MOLECULAR-CLONING REVEALS THE EXISTENCE OF A 4TH-GAMMA-SUBUNIT OF THEVERTEBRATE BRAIN GABA(A) RECEPTOR

We have isolated a cDNA, from the chicken, that encodes a fourth type of gamma subunit of the vertebrate brain GABA(A) receptor. The mature polypeptide (which we name gamma4) displays 67%, 69% and 70% identity, respectively, to the rat gamma1, gamma2 and gamma3 subunits. In the d eveloping chicken brain, the gamma4-subunit mRNA is first detected at embryonic day 13; the transcript level then increases progressively du ring embryogenesis. In situ hybridization reveals that the gamma4-subu nit mRNA is abundant in several brain regions, including the ectostria tum, nucleus rotundus and hyperstriatum ventrale, which are involved i n visual processing and learning.