Vanishing white matter (VWM) disease is an autosomal recessive disorder that affects the central nervous system of a patient, and is caused by the development of pathogenic mutations in any of the EIF2B1-5 genes. Any dysfunction of the EIF2B1-5 gene encoded eIF2B causes stress-provoked episodic rapid neurological deterioration in the patient, followed by a chronic progressive disease course. We present the case of a patient with an infantile-onset VWM with the pre-described specific clinical course, subsequent neurological aggravation induced by each viral infection, and the noted consequent progression into a comatose state. Although the initial brain magnetic resonance imaging did not reveal specific pathognomonic signs of VWM to distinguish it from other types of demyelinating leukodystrophy, the next-generation sequencing studies identified heterozygous missense variants in EIF2B3, including a novel variant in exon 7 (C706G), as well as a 0.008% frequency reported variant in exon 2 (T89C). Hence, the characteristic of unbiased genomic sequencing can clinically affect patient care and decisionmaking, especially in terms of the consideration of genetic disorders such as leukoencephalopathy in pediatric patients.
Brain ; Central Nervous System ; Coma ; Eukaryotic Initiation Factor-2B ; Exome ; Exons ; Humans ; Leukoencephalopathies ; Magnetic Resonance Imaging ; Patient Care ; White Matter

OBJECTIVETo investigate the in vivo functional roles of the La autoantigen (La), the human homologue of the 33-kDa vesicle-associated membrane protein-associated protein (hVAP-33), and the subunit gamma of the human eukaryotic initiation factors 2B (eIF2Bgamma) as co-infection factors supporting chronic infection with hepatitis C virus (HCV).

METHODSSmall interfering (si)RNAs were designed against the HCV internal ribosome entry site (IRES) and transfected into Huh7 cells chronically infected with the HCV pseudovirus (designated as Huh7-HCV cells). The IRES siRNA producing the most effective silencing was selected for further analysis by fluorescence quantitative polymerase chain reaction (qPCR). siRNAs designed against La, hVAP-33, and eIF2Bgamma and the IRES-specific siRNA were then transfected, respectively or in various combinations, into the Huh7-HCV cell line for 48 h. The delta CT values were calculated and used to compare the HCV inhibitive efficacies of the siRNAs in isolation or in combination. Western blotting analysis was used to compare the quantity of core protein expression in each group.

RESULTSThe four gene-specific siRNAs, in isolation or in combination, caused inhibition of HCV replication and gene and protein expressions to varying degrees. The combination of La + IRES siRNAs produced the strongest inhibition of HCV core antigen expression. The combinations of hVAP-33 + IRES siRNAs and eIF2Bgamma + IRES siRNAs produced stronger inhibitions of HCV replication and gene and protein expressions than either hVAP-33 siRNA or eIF2Bgamma siRNA alone.

CONCLUSIONLa, hVAP-33, and eIF2Bgamma act as co-infection factors of HCV chronic infection in vivo. HCV replication and gene and protein expression can be inhibited significantly by RNA interference of these co-infection factors and/or HCV IRES.

Autoantigens ; genetics ; Cell Line ; Eukaryotic Initiation Factor-2B ; genetics ; Hepacivirus ; immunology ; physiology ; Humans ; RNA, Small Interfering ; genetics ; Ribonucleoproteins ; genetics ; Vesicular Transport Proteins ; genetics ; Virus Replication

BACKGROUNDVanishing white matter disease (VWM), a human autosomal recessive inherited leukoencephalopathy, is due to mutations in eukaryotic initiation factor 2B (eIF2B). eIF2B is responsible for the initiation of protein synthesis by its guanine nucleotide exchange factor (GEF) activity. Mutations of eIF2B impair GEF activity at different degree. Previous studies implied improperly activated unfolded protein response (UPR) and endoplasmic reticulum stress (ERS) participated in the pathogenesis of VWM. Autophagy relieves endoplasmic reticulum load by eliminating the unfolded protein. It is still unknown the effects of genotypes on the pathogenesis. In this work, UPR and autophagy flux were analyzed with different mutational types.

METHODSERS tolerance, reflected by apoptosis and cell viability, was detected in human oligodendrocyte cell line transfected with the wild type, or different mutations of p. Arg113His, p. Arg269FNx01 or p. Ser610-Asp613del in eIF2Bε. A representative UPR-PERK component of activating transcription factor 4 (ATF4) was measured under the basal condition and ERS induction. Autophagy was analyzed the flux in the presence of lysosomal inhibitors.

RESULTSThe degree of ERS tolerance varied in different genotypes. The truncated or deletion mutant showed prominent apoptosis cell viability declination after ERS induction. The most seriously damaged GEF activity of p. Arg269FNx01 group underwent spontaneous apoptosis. The truncated or deletion mutant showed elevated ATF4 under basal as well as ERS condition. Decreased expression of LC3-I and LC3-II in the mutants reflected an impaired autophagy flux, which was more obvious in the truncated or deletion mutants after ERS induction.

CONCLUSIONSGEF activities in different genotypes could influence the cell ERS tolerance as well as compensatory pathways of UPR and autophagy. Oligodendrocytes with truncated or deletion mutants showed less tolerable to ERS.

Cell Line ; Endoplasmic Reticulum Stress ; genetics ; physiology ; Eukaryotic Initiation Factor-2B ; genetics ; Humans ; Mutation ; genetics ; Oligodendroglia ; metabolism ; Unfolded Protein Response ; genetics ; physiology

Eukaryotic translation initiation factor eIF2B, the guanine nucleotide exchange factor (GEF) for eIF2, catalyzes conversion of eIF2·GDP to eIF2·GTP. The eIF2B is composed of five subunits, α, β, γ, δ and ɛ, within which the ɛ subunit is responsible for catalyzing the guanine exchange reaction. Here we present the crystal structure of the C-terminal domain of human eIF2Bɛ (eIF2Bɛ-CTD) at 2.0-Å resolution. The structure resembles a HEAT motif and three charge-rich areas on its surface can be identified. When compared to yeast eIF2Bɛ-CTD, one area involves highly conserved AA boxes while the other two are only partially conserved. In addition, the previously reported mutations in human eIF2Bɛ-CTD, which are related to the loss of the GEF activity and human VWM disease, have been discussed. Based on the structure, most of such mutations tend to destabilize the HEAT motif.
Amino Acid Motifs ; Amino Acid Sequence ; Catalytic Domain ; Crystallography, X-Ray ; Eukaryotic Initiation Factor-2B ; biosynthesis ; chemistry ; Humans ; Molecular Sequence Data ; Protein Structure, Tertiary ; Protein Subunits ; biosynthesis ; chemistry ; Recombinant Proteins ; biosynthesis ; chemistry ; Sequence Alignment ; Structural Homology, Protein ; Surface Properties