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van Leeuwen FW, Fischer DF, Kamel D, Sluijs JA, Sonnemans MA, Benne R, Swaab DF, Salehi A, Hol EM. Molecular misreading: a new type of transcript mutation expressed during aging. Neurobiol Aging 2000; 21:879-91. [PMID: 11124436 DOI: 10.1016/s0197-4580(00)00151-2] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Dinucleotide deletions (e.g. DeltaGA, DeltaGU) are created by molecular misreading in or adjacent to GAGAG motifs of neuronal mRNAs. As a result, the reading frame shifts to the +1 frame, and so-called "+1 proteins" are subsequently synthesized. +1 Proteins have a wild-type N-terminus, but an aberrant C-terminus downstream from the site of the dinucleotide deletion. Molecular misreading was discovered in the rat vasopressin gene associated with diabetes insipidus and subsequently in human genes linked to Alzheimer's disease (AD), e.g. beta amyloid precursor protein (betaAPP) and ubiquitin-B (UBB). Furthermore, betaAPP(+1) and UBB(+1) proteins accumulate in the neuropathological hallmarks (i.e. in the tangles, neuritic plaques, and neuropil threads) of AD. As these +1 proteins were also found in elderly nondemented controls, but not in younger ones (<51 years), molecular misreading in nondividing cells might act as a factor that only becomes manifest at an advanced age. Frameshift mutations (UBB(+1)) and pretangle staining (Alz-50 and MC1) seem to occur independently of each other during early stages of AD. We recently detected +1 proteins, not only in proliferating cells present in non-neuronal tissues such as the liver and epididymis, but also in neuroblastoma cell lines. These observations suggest that molecular misreading is a general source of transcript errors that are involved in cellular derangements in various age-related pathologies.
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Affiliation(s)
- F W van Leeuwen
- Netherlands Institute for Brain Research, Meibergdreef 33, 1105 AZ, Amsterdam, The Netherlands
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Van Leeuwen FW, Hol EM, Hermanussen RW, Sonnemans MA, Moraal E, Fischer DF, Evans DA, Chooi KF, Burbach JP, Murphy D. Molecular misreading in non-neuronal cells. FASEB J 2000; 14:1595-602. [PMID: 10928994 DOI: 10.1096/fj.14.11.1595] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
+1 Frame-shifted proteins such as amyloid precursor protein(+1) and ubiquitin-B(+1) have been identified in the neuropathological hallmarks of Alzheimer's disease. These frameshifts are caused by dinucleotide deletions in GAGAG motifs of messenger RNA encoded by genes that have maintained the unchanged wild-type DNA sequence. This process is termed 'molecular misreading'. A key question is whether this process is confined to neurons or whether it could also occur in non-neuronal cells. A transgenic mouse line (MV-B) carrying multiple copies of a rat vasopressin minigene as a reporter driven by the MMTV-LTR promotor was used to screen non-neuronal tissues for molecular misreading by means of detection of the rat vasopressin(+1) protein and mutated mRNA. Molecular misreading was demonstrated to occur in several organs (e.g., epididymis and the parotid gland) where transgenic vasopressin expression is abundant, but its penetrance is variable both between and within tissues. This implies that non-neural tissues too, could be affected by cellular derangements caused by molecular misreading.
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Affiliation(s)
- F W Van Leeuwen
- Netherlands Institute for Brain Research, Research Group Molecular Misreading, Amsterdam, The Netherlands.
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Hermens WT, ter Brake O, Dijkhuizen PA, Sonnemans MA, Grimm D, Kleinschmidt JA, Verhaagen J. Purification of recombinant adeno-associated virus by iodixanol gradient ultracentrifugation allows rapid and reproducible preparation of vector stocks for gene transfer in the nervous system. Hum Gene Ther 1999; 10:1885-91. [PMID: 10446928 DOI: 10.1089/10430349950017563] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Recombinant adeno-associated virus (rAAV) vectors have become attractive tools for in vivo gene transfer. The production and purification of high-titer rAAV vector stocks for experimental and therapeutic gene transfer continue to undergo improvement. Standard rAAV vector purification protocols include the purification of the vector by cesium chloride (CsCl)-density gradient centrifugation followed by extensive desalination via dialysis against a physiological buffer for in vivo use. These procedures are extremely time consuming and frequently result in a substantial loss of the infectious vector titer. As an alternative to CsCl we have investigated the use of Iodixanol, an X-ray contrast solution, as the density-gradient medium. Purification of rAAV vectors by Iodixanol shortened the centrifugation period to 3 hr and resulted in reproducible concentration and purification of rAAV-vector stocks. We show that injection of rAAV derived from an Iodixanol gradient can be used for in vivo gene transfer applications in the brain and spinal cord without detectable cytopathic effects and directing stable transgene expression for at least 2 months.
