Biomedical subjects

Benjamin D Philpot

Publications and source records attributed to Benjamin D Philpot.

7 recordsLinked to original sources

PubMed2026

A dual-reporter mouse for therapeutic discovery in Angelman syndrome.

Angelman syndrome is a neurodevelopmental disorder caused by loss of the maternal UBE3A allele, the sole source of UBE3A in mature neurons owing to epigenetic silencing of the paternal allele. Although emerging therapies are being developed to restore UBE3A expression by activating the dormant paternal UBE3A allele, existing mouse models for such preclinical studies have limited throughput and utility, creating bottlenecks for both in vitro therapeutic screening and in vivo characterization. To address this, we developed the Ube3a-INSG dual-reporter knockin mouse, in which an IRES-Nanoluciferase-T2A-Sun1-sfGFP (INSG) cassette was inserted downstream of the endogenous Ube3a stop codon. The INSG model preserves UBE3A protein levels and function while enabling 2 complementary allele-specific readouts: Sun1-sfGFP and Nanoluciferase. We show that Sun1-sfGFP, a nuclear envelope-localized reporter, enables single-cell fluorescence analysis, whole-brain light-sheet imaging, and nuclear quantification by flow cytometry. Further, Nanoluciferase supports high-throughput luminescence assays for sensitive pharmacological profiling in cultured neurons and noninvasive in vivo bioluminescence imaging for pharmacodynamic assessment. By combining scalable screening, cellular analysis, and real-time in vivo monitoring in a single model, the Ube3a-INSG dual-reporter mouse provides a powerful platform to accelerate therapeutic development centered on UBE3A.

Animals↗

PubMed2005

Visual deprivation modifies both presynaptic glutamate release and the composition of perisynaptic/extrasynaptic NMDA receptors in adult visual cortex.

Use-dependent modifications of synapses have been well described in the developing visual cortex, but the ability for experience to modify synapses in the adult visual cortex is poorly understood. We found that 10 d of late-onset visual deprivation modifies both presynaptic and postsynaptic elements at the layer 4-->2/3 connection in the visual cortex of adult mice, and these changes differ from those observed in juveniles. Although visual deprivation in juvenile mice modifies the subunit composition and increases the current duration of synaptic NMDA receptors (NMDARs), no such effect is observed at synapses between layer 4 and layer 2/3 pyramidal neurons in adult mice. Surprisingly, visual deprivation in adult mice enhances the temporal summation of NMDAR-mediated currents induced by bursts of high-frequency stimulation. The enhanced temporal summation of NMDAR-mediated currents in deprived cortex could not be explained by a reduction in the rate of synaptic depression, because our data indicate that late-onset visual deprivation actually increases the rate of synaptic depression. Biochemical and electrophysiological evidence instead suggest that the enhanced temporal summation in adult mice could be accounted for by a change in the molecular composition of NMDARs at perisynaptic/extrasynaptic sites. Our data demonstrate that the experience-dependent modifications observed in the adult visual cortex are different from those observed during development. These differences may help to explain the unique consequences of sensory deprivation on plasticity in the developing versus mature cortex.

Age Factors↗

PubMed2005

Sniffing Out NMDA Receptors in the Olfactory Cortex.

Selective olfactory learning is essential for survival in most newborn mammals. Findings by Franks and Isaacson in this issue of Neuron suggest that early olfactory learning might be selective, in part because olfactory experience downregulates NMDA receptors at primary inputs to the olfactory cortex.

Animals↗

PubMed2004

Significance of N-methyl-D-aspartate (NMDA) receptor-mediated signaling in human keratinocytes.

Increasing data suggest that glutamate might act as a cell-signaling molecule in non-neuronal tissues such as the skin. Here we demonstrate the presence of functional N-methyl-D-aspartate (NMDA)-type glutamate receptors in human keratinocytes. NMDA receptor expression strongly reflects the degree of cell-to-cell contact. Wounding polarizes the expression of NMDA receptors in keratinocytes involved in re-epithelialization, and the process of re-epithelialization is inhibited by NMDA receptor activation. We also demonstrate that squamous cell carcinomas lack NMDA receptors. Our data suggest that Ca2+ entry through NMDA receptors influences the cycle of keratinocyte proliferation, differentiation, and migration during epithelialization. Moreover, NMDA receptor activation might play a role in contact-mediated inhibition of growth, a process that is absent during neoplastic pathology. This receptor may serve as a pharmacological target for modulating keratinocyte behavior and treating cutaneous disorders.

Aniline Compounds↗

PubMed2003

Evidence for altered NMDA receptor function as a basis for metaplasticity in visual cortex.

Sensory deprivation alters the properties of synaptic plasticity induced in the superficial layers of the visual cortex, facilitating long-term potentiation and reducing long-term depression (LTD) across a range of stimulation frequencies. Available data are compatible with either a downregulation of the mechanisms of LTD or an upregulation of NMDA receptor function in the visual cortex of dark-reared animals. Here, we provide evidence for enhanced NMDA receptor function by showing that deprivation produces a horizontal shift in the frequency-response function, decreasing LTD in response to 1 Hz stimulation, but increasing LTD in response to 0.5 Hz stimulation. In addition, we show that the effects of dark-rearing on the frequency dependence of LTD can be reversed acutely by partial NMDA receptor blockade. Finally, we show that an in vivo manipulation that rapidly downregulates NMDA receptor function in the visual cortex, brief light exposure, also rapidly reverses the effect of dark-rearing on LTD.

Animals↗

PubMed2003

NMDA receptor-dependent ocular dominance plasticity in adult visual cortex.

The binocular region of mouse visual cortex is strongly dominated by inputs from the contralateral eye. Here we show in adult mice that depriving the dominant contralateral eye of vision leads to a persistent, NMDA receptor-dependent enhancement of the weak ipsilateral-eye inputs. These data provide in vivo evidence for metaplasticity as a mechanism for binocular competition and demonstrate that an ocular dominance shift can occur solely by the mechanisms of response enhancement. They also show that adult mouse visual cortex has a far greater potential for experience-dependent plasticity than previously appreciated. These insights may force a revision in how data on ocular dominance plasticity in mutant mice have been interpreted.

Aging↗

PubMed2002

Synaptic plasticity in an altered state.

In this issue of Neuron, record from synaptically coupled pairs of CA3 neurons to closely examine the induction of synaptic depression at a small number of identified synapses. The authors provide convincing evidence that the activation history of a synapse determines both the ability of a synapse to depress and the mechanism of depression.

Animals↗