Overexpression of PTP1B counteracts the effects of Aβ on dendrite patterning (A, B, C) and neuron death (D, E). Cultured hippocampal neurons (40,000 cells/cm2, 7 DIV) were co-transfected with the EGFP and PTP1B plasmids, treated with Aβ (5 μM) and incubated for a further 16 h to analyse dendrite patterning (A, B, C). (A) Representative micrographs of cultured hippocampal neurons at 7 DIV treated with Aβ and/or transfected with PTP1B. EGFP immunostaining is in green and the transfected HA-tagged PTP1B in red. (B, C) Quantification of the relative dendrite length (B) and primary dendrite number (C) in the four conditions indicated. Note that overexpression of PTP1B increased dendrite length and prevented the morphological effects of Aβ. (D, E) Hippocampal neurons (30,000 cells/cm2) were cultured for 7 days and then treated with Aβ (5 μM). Two days later, the neurons were transfected with the PTP1B expressing plasmid, and on the following day the cells were stained and the live cells determined as described in the Methods. (D) Representative micrographs of double-labelled cultured hippocampal neurons under the four conditions described. EGFP immunostaining is in green, the transfected HA-tagged PTP1B in red and the DAPI stained nuclei are blue. (E) Quantification of live cells. Note that transfection with the PTP1B expressing plasmid rescued a significant number of neurons from Aβ-induced neuron death.