At the journal club held on 17 September, 2018 Down's syndrome as a genetic condition characterized by the presence of an additional copy of chromosome 21 was introduced.
Recently it has been discovered that the additional copy of chromosome 21 in Down's syndrome reduces the production of SNX27 in the brain and results in synaptic dysfunction. By re-introducing SNX27 into the brain, memory could be restored hence suggesting that SNX27 is an essential protein for memory and learning. A concomitant reduced expression of SNX27 and CCAAT/enhancer binding protein b (C/EBPb) in Down’s syndrome brains and identify C/EBPb as a transcription factor for SNX27. Down’s syndrome causes overexpression of miR-155, a chromosome 21–encoded microRNA that negatively regulates C/EBPb, thereby reducing SNX27 expression and resulting in synaptic dysfunction.
Upregulating SNX27 in the hippocampus of Down’s syndrome mice rescues synaptic and cognitive deficits. Identification of the role of SNX27 in synaptic function establishes a new molecular mechanism of Down’s syndrome pathogenesis. Accordingly, inhibition of miR-155 seems a promising way to reactive SNX27 protein.