The Infantile Leukoencephalopathy-Associated Mutation of C11ORF73/HIKESHI Proteins Generates de novo Interactive Activity with Filamin A, Inhibiting Oligodendroglial Cell Morphological Differentiation.

Genetic hypomyelinating diseases are a heterogeneous group of disorders involving the white matter. One infantile hypomyelinating leukoencephalopathy is associated with the homozygous variant (Cys4-to-Ser (C4S)) of the c11orf73 gene. Methods: We observed that in mouse oligodendroglial FBD-102b cells, the C4S mutant proteins but not the wild type ones of C11orf73 are microscopically localized in the lysosome. And, they downregulate lysosome-related signaling in an immunoblotting technique. Results: The C4S mutant proteins specifically interact with Filamin A, which is known to anchor transmembrane proteins to the actin cytoskeleton; the C4S mutant proteins and Filamin A are also observed in the lysosome fraction. While parental FBD-102b cells and cells harboring the wild type constructs exhibit morphological differentiation, cells harboring C4S mutant constructs do not. It may be that morphological differentiation is inhibited because expression of these C4S mutant proteins leads to defects in the actin cytoskeletal network involving Filamin A. Conclusions: The findings that leukoencephalopathy-associated C11ORF73 mutant proteins specifically interact with Filamin A, are localized in the lysosome, and inhibit morphological differentiation shed light on the molecular and cellular pathological mechanisms that underlie infantile hypomyelinating leukoencephalopathy.

PP1C and PP2A are p70S6K Phosphatases Whose Inhibition Ameliorates HLD12-Associated Inhibition of Oligodendroglial Cell Morphological Differentiation.

Myelin sheaths created by oligodendroglial cells encase neuronal axons to achieve saltatory conduction and protect axons. Pelizaeus-Merzbacher disease (PMD) is a prototypic, hereditary demyelinating oligodendroglial disease of the central nervous system (CNS), and is currently known as hypomyelinating leukodystrophy 1 (HLD1). HLD12 is an autosomal recessive disorder responsible for the gene that encodes vacuolar protein sorting-associated protein 11 homolog (VPS11). VPS11 is a member of the molecular group controlling the early endosome antigen 1 (EEA1)- and Rab7-positive vesicle-mediated protein trafficking to the lysosomal compartments. Herein, we show that the HLD12-associated Cys846-to-Gly (C846G) mutation of VPS11 leads to its aggregate formation with downregulated signaling through 70 kDa S6 protein kinase (p70S6K) in the oligodendroglial cell line FBD-102b as the model. In contrast, wild-type proteins are localized in both EEA1- and Rab7-positive vesicles. Cells harboring the C846G mutant constructs decrease differentiated phenotypes with web-like structures following differentiation, whereas parental cells exhibit them suitably. It is of note that we identify PP1C and PP2A as the protein phosphatases for phosphorylated Thr-389 of p70S6K essential for kinase activation in cells. The respective knockdown experiments or inhibitor treatment stimulates phosphorylation of p70S6K and ameliorates the inhibition of morphological differentiation, as well as the formation of protein aggregates. These results indicate that inhibition of p70S6K phosphatases PP1C and PP2A improves the defective morphological differentiation associated with HLD12 mutation, thereby hinting at amelioration based on a possible molecular and cellular pathological mechanism underlying HLD12.

Hypomyelinating leukodystrophy-associated mutation of RARS leads it to the lysosome, inhibiting oligodendroglial morphological differentiation.

Pelizaeus-Merzbacher disease (PMD) is a central nervous system (CNS) demyelinating disease in human, currently known as prototypic hypomyelinating leukodystrophy 1 (HLD1). The gene responsible for HLD1 encodes proteolipid protein 1 (PLP1), which is the major myelin protein produced by oligodendrocytes. HLD9 is an autosomal recessive disorder responsible for the gene differing from the plp1 gene. The hld9 gene encodes arginyl-tRNA synthetase (RARS), which belongs to a family of cytoplasmic aminoacyl-tRNA synthetases. Herein we show that HLD9-associated missense mutation of Ser456-to-Leu (S456L) localizes RARS proteins as aggregates into the lysosome but not into the endoplasmic reticulum (ER) and the Golgi body. In contrast, wild-type proteins indeed distribute throughout the cytoplasm. Expression of S456L mutant constructs in cells decreases lysosome-related signaling through ribosomal S6 protein phosphorylation, which is known to be required for myelin formation. Cells harboring the S456L mutant constructs fail to exhibit phenotypes with myelin web-like structures following differentiation in FBD-102b cells, as part of the mammalian oligodendroglial cell model, whereas parental cells exhibit them. Collectively, HLD9-associated RARS mutant proteins are specifically localized in the lysosome with downregulation of S6 phosphorylation involved in myelin formation, inhibiting differentiation in FBD-102b cells. These results present some of the molecular and cellular pathological mechanisms for defect in myelin formation underlying HLD9.

Loss of hepatitis C virus RNA after parturition in female patients with chronic HCV infection.

It is unclear whether pregnancy has any influence on chronic hepatitis C virus (HCV) infection. The aim of this study was to investigate the relationship between pregnancy and parturition with HCV viremia levels and the natural resolution of HCV RNA. Twenty-two pregnant patients and 120 nonpregnant control female patients, both positive for anti-HCV and HCV RNA, were studied. The HCV core protein levels were quantified by enzyme immunoassay, and HCV RNA was detected by reverse transcription-polymerase chain reaction (RT-PCR). Of the pregnant group, two females whose HCV RNA was negative continuously for more than 6 months lost HCV RNA permanently after parturition, and one female whose level of HCV core protein was intermittently under the limit of detection level lost HCV RNA intermittently. In the control group, only one female lost HCV RNA persistently, and one lost HCV RNA intermittently after she developed liver cirrhosis. At 3 months after parturition, the HCV core protein level was <15 fmol/L in all patients who lost HCV RNA, while the HCV core protein level was >/=15 fmol/L in 81.3% of the patients who persistently had HCV RNA (P = 0.03). Significantly more pregnant patients lost HCV RNA than did nonpregnant controls. These findings suggest that pregnancy and parturition appear to influence the clinical course of HCV infection.