The MORC2 p.S87L mutation reduces proliferation of pluripotent stem cells derived from a patient with the spinal muscular atrophy-like phenotype by inhibiting proliferation-related signaling pathways

Mutations in the microrchidia CW-type zinc finger protein 2(MORC2)gene are the causative agent of Charcot-Marie-Tooth disease type 2Z(CMT2Z),and the hotspot mutation p.S87L is associated with a more seve re spinal muscular atrophy-like clinical phenotype.The aims of this study were to determine the mechanism of the severe phenotype caused by the MORC2 p.S87L mutation and to explore potential treatment strategies.Epithelial cells were isolated from urine samples from a spinal muscular atrophy(SMA)-like patient[MORC2 p.S87L),a CMT2Z patient[MORC2 p.Q400R),and a healthy control and induced to generate pluripotent stem cells,which were then differentiated into motor neuron precursor cells.Next-generation RNA sequencing followed by KEGG pathway enrichment analysis revealed that differentially expressed genes involved in the PI3K/Akt and MAP K/ERK signaling pathways were enriched in the p.S87L SMA-like patient group and were significantly downregulated in induced pluripotent stem cells.Reduced proliferation was observed in the induced pluripotent stem cells and motor neuron precursor cells derived from the p.S87L SMA-like patient group compared with the CMT2Z patient group and the healthy control.G0/G1 phase cell cycle arrest was observed in induced pluripotent stem cells derived from the p.S87L SMA-like patient.MORC2 p.S87Lspecific antisense oligonucleotides(p.S87L-ASO-targeting)showed significant efficacy in improving cell prolife ration and activating the PI3K/Akt and MAP K/ERK pathways in induced pluripotent stem cells.Howeve r,p.S87L-ASO-ta rgeting did not rescue prolife ration of motor neuron precursor cells.These findings suggest that downregulation of the PI3K/Akt and MAP K/ERK signaling pathways leading to reduced cell proliferation and G0/G1 phase cell cycle arrest in induced pluripotent stem cells might be the underlying mechanism of the severe p.S87L SMA-like phenotype.p.S87L-ASO-targeting treatment can alleviate disordered cell proliferation in the early stage of pluripotent stem cell induction.

Clinical classification and gene mutation of Chinese probands with Charcot-Marie-Tooth disease Analysis of 57 cases

Charcot-Marie-Tooth （CMT） disease is the most common inherited peripheral neuropathic disorder. CMT is clinically and genetically heterogeneous. To date, 27 genes associated with the disease have been cloned. The present study carried out clinical classification according to clinical, electrophysiological and pathological features, conducted inheritance classification according to inheritance patterns, and performed mutation analysis of 13 CMT disease genes （PMP22, CX32, HSPB1, MNF2, MPZ, HSPB8, GDAP1, NFL, EGR2, SIMPLE, RAB7, LMNA, MTMR2） in 57 Chinese probands with CMT. Five cases of AD-CMT1 and 13 cases of sporadic CMT1 were diagnosed as CMT1A; five cases of X-CMT1, one case of X-CMT2 and one case of sporadic CMT1 were diagnosed as CMTXl; four cases of AD-CMT2 were diagnosed as CMT2F; one case of AD-CMT2 and one case of sporadic CMT2 were diagnosed as CMT2A2; one case of AD-CMT2 was diagnosed as CMT2L; one case of AD-CMT2 was diagnosed as CMT2J; one case of AR-CMT1 was diagnosed as CMT4A. Among the 57 CMT probands, seven genotypes were determined among 34 patients, with a detection rate of 59.6%. The results indicated that the clinical classification and inheritance classification are indispensable for selecting potential disease genes for mutation detection, and for efficient molecular diagnosis.

A novel transgenic mouse model of Chinese CharcotMarie-Tooth disease type 2L

We previously found that the K141N mutation in heat shock protein B8 （HSPB8） was responsible for Charcot-Marie-Tooth disease type 2L in a large Chinese family. The objective of the present study was to generate a transgenic mouse model bearing the K141N mutation in the human HSPB8 gene, and to determine whether this K141NHSPB8 transgenic mouse model would manifest the clinical phenotype of Charcot-Marie-Tooth disease type 2L, and consequently be suitable for use in studies of disease pathogenesis. Transgenic mice overexpressing K141N HSPB8 were generated using K141N mutant HSPB8 cDNA cloned into a pCAGGS plasmid driven by a human cytomegalovirus expression system. PCR and western blot analysis confirmed integration of the KI41NHSPB8 gene and widespread expression in tissues of the transgenic mice. The K141N HSPB8 transgenic mice exhibited decreased muscle strength in the hind limbs and impaired motor coordination, but no obvious sensory disturbance at 6 months of age by behavioral assessment. Electrophysiological analysis showed that the compound motor action potential amplitude in the sciatic nerve was significantly decreased, but motor nerve conduction velocity remained normal at 6 months of age. Pathological analysis of the sciatic nerve showed reduced myelinated fiber density, notable axonal edema and vacuolar degeneration in K141N HSPB8 transgenic mice, suggesting axonal involvement in the peripheral nerve damage in these animals. These findings indicate that the KI4mHSPB8 transgenic mouse successfully models Charcot-Marie-Tooth disease type 2L and can be used to study the pathogenesis of the disease.

Rapid genetic screening of Charcot-Marie-Tooth disease type 1A and hereditary neuropathy with liability to pressure palsies patients

We used the allele-specific PCR-double digestion method on peripheral myelin protein 22 （PMP22） to determine duplication and deletion mutations in the proband and family members of one family with Charcot-Marie-Tooth disease type 1 and one family with hereditary neuropathy with liability to pressure palsies. The proband and one subclinical family member from the Charcot-Marie-Tooth disease type 1 family had a PMP22 gene duplication; one patient from the hereditary neuropathy with liability to pressure palsies family had a PMP22 gene deletion. Electron microscopic analysis of ultrathin sections of the superficial peroneal nerve from the two probands demonstrated demyelination and myelin sheath hyperplasia, as well as an ＇onion-like＇ structure in the Charcot-Marie-Tooth disease type 1A patient. We observed an irregular thickened myelin sheath and ＇mouse-nibbled＇-Iike changes in the patient with hereditary neuropathy with liability to pressure palsies. In the Charcot-Marie-Tooth disease type 1A patient, nerve electrophysiological examination revealed moderate-to-severe reductions in the motor and sensory conduction velocities of the bilateral median nerve, ulnar nerve, tibial nerve, and sural nerve. Moreover, the compound muscle action potential amplitude was decreased. In the patient with hereditary neuropathy with liability to pressure palsies, the nerve conduction velocity of the bilateral tibial nerve and sural nerve was moderately reduced, and the nerve conduction velocity of the median nerve and ulnar nerve of both upper extremities was slightly reduced.

Recommendations for the diagnosis and treatment of paroxysmal kinesigemc dyskinesia: an expert consensus in China

Paroxysmal dyskinesias are a group of neurological diseases characterized by intermittent episodes of involuntary movements with different causes.Paroxysmal kinesigenic dyskinesia(PKD)is the most common type of paroxysmal dyskinesia and can be divided into primary and secondary types based on the etiology.Clinically,PKD is characterized by recurrent and transient attacks of involuntary movements precipitated by a sudden voluntary action.The major cause of primary PKD is genetic abnormalities,and the inheritance pattern of PKD is mainly autosomal-dominant with incomplete penetrance.The proline-rich transmembrane protein 2(PRRT2)was the first identified causative gene of PKD,accounting for the majority of PKD cases worldwide.An increasing number of studies has revealed the clinical and genetic characteristics,as well as the underlying mechanisms of PKD.By seeking the views of domestic experts,we propose an expert consensus regarding the diagnosis and treatment of PKD to help establish standardized clinical evaluation and therapies for PKD.In this consensus,we review the clinical manifestations,etiology,clinical diagnostic criteria and therapeutic recommendations for PKD,and results of genetic analyses in PKD patients performed in domestic hospitals.

Intermediate Charcot-Marie-Tooth disease

Charcot-Marie-Tooth（CMT） disease is a common neurogenetic disorder and its heterogeneity is a challenge for genetic diagnostics. The genetic diagnostic procedures for a CMT patient can be explored according to the electrophysiological criteria： very slow motor nerve conduction velocity（MNCV）（〈15 m/s）, slow MNCV（15–25 m/s）, intermediate MNCV（25–45 m/s）, and normal MNCV（〉45 m/s）. Based on the inheritance pattern, intermediate CMT can be divided into dominant（DI-CMT） and recessive types（RI-CMT）. GJB1 is currently considered to be associated with X-linked DI-CMT, and MPZ, INF2, DNM2, YARS, GNB4, NEFL, and MFN2 are associated with autosomal DI-CMT. Moreover, GDAP1, KARS, and PLEKHG5 are associated with RI-CMT. Identification of these genes is not only important for patients and families but also provides new information about pathogenesis. It is hoped that this review will lead to a better understanding of intermediate CMT and provide a detailed diagnostic procedure for intermediate CMT.