one alone (Menichella et al, 2003;Odermatt et al, 2003). However, loss-of-function mutations in GJC2 encoding Cx47 in humans cause PelizeausMerzbacher-like disease (Uhlenberg et al, 2004;Tress et al, 2011). Thus, in humans and not in mice the loss of Cx47 alone produces a severe leukodystrophy.…”