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Affiliation(s)
- W T Hermens
- Graduate School for Neurosciences Amsterdam, Netherlands Institute for Brain Research
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Hol EM, Neubauer A, de Kleijn DP, Sluijs JA, Ramdjielal RD, Sonnemans MA, van Leeuwen FW. Dinucleotide deletions in neuronal transcripts: a novel type of mutation in non-familial Alzheimer's disease and Down syndrome patients. Prog Brain Res 1999; 117:379-95. [PMID: 9932421 DOI: 10.1016/s0079-6123(08)64028-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Affiliation(s)
- E M Hol
- Graduate School for Neurosciences Amsterdam, Netherlands Institute for Brain Research, The Netherlands.
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van Leeuwen FW, de Kleijn DP, van den Hurk HH, Neubauer A, Sonnemans MA, Sluijs JA, Köycü S, Ramdjielal RD, Salehi A, Martens GJ, Grosveld FG, Peter J, Burbach H, Hol EM. Frameshift mutants of beta amyloid precursor protein and ubiquitin-B in Alzheimer's and Down patients. Science 1998; 279:242-7. [PMID: 9422699 DOI: 10.1126/science.279.5348.242] [Citation(s) in RCA: 452] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The cerebral cortex of Alzheimer's and Down syndrome patients is characterized by the presence of protein deposits in neurofibrillary tangles, neuritic plaques, and neuropil threads. These structures were shown to contain forms of beta amyloid precursor protein and ubiquitin-B that are aberrant (+1 proteins) in the carboxyl terminus. The +1 proteins were not found in young control patients, whereas the presence of ubiquitin-B+1 in elderly control patients may indicate early stages of neurodegeneration. The two species of +1 proteins displayed cellular colocalization, suggesting a common origin, operating at the transcriptional level or by posttranscriptional editing of RNA. This type of transcript mutation is likely an important factor in the widely occurring nonfamilial early- and late-onset forms of Alzheimer's disease.
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Affiliation(s)
- F W van Leeuwen
- Graduate School for Neurosciences Amsterdam, Netherlands Institute for Brain Research, 1105 AZ Amsterdam, The Netherlands.
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Gabreëls BA, Verwer RW, Sonnemans MA, Sluiter AA, Ang CW, van Leeuwen FW. Lack of translation of normal 7B2 mRNA levels in hypothalamic mutant vasopressin cells of the homozygous Brattleboro rat. Neurosci Lett 1997; 239:5-8. [PMID: 9547170 DOI: 10.1016/s0304-3940(97)00883-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The homozygous Brattleboro rat (di/di) synthesizes a vasopressin (VP) precursor with an aberrant C-terminus, which causes a hypothalamic form of diabetes insipidus. The neuroendocrine polypeptide 7B2 is present in VP and oxytocin (OT) neurons of the supraoptic and paraventricular nucleus of the hypothalamus in wild type rats. However, in the di/di rat 7B2 immunoreactivity is absent in the VP cell population, whereas 7B2 levels within the OT cells are unaffected. Remarkably, there is no obvious difference in 7B2 transcript levels between VP and OT neurons in the di/di rat hypothalamus. This study shows that the presence of mRNA does not automatically result in the subsequent synthesis of its protein. Cellular mechanisms underlying this discrepancy are discussed.
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Affiliation(s)
- B A Gabreëls
- Graduate School Neurosciences, Netherlands Institute for Brain Research, Amsterdam ZO.
