ELF a β-spectrin is a neuronal precursor cell marker in developing mammalian brain; structure and organization of the elf/β-G spectrin gene

Spectrins play a pivotal role in axonal transport, neurite extension, the organization of synaptic vesicles, as well as for protein sorting in the Golgi apparatus and cell membrane. Among spectrins there is great variability in sequence composition, tissue distribution, and function, with two known genes encoding the α-chain, and at least five encoding the β-chain. It remains unclear as to whether novel β-spectrins such as elf1-4 are distinct genes or β-G-spectrin isoforms. The role for ELF in the developing nervous system has not been identified to date. In this study we demonstrate the genomic structure of elf-3, as well as the expression of ELF in the developing mouse brain using a peptide specific antibody against its distinctive amino-terminal end. Full genomic structural analyses reveal that elf-3 is composed of 31 exons spanning ∼67 kb, and confirm that elf and mouse brain β-G-spectrin share multiple exons, with a complex form of exon/intron usage. In embryonic stages, E9-12, anti-ELF localized to the primary brain vesicular cells that also labeled strongly with anti-nestin but not antivimentin. At E12-14, anti-ELF localized to axonal sprouts in the developing neuroblasts of cortex and purkinje cell layer of the cerebellum, as well as in cell bodies in the diencephalon and metencephalon. Double labeling identified significant co-localization of anti-ELF, nestin and dystrophin in sub ventricular zone cells and in stellate-like cells of the developing forebrain. These studies define clearly the expression of ELF, a new isoform of β-G-spectrin in the developing brain. Based on its expression pattern, ELF may have a role in neural stem cell development and is a marker of axonal sprouting in mid stages of embryonic development.