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Pathogenesis of autosomal dominant hereditary spastic paraplegia (SPG6) revealed by a rat model.

Watanabe F, Arnold WD, Hammer RE, Ghodsizadeh O, Moti H, Schumer M, Hashmi A, Hernandez A, Sneh A, Sahenk Z, Kisanuki YY - J. Neuropathol. Exp. Neurol. (2013)

Bottom Line: Hereditary spastic paraplegias (HSPs) are characterized by progressive spasticity and weakness in the lower extremities that result from length-dependent central to peripheral axonal degeneration.Detailed morphologic analyses reveal unique histopathologic findings, including the accumulation of tubulovesicular organelles with endosomal features that start at axonal and dendritic terminals, followed by multifocal vacuolar degeneration in both the CNS and peripheral nerves.This Thy1.2-hNIPA1 Tg rat model may serve as a valuable tool for understanding endosomal trafficking in the pathogenesis of a subgroup of HSP with an abnormal interaction with bone morphogenetic protein type II receptor, as well as for developing potential therapeutic strategies for diseases with axonal degeneration and similar pathogenetic mechanisms.

View Article: PubMed Central - PubMed

Affiliation: From the Department of Neurology, The Ohio State University, Columbus, Ohio (FW, WDA, OG, HM, MS, AH, AH, ZS, YYK); The Department of Biochemistry, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas (REH); Department of Pediatrics and Pathology, The Ohio State University/Nationwide Children's Hospital (ZS); and Center for Gene Therapy, The Research Institute, Nationwide Children's Hospital (ZS), Columbus, Ohio.

ABSTRACT
Hereditary spastic paraplegias (HSPs) are characterized by progressive spasticity and weakness in the lower extremities that result from length-dependent central to peripheral axonal degeneration. Mutations in the non-imprinted Prader-Willi/Angelman syndrome locus 1 (NIPA1) transmembrane protein cause an autosomal dominant form of HSP (SPG6). Here, we report that transgenic (Tg) rats expressing a human NIPA1/SPG6 mutation in neurons (Thy1.2-hNIPA1) show marked early onset behavioral and electrophysiologic abnormalities. Detailed morphologic analyses reveal unique histopathologic findings, including the accumulation of tubulovesicular organelles with endosomal features that start at axonal and dendritic terminals, followed by multifocal vacuolar degeneration in both the CNS and peripheral nerves. In addition, the NIPA1 mutation in the spinal cord from older Tg rats results in an increase in bone morphogenetic protein type II receptor expression, suggesting that its degradation is impaired. This Thy1.2-hNIPA1 Tg rat model may serve as a valuable tool for understanding endosomal trafficking in the pathogenesis of a subgroup of HSP with an abnormal interaction with bone morphogenetic protein type II receptor, as well as for developing potential therapeutic strategies for diseases with axonal degeneration and similar pathogenetic mechanisms.

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Thy1.2-hNIPA1G106R transgenic (Tg) rat. (A) The transgene construct was created using the mouse Thy1.2 promoter and human NIPA1G106R mutant cDNA. (B) RT-PCR of the transgene, human non-imprinted Prader-Willi/Angelman syndrome locus 1 (NIPA1) (first row), endogenous rat NIPA1 (third row), and glyceraldehyde-3-phosphate dehydrogenase ([GAPDH] fifth row) in major organs from Thy1.2-hNIPAG106R rat at 4 weeks of age. Transgene expression was detected specifically in the brain and spinal cord compared with ubiquitous expression of endogenous NIPA1. NC, negative control (absence of RNA template); RT, reverse transcriptase. (C) Quantitative PCR of endogenous NIPA1 mRNA expression in the brain and spinal cord between age-matched (4 weeks) wild-type (WT) and Thy1.2-hNIPAG106R rats (n = 3 in each group). WT NIPA1 expression standardized by GAPDH was set as 1. There was no apparent difference in endogenous NIPA1 expression between WT and Thy1.2-hNIPAG106R Tg rats. NS, not significant. (D) Age-matched young (4 weeks) and old (33 weeks) WT and Thy1.2-hNIPA1G106R Tg rats (n = 3 in each group) were compared for NIPA1 protein expression (standardized by β-actin is set as 1). There was no apparent difference detected in the amount of NIPA1 between WT and Thy1.2-hNIPA1G106R Tg rats at different ages.
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Figure 1: Thy1.2-hNIPA1G106R transgenic (Tg) rat. (A) The transgene construct was created using the mouse Thy1.2 promoter and human NIPA1G106R mutant cDNA. (B) RT-PCR of the transgene, human non-imprinted Prader-Willi/Angelman syndrome locus 1 (NIPA1) (first row), endogenous rat NIPA1 (third row), and glyceraldehyde-3-phosphate dehydrogenase ([GAPDH] fifth row) in major organs from Thy1.2-hNIPAG106R rat at 4 weeks of age. Transgene expression was detected specifically in the brain and spinal cord compared with ubiquitous expression of endogenous NIPA1. NC, negative control (absence of RNA template); RT, reverse transcriptase. (C) Quantitative PCR of endogenous NIPA1 mRNA expression in the brain and spinal cord between age-matched (4 weeks) wild-type (WT) and Thy1.2-hNIPAG106R rats (n = 3 in each group). WT NIPA1 expression standardized by GAPDH was set as 1. There was no apparent difference in endogenous NIPA1 expression between WT and Thy1.2-hNIPAG106R Tg rats. NS, not significant. (D) Age-matched young (4 weeks) and old (33 weeks) WT and Thy1.2-hNIPA1G106R Tg rats (n = 3 in each group) were compared for NIPA1 protein expression (standardized by β-actin is set as 1). There was no apparent difference detected in the amount of NIPA1 between WT and Thy1.2-hNIPA1G106R Tg rats at different ages.

