Distinct promoters direct neuronal and nonneuronal expression of rat aromatic L-amino acid decarboxylase.

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177

The trace biogenic amine tyramine is present in the nervous systems of animals ranging in complexity from nematodes to mammals. Tyramine is synthesized from tyrosine by the enzyme tyrosine decarboxylase (TDC), a member of the aromatic amino acid family, but this enzyme has not been identified in Drosophila or in higher animals. To further clarify the roles of tyramine and its metabolite octopamine, we have cloned two TDC genes from Drosophila melanogaster, dTdc1 and dTdc2. Although both gene products have TDC activity in vivo, dTdc1 is expressed nonneurally, whereas dTdc2 is expressed neurally. Flies with a mutation in dTdc2 lack neural tyramine and octopamine and are female sterile due to egg retention. Although other Drosophila mutants that lack octopamine retain eggs completely within the ovaries, dTdc2 mutants release eggs into the oviducts but are unable to deposit them. This specific sterility phenotype can be partially rescued by driving the expression of dTdc2 in a dTdc2-specific pattern, whereas driving the expression of dTdc1 in the same pattern results in a complete rescue. The disparity in rescue efficiencies between the ectopically expressed Tdc genes may reflect the differential activities of these gene products. The egg retention phenotype of the dTdc2 mutant and the phenotypes associated with ectopic dTdc expression contribute to a model in which octopamine and tyramine have distinct and separable neural activities.Tyramine, octopamine, and other "trace" biogenic amines are found in most organisms, including bacteria, fungi, and plants, and in animals ranging in complexity from nematodes to mammals. Despite their wide distribution, the biological roles of trace amines are poorly understood. In vertebrates, trace amines are present in low levels and can displace classical biogenic amines from their stores and stimulate outward neurotransmitter efflux from biogenic amine transporters (1). Although there are currently no data to suggest that there are dedicated synapses for trace amines in the brain, the recent discovery of G-protein-coupled receptors that are selectively Additionally, tyramine affects chloride permeability in the Drosophila Malpighian tubule (7), relaxation of muscle tone in the locust oviduct (8), and behavioral responses to cocaine in Drosophila (9).Octopamine in invertebrates is often considered to be the functional homolog of vertebrate norepinephrine and is involved in a diverse range of physiological processes (reviewed in Ref. 10), including Drosophila female fertility. Flies that lack a functional octopamine receptor or cannot synthesize octopamine due to a null allele of tyramine ␤-hydroxylase (T␤h) 2 show a complete egg retention phenotype (11-13). The sterility of T␤h null females is due to a defect in ovulation, which can be rescued by octopamine feeding or by driving the ectopic expression of a T␤h transgene in several driver lines that show overlapping expression in the thoracic tip of the CNS (12, 13).The first step in octopamine biosynthesis is catalyzed by tyrosine...

Section: Resultsmentioning

confidence: 99%

Two Functional but Noncomplementing Drosophila Tyrosine Decarboxylase Genes

Cole

Carney

McClung³

et al. 2005

305

177

“…This example of alternative splicing in exon 1B versus exon 1C yields multiple RNA transcripts and has also been described for exon 9 in the human PS-1 gene (16). Two distinct transcription start sites, however, have been reported for only a few genes including human catechol-O-methyl transferase (24), mouse neurotrophin-3 (25), and rat aromatic Lamino acid decarboxylase (26). In these cases, each transcriptional start site was associated with a distinct promoter so that a stoichiometry of one promoter per transcription start site was observed.…”

