Expression of acyl-CoA hydrolase in the developing mouse brain.

Brain acyl-CoA hydrolase (BACH) is a cytosolic enzyme responsible for the brain long-chain acyl-CoA thioesterase activity, that is the highest in the body. BACH was detected in the mouse brain as early as embryonic day (E) 11.5 by immunoblotting. The level of the major isoform (43-kDa) was low until E12.5, but promptly elevated to a peak 7 days after birth. Thereafter, it declined somewhat and reached a steady-state level in adulthood. These changes in BACH expression were approximately reflected in the palmitoyl-CoA hydrolyzing activity in the developing mouse brain, and the time course was quite similar to that of microtubule-associated protein 2 (MAP2) expression. In immunohistochemistry of E14.5 embryo brains, cells expressing BACH almost coincided with the cells committed to the neuronal lineage, which expressed MAP2 but not nestin. These results indicate that BACH expression is induced during embryogenesis in association with neuronal differentiation, and persists after terminal differentiation into neurons in postnatal stages, resulting in the constitutive high expression of BACH in the adult brain in a neuron-specific manner.