Dopamine D2 receptor subtypes couple to different second messenger systems.
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Animals↗
Biomedical subjects
K Y Gandelman
Publications and source records attributed to K Y Gandelman.
Molecular definition of the smallest region of deletion overlap in the Wolf-Hirschhorn syndrome.
Wolf-Hirschhorn syndrome (WHS), associated with a deletion of chromosome 4p, is characterized by mental and growth retardation and typical facial dysmorphism. A girl with clinical features of WHS was found to carry a subtle deletion of chromosome 4p. Initially suggested by high-resolution chromosome analysis, her deletion was confirmed by fluorescence in situ hybridization (FISH) with cosmid probes, E13 and Y2, of D4S113. To delineate this 4p deletion, we performed a series of FISH and pulsed-field gel electrophoresis analyses by using probes from 4p16.3. A deletion of approximately 2.5 Mb with the breakpoint at approximately 80 kb distal to D4S43 was defined in this patient and appears to be the smallest WHS deletion so far identified. To further refine the WHS critical region, we have studied three unrelated patients with presumptive 4p deletions, two resulting from unbalanced segregations of parental chromosomal translocations and one resulting from an apparently de novo unbalanced translocation. Larger deletions were identified in two patients with WHS. One patient who did not clinically present with WHS had a smaller deletion that thus eliminates the distal 100-300 kb from the telomere as being part of the WHS region. This study has localized the WHS region to approximately 2 Mb between D4S43 and D4S142.
Abnormalities, Multiple↗
Analysis of the structure and expression of the human dopamine D2A receptor gene.
In order to study the possible involvement of dopamine receptors in the pathophysiology of various neurological and psychiatric disorders, we have isolated the human D2A gene. Like the rat D2A gene, the human gene contains at least eight exons and spans at least 52 kb. Exons 2-8 are clustered within 14 kb of genome. Exon 1 is separated from exon 2 by at least 38 kb. We and others have shown that alternative utilization of exon 6 gives rise to alternative D2A transcripts. Despite the extreme size of intron 1, no alternative transcription between exons 1 and 2 can be detected in basal ganglia and pituitary using polymerase chain reaction analysis. The relative abundance and tissue distribution of the alternative D2A transcripts were examined in 18 human brain regions. The relative expression of the transcripts varied by at least 70-fold across the brain regions surveyed. As expected, high levels of transcripts were detected in caudate, putamen, and pituitary. Moderate levels were detected in regions of catecholamine-containing cell bodies and in the amygdala. In contrast to the rat brain, very low levels of transcripts were detected in cortical regions.
Base Sequence↗
Organization and expression of the rat D2A receptor gene: identification of alternative transcripts and a variant donor splice site.
We have recently reported the creation of a cell line expressing D2 receptors encoded by a gene distinct from that described by Bunzow et al. [Bunzow, J. R., Van Tol, H. H. M., Grandy, D. K., Albert, P., Salon, J., Christie, M., Machida, C. A., Neve, K., & Civelli, O. (1988) Nature 336, 783-787]. To provide a framework for understanding structural differences between these and other G-protein-coupled receptors, the structure of the rat gene coding for the Bunzow et al. cDNA (called D2A here) was delineated. The D2A gene contains eight exons and spans at least 50 kb. Sets of oligonucleotide primers were used in combination with the polymerase chain reaction (PCR) to determine the presence of alternative transcripts within the introns. In contrast to other G-protein-coupled receptors, the D2A gene undergoes alternative RNA processing within intron 5, resulting in an insertion of 29 amino acids to the predicted 415 amino acid sequence of the D2A protein. By use of the PCR assay the relative abundance and tissue distribution of the alternative D2A transcripts (herein termed D2A415 and D2A444) were determined. A variant donor splice site was also identified at the end of exon 4, a GC dinucleotide instead of the canonical GT. The variant dinucleotide was also present in the mouse but not in the human D2A gene.
Animals↗
Species and regional differences in the expression of cell-type specific elements at the human and rat tyrosine hydroxylase gene loci.
The expression of the catecholamine biosynthetic enzyme, tyrosine hydroxylase (TH), is confined to several different types of neuroendocrine cells. Using a transient assay system, we examined more than 10 kb of the human TH gene and 6.5 kb of 5' flanking sequences of the rat TH gene for DNA elements that confer cell-type specific expression. Surprisingly, these elements do not appear to be conserved in position or sequence across species. When plasmids containing DNA sequences - 749 bp from the transcription start site of the rat gene were introduced into PC12 cells, up to sixfold higher levels of expression were observed as compared to the same fragments introduced into HepG2 cells or LAN-1 cells. In contrast to the rat gene, analogous fragments of the human 5' promoter failed to confer cell-type specific expression. However, when plasmids containing a truncated thymidine kinase promoter and either orientation of a 760 by 3' human TH gene fragment were introduced into PC12 and LAN-1 cells, we observed a six- and 3.5-fold increase, respectively, over that observed for HepG2 cells. Subsequent deletion of this fragment led to significant activation of transcription in PC12 and HepG2 cell lines. These data indicate the presence of multiple elements contributing to the cell-type specific expression of tyrosine hydroxylase genes.
Adrenal Gland Neoplasms↗
Cyclic AMP regulation of P0 glycoprotein and myelin basic protein gene expression in semi-differentiated peripheral neurinoma cell line D6P2T.
We have analyzed the effects of cAMP-elevating drugs (dibutyryl cAMP, forskolin, and isobutyl methylxanthine) on growth properties and myelin-specific gene expression in the peripheral neurinoma cell line D6P2T. The steady-state levels of RNA and polypeptide for the two major PNS myelin proteins, P0 glycoprotein (P0) and myelin basic protein (MBP), were measured by Northern blotting and immunoblotting, respectively. The levels of the two RNAs in individual cells were examined by in situ hybridization. The transcriptional activities of the P0 and MBP genes were analyzed by nuclear run-off experiments. Treatment with cAMP-elevating agents caused cell aggregation and dose-dependent increase in growth control. Expression of P0 RNA was constitutive in untreated cells and was repressed at high doses. Expression of MBP RNA was induced at low doses and repressed at higher doses. For both MBP and P0 the effects on gene expression were first detected after a lag of approximately 6 h, were manifested in all cells and were mediated, at least in part, at the transcriptional level. The level of P0 polypeptide was proportional to the level of P0 RNA, but MBP polypeptide was not detectable even under conditions where MBP RNA was induced. The results with this clonal model suggest that cAMP plays a pivotal role in regulation of growth and gene expression during Schwann cell differentiation.
1-Methyl-3-isobutylxanthine↗