Single-Cell RNA-seq Reveals Profound Alterations in Mechanosensitive Dorsal Root Ganglion Neurons with Vitamin E Deficiency

Abstract

SummaryNinety percent of Americans consume less than the estimated average requirements of dietary vitamin E (vitE). Severe vitE deficiency due to genetic mutations in the tocopherol transfer protein (TTPA) in humans results in ataxia with vitE deficiency (AVED), with proprioceptive deficits and somatosensory degeneration arising from dorsal root ganglia neurons (DRGNs). Single-cell RNA-sequencing of DRGNs was performed in Ttpa−/− mice, an established model of AVED. In stark contrast to expected changes in proprioceptive neurons, Ttpa−/− DRGNs showed marked upregulation of voltage-gated Ca2+ and K+ channels in mechanosensitive, tyrosine-hydroxylase positive (TH+) DRGNs. The ensuing significant conductance changes resulted in reduced excitability in mechanosensitive Ttpa−/− DRGNs. A highly supplemented vitE diet (600 mg dl-α-tocopheryl acetate/kg diet) prevented the cellular and molecular alterations and improved mechanosensation. VitE deficiency profoundly alters the molecular signature and functional properties of mechanosensitive TH+ DRGN, representing an intriguing shift of the prevailing paradigm from proprioception to mechanical sensation.

Natural and Synthetic α-Tocopherol Modulate the Neuroinflammatory Response in the Spinal Cord of Adult Ttpa-null Mice

“…We confirmed ( 9 ) that Necab1 , a calcium-binding protein, is consistently downregulated (∼0.2-fold change) in cerebella of Ttpa − / − mice, regardless of brain α-T status. These Necab1 results corroborate previous reports showing that Ttpa − / − mice have dysregulated expression of genes encoding calcium channels ( 32 ) and calcium signal transducing proteins ( 30 ) in neural tissues (dorsal root ganglia and cerebral cortex, respectively). These transcriptomic changes throughout the nervous system could cause diverse and detrimental downstream consequences related to cellular signaling, synaptic function, and energy metabolism, culminating in neurodegenerative pathologies ( 41 ).…”

“…Actin B1 ( Actb1 ) was used as the housekeeping gene. Genes related to oxidative stress and myelination were selected based on findings from previous Ttpa −/− mouse studies ( 9 , 25 , 30 – 32 ) ( Table 1 ). Primers were purchased from Integrated DNA Technologies, and primer sequences are listed in Supplemental Table 1 .…”

Vitamin E Deficiency Disrupts Gene Expression Networks during Zebrafish Development

“…Unfortunately, comparisons between species including the mouse, rat, and horse, between tissue types, and by age of development are limited. Thus, we found little to no overlap between our dataset and that of others published [ 64 , 65 , 66 , 67 ]. It is most likely that the zebrafish embryo prior to 24 hpf simply does not share similar gene expression profiles of highly differentiated tissues such as the cerebellum, spinal cord or liver.…”

RedEfish: Generation of the Polycistronic mScarlet: GSG-T2A: Ttpa Zebrafish Line

“…Ttpa is found in the cerebellum of adult rats [ 75 ] and in mice with VitE deficiency caused by deletion of Ttpa exhibit lipofuscin accumulation as a result of oxidative damage specifically in the dorsal root ganglia (DRG) [ 76 ]. DRG from Ttpa -/- mice have increased apoptosis [ 77 ], causing reduced mechanosensitivity and excitability prevented only by very high levels of VitE supplementation [ 78 ]. Additionally, we found that the DRG was disrupted in VitE deficient zebrafish embryos [ 28 ].…”