A Phenotypic Switch of Differentiated Glial Cells to Dedifferentiated Cells Is Regulated by Folate Receptor α.

In a previous study, we showed that folate receptor-α (FRα) translocates to the nucleus where it acts as a transcription factor and upregulates Hes1, Oct4, Sox2, and Klf4 genes responsible for pluripotency. Here, we show that acetylation and phosphorylation of FRα favor its nuclear translocation in the presence of folate and can cause a phenotypic switch from differentiated glial cells to dedifferentiated cells. shRNA-FRα mediated knockdown of FRα was used to confirm the role of FRα in dedifferentiation. Ocimum sanctum hydrophilic fraction-1 treatment not only blocks the folate mediated dedifferentiation of glial cells but also promotes redifferentiation of dedifferentiated glial cells, possibly by reducing the nuclear translocation of ~38 kDa FRα and subsequent interaction with chromatin assembly factor-1. Stem Cells 2019;37:1441-1454.

Erythropoietin-mediated activation of aquaporin-4 channel for the treatment of experimental hydrocephalus.

OBJECTIVE: In this study, we investigate a neuroprotective agent, erythropoietin (EPO), in animal hydrocephalus model and its potential reversal effects on hydrocephalus by altering the expression of aquaporin-4 (AQP4). METHODS: Obstructive hydrocephalus was induced in 2-week-old rat pups by injecting kaolin (50 µl, 10 mg/ml in saline) into the cisterna magna, while the control pups received only saline. Kaolin-injected pups were divided into two groups on the fifth day after kaolin injection; one group received intra-peritoneal (i.p.) EPO (1 µg/pup) for 5 consecutive days, while other group received i.p. saline for 5 days. The effects of EPO on hydrocephalus were investigated by studying cerebral ventricle size and structural ependymal changes. We examined also the EPO effects on AQP4 expression and microRNA expression. RESULTS: EPO treatment significantly reduced dilation of the cerebral ventricle and denudation of ependymal line in hydrocephalic pups comparing with the control group. Increased expression of AQP4 in periventricular ependymal lining and cultured astrocytes and increased vascular formation were noted after EPO treatment. Additionally, we identified miR-668 as an endogenous regulator of AQP4 in response to EPO. Anti-miR-668 dampened EPO-induced activation of AQP4 expression. CONCLUSIONS: Together, our results show that EPO-mediated upregulation of AQP4 significantly reduces dilation of the cerebral ventricles in obstructive hydrocephalus pups and may lead to potential therapeutic options for hydrocephalus.

Folate receptor alpha is more than just a folate transporter.

Until recently folate receptor alpha (FRα) has only been considered as a folate transporter. However, a novel role of FRα as a transcription factor was reported by our lab. More recently our lab showed a novel pleiotropic role of FRα: (a) direct transcriptional activation of Oct4, Sox2, and Klf4 genes; and (b) repression of biogenesis of miRNAs that target these genes or their effector molecules. These observations beg a question: "Can a simple molecule such as folate be used to manipulate the production and/or differentiation of endogenous neural stem cells (NSCs), which may hold promise for future therapies?" Conditions such as spinal cord injury, motor neuron diseases, Alzheimer's disease and multiple sclerosis may benefit from increasing stem cell pool and promoting specific pathways of differentiation. On the flip-side, these NSCs may also contribute to some CNS tumors therefore promoting differentiation could prove more beneficial. FRα may hold promises for both since it has the potential to remodel chromatin in a context dependent manner. In this commentary we discuss our previous data and new questions arising in the context of the new role for FRα.

Folate Receptor Alpha Upregulates Oct4, Sox2 and Klf4 and Downregulates miR-138 and miR-let-7 in Cranial Neural Crest Cells.

Prenatal folic acid (FA) supplementation prevents neural tube defects. Folate receptor alpha (FRα) is critical for embryonic development, including neural crest (NC) development. Previously we showed that FRα translocates to the nucleus in response to FA, where it acts as a transcription factor. In this study, we examined if FA through interaction with FRα regulates stem cell characteristics of cranial neural crest cells (CNCCs)-critical for normal development. We hypothesized that FRα upregulates coding genes and simultaneously downregulates non-coding miRNA which targets coding genes in CNCCs. Quantitative RT-PCR and chromatin immunoprecipitation showed that FRα upregulates Oct4, Sox2, and Klf4 by binding to their cis-regulator elements-5' enhancer/promoters defined by H3K27Ac and p300 occupancy. FA via FRα downregulates miRNAs, miR-138 and miR-let-7, which target Oct4 and Trim71 (an Oct4 downstream effector), respectively. Co-immunoprecipitation data suggests that FRα interacts with the Drosha-DGCR8 complex to affect pre-miRNA processing. Transfecting anti-miR-138 or anti-miR-let-7 into non-proliferating neural crest cells (NCCs) derived from Splotch (Sp-/- ), restored their proliferation potential. In summary, these results suggest a novel pleiotropic role of FRα: (a) direct activation of Oct4, Sox2, and Klf4 genes; and (b) repression of biogenesis of miRNAs that target these genes or their effector molecules. Stem Cells 2016;34:2721-2732.