Journal of Neuroscience, Vol 5, 1781-1802, Copyright © 1985 by Society for Neuroscience
Immunocytochemical mapping of 1B236, a brain-specific neuronal polypeptide deduced from the sequence of a cloned mRNA
FE Bloom, EL Battenberg, RJ Milner and JG Sutcliffe
The 318-amino acid, carboxy-terminal sequence of the putative brain-
specific polypeptide 1B236 was deduced from the nucleotide sequence of its
cloned brain-specific mRNA. Antisera raised against selected synthetic
peptide fragments of this protein were used to map the cellular location of
the presumptive gene product in the brains of normal or
colchicine-pretreated adult rats. Antisera directed against any of three
C-terminally located, but nonoverlapping, nonhomologous, synthetic peptide
segments (P5, P6, or P7) produced virtually identical maps of intensely
immunoreactive neuropil staining. The immunoreactivity was distributed
heterogeneously and was most pronounced within olfactory, somatosensory,
and limbic systems, and was more modest in certain motor and auditory
structures. In colchicine- pretreated rats, large, multipolar perikarya
were observed within the amygdala, caudate-putamen, cingulate, parietal,
and piriform cortices, as well as in particular diencephalic and pontine
nuclei. Smaller immunoreactive neurons with more limited dendritic
extensions were observed in the olfactory bulb, the cerebellar cortex, and
the dorsal horn and intermediolateral cell columns of the spinal cord. No
immunoreactivity was observed in visceral structures innervated by the
autonomic nervous system or in non-neural tissues. In addition to the
virtually superimposable maps produced by antisera to all three synthetic
fragments selected from the C-terminus of 1B236, some uniquely reactive
sites were seen. Antisera to the most N-terminal of the three synthetic
immunogens (P5) were reactive with neurons of the medial trapezoid nucleus
and in nerve terminals surrounding the deep cerebellar nuclei. Antisera
against the most C-terminal synthetic immunogen (P7) were reactive with
neurons of the paraventricular and supraoptic hypothalamic nuclei. These
data demonstrate that the 1B236 protein is located within selected neuronal
elements within functionally related cellular circuits established more
formally by other methods. Our data show that protein 1B236-immunoreactive
cells share at least the expression of this protein and suggest that these
cells may also be related epigenetically or evolutionarily. These data,
together with other subcellular, ultrastructural, and electrophysiological
properties of 1B236, suggest that this protein could be considered as a
prohormone capable of yielding several final candidate transmitter
products.