NS-Pten KO Mice Exhibit Motor Seizures, Impaired Motor Performance, and Altered Markers of Vitamin D Signaling and Metabolism in the Cerebellum That Are Uncorrected by High Dose Vitamin D
Abstract number :
3.035
Submission category :
1. Basic Mechanisms / 1D. Mechanisms of Therapeutic Interventions
Year :
2023
Submission ID :
740
Source :
www.aesnet.org
Presentation date :
12/4/2023 12:00:00 AM
Published date :
Authors :
Presenting Author: David Narvaiz, MA – Baylor University
Katherine Blandin, MA – Baylor University; Grace O'Neill, BS – Baylor University; Jacob Pilcher, BS – Baylor University; Danielle Santana-Coelho, PhD – Baylor University; Ashley Smelley, none – Baylor University; Doan tran, BS – Baylor University
Rationale: Genetic mutations that cause hyperactive mechanistic target of rapamycin (mTOR) signaling in the cerebellum lead to disrupted cerebellar growth, debilitating motor impairments, and may contribute to the development of epilepsy. mTOR inhibitors can reduce seizures and prevent behavioral impairments but are associated with serious side effects. Thus, a critical need for better therapies to treat individuals with hyperactive mTOR induced motor impairments and epilepsy remains. Vitamin D has been shown to suppress mTOR signaling and abate seizure severity. However, it has not been determined if vitamin D can ameliorate the development of motor impairments and epilepsy induced by hyperactive mTOR signaling. Here, we determine the effects of high dose vitamin D on cerebellar growth, mTOR signaling, and markers of vitamin D signaling and metabolism in a mouse model of hyperactive mTOR induced epilepsy and ataxia.
Methods: Male and female neuronal subset specific Pten knockout (KO) and wildtype (WT) mice were provided either a diet supplemented with 20,000 IU/Kg of vitamin D3 or a standard mouse chow containing 1,500 IU/Kg of vitamin D3 starting at four weeks and were maintained on the diet for the remainder of the experiment. At six weeks, mice underwent testing for motor performance in the sticker removal, spontaneous activity in a cylinder and rotarod tests. Mice were then recorded one hour a day for ten days during weeks nine and ten to determine the day to first motor seizure, seizure frequency, and the total duration of time spent seizing. The cerebellum was weighed and then analyzed for alterations to vitamin D and mTOR signaling by qPCR and western blot.
Results: KO mice exhibit baseline impairments in expression of the vitamin D receptor, Vdr, and in Cyp24a1, the enzyme responsible for converting vitamin D into its inactive components. KO mice showed increased phosphorylation of AKT, S6 (S240/244) and S6 (S235/236) in the cerebellum, and were found to have increased cerebellar weight, motor seizures, and impaired motor performance in all behavioral tasks. S6 (S235/236) was marginally suppressed by high dose vitamin D. However, no other measures were corrected by high dose vitamin D and instead led to increased cerebellar growth in WT mice and impaired rotarod performance in both KO and WT mice.
Conclusions: In addition to confirming motor impairments and describing motor seizures in the NS-PTEN KO mice, we also provide evidence that KO mice may exhibit intrinsic impairments in vitamin D signaling. Although high dose vitamin D at this dose had no effect on mTOR signaling, led to increased cerebellar growth in WT mice, and impaired rotarod performance in all mice, these data may suggest that this dose lies on the far side of a U-shaped curve of effects, leading to impairments. Future work determining a dose response curve of vitamin D on neuronal mTOR signaling are expressly needed.
Funding: NIH Grant R15S088776
Basic Mechanisms