Altered ratios of alternatively spliced long and short gamma2 subunit mRNAs of the gamma-amino butyrate type A receptor in prefrontal cortex of schizophrenics.

The relative abundance of alternatively spliced long (gamma2L) and short (gamma2S) mRNAs of the gamma2 subunit of the gamma-amino butyrate type A (GABAA) receptor was examined in dorsolateral prefrontal cortex of schizophrenics and matched controls by using in situ hybridization histochemistry and semiquantitative reverse transcription-PCR (RT-PCR) amplification. A cRNA probe identifying both mRNAs showed that the transcripts are normally expressed at moderately high levels in the prefrontal cortex. Consistent with previous studies, overall levels of gamma2 transcripts in prefrontal cortex of brains from schizophrenics were reduced by 28.0%, although this reduction did not reach statistical significance. RT-PCR, performed under nonsaturating conditions on total RNA from the same blocks of tissue used for in situ hybridization histochemistry, revealed a marked reduction in the relative proportion of gamma2S transcripts in schizophrenic brains compared with controls. In schizophrenics, gamma2S transcripts had fallen to 51.7% (+/-7.9% SE; P < 0.0001) relative to control levels. Levels of gamma2L transcripts showed only a small and nonsignificant reduction of 16. 9% (+/-12.0% SE, P > 0.05). These findings indicate differential transcriptional regulation of two functionally distinct isoforms of one of the major GABAA receptor subunits in the prefrontal cortex of schizophrenics. The specific reduction in relative abundance of gamma2S mRNAs and the associated relative increase in gamma2L mRNAs should result in functionally less active GABAA receptors and have severe consequences for cortical integrative function.