DEVELOPMENTAL ROLE OF FATTY-ACID-BINDING PROTEINS IN MOUSE-BRAIN

While the functions of the cytoplasmic fatty acid-binding proteins (FA BPs) are not well defined, one possibility in neural tissue is in esta blishing and maintaining the high levels of polyunsaturated fatty acid s in membrane lipids characteristic of this tissue and thought essenti al for normal function. We investigated the reactivity of a protein in developing mouse brain to antiserum prepared against rat heart (H)-FA BP. By immunoblot analysis, levels of H-FABP in brain were nearly unde tectable until fetal day 17-19, after which levels increased until at least postnatal day 14. Levels of H-FABP were lower in the adult mouse brain, suggesting a function for the protein during differentiation o f neural tissue. In immunohistochemical studies with postnatal day 14 mouse brain, the most intensely stained area was the choroid plexus. H -FABP also localized to regions of the somatosensory cortex and to the spinal trigeminal nucleus. In addition, H-FABP was present in the tha lamus, entorhinal and piriform cortex, and throughout the pontine and medullary nuclei. Tracts related to the auditory system, including ven tral cochlear nucleus and lateral lemniscus, also were H-FABP-positive . In cerebellum, the molecular layer was heavily labeled in cells and processes; in the granule cell layer, there was punctate staining sugg estive of messy fiber terminals. Small cells adjacent to Purkinje cell s were intensely stained, while the Purkinje cells were negative. We c onclude that H-FABP in brain participates in neurite formation and syn apse maturation, and may be related to the similar pattern of expressi on of GABA related markers.