Developmental role of fatty acid-binding proteins in mouse brain.

While the functions of the cytoplasmic fatty acid-binding proteins (FABPs) are not well defined, one possibility in neural tissue is in establishing and maintaining the high levels of polyunsaturated fatty acids in membrane lipids characteristic of this tissue and thought essential for normal function. We investigated the reactivity of a protein in developing mouse brain to antiserum prepared against rat heart (H)-FABP. By immunoblot analysis, levels of H-FABP in brain were nearly undetectable 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 of 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 thalamus, entorhinal and piriform cortex, and throughout the pontine and medullary nuclei. Tracts related to the auditory system, including ventral 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 suggestive of mossy fiber terminals. Small cells adjacent to Purkinje cells were intensely stained, while the Purkinje cells were negative. We conclude that H-FABP in brain participates in neurite formation and synapse maturation, and may be related to the similar pattern of expression of GABA related markers.