Section: Discussionmentioning

confidence: 99%

Transcriptional Regulation of the Mouse Presenilin-1 Gene

Mitsuda¹,

Roses²,

Vitek³

1997

The presenilin-1 (PS-1) gene encodes at least three separate mRNA transcripts from its 12 exons, which are spread over 50 kilobase pairs of mouse DNA. The first transcript begins with exon 1A, whereas the other transcripts begin with exon 1B. Different portions of exon 1B are spliced to give long and short mRNAs. The expression of all of these transcripts depends on a single promoter located just upstream of exon 1A. Although this region lacks a TATA box and a number of common initiator sequences, it does contain a CAAT box, a heatshock responsive element, a polyomavirus enhancer activator-3 site, an Ets 1-3 site, and multiple-Sp1 and multiple-Ap2 binding sites, which are typically found in eukaryotic promoters. We have combined a reporter gene with various portions of this putative PS-1 promoter and measured firefly luciferase activity relative to an internal renilla luciferase standard. We identified a 25-base pair fragment spanning the 5-transcription start site of exon 1A as containing the core of the promoter activity. The sequences downstream of this region had undetectable promoter activity, suggesting that this core element is the gene's only promoter, and it controls expression of all three transcripts. Although human PS-1 mRNA expression is clearly different from the mouse PS-1 mRNA pattern, the human and mouse core promoters do share limited homology.

“…While the coding region is identical in both forms, liver and kidney AADC mRNA contains a short 5Ј-untranslated region (UTR) which is entirely unrelated to the 5Ј-UTR found in AADC mRNA expressed in tissues of neuronal origin. We have previously shown that, within the rat AADC gene, dual promoters direct the expression of these tissue-specific forms of AADC mRNA resulting in the alternative use of two untranslated exons (9). This has also been shown by others for the rat (10) and human (11-13) AADC gene.…”

mentioning

confidence: 93%

“…The AADC Nonneuronal Promoter Directs Tissue-specific Expression of the Luciferase Reporter Gene-We have previously identified the location of the nonneuronal transcription start site of the rat AADC gene (9). To identify cis-acting elements in the nonneuronal AADC promoter, 1111 bp of the region 5Ј of this transcription start site were placed upstream of the firefly luciferase reporter gene in the pGL2 basic vector expression ( Fig.…”

Section: Llc-pk 1 Cells Express the Nonneuronal Form Of Aadc Mrna-mentioning

confidence: 99%

See 1 more Smart Citation

Tissue-specific Expression of the Nonneuronal Promoter of the Aromatic L-Amino Acid Decarboxylase Gene Is Regulated by Hepatocyte Nuclear Factor 1

Aguanno¹,

Afar

Albert

1996

The rat aromatic L-amino acid decarboxylase (AADC) gene contains alternative promoters which direct expression of neuronal and nonneuronal mRNAs that differ only in their 5-untranslated regions (UTRs). We have analyzed the expression of the nonneuronal promoter of the rat AADC gene in the kidney epithelial cell line LLC-PK 1 and in cells which do not express the nonneuronal form of AADC by transient transfection. These studies revealed that the first 1.1 kilobases of the nonneuronal promoter, including the nonneuronal-specific 5-UTR (Exon 1), contains sufficient information to direct tissue-specific expression. Serial deletions of this promoter localized the cis-active element to a region between ؊52 and ؊28 base pairs upstream of the nonneuronal transcription start site. An A/T-rich sequence, within this region which we have termed KL-1, was found to bind a kidney and liver-specific factor by DNase footprint analysis and was capable of directing tissue-specific expression from a heterologous promoter. Moreover, when the KL-1 sequence was mutated in the context of the entire promoter sequence, all transcriptional activity was abolished. DNA sequence comparison revealed that the KL-1 fragment is highly homologous to the binding site for hepatocyte nuclear factor-1 (HNF-1). Mobility shift studies utilizing an antibody to HNF-1 demonstrated binding of HNF-1 to the KL-1 fragment and cotransfection of HNF-1 cDNA into cells which do not express the nonneuronal form of AADC resulted in activation of transfected AADC nonneuronal promoter constructs. These results strongly suggest that the transcription factor which regulates the tissue-specific expression of the nonneuronal form of AADC mRNA is HNF-1.