Developmentally regulated expression of GABA receptor rho 1, and rho 2 subunits, L7 and cone-rod homeobox (CRX) genes in mouse retina

In this study, we compared the temporal expression pattern of four retinal genes; rho1 and rho2 that encode subunits of GABA(c) receptors, L7 that enc odes Purkinje cell protein and CRX that encodes the cone-rod homeobox trans cription factor. A reverse-transcription-polymerase chain reaction (RT-PCR) strategy that generated a linear correlation between the amount of retinal RNA and the amount of amplified product was used to quantify transcripts f rom each gene. Results with this method showed that the rho1 and L7 have si milar developmental patterns. Both exhibit basal level expression before P7 . From P7 to P20, the RNA levels for both genes were increased about 12-fol d. After P20, the RNA levels remained unchanged. Compared to rho1 and L7, e xpression of rho2 began later, since the rho2 RNA could not be detected unt il P10. At P10, the rho2 RNA level was about 10% of its level at P35. Expre ssion of rho2 reached its peak at a later developmental stage compared to t hat of rho1 and L7. The different temporal patterns were confirmed by co-am plification of rho1, rho2, and L7 in a single PCR tube. CRX RNA was detecte d at embryonic day 15 (E15) and increased progressively, in agreement with a prior study using in situ hybridization. These data, combined with eviden ce that the tissue distribution of rho1 and L7 RNA in the CNS are similar, indicates that rho1 and L7 may share common transcriptional regulatory elem ents. Furthermore, the difference in the timing of rho subunit expression s uggests that the subunit composition of GABA, receptors vary during retinal development. (C) 2001 Elsevier Science B.V. All rights reserved.