A new brain-derived neurotrophic factor transcript and decrease in brain-derived neurotrophic factor transcripts 1, 2 and 3 in Alzheimer’s disease parietal cortex Diego Garzon, Guanhua Yu and Margaret Fahnestock Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, Ontario, Canada Abstract Brain-derived neurotrophic factor (BDNF) supports hippo- campal, cortical and basal forebrain cholinergic neurons, which lose function in Alzheimer’s disease. In Alzheimer’s tissues such as hippocampus and parietal cortex, brain- derived neurotrophic factor mRNA is decreased three- to four- fold compared with controls. However, the molecular mechanism of the down-regulation of BDNF in Alzheimer’s disease is unknown. The human brain-derived neurotrophic factor gene has multiple promoters governing six non-coding upstream exons that are spliced to one downstream coding exon, leading to six different transcripts. Here we report an alternate human splice variant within exon 4I for a total of seven transcripts. Previous brain-derived neurotrophic factor mRNA measurements in Alzheimer’s disease tissue were done using the downstream coding exon present in all tran- scripts. Using RT-PCR primers specific for each upstream exon, we observe a significant decrease in three human brain- derived neurotrophic factor mRNA transcripts in Alzheimer’s disease samples compared with controls. Transcripts 1 and 3 each exhibit a two-fold decrease, and transcript 2 shows a five-fold decrease. There are no significant differences between control and Alzheimer’s disease samples for the other transcripts, including the new splice variant. In rat, both transcripts 1 and 3 are regulated through the transcription factor cAMP response element binding protein, whose phos- phorylation is decreased in the Alzheimer’s disease brain. This could lead to specific down-regulation of the brain- derived neurotrophic factor transcripts shown here. Keywords: brain-derived neurotrophic factor, gene expres- sion, human, mRNA, RT-PCR. J. Neurochem. (2002) 82, 1058–1064. Brain-derived neurotrophic factor (BDNF) is highly expressed and is distributed widely throughout the CNS, specifically in the hippocampal formation, cerebral cortex, and amygdaloid complex (Ernfors et al. 1990; Hofer et al. 1990; Phillips et al. 1990; Wetmore et al. 1990). BDNF promotes the survival and function of hippocampal and cortical neurons (Ghosh et al. 1994; Lindholm et al. 1996; Lowenstein and Arsenault 1996), cholinergic neurons (Alderson et al. 1990; Knusel et al. 1991) and nigral dopaminergic neurons (Hyman et al. 1991; Knusel et al. 1991).BDNFisalsoimportantforsynaptictransmissionand the excitatory properties of these neurons (Patterson et al. 1992; Castren et al. 1993; Dragunow et al. 1993; Kang and Schuman 1995; Scharfman 1997; Osehobo et al. 1999; McLean et al. 2000). Basal forebrain cholinergic, cortical, and hippocampal neurons lose function and synaptic connectivity in Alzhei- mer’s disease (AD) (Coyle et al. 1983; Whitehouse et al. 1982; Cuello and Sofroniew 1984; Etienne et al.1986;Hefti andWeiner1986;Mann1991).Thismayoccurbecauseofa deficit in BDNF in the AD brain. A 3–4-fold reduction in BDNF mRNA has been amply documented in the hippo- campus and parietal cortex (Phillips et al. 1991; Holsinger et al. 2000). Protein levels of BDNF have been shown to decrease in Alzheimer’s disease entorhinal cortex, hippo- campus and temporal, frontal and parietal cortex (Narisawa- Saito et al. 1996; Connor et al. 1997; Ferrer et al. 1999; Hock et al. 2000). However, the transcriptional regulation of the human BDNF gene has not been studied, and so the ReceivedFebruary20,2002;revisedmanuscriptreceivedMay10,2002; accepted May 13, 2002. Address correspondence and reprint requests to Dr Margaret Fahne- stock, Department of Psychiatry and Behavioural Neurosciences, McMaster University, 1200 Main Street West, Hamilton, Ontario, Canada L8N 3Z5. E-mail: fahnest@mcmaster.ca Abbreviations used: AD, Alzheimer’s disease; BDNF, brain-derived neurotrophic factor; CRE, cAMP response element; CREB, cAMP response element binding protein. Journal of Neurochemistry , 2002, 82, 1058–1064 1058 Ó 2002 International Society for Neurochemistry, Journal of Neurochemistry , 82, 1058–1064