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Holtmaat AJ, Hermens WT, Sonnemans MA, Giger RJ, Van Leeuwen FW, Kaplitt MG, Oestreicher AB, Gispen WH, Verhaagen J. Adenoviral vector-mediated expression of B-50/GAP-43 induces alterations in the membrane organization of olfactory axon terminals in vivo. J Neurosci 1997; 17:6575-86. [PMID: 9254670 PMCID: PMC6573140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
B-50/GAP-43 is an intraneuronal membrane-associated growth cone protein with an important role in axonal growth and regeneration. By using adenoviral vector-directed expression of B-50/GAP-43 we studied the morphogenic action of B-50/GAP-43 in mature primary olfactory neurons that have established functional synaptic connections. B-50/GAP-43 induced gradual alterations in the morphology of olfactory synapses. In the first days after overexpression, small protrusions originating from the preterminal axon shaft and from the actual synaptic bouton were formed. With time the progressive formation of multiple ultraterminal branches resulted in axonal labyrinths composed of tightly packed sheaths of neuronal membrane. Thus, B-50/GAP-43 is a protein that can promote neuronal membrane expansion at synaptic boutons. This function of B-50/GAP-43 suggests that this protein may subserve an important role in ongoing structural synaptic plasticity in adult neurons and in neuronal membrane repair after injury to synaptic fields.
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Affiliation(s)
- A J Holtmaat
- Graduate School Neurosciences Amsterdam, Netherlands Institute for Brain Research, 1105 AZ Amsterdam-ZO, The Netherlands
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Ang CW, Dotman CH, Winkler H, Fischer-Colbrie R, Sonnemans MA, Van Leeuwen FW. Specific expression of secretogranin II in magnocellular vasopressin neurons of the rat supraoptic and paraventricular nucleus in response to osmotic stimulation. Brain Res 1997; 765:13-20. [PMID: 9310389 DOI: 10.1016/s0006-8993(97)00462-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
As secretogranin II is considered to be a marker for the regulated secretory pathway, its distribution in the hypothalamo-neurohypophyseal system of salt-loaded Wistar rats was studied in detail by immunocytochemistry. Although after an osmotic challenge both vasopressin and oxytocin neurons are stimulated, secretogranin II was exclusively expressed in a subpopulation of vasopressinergic magnocellular neurons in the supraoptic and paraventricular nucleus of Wistar rats. Secretogranin II was only surely visualized after a combination of osmotic challenge and blockade of axonal transport by colchicine treatment. When these pre-treatments were not performed, only punctate fibers situated around the magnocellular neurons within the paraventricular and supraoptic nucleus were observed. Oxytocinergic magnocellular neurons never displayed any secretogranin II immunoreactivity, not even during lactation and after colchicine treatment. These findings suggest that secretogranin II is of functional importance during enhanced secretory activity within vasopressinergic neurons.
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Affiliation(s)
- C W Ang
- Netherlands Institute for Brain Research, Amsterdam
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Pu LP, Van Leeuwen FW, Tracer HL, Sonnemans MA, Loh YP. Localization of vasopressin mRNA and immunoreactivity in pituicytes of pituitary stalk-transected rats after osmotic stimulation. Proc Natl Acad Sci U S A 1995; 92:10653-7. [PMID: 7479859 PMCID: PMC40670 DOI: 10.1073/pnas.92.23.10653] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The presence of [arginine] vasopressin (AVP) mRNA and AVP immunoreactivity in pituicytes of the neural lobe (NL) of intact and pituitary stalk-transected rats, with and without osmotic stimulation, was examined. AVP mRNA was analyzed by Northern blotting, as well as by in situ hybridization in combination with immunocytochemistry using anti-glial fibrillary acidic protein (GFAP) as a marker for pituicytes. In intact rats, a poly(A) tail-truncated 0.62-kb AVP mRNA was detected in the NL and was found to increase 10-fold with 7 days of continuous salt loading. Morphological analysis of the NL of 7-day salt-loaded rats revealed the presence of AVP mRNA in a significant number of GFAP-positive pituicytes in the NL and in areas most probably containing nerve fibers. Eight days after pituitary stalk transection the NL AVP mRNA diminished in animals given water to drink, whereas in those given 2% saline for 18 h followed by 6 h of water, a treatment repeated on 6 successive days beginning 2 days after surgery, the 0.62-kb AVP mRNA was present. The AVP mRNA in the pituitary stalk-transected, salt-loaded rats showed an exclusive cellular distribution in the NL, indicative of localization in pituicytes. Immunoelectron microscopy showed the presence of AVP immunoreactivity in a subpopulation of pituicytes 7 and 10 days after pituitary stalk transection in salt-loaded animals, when almost all AVP fibers had disappeared from the NL. These data show that a subset of pituicytes in the NL is activated to synthesize AVP mRNA and AVP in response to osmotic stimulation.
