Abnormal regulation of the myelin basic protein gene during development of the myelin-deficient mouse

Immunopanning selection of A2B5-positive cells increased the differentiation efficiency of induced pluripotent stem cells into oligodendrocytes

Oligodendrocytes are the myelinating cells of the central nervous system (CNS), and defects in these cells can result in CNS dysfunction. Although oligodendrocyte precursor cell (OPC) transplantation therapy is an effective cure for several disorders, there is no readily available source of these cells. Recent studies have described the generation of induced pluripotent stem cell (iPSC) from somatic cells, leading to speculation that this technique might become a novel therapeutic tool in regenerative medicine. In a previous study, we were able to produce O4 positive (O4(+)) oligodendrocytes from mouse iPSC in vitro. Unfortunately, the efficiency of differentiation achieved was relatively low (2.3%). In the current study, we improved the differentiation efficiency using a mouse monoclonal antibody (A2B5) to select cells of oligodendrocyte lineage. During in vitro differentiation, we purified A2B5-positive (A2B5(+)) cells by immunopanning from a mixed culture of iPSC-derived cells. This procedure increased the differentiation efficiency of O4(+) oligodendrocytes to 43.5%. We also examined the expression of myelin basic protein (MBP), a marker of mature oligodendrocytes. After 21 days of terminal differentiation, 62.3% of iPSC-derived O4(+) oligodendrocytes expressed MBP.

Regulation and differential expression of tau mRNA isoforms as oligodendrocytes mature in vivo: implications for myelination

Oligodendrocytes and neurons derive from the same cell type but develop distinct morphologic and functional properties as they mature in vivo. Both cells express tau protein, a developmentally regulated protein in the central nervous system. The regulation of tau has been investigated extensively in neurons but not in oligodendrocytes, so we studied regulation of tau in oligodendrocytes in vivo. The amino-derived tau isoforms consist of isoforms with zero (A0), one (A1), or two (A2) inserts. We examined the developmental regulation of tau mRNA isoforms at the amino domain by comparing tau expression in oligodendrocytes (OLGs) isolated from 1- and 20-day-old rat brain and in age-matched cortex, which abounds in neurons. In the rat brain, myelination peaks at 20 days. By using semiquantitative RT-PCR, we found that OLGs and cortex from 1-day-old rat brain largely had amino-derived tau isoforms with no insert, whereas OLGs from 20-day-old rat brain had similar levels of amino-derived tau isoforms with no insert or with one insert. We also found that 20-day-old OLGs had twofold more tau mRNA levels than younger OLGs. In contrast to OLGs from 20-day-old rat brain, age-matched cortex had comparable levels of A0, A1, and A2 tau amino-derived isoforms. Further, younger and older OLGs had a reciprocal pattern of expression of both carboxy-derived tau mRNA isoforms with either three (3R) or four (4R) repeats. In contrast, younger and older cortex expressed either 3R or 4R tau. This study showed an upregulation of tau mRNA and cell-specific tau mRNA isoform expression in OLGs forming myelin.