The RNA of the glutamate transporter EAAT2 is variably spliced in amyotrophic lateral sclerosis and normal individuals

Impaired re-uptake of synaptic glutamate, and a reduced expression of the g lutamate transporter EAAT2 have been found in the motor cortex of patients with amyotrophic lateral sclerosis (ALS). Two splice forms of the EAAT2 RNA resulting from retention of intronic sequences (EAAT2/Int) and deletion of one protein coding exon (EAAT2/C1) have been reported to account for the E AAT2 protein loss in ALS. In this study we investigated the presence of two known (EAAT2/C1; EAAT2/Int) and three novel (EAAT2/C2-4) EAAT2 RNA in moto r cortex of 17 ALS cases and 11 controls. Reverse transcription and PCR wer e carried out to amplify the complementary DNA of the complete and variably spliced EAAT2 transcripts. Nested PCR was followed to generate amplicons s pecific for EAAT2/C1-4 and EAAT2/Int. EAAT2/Int was detected in 59% of ALS specimens as compared to 36% of controls showing a trend but no statistical significance of a more frequent expression in ALS (Type I error 24.6%). EA AT2/C1-4 were found to be equally expressed in ALS patients and controls. O ur results indicate that the involvement of EAAT2 transcripts in ALS is unl ikely to be primary, and more complex than previously recognized. Alteratio ns of quantitative expression of distinct EAAT2 splice forms in ALS cannot be excluded from this study and remain to be investigated. (C) 1999 Publish ed by Elsevier Science B.V. All rights reserved.