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Affiliation(s)
- L P Pu
- Section on Cellular Neurobiology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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Adan RA, Van Leeuwen FW, Sonnemans MA, Brouns M, Hoffman G, Verbalis JG, Burbach JP. Rat oxytocin receptor in brain, pituitary, mammary gland, and uterus: partial sequence and immunocytochemical localization. Endocrinology 1995; 136:4022-8. [PMID: 7649111 DOI: 10.1210/endo.136.9.7649111] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Partial complementary DNAs of an oxytocin (OT) receptor were cloned from rat brain and uterus. The complementary DNAs encoded for the same amino acid sequence, which showed a high degree of homology with the human and porcine uterine OT receptors, except for a region in the third intracellular loop. Antibodies were raised against nonoverlapping sequences of the third intracellular loop of this rat OT receptor. Using these antisera, OT receptor expression was demonstrated in the brain, pituitary, mammary gland, and uterus by immunocytochemistry. In the brain, several areas including the ventromedial hypothalamus, the bed nucleus of the stria terminalis, the ventral pallidum, the paraventricular nucleus, and the dorsal part of the supraoptic nucleus, demonstrated OT-receptor immunoreactivity. However, no immunoreactivity was detected in two areas of the brain known to contain dense OT-binding sites by receptor autoradiography studies: the ventral hippocampus and the central nucleus of the amygdala. In the pituitary, both the anterior and posterior lobes were positive for OT receptor immunoreactivity, whereas the intermediate lobe was negative. These results demonstrate that the same receptor type is expressed in both peripheral OT target tissues and the brain, and also suggest the possibility that a different OT receptor subtype may be present in some areas of the brain.
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Affiliation(s)
- R A Adan
- Rudolf Magnus Institute for Neurosciences, Department of Pharmacology, Utrecht University, The Netherlands
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Evans DA, van der Kleij AA, Sonnemans MA, Burbach JP, van Leeuwen FW. Frameshift mutations at two hotspots in vasopressin transcripts in post-mitotic neurons. Proc Natl Acad Sci U S A 1994; 91:6059-63. [PMID: 8016115 PMCID: PMC44137 DOI: 10.1073/pnas.91.13.6059] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Mutations in DNA underlie carcinogenesis, inherited pathology, and aging and are generally thought to be introduced during meiosis and mitosis. Here we report that in post-mitotic neurons specific frameshift mutations occur at high frequency. These mutations were identified in vasopressin transcripts in magnocellular neurons of the homozygous Brattleboro rat and predominantly consist of a GA deletion in GAGAG motifs. Immunocytochemistry provides evidence for similar events in wild-type rats. However, the diseased state of the Brattleboro rat, resulting in a permanent activation of vasopressin neurons, enhanced the mutational rate. These data reveal hitherto unrecognized somatic mutations in nondividing neurons.
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Affiliation(s)
- D A Evans
- Rudolf Magnus Institute for Neurosciences, Department of Medical Pharmacology, Utrecht University, The Netherlands
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van Leeuwen FW, Evans DA, Meloen R, Sonnemans MA. Differential neurophysin immunoreactivities in solitary magnocellular neurons of the homozygous Brattleboro rat indicate an altered neurophysin moiety. Brain Res 1994; 635:328-30. [PMID: 8173971 DOI: 10.1016/0006-8993(94)91456-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In the homozygous Brattleboro rat (di/di) a single base deletion in the vasopressin (VP) gene causes diabetes insipidus, resulting in the synthesis of a VP precursor with a different C-terminus. We reported previously that a small number of post-mitotic VP neurons in di/di rats undergo a switch to a heterozygous phenotype, suggesting the existence of VP mRNAs with a restored reading frame coding for a normal VP precursor. In the present study we report that the increase in the number of these revertant cells declines after 79 weeks of age. Furthermore, we provide evidence that the neurophysin (NP) moiety in solitary neurons is different from normal NP. Comparing the immunoreactivities of two different NP antibodies we deduced that the restoration of the reading frame may take place downstream of the deletion between amino acids 75 and 93 of the VP-NP.
