Differential expression ofrab3 isoforms in oligodendrocytes and astrocytes

Phenylketonuria is caused by specific mutations in the phenylalanine hydroxylase gene and is characterized by elevated blood phenylalanine levels, hypomyelination in forebrain structures, reduced dopamine levels, and cognitive difficulties. To determine whether brain tyrosine levels and/or myelination play a role in the up-regulation of dopamine, phenylketonuric mice were placed on a low phenylalanine diet for 4 weeks and as blood phenylalanine levels dropped to normal, the relationships between phenylalanine, tyrosine, dopamine, myelin proteins, and axonal proteins in frontal cortex and striatum were determined using gas chromatography mass spectrometry, histology, and western blotting techniques. Blood phenylalanine rapidly decreased from an eight-fold elevation to near control levels, and blood tyrosine gradually rose from about 50% to near normal values. In frontal cortex and striatum, phenylalanine levels dropped to 2-and 1.5-fold elevations above control, respectively, and tyrosine levels increased but remained less than 70% of control in both structures. In frontal cortex, increases in dopamine and myelin basic protein occurred in a similar biphasic pattern, reaching near normal levels by week 4. In striatum, dopamine and MBP dramatically increased to near normal levels in the first week. Myelination was confirmed histologically and by western blot quantification of phosphorylated neurofilaments. In summary, our results showed: (i) an increase in dopamine despite low brain tyrosine levels and (ii) similar recovery patterns for myelination and dopamine. Since myelin/axonal interactions trigger signaling pathways that result in axonal maturation, we speculate that this interaction also may trigger signals that up-regulate neurotransmitter synthesis. Keywords: axon, blood-brain barrier, dopamine, myelin, phenylketonuria, tyrosine. In the CNS, oligodendrocytes extend numerous processes, and from the distal tip of each process, a membrane sheet is assembled and wrapped around a segment of axon as an internode of myelin. Myelin is a highly metabolically active membrane that, under normal conditions, remains connected to and is supported by the oligodendrocyte cell body for the life span of the oligodendrocyte. Myelin is essential for the rapid conduction of action potentials and, therefore, there may be devastating consequences if oligodendrocytes fail to produce myelin (hypomyelination) or lose their myelin (demyelination) as a consequence of disease.One disease in which hypomyelination occurs in specific forebrain tracts, but neurons and their axons are spared, is the autosomal recessive disorder phenylketonuria (PKU) (Malamud 1966;Dyer et al. 1996). PKU is caused by a rise in blood phenylalanine (Phe) levels, due to a deficiency in the enzyme phenylalanine hydroxylase (PAH) (Jervis 1953). PAH is expressed primarily in liver and not in brain, and catalyzes the conversion of Phe to tyrosine (Hsieh and Berry 1979). Blood Phe levels normally are about 121 lM; however, in untreated individuals (and mice) ...

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“…Myelin is a highly metabolically active, extremely large membrane (for review, see Holtzman et al . 1996; Madison et al . 1996; Dyer 1999).…”

Section: Discussionmentioning

confidence: 99%

Relationship between myelin production and dopamine synthesis in the PKU mouse brain

Joseph

Dyer

2003

Journal of Neurochemistry

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“…gene expression intrinsically programmed in Pro-OLs, which involves the down-regulation of gene expression facilitating the mitogenic response of OL progenitor cells to growth factors (Hart et al, 1992;Barnett et al, 1995) and the up-regulation of factors controlling myelin gene expression (Collarini et al, 1992;Kim and Hudson, 1992;Haas et al, 1995;Grinspan et al, 1993;Gordon et al, 1990) and proteins that perform posttranslational processing and trafficking functions for the assembly of an intact myelin membrane Huber et al, 1994;Kim et al, 1995;Madison et al, 1996).…”

Section: W H H Krueger Et Almentioning

confidence: 99%

“…We have exploited the ability to regulate normal OL lineage progression to identify genes that are activated during the transition from Pro-OLs to OLs (Huber et al, 1994;Kim et al, 1995;Bansal et al, 1996a,b;Madison et al, 1996). Using R-mAb perturbation of the OL lineage progression, two cell populations were created that consisted of "blocked OLs," which have predominantly ceased proliferation but were unable to initiate terminal differentiation, and "released OLs," which were resuming lineage progression and entering terminal differentiation.…”

