Thiamine metabolism is critical for regulating correlated growth of dendrite arbors and neuronal somata

Huimin Liu,Yuan Lu,Xiang Yu,Chunjiu Zhong,Zhongfeng Wang,Shaoming Sang

doi:10.1038/s41598-017-05476-w

Abstract

Thiamine is critical for cellular function, as its phosphorylated and active form, thiamine diphosphate (TDP), acts as coenzyme for three key enzymes in glucose metabolism. Mutations in thiamine transporter, TDP synthesizing enzyme or carrier, including solute carrier family 19 member 3 (SLC19A3), thiamine pyrophosphokinase (TPK1) and solute carrier family 25 member 19 (SLC25A19), have been associated with developmental neurological disorders, including microcephaly and Leigh syndrome. However, little is known about how thiamine metabolism regulates neuronal morphology at the cellular level. Here, using primary rat hippocampal neuronal cultures, we showed that reducing the expression of Tpk1, Slc25a19 or Slc19a3 in individual neurons significantly reduced dendrite complexity, as measured by total dendritic branch tip number (TDBTN) and total dendritic branch length (TDBL). The specificity of the RNAi effects were verified by overexpression of RNAi resistant human constructs. Importantly, changes in both TDBTN and TDBL tightly correlated with reduction in soma size, demonstrating coordinated regulation of soma and dendrite growth by thiamine. The requirement of thiamine metabolism for coordinated somata and dendrite growth is highly consistent with the microcephaly and neurodegenerative phenotypes observed in thiamine loss-of-function diseases.

Highlights

Thiamine (T), known as thiamin or Vitamin B1, is a water-soluble B vitamin that upon uptake, is rapidly phosphorylated by thiamine pyrophosphokinase (TPK1) in the cytoplasm to form thiamine diphosphate (TDP)[1,2,3]
We first investigated the function of Tpk[1], the kinase that catalyzes the transfer of two phosphate groups from adenosine triphosphate (ATP) to thiamine to produce TDP16, 17, the active form of thiamine
As compared to neurons transfected with the control RNAi construct, those expressing Tpk[1] RNAi had significantly lower dendrite complexity on DIV 12 and DIV 16, but not at the earlier time point of DIV 8 (Fig. 1A–C), as measured by reduced total dendritic branch tip number (TDBTN) (Fig. 1B) and total dendritic branch length (TDBL) (Fig. 1C)

Summary

Introduction

Thiamine (T), known as thiamin or Vitamin B1, is a water-soluble B vitamin that upon uptake, is rapidly phosphorylated by thiamine pyrophosphokinase (TPK1) in the cytoplasm to form thiamine diphosphate (TDP)[1,2,3]. Little is known about the function of this pathway at the cellular level We approach this question by knocking down each of three molecules key to thiamine metabolism, namely Tpk[1], Slc25a19 and Slc19a3, and assaying the resulting effect on neuronal morphology using dissociated primary hippocampal www.nature.com/scientificreports/. Our results showed that all three genes had important functions in coordinately regulating dendritic arborization and neuronal soma size These effects were mimicked by pharmacological inhibition of thiamine metabolism, and could be rescued by overexpression of RNAi-resistant human sequences, demonstrating specificity of the phenotypes and conserved functions of the thiamine metabolizing enzymes. These results provide further evidence for a critical role of thiamine metabolism during neuronal development

Methods

Results

Conclusion