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Affiliation(s)
- F W van Leeuwen
- Graduate School of Neurosciences Amsterdam, Netherlands Institute for Brain Research
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Boersma CJ, Sonnemans MA, Van Leeuwen FW. Immunocytochemical localization of neuropeptide FF (FMRF amide-like peptide) in the hypothalamo-neurohypophyseal system of Wistar and Brattleboro rats by light and electron microscopy. J Comp Neurol 1993; 336:555-70. [PMID: 8245225 DOI: 10.1002/cne.903360408] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Neuropeptide FF (F8Famide, FMRFamide-like, or morphine modulating peptide) immunoreactivity was localized by light and electron microscopy in the hypothalamo-neurohypophyseal system of Wistar and Brattleboro rats. In Wistar rats neuropeptide FF was present in part of the magnocellular neurones of the paraventricular and supraoptic nuclei in which it was coexpressed with vasopressin. Neuropeptide FF containing fibres were present in the paraventricular and the supraoptic nuclei, and in the central part of the neural lobe. At the electron microscopic level, neuropeptide FF containing nerve terminals in the neural lobe formed synaptoid contacts exclusively with pituicytes. No neuropeptide FF containing neurovascular contacts or contacts with other neuronal structures were observed. In contrast with Wistar rats, neuropeptide FF was almost completely absent in cell bodies of the paraventricular and supraoptic nuclei, and in fibres of the neural lobe in Brattleboro rats. Only a few solitary cells could be observed in these structures. The present results demonstrate that neuropeptide FF coexists with vasopressin within the hypothalamo-neurohypophyseal system. As we did not observe neuropeptide FF containing neurovascular contacts, neuropeptide FF containing nerve terminals probably have a local function within the neural lobe. Neuropeptide FF may be involved in the modulation of oxytocin and vasopressin release, with the pituicyte as an intermediate cell.
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Affiliation(s)
- C J Boersma
- Graduate School Neurosciences Amsterdam, Netherlands Institute for Brain Research
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Boersma CJ, Sonnemans MA, Van Leeuwen FW. Immunoelectron microscopic demonstration of oxytocin and vasopressin in pituicytes and in nerve terminals forming synaptoid contacts with pituicytes in the rat neural lobe. Brain Res 1993; 611:117-29. [PMID: 8518939 DOI: 10.1016/0006-8993(93)91783-o] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A pre-embedding immunoelectron microscopic technique was used to obtain morphological evidence for a role of oxytocin and vasopressin in the regulation of their own or each others release from the neural lobe. No synaptoid contacts of oxytocin- or vasopressin-containing axons with other neuronal structures were observed. However, synaptoid contacts of oxytocin- and vasopressin-containing nerve terminals and Herring bodies with pituicytes were frequently observed. These findings suggest that the pituicyte may participate in auto- and/or cross-regulation of oxytocin and vasopressin release. Moreover, oxytocin and vasopressin precursor-derived peptides were found in the cytoplasm of some pituicytes, an unexpected finding that will be discussed.
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Affiliation(s)
- C J Boersma
- Netherlands Institute for Brain Research, Amsterdam
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15
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Gabreëls BA, Sonnemans MA, Seidah NG, Chrétien M, van Leeuwen FW. Dynamics of 7B2 and galanin expression in solitary magnocellular hypothalamic vasopressin neurons of the homozygous Brattleboro rat. Brain Res 1992; 585:275-82. [PMID: 1380870 DOI: 10.1016/0006-8993(92)91218-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The homozygous Brattleboro rat (di/di), displaying a hypothalamic form of diabetes insipidus, synthesizes a vasopressin (VP) precursor with an abnormal C-terminus. The phenotypic expression of coexisting peptides in mutant magnocellular VP cells shows a differential pattern. 7B2 is one of the peptides which is not detectable, whereas there is a clear galanin expression. During postnatal life a small but increasing number of solitary post-mitotic VP neurons of the di/di rat undergoes a switch to a heterozygous phenotype. Here we report the presence of 7B2 and galanin in these heterozygous cells, which suggests that for the expression of 7B2, but not for that of galanin, the relative amount of mutant VP precursor must be diminished. Possible underlying mechanisms for this differential phenotypic expression of coexisting peptides are compartmentalization of precursor synthesis within the RER or a competition for sites involved in the translocation of the functionally reduced RER.
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Affiliation(s)
- B A Gabreëls
- Netherlands Institute for Brain Research, Amsterdam
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