Expression of erbA[alpha] and [beta] mRNAs in regions of adult rat brain

Abstract

The proto-oncogenes erbAa and erbA[beta] together encode three functional thyroid hormone receptors (erbAol, [beta]1, and [beta]2), as well as two proteins (erbA[sigma] 2 and [alpha]3) that do not bind T3. The erbA[alpha]2 protein has been shown to inhibit the T3 inductive effects of functional receptors, and [alpha]2 mRNA is expressed at high levels in adult rat brain. Thus, expression of erbA[alpha]2 may explain the observation that adult rat brain is not a T3 responsive organ, despite the presence of T3 receptors. However, expression of the different erbA mRNAs has not been studied within distinct regions of rat brain. To gain further insight into the roles of these molecules, we have used polymerase chain reaction to investigate the expression of all five erbA mRNAs within discrete regions of adult rat brain. The results indicate that all three erbAa mRNAs are expressed in all regions studied (brainstem, cerebellum, cortex, hippocampus, pituitary, quadrigeminal plate, striatum, and thalamus). All regions contained less erbA[alpha]3 RNA than either [alpha]1 or [alpha]2. Expression of [alpha]2 exceeded that of [alpha]l in all regions except striatum. ErbA[beta]l was expressed in all brain regions, whereas erbA[beta]2 was confined to the pituitary.AbstractThyroid hormone receptor; Polymerase chain reaction