GJA1 and early-onset autosomal dominant Alzheimer disease: Cx43 is widely expressed in the CNS, especially neurons, microglia, astrocytes, and oligodendrocytes [26,27,28], and has been shown to be involved in various neurodegenerative diseases, including Alzheimer’s disease [29], Parkinson’s disease [30], multiple sclerosis [31], epilepsy [32] and prion diseases [33].