Section: W H H Krueger Et Almentioning

confidence: 99%

“…OL progenitors obtained from mixed primary cultures (above) by overnight shaking (McCarthy and de Vellis, 1980) were further enriched (~97%)by differential adhesion and complement lysis; highly enriched, stage-specific OL populations were then obtained by selective growth factor treatment (reviewed and described in Bansal et al,I 996a) and characterized by immunofluorescence microscopy using the monoclonal antibodies A2B5, 04, and 01, and anti-myelin basic protein (anti-MBP) rabbit antiserum (Sommer and Schachner, 1981;Schnitzer and Schachner, 1982;Pfeiffer et al, 1993;Huber et al, 1994;Bansal et al, 1996a,b;Madison et al, 1996). The resulting populations consisted routinely of~-~96%A2B5~/<4%04 (early progenitors), >85% O4~/<l%01 (late progenitors = prooligodendrocytes), >80% 01 + / <1% MBP -(immature OLs), and >90% 01~I>45%MBP~(maturing OLs).…”

Section: Cell Culture and Immunofluorescencementioning

confidence: 99%

“…A key event in the OL lineage is the transition from proliferative prooligodendroblasts (Pro-OLs) or late progenitors to postmitotic OLs (Gard and Pfeiffer, 1990;. This transition occurs rapidly in culture in defined medium Pfeiffer, 1990, 1993) that lacks cell cyclestimulating agents and can be reversibly blocked by culturing the cells in the presence of either the monoclonal antibody R-mAb Pfeiffer, 1989, 1994) or fibroblast growth factor-2 (FGF-2) (Eccleston and Silberberg, 1985;McKinnon et al, 1990;Mayer et al, 1993;Bansal and Pfeiffer, 1994;Bansal et al, 1996a,b;Madison et al, 1996), leading to the accumulation of Pro-OLs at the transition interface. The cells rapidly resume normal differentiation as a developmentally synchronized population when the antibody or growth factor is removed, as indicated by the reinitiation and maintenance of the sequential and temporal pattern of glycolipid and protein expression characteristic for normal OL differentiation in untreated cultures at the comparable stage.…”

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confidence: 99%

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TPO1, a Member of a Novel Protein Family, Is Developmentally Regulated in Cultured Oligodendrocytes

Krueger

Gonye

Madison

et al. 1997

Journal of Neurochemistry

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Although the myelin membrane contains only a small set of major proteins, more sensitive assays indicate the presence of a plethora of uncharacterized proteins. We have used an antibody perturbation approach to reversibly block the differentiation of prooligodendroblasts into myelinating cells, and, in combination with a differential screening procedure, identified novel mRNAs that are activated during this period. One cDNA, TPO1, recognizes a 5.5-kb mRNA that is strongly up-regulated in oligodendrocytes after release of the differentiation block and that is expressed at high levels in brain tissue during active myelination. This cDNA represents at least two mRNAs differing from each other in their 5'-termini. The TPO1 cDNA contains an open reading frame of 1,380 bp, encoding a protein of 51 .8 kDa with a predicted pi of 9.1 that contains two regions homologous to nonclassic zinc finger motifs. Subceilular localization studies suggest the enriched presence of TPO1 in spherical structures along the major cytoplasmic processes of oligodendrocytes. TPO1, along with homologues expressed in testis, placenta, and PC12 cells, form a novel family of proteins with multiple hydrophobic domains possibly serving as membrane spanning regions. We postulate that in oligodendrocytes, TPO1 encodes a protein factor involved in myeiin biogenesis. Key Words: TPO1 -Oligodendrocyte development-Myelin-Zinc finger-Membrane protein-OB-fold.

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Quantification of cellular properties from external fields and resulting induced velocity: Magnetic susceptibility

Chalmers¹,

Haam²,

Zhao³

et al. 1999

Biotechnol. Bioeng.

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An experimental technique is discussed in which the magnetic susceptibility of immunomagnetically labeled cells can be determined on a cell‐by‐cell basis. This technique is based on determining the magnetically induced velocity that an immunomagnetically labeled cell has in a well‐defined magnetic energy gradient. This velocity is determined through the use of video recordings of microscopic images of cells moving in the magnetic energy gradient. These video images are then computer digitized and processed using a computer algorithm, cell tracking velocimetry, which allows larger numbers (>103) of cells to be analyzed. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 64:519–526, 1999.

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Differential expression ofrab3 isoforms in oligodendrocytes and astrocytes

Cited by 60 publications

References 43 publications

Relationship between myelin production and dopamine synthesis in the PKU mouse brain

Relationship between myelin production and dopamine synthesis in the PKU mouse brain

TPO1, a Member of a Novel Protein Family, Is Developmentally Regulated in Cultured Oligodendrocytes

Quantification of cellular properties from external fields and resulting induced velocity: Magnetic susceptibility

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