DIFFERENCES IN THE LEVELS OF RAT GABABR1A, GABABR1B, GABABR1F, GABABR2, AND GABABRL TRANSCRIPTS SUGGEST A LACK OF COORDINATE REGULATION DURING EMBRYONIC DEVELOPMENT

STELLA MARTIN; JANINE STEIGER; MARIA CLARA GRAVIELLE; SHELLEY RUSSEK; DAVID FARB

Nueva Orleans

Congreso; XXXIII Reunión Anual de la Society for Neurocience; 2003

Reunión Anual de la Society for Neurocience

The requirement of two distinct GABABR subunits for the formation of a functional receptor suggests that their genes may be coordinately regulated. We examined whether transcripts for rat GABABR1 and GABABR2 are present at similar levels during embryonic development using RNase protection and in situ hybridization. Results suggest that GABABR1 may function without GABABR2 in parts of the nervous system or may form dimers with a different partner. A novel GABABR cDNA, termed GABABL, has been cloned (Calver et al., 2003). We used real-time PCR to examine whether the presence of GABABL transcripts is consistent with GABABL being a possible partner for GABABR1 in the olfactory bulb and the striatum, where GABABR2 levels are very low. Two different primers and probe sets were used to examine GABABL expression in the adult whole brain, cortex, olfactory bulb and striatum. GABABL transcripts are found in olfactory bulb and striatum to a similar degree as in whole brain. Results of real-time PCR with GABABR2 primers are consistent with our results of in situ hybridization and RNase protection indicating that GABABR2 transcripts are not uniformly present and are at much lower levels in the striatum and olfactory bulb. Three GABABR1 gene transcripts were measured by real-time PCR: GABABR1a, GABABR1b and GABABR1f. Unlike GABABR2 and more like GABABL, GABABR1a and GABABR1b transcripts are all detectable at similar levels in all regions examined. Transcript levels were measured in the embryo at E17 for all GABABR primer sets. GABABL is 5 times and GABABR1f is 3.5 times more highly expressed in the E17 embryo than in the adult. Whereas GABABR1a, GABABR1b and GABABR2 are 2.4, 7 and 8 times respectively, more highly expressed in the adult rat brain than the E17 embryo.