Selective reduction of KCNA4 in vulnerable glutamatergic-serotonin neurons of the dorsal raphe nucleus in Alzheimers Disease
INTRODUCTIONWe previously demonstrated that htau mice recapitulate many neuropsychiatric features of early Alzheimers disease (AD), and that the dorsal raphe nucleus (DRN) contains distinct subregions. Herein, we investigate vulnerability of the centromedial DRN to pathologically-phosphorylated tau (pTau), a region composed predominantly of dually serotonergic/glutamatergic (5HT/glut) neurons. METHODSWe use computational, molecular, biophysical, and behavioral techniques to assess the centromedial DRN across preclinical and post-mortem settings. RESULTSThe centromedial DRN contains 5HT/glut neurons that differentially express ion-channel genes in the htau mouse. 5HT/glut neurons exhibit increased excitability, which we demonstrate may dually promote pTau accumulation and the severity of depressive-like behaviors in htau mice. At Braak 2, KCNA4 is reduced in 5HT/glut neurons in AD, which are especially vulnerable to pTau compared to 5HT-nonglut neurons. DISCUSSIONTau-mediated dysfunction of the DRN may be driven by changes in ion channel activity that concomitantly promote the spread of pTau in Braak progression.