Thymocytes Express thegolliProducts of the Myelin Basic Protein Gene and Levels of Expression Are Stage Dependent

Abstract

The golli products of the myelin basic protein gene have been shown to be expressed in mouse thymus and brain. The full repertoire of thymic cell types expressing golli products has not yet been determined, although immunoreactivity has been found in some macrophages. We have analyzed the cellular expression of golli mRNAs and proteins in the thymus. The results showed that MTS5+ cortical/MTS10+ medullary epithelial cells and NLDC145+ dendritic cells did not express golli, while some macrophages did exhibit strong immunoreactivity. Golli mRNAs were not detected in macrophages by in situ hybridization. Thymocytes expressed significant levels of golli mRNAs and proteins by in situ hybridization and immunohistochemistry. Interestingly, golli immunoreactivity varied with thymocyte stage of differentiation. For example, CD4−CD8− (double-negative) thymocytes expressed relatively high levels of golli. Upon further differentiation into CD4−CD8− (double-positive) thymocytes, golli protein expression declined dramatically. When thymocytes developed into CD8− or CD4+ (single-positive) thymocytes, golli protein expression increased again, but it never achieved the levels found in double-negative thymocytes. Thus, the altered levels of expression of golli proteins in developing thymocytes correlated with the transitions from double-negative to double-positive and double-positive to single-positive stages. The lack of significant golli expression in thymic stromal cells may offer an alternative explanation for the mechanism of inefficient negative selection of those autoreactive thymocytes with specificity for myelin basic proteins.

The myelin basic protein gene is expressed in differentiated blood cell lineages and in hemopoietic progenitors

“…The report by J.-M. Feng et al (31) of HMBP RNAs in thymus cells showed that these quite unexpected data were reproducible and that indeed T cells do produce HMBP proteins. However, we did not observe ''altered levels of expression in developing thymocytes and lack of significant expression in thymic stromal cells,'' and furthermore, HMBP was not detected within T cell nuclei, as J.-M. Feng et al reported, even at the ultrastructural level.…”

Minireview: Expression and Function of Golli Protein in Immune System

“…A series of immunological studies performed by Voskuhl's group showed that the MBP epitopes within golli proteins could be recognized by T-cells lines derived from SJL mice specific for the immunodominant (MBP 83-102 ) and subdominant (MBP [19][20][21][22][23][24][25][26][27] ) epitopes, implying that the golli protein could potentially serve as an additional source of MBP epitopes [7,8]. During relapsing experimental autoimmune encephalomyelitis (EAE), the response of T-cells spreads to epitopes other than the disease-initiating myelin protein epitopes.…”

Increased Expression of Golli Myelin Basic Proteins Enhances Calcium Influx into Oligodendroglial Cells

“…In mouse, three golli products have been identified: BG21, J37, and TP8 . Unlike the classic MBPs, golli proteins are expressed in myelin-forming cells as well as in neurons in the CNS and peripheral nervous system (Landry et al, , 1997(Landry et al, , 1998Pribyl et al, 1996) and in macrophages and T-cells in the immune system (Feng et al, 2000). Golli proteins first appear in many neurons when they are extending processes for migration, establishment of connections and, in the case of oligodendrocytes (OLs), before myelination (Landry et al, , 1997(Landry et al, , 1998Pribyl et al, 1996).…”