CMT2Q-causing mutation in the Dhtkd1 gene lead to sensory defects, mitochondrial accumulation and altered metabolism in a knock-in mouse model

Chun-Jie Luan,Robert Prior,Lei Chen,Ying Kuang,Zhu-Gang Wang,Su-Ying Dang,Xi-Wei Wei,Ludo Van Den Bosch,Ming-Min Gu,Yimin He,Wenting Guo,Xihua Li,Yan Chen

doi:10.1186/s40478-020-00901-0

Abstract

Charcot-Marie-Tooth disease (CMT) is a group of inherited neurological disorders of the peripheral nervous system. CMT is subdivided into two main types: a demyelinating form, known as CMT1, and an axonal form, known as CMT2. Nearly 30 genes have been identified as a cause of CMT2. One of these is the ‘dehydrogenase E1 and transketolase domain containing 1’ (DHTKD1) gene. We previously demonstrated that a nonsense mutation [c.1455 T > G (p.Y485*)] in exon 8 of DHTKD1 is one of the disease-causing mutations in CMT2Q (MIM 615025). The aim of the current study was to investigate whether human disease-causing mutations in the Dhtkd1 gene cause CMT2Q phenotypes in a mouse model in order to investigate the physiological function and pathogenic mechanisms associated with mutations in the Dhtkd1 gene in vivo. Therefore, we generated a knock-in mouse model with the Dhtkd1Y486* point mutation. We observed that the Dhtkd1 expression level in sciatic nerve of knock-in mice was significantly lower than in wild-type mice. Moreover, a histopathological phenotype was observed, reminiscent of a peripheral neuropathy, including reduced large axon diameter and abnormal myelination in peripheral nerves. The knock-in mice also displayed clear sensory defects, while no abnormalities in the motor performance were observed. In addition, accumulation of mitochondria and an elevated energy metabolic state was observed in the knock-in mice. Taken together, our study indicates that the Dhtkd1Y486* knock-in mice partially recapitulate the clinical phenotypes of CMT2Q patients and we hypothesize that there might be a compensatory effect from the elevated metabolic state in the knock-in mice that enables them to maintain their normal locomotor function.

Highlights

The name Charcot-Marie-Tooth disease (CMT) originates from the French neurologists Jean Martin Charcot and Pierre Marie, as well as the English neurologist Howard Tooth, who first described the disease in 1886 [1]
Development of a Dhtkd1Y486* knock-in mouse model that mimics nonsense-mediated mRNA decay (NMD) observed in CMT2Q patients To generate the Dhtkd1Y486* knock-in mice, we constructed a targeting vector using the Red/ET cloning method and used homologous recombination in the embryonic stem (ES) cells to obtain the Dhtkd1Y486* mutation in mice [13]
Nine ES cell clones were identified as being positive by polymerase chain reaction (PCR) using primers P1 and P2 directed to the 5′ arm and primers P3 and P4 to the 3′ arm (Fig. 1b)

Summary

Introduction

The name Charcot-Marie-Tooth disease (CMT) originates from the French neurologists Jean Martin Charcot and Pierre Marie, as well as the English neurologist Howard Tooth, who first described the disease in 1886 [1]. CMT is a heterogeneous group of diseases with more than 80 disease-associated genes identified to date [4]. Several CMT2-causing genes are mitochondria- specific genes, and/or lead to defects in mitochondrial function, axonal transport, and/or in the axonal cytoskeleton [2, 5, 6]. Mitochondrial dysfunction has been suggested as a critical pathological component of the disease mechanisms of CMT2. These deficits in mitochondrial function and transport could dramatically affect the peripheral nerves by depriving the distal axon of an important energy source [6,7,8]

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