Identification of Tmem10 as a Novel Late-stage Oligodendrocytes Marker for Detecting Hypomyelination

Oligodendrocytes ensheath axons to form compact insulating multilamellar structures known as myelin. Tmem10 is a novel type I transmembrane glycoprotein that is highly expressed in oligodendrocytes and whose biological function remains largely unknown. Furthermore, the expression pattern of Tmem10 remains a matter of some controversy. Given the inconsistency of its expression pattern and the lack of validated specific antibodies, Tmem10 is not widely accepted as a marker for mature oligodendrocytes. As a means to solve these problems and to aid future studies of oligodendrocyte-associated diseases, we have generated a highly specific Tmem10 antibody. Using this Tmem10 antibody, we clarify that Tmem10 protein is firstly expressed at 2 weeks in the postnatal mouse brain with age-related increase, only in the central nervous system (CNS). We also reveal that Tmem10 is expressed specifically in late stage oligodendrocytes and later than MAG, a late-stage myelin marker. Finally, we show that Tmem10 co-expresses with MOG- and MBP-positive myelin fibers and is dramatically reduced in a hypomyelination mouse model. In conclusion, our study demonstrates that Tmem10 can be used as a specific marker for myelinating oligodendrocytes and perhaps for the evaluation of myelination diseases, such as multiple sclerosis.     

MicroRNA: Key regulators of oligodendrocyte development and pathobiology

MicroRNAs (miRNAs or miRs) are a group of small non-coding RNAs that function through binding to messenger RNA (mRNA) targets and downregulating gene expression. miRNAs have been shown to regulate many cellular functions including proliferation, differentiation, development and apoptosis. Recently, evidence has grown which shows the involvement of miRs in oligodendrocyte (OL) specification and development. In particular, miRs-138, -219, -338, and -9 have been classified as key regulators of OL development, acting at various points in the OL lineage and influencing precursor cell transit into mature myelinating OLs. Many studies have emerged which link miRNAs with OL and myelin pathology in various central nervous system (CNS) diseases including multiple sclerosis (MS), ischemic stroke, spinal cord injury, and adult-onset autosomal dominant leukodystrophy (ADLD).     

Pattern of structural differentiation in the optic nerve of trout (Salmo gairdneri)

Summary The development of the trout optic nerve is quantitatively described from early ontogenesis into adulthood. The nerve is oval in cross section until stage 34, thereafter the formation of vertically aligned parallel folds can be observed and thus the unique shape of a folded ribbon is gradually attained. Quantitative measurements revealed a linear increase in cross sectional area, caused in part by the formation of new folds and in part by an increase in size of the preexisting ones. We attribute the continuous expansion of individual folds to an increase in fiber size subsequent to myelination rather than to the addition of new fibers. The total number of glial cells increased concomitantly per fold.Myelinogenesis starst at stage 33 with the ensheathement of axons beginning at the dorsal edge of the primary fold and follows a highly ordered pattern throughout development, strictly succeeding neural outgrowth. The functional significance of this pattern is discussed.     

Phosphorylation of Nuclear Proteins in Myelinating Oligodendrocytes and Its Control by Cyclic AMP

Oligodendroglial nuclei isolated from rat brains at different stages of myelinogenesis (10, 18, and 30 days of age) were incubated with [gamma-32P]ATP and extracted with 0.75 M perchloric acid to yield a fraction of nonacidic chromatin proteins. The protein extracts were then analyzed by polyacrylamide gel electrophoresis. The phosphorylation pattern of these proteins was found to be different for different age groups. In 10-day-old rat oligodendrocytes the most extensive phosphorylation occurred in low molecular mass species (less than 30 kDa), in contrast to fractions obtained from 18- and 30-day-old rat oligodendrocytes which showed a significantly higher labeling of the proteins with molecular masses greater than 30 kDa. The phosphorylation of the latter species was greatly stimulated by the presence of cyclic AMP in the incubation media. The results suggest that the phosphorylation of specific nuclear proteins, which may play a regulatory role at different stages of oligodendroglial maturation and myelinogenesis, may be at least partially modulated by intracellular cyclic AMP.     

Neuraminidase Activities in Oligodendroglial Cells of the Rat Brain

Neuraminidase activities in oligodendroglial cells were characterized using rats of different ages. Rat oligodendroglial cells had intrinsic neuraminidase activities directed toward GM3 and N-acetylneuramin(2-3)lactitol (NL). Developmental profiles of the neuraminidase activities toward the two substrates in oligodendroglial cells were different from each other. The neuraminidase activity toward GM3 increased rapidly with the onset of active myelination and, after 26 days of development, reached the adult level which was about 18 times higher than that in myelin. At the adult age, oligodendroglial cells had the highest neuraminidase activity toward GM3 among the individual brain cell types examined. The activity of NL-neuraminidase showed a less remarkable developmental profile, with a peak value at 26 days. The UDP-galactose:ceramide galactosyltransferase activity in oligodendroglial cells increased during the period of active myelination and, afterward, returned to the basal level. The enrichment and unique developmental profile in oligodendroglial cells of the neuraminidase activity toward GM3 suggest that this enzyme may play an important role in the formation and maintenance of the myelin sheath.     

Presence of myelin-like structures in tanniferous vascular parenchyma cells ofSalix dasyclados Wim.

Summary In the cambial region ofSalix dasyclados plants, extensive spherical formations of myelin-like lamellar configurations were found during the transit period between winter dormancy and reactivation of growth in early spring. The lamellar structures occurred in parenchyma cells containing tannins and were associated with spherosomes. Cytomembranes in tannin-containing cells appeared with negative contrast on electron micrographs, indicating the presence of tanniferous substances in the cytoplasm.Abbreviation R_G relative growth rate (% fresh weight increase per day)     

Enzyme Immunoassay of the Myelin Basic Protein

Abstract: An enzyme immunoassay using a double-antibody solid-phase technique for myelin basic protein (MBP) has been developed. Antisera were prepared by immunizing rabbits with the purified MBP from chick brain. The conjugation of MBP with horseradish peroxidase was performed by the periodate oxidation method in triethanolamine-acetate buffer (pH 8.5). The sample, antiserum, and conjugate were incubated at 4°C for 16 h, after which the insoluble second antibody was added and the reaction mixture was incubated at 4°C for 3 h. The peroxidase activity of the insoluble conjugate was assayed fluorometrically with hydrogen peroxide and 3-( p -hydroxyphenyl)propionic acid as substrates. The method had an analytical range from 50 pg to 1 ng (from 2.3 × 10⁻¹⁵ to 4.5 × 10⁻¹⁴ mol). The within-assay coefficient of variation (CV) was between 4 and 11% and the between-assay CV for 200 and 400 pg of MBP was 5.5 and 7.1%, respectively. A weak cross-reactivity was observed between chick MBP and bovine MBP, while no reactivity was shown with calf thymus histone. The MBP content of the brain during development increased markedly from the 3rd embryonic week to the 3rd post-hatch week (from 0.01 to 2.4 mg/g of fresh tissue), and the adult level was 3.2 mg/g of fresh tissue.