Structure and expression of canary myc family genes

Characterization of a novel protein regulated during the critical period for song learning in the zebra finch

A male zebra finch learns a song by listening to a tutor, but song learning is normally restricted to a critical period in juvenile development. Here we identify an RNA whose expression in the song control circuit is altered during this critical period. The RNA encodes a soluble presynaptic protein that forms a predicted amphipathic alpha helix typical of the lipid-binding domain in apolipoproteins. We show this protein, which we call synelfin, to be the homolog of the human non-A beta component (and its precursor) recently purified from Alzheimer's disease amyloid. We suggest this highly conserved protein may serve a novel function critical to the regulation of vertebrate neural plasticity.

The canary androgen receptor mRNA is localized in the song control nuclei of the brain and is rapidly regulated by testosterone

Singing in canaries is an androgen-inducible behavior, under the control of an identified motor pathway, which includes several discrete "song nuclei" in the telencephalon. To determine whether the mRNA for the canary androgen receptor (cAR) is expressed in these song control nuclei, we synthesized probes from the recently cloned cAR cDNA and used in situ hybridization to examine spring male canary brain sections. Concentrations of cAR mRNA are detectable in several of the song control nuclei of the forebrain, including high vocal center (HVC), lateral magnocellular nucleus of the anterior neostriatum and robust nucleus of the archistriatum. In addition, we also show that testosterone treatment rapidly induces a significant reduction of cAR mRNA levels in nucleus HVC of females. Since the effects of androgen on singing behavior occur much more slowly, the behavioral effects are probably a secondary or independent result of androgen's primary and immediate action on target gene transcription.

Immediate-early gene responses in the avian song control system: cloning and expression analysis of the canary c-jun cDNA

Previous studies have shown that song presentation results in a rapid rise in mRNA levels for the ZENK gene (the avian homologue of zif-268, Egr-1, NGFI-A, and Krox-24) in specific parts of the songbird forbrain. Metrazole-induced seizures also cause an increase in ZENK mRNA, even more widely throughout the telencephalon. Surprisingly, however, little or no ZENK induction by either stimulus was observed in several forebrain areas involved in auditory processing and song production. To learn whether this pattern of regulation is specific to ZENK, we examined the response of another 'immediate-early' gene, c-jun. Here we first describe the identification, cloning and sequence analysis of a canary cDNA encoding c-jun. Then, by in situ hybridization we show that c-jun is also induced by song or seizure, and in a pattern mostly similar to ZENK. As with ZENK, no induction of c-jun is observed in the androgen receptor-containing song nuclei or within the primary thalamo-recipient auditory area of the forebrain. Thus common immediate early gene responses appear to be selectively uncoupled from physiological activation in these specific forebrain regions, which are also characterized by tight developmental, hormonal and seasonal regulation.

Transition of localization of the N-Myc protein from nucleus to cytoplasm in differentiating neurons

N-myc is a developmentally regulated proto-oncogene encoding a putative sequence-specific DNA-binding protein. Previous studies on tissue distribution of N-myc transcripts indicated that one of the major sites of N-myc expression is the CNS and neural crest derivatives in developing embryos. We investigated N-Myc protein expression in embryonic neural tissues and found that the protein was usually localized in the nucleus, but accumulated in the cytoplasm upon differentiation of specific classes of neurons, e.g., retinal ganglion cells, neurons of spinal ganglia, and Purkinje cells of the cerebellum. The change of localization of N-Myc from the nucleus to the cytoplasm indicates a novel feature of regulation of myc family proteins and suggests functions of N-myc in the cytoplasm of maturing neurons.

Differential regulation in the avian song control circuit of an mRNA predicting a highly conserved protein related to protein kinase C and the bcr oncogene

An RNA identified by differential cDNA cloning (HAT-2) is highly enriched in canary forebrain in areas associated with the control of complex learned behaviors and higher perceptual processes. The nucleotide sequence predicts a protein that is 96% identical to the product of the n-chimaerin gene isolated from human brain and contains two identifiable domains suggesting a novel role in signal transduction processes. One domain is similar to the sequence in protein kinase C which mediates diacylglycerol binding and regulation. The second domain is similar to a portion of BCR, a GTPase-activating protein encoded by the breakpoint cluster region gene. In male canaries examined during the song season, HAT-2 RNA shows variable expression within the song control circuit, and is notably less abundant in the three nuclei which concentrate androgens (HVC, RA and L-MAN). A fundamental function in the vertebrate forebrain and a possible role in the regulation of neural plasticity are suggested by the conserved structure and pattern of expression of this gene in the brain.