Mentions: We used the neuron-specific mouse Thy1.2 promoter (20) to express human NIPA1G106R mutant cDNA in rats (Fig. 1A). From the initial 13 founders, 2 representative lines (A and B) were selected based on their phenotype and expression of the transgene for further characterization. Line A presented with an earlier-onset more robust phenotype than line B and was used throughout the studies. Figure 1B shows that the transgene is specifically expressed within neural tissues as compared with ubiquitous expression of endogenous rat NIPA1 mRNA. This expression pattern is consistent with previous reports in mice (18) and humans (25). Figure 1C shows that human transgene expression does not affect the expression of endogenous rat NIPA1 mRNA. Figure 1D shows that the estimated amount of NIPA1 protein (consisting of a ∼34-kDa and a ∼40-kDa band [as shown in Fig. 7A]) is not different between the brains of wild-type and Thy1.2-hNIPA1G106R Tg rats at different ages.


Pathogenesis of autosomal dominant hereditary spastic paraplegia (SPG6) revealed by a rat model.

Watanabe F, Arnold WD, Hammer RE, Ghodsizadeh O, Moti H, Schumer M, Hashmi A, Hernandez A, Sneh A, Sahenk Z, Kisanuki YY - J. Neuropathol. Exp. Neurol. (2013)

Thy1.2-hNIPA1G106R transgenic (Tg) rat. (A) The transgene construct was created using the mouse Thy1.2 promoter and human NIPA1G106R mutant cDNA. (B) RT-PCR of the transgene, human non-imprinted Prader-Willi/Angelman syndrome locus 1 (NIPA1) (first row), endogenous rat NIPA1 (third row), and glyceraldehyde-3-phosphate dehydrogenase ([GAPDH] fifth row) in major organs from Thy1.2-hNIPAG106R rat at 4 weeks of age. Transgene expression was detected specifically in the brain and spinal cord compared with ubiquitous expression of endogenous NIPA1. NC, negative control (absence of RNA template); RT, reverse transcriptase. (C) Quantitative PCR of endogenous NIPA1 mRNA expression in the brain and spinal cord between age-matched (4 weeks) wild-type (WT) and Thy1.2-hNIPAG106R rats (n = 3 in each group). WT NIPA1 expression standardized by GAPDH was set as 1. There was no apparent difference in endogenous NIPA1 expression between WT and Thy1.2-hNIPAG106R Tg rats. NS, not significant. (D) Age-matched young (4 weeks) and old (33 weeks) WT and Thy1.2-hNIPA1G106R Tg rats (n = 3 in each group) were compared for NIPA1 protein expression (standardized by β-actin is set as 1). There was no apparent difference detected in the amount of NIPA1 between WT and Thy1.2-hNIPA1G106R Tg rats at different ages.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3814936&req=5

Figure 1: Thy1.2-hNIPA1G106R transgenic (Tg) rat. (A) The transgene construct was created using the mouse Thy1.2 promoter and human NIPA1G106R mutant cDNA. (B) RT-PCR of the transgene, human non-imprinted Prader-Willi/Angelman syndrome locus 1 (NIPA1) (first row), endogenous rat NIPA1 (third row), and glyceraldehyde-3-phosphate dehydrogenase ([GAPDH] fifth row) in major organs from Thy1.2-hNIPAG106R rat at 4 weeks of age. Transgene expression was detected specifically in the brain and spinal cord compared with ubiquitous expression of endogenous NIPA1. NC, negative control (absence of RNA template); RT, reverse transcriptase. (C) Quantitative PCR of endogenous NIPA1 mRNA expression in the brain and spinal cord between age-matched (4 weeks) wild-type (WT) and Thy1.2-hNIPAG106R rats (n = 3 in each group). WT NIPA1 expression standardized by GAPDH was set as 1. There was no apparent difference in endogenous NIPA1 expression between WT and Thy1.2-hNIPAG106R Tg rats. NS, not significant. (D) Age-matched young (4 weeks) and old (33 weeks) WT and Thy1.2-hNIPA1G106R Tg rats (n = 3 in each group) were compared for NIPA1 protein expression (standardized by β-actin is set as 1). There was no apparent difference detected in the amount of NIPA1 between WT and Thy1.2-hNIPA1G106R Tg rats at different ages.
Mentions: We used the neuron-specific mouse Thy1.2 promoter (20) to express human NIPA1G106R mutant cDNA in rats (Fig. 1A). From the initial 13 founders, 2 representative lines (A and B) were selected based on their phenotype and expression of the transgene for further characterization. Line A presented with an earlier-onset more robust phenotype than line B and was used throughout the studies. Figure 1B shows that the transgene is specifically expressed within neural tissues as compared with ubiquitous expression of endogenous rat NIPA1 mRNA. This expression pattern is consistent with previous reports in mice (18) and humans (25). Figure 1C shows that human transgene expression does not affect the expression of endogenous rat NIPA1 mRNA. Figure 1D shows that the estimated amount of NIPA1 protein (consisting of a ∼34-kDa and a ∼40-kDa band [as shown in Fig. 7A]) is not different between the brains of wild-type and Thy1.2-hNIPA1G106R Tg rats at different ages.

Bottom Line: Hereditary spastic paraplegias (HSPs) are characterized by progressive spasticity and weakness in the lower extremities that result from length-dependent central to peripheral axonal degeneration.Detailed morphologic analyses reveal unique histopathologic findings, including the accumulation of tubulovesicular organelles with endosomal features that start at axonal and dendritic terminals, followed by multifocal vacuolar degeneration in both the CNS and peripheral nerves.This Thy1.2-hNIPA1 Tg rat model may serve as a valuable tool for understanding endosomal trafficking in the pathogenesis of a subgroup of HSP with an abnormal interaction with bone morphogenetic protein type II receptor, as well as for developing potential therapeutic strategies for diseases with axonal degeneration and similar pathogenetic mechanisms.

View Article: PubMed Central - PubMed

Affiliation: From the Department of Neurology, The Ohio State University, Columbus, Ohio (FW, WDA, OG, HM, MS, AH, AH, ZS, YYK); The Department of Biochemistry, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas (REH); Department of Pediatrics and Pathology, The Ohio State University/Nationwide Children's Hospital (ZS); and Center for Gene Therapy, The Research Institute, Nationwide Children's Hospital (ZS), Columbus, Ohio.

ABSTRACT
Hereditary spastic paraplegias (HSPs) are characterized by progressive spasticity and weakness in the lower extremities that result from length-dependent central to peripheral axonal degeneration. Mutations in the non-imprinted Prader-Willi/Angelman syndrome locus 1 (NIPA1) transmembrane protein cause an autosomal dominant form of HSP (SPG6). Here, we report that transgenic (Tg) rats expressing a human NIPA1/SPG6 mutation in neurons (Thy1.2-hNIPA1) show marked early onset behavioral and electrophysiologic abnormalities. Detailed morphologic analyses reveal unique histopathologic findings, including the accumulation of tubulovesicular organelles with endosomal features that start at axonal and dendritic terminals, followed by multifocal vacuolar degeneration in both the CNS and peripheral nerves. In addition, the NIPA1 mutation in the spinal cord from older Tg rats results in an increase in bone morphogenetic protein type II receptor expression, suggesting that its degradation is impaired. This Thy1.2-hNIPA1 Tg rat model may serve as a valuable tool for understanding endosomal trafficking in the pathogenesis of a subgroup of HSP with an abnormal interaction with bone morphogenetic protein type II receptor, as well as for developing potential therapeutic strategies for diseases with axonal degeneration and similar pathogenetic mechanisms.

Show MeSH
Related in: MedlinePlus