Independent expression of the α and β c-erbA genes in developing rat brain

Abstract

Thyroid hormone is important for normal brain development. Cellular responses to thyroid hormone are mediated by multiple nuclear receptors, classified into α- and β-subtypes. In the rat, expression of both the α and βgenes results in several translation products. By using cRNA probes common to α transcripts or specific for α-1 and β-1, we have studied the distribution of these transcripts in rat brain at different stages of development from embryonic day 14 to adult age by using in situ hybridization histochemistry. On embryonic day 14, the α-1 mRNA is already widely expressed at a low level in the developing brain. The α-1 mRNA is developmentally regulated and showed a peak in expression during the first 3 postnatal weeks in the cerebral cortex, amygdala, hippocampus, and cerebellum. The probe common to the a transcripts detected a widespread distribution and high levels of these forms in the same regions throughout postnatal development. The level of β-1 mRNA before birth was low or undetectable. The β-1 transcript showed developmental regulation as well, with a high level at birth in the mitral cell layer of the olfactory bulb, accumbens nucleus, caudate, and hippocampal field CA1 and increasing levels in other regions later during development. Complementary expression of the a and β forms was seen in the cerebral cortex and hippocampus. The differential temporal and spatial distribution as well as coexpression at comparable levels in certain brain regions suggest different roles for the c-erbA proteins during brain development and in the mature animal. Copyright © 1991 by The Endocrine Society.