AMPHOTERIN (P-30, HMG-1) AND RIP ARE EARLY MARKERS OF OLIGODENDROCYTES IN THE DEVELOPING RAT SPINAL-CORD

We have determined the cellular localization of the neurite outgrowth- promoting protein, amphoterin (p30), within the developing rat spinal cord in order to gain insight into possible function(s). Both neurons and oligodendrocytes are labelled by anti-amphoterin antibodies in tis sue sections. Double labelling confirmed that labelled non-neuronal ce lls were oligodendrocytes and not astrocytes. White matter cells label led by anti-amphoterin were first apparent in the spinal cord at embry onic day 18 (E18). The spinal cord white matter was most densely popul ated by amphoterin immunoreactive oligodendrocytes during the first po stnatal week. In the adult spinal cord anti-amphoterin-labelled oligod endrocytes were infrequent. Neