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Toward a Broader View of Ube3a in a Mouse Model of Angelman Syndrome: Expression in Brain, Spinal Cord, Sciatic Nerve and Glial Cells.

Grier MD, Carson RP, Lagrange AH - PLoS ONE (2015)

Bottom Line: Utilizing enriched primary cultures of oligodendrocytes and astrocytes, we show that Ube3a is expressed, but not imprinted in these cell types.To determine the temporal expression pattern and silencing, we analyzed Ube3a expression in AS mice at several time points.We confirm relaxed imprinting of Ube3a in neurons of the postnatal developing cortex, but not in structures in which neurogenesis and migration are more complete.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37232-8552, United States of America.

ABSTRACT
Angelman Syndrome (AS) is a devastating neurodevelopmental disorder characterized by developmental delay, speech impairment, movement disorder, sleep disorders and refractory epilepsy. AS is caused by loss of the Ube3a protein encoded for by the imprinted Ube3a gene. Ube3a is expressed nearly exclusively from the maternal chromosome in mature neurons. While imprinting in neurons of the brain has been well described, the imprinting and expression of Ube3a in other neural tissues remains relatively unexplored. Moreover, given the overwhelming deficits in brain function in AS patients, the possibility of disrupted Ube3a expression in the infratentorial nervous system and its consequent disability have been largely ignored. We evaluated the imprinting status of Ube3a in the spinal cord and sciatic nerve and show that it is also imprinted in these neural tissues. Furthermore, a growing body of clinical and radiological evidence has suggested that myelin dysfunction may contribute to morbidity in many neurodevelopmental syndromes. However, findings regarding Ube3a expression in non-neuronal cells of the brain have varied. Utilizing enriched primary cultures of oligodendrocytes and astrocytes, we show that Ube3a is expressed, but not imprinted in these cell types. Unlike many other neurodevelopmental disorders, AS symptoms do not become apparent until roughly 6 to 12 months of age. To determine the temporal expression pattern and silencing, we analyzed Ube3a expression in AS mice at several time points. We confirm relaxed imprinting of Ube3a in neurons of the postnatal developing cortex, but not in structures in which neurogenesis and migration are more complete. This furthers the hypothesis that the apparently normal window of development in AS patients is supported by an incompletely silenced paternal allele in developing neurons, resulting in a relative preservation of Ube3a expression during this crucial epoch of early development.

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Ube3a expression time course in cortical lysates.A). Representative data for expression of Ube3a in P0, P3, P6 and P42 cortical lysates. B) Quantification of Ube3a expression at various time points. P0 cortical lysates express approximately 25% of WT protein, compared to approximately 5% of WT expression at P3 and later. *** indicates P ≤.0001 by a one-way ANOVA with Tukey's multiple comparison test comparing AS animals at each time point. n = 7–10 per group.
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pone.0124649.g005: Ube3a expression time course in cortical lysates.A). Representative data for expression of Ube3a in P0, P3, P6 and P42 cortical lysates. B) Quantification of Ube3a expression at various time points. P0 cortical lysates express approximately 25% of WT protein, compared to approximately 5% of WT expression at P3 and later. *** indicates P ≤.0001 by a one-way ANOVA with Tukey's multiple comparison test comparing AS animals at each time point. n = 7–10 per group.

Mentions: As much of the research done on AS mice has been carried out in adult animals, the developmental profile of Ube3a expression and consequences of lingering paternal Ube3a expression in early development had been largely ignored until recently. A recently published report indicates that imprinting of Ube3a is incomplete in neonatal AS mice. This is believed to be due to incompletely silenced paternal allele[8]. Additionally, work in induced pluripotent stem cells (iPSCs) derived from AS patients suggests that the Ube3a-ATS transcript responsible for silencing the paternal allele of Ube3a is not expressed until very late in neurogenesis[23]. To determine the developmental expression pattern of Ube3a in mice, cortical lysates from several developmental time points were assayed for Ube3a expression. As expected, P42 mice had very little, <10% of WT, Ube3a protein in the cortex. However, at P0 we observed approximately 25% of WT Ube3a expressed in cortical lysates (Fig 5). This level of expression rapidly dropped over the next 3 days and was indistinguishable from P42 levels by P3 (Fig 5). This is in contrast to sub-cortical and cerebellar tissue in which Ube3a expression was at near-P42 levels at birth (Fig 6). These data further support a regional and developmental regulation for imprinting of Ube3a in neurons.


Toward a Broader View of Ube3a in a Mouse Model of Angelman Syndrome: Expression in Brain, Spinal Cord, Sciatic Nerve and Glial Cells.

Grier MD, Carson RP, Lagrange AH - PLoS ONE (2015)

Ube3a expression time course in cortical lysates.A). Representative data for expression of Ube3a in P0, P3, P6 and P42 cortical lysates. B) Quantification of Ube3a expression at various time points. P0 cortical lysates express approximately 25% of WT protein, compared to approximately 5% of WT expression at P3 and later. *** indicates P ≤.0001 by a one-way ANOVA with Tukey's multiple comparison test comparing AS animals at each time point. n = 7–10 per group.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4403805&req=5

pone.0124649.g005: Ube3a expression time course in cortical lysates.A). Representative data for expression of Ube3a in P0, P3, P6 and P42 cortical lysates. B) Quantification of Ube3a expression at various time points. P0 cortical lysates express approximately 25% of WT protein, compared to approximately 5% of WT expression at P3 and later. *** indicates P ≤.0001 by a one-way ANOVA with Tukey's multiple comparison test comparing AS animals at each time point. n = 7–10 per group.
Mentions: As much of the research done on AS mice has been carried out in adult animals, the developmental profile of Ube3a expression and consequences of lingering paternal Ube3a expression in early development had been largely ignored until recently. A recently published report indicates that imprinting of Ube3a is incomplete in neonatal AS mice. This is believed to be due to incompletely silenced paternal allele[8]. Additionally, work in induced pluripotent stem cells (iPSCs) derived from AS patients suggests that the Ube3a-ATS transcript responsible for silencing the paternal allele of Ube3a is not expressed until very late in neurogenesis[23]. To determine the developmental expression pattern of Ube3a in mice, cortical lysates from several developmental time points were assayed for Ube3a expression. As expected, P42 mice had very little, <10% of WT, Ube3a protein in the cortex. However, at P0 we observed approximately 25% of WT Ube3a expressed in cortical lysates (Fig 5). This level of expression rapidly dropped over the next 3 days and was indistinguishable from P42 levels by P3 (Fig 5). This is in contrast to sub-cortical and cerebellar tissue in which Ube3a expression was at near-P42 levels at birth (Fig 6). These data further support a regional and developmental regulation for imprinting of Ube3a in neurons.

Bottom Line: Utilizing enriched primary cultures of oligodendrocytes and astrocytes, we show that Ube3a is expressed, but not imprinted in these cell types.To determine the temporal expression pattern and silencing, we analyzed Ube3a expression in AS mice at several time points.We confirm relaxed imprinting of Ube3a in neurons of the postnatal developing cortex, but not in structures in which neurogenesis and migration are more complete.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37232-8552, United States of America.

ABSTRACT
Angelman Syndrome (AS) is a devastating neurodevelopmental disorder characterized by developmental delay, speech impairment, movement disorder, sleep disorders and refractory epilepsy. AS is caused by loss of the Ube3a protein encoded for by the imprinted Ube3a gene. Ube3a is expressed nearly exclusively from the maternal chromosome in mature neurons. While imprinting in neurons of the brain has been well described, the imprinting and expression of Ube3a in other neural tissues remains relatively unexplored. Moreover, given the overwhelming deficits in brain function in AS patients, the possibility of disrupted Ube3a expression in the infratentorial nervous system and its consequent disability have been largely ignored. We evaluated the imprinting status of Ube3a in the spinal cord and sciatic nerve and show that it is also imprinted in these neural tissues. Furthermore, a growing body of clinical and radiological evidence has suggested that myelin dysfunction may contribute to morbidity in many neurodevelopmental syndromes. However, findings regarding Ube3a expression in non-neuronal cells of the brain have varied. Utilizing enriched primary cultures of oligodendrocytes and astrocytes, we show that Ube3a is expressed, but not imprinted in these cell types. Unlike many other neurodevelopmental disorders, AS symptoms do not become apparent until roughly 6 to 12 months of age. To determine the temporal expression pattern and silencing, we analyzed Ube3a expression in AS mice at several time points. We confirm relaxed imprinting of Ube3a in neurons of the postnatal developing cortex, but not in structures in which neurogenesis and migration are more complete. This furthers the hypothesis that the apparently normal window of development in AS patients is supported by an incompletely silenced paternal allele in developing neurons, resulting in a relative preservation of Ube3a expression during this crucial epoch of early development.

Show MeSH
Related in: MedlinePlus