Charcot-Marie-Tooth disease (CMT) is a genetically heterogeneous disorder that has been associated with alterations of several proteins: peripheral myelin protein 22, myelin protein zero, connexin 32, early growth response factor 2, periaxin, myotubularin related protein 2, N-myc downstream regulated gene 1 product, neurofilament light chain, and kinesin 1B.
Our results suggest that alterations in the formation of a normal IF network in neurons elicited by these NFL mutations may contribute to the development of Charcot-Marie-Tooth neuropathy.
The novel neurofilament light (NEFL) mutation Glu397Lys is associated with a clinically and morphologically heterogeneous type of Charcot-Marie-Tooth neuropathy.
We examined CMT1A duplication of 17p11.2-p12, mutations of PMP22, MPZ (P0), GJB1 (Cx32), EGR2 and NEFL genes in 57 Korean families with patients diagnosed as having Charcot-Marie-Tooth (CMT) disease.
Defective transport of the mutant NFL subunits was observed for all the CMT-linked NFL mutations, but the characteristics of this defect also depended on the specific mutation.
Recently a set of mutations in the neurofilament light gene (NF-L) was reported in patients suffering from axonal and demyelinating forms of Charcot-Marie-Tooth disease (CMT1 and CMT2).
We demonstrated that the Charcot-Marie-Tooth-linked neurofilament light mutations: (i) affect the axonal transport of mutant neurofilaments; (ii) have a dominant-negative effect on the transport of wild-type neurofilaments; (iii) affect the transport of mitochondria and the anterograde axonal transport marker human amyloid precursor protein; (iv) result in alterations of retrograde axonal transport and (v) cause fragmentation of the Golgi apparatus.
Because the I214M amino acid substitution in the NEFL protein was not detected in a CMT affected brother of the proband, its pathogenic effect became unclear.
We performed a mutational analysis of NEFL in a series of 177 index cases with CMT and without mutations in the genes for peripheral myelin protein zero (MPZ), peripheral myelin protein 22 (PMP22) and connexin 32 (GJB1); the motor nerve conduction velocity (MNCV) at the median nerve was below 38 m/s in 76 cases and above 38 m/s in 101.
This study demonstrated normal function of the low-molecular-weight neurofilament protein (NFL) in mitochondrial dynamics and disruption in Charcot-Marie-Tooth disease (CMT) due to mutations in the Nefl gene.
In the context of inherited neuropathy, giant axons are typically associated with autosomal recessive giant axonal neuropathy caused by gigaxonin mutations but have also been reported in association with NEFL- and SH3TC2-associated Charcot-Marie-Tooth disease.
Although evidence suggests that there is a correlation between NEFL expression and cancer, studies regarding the role of the NEFL protein have been mostly limited to neurological diseases, such as Charcot-Marie-Tooth's disease (CMT).
In MPZ-associated CMT, increased CSAs were found in the median nerve at wrist and in the great auricular nerve, whereas it was not increased in patients with NEFL-associated CMT.
iPSC lines from patients with two distinct forms of axonal CMT (CMT2A and CMT2E) were differentiated into spinal cord motor neurons and used to study axonal structure and function and electrophysiological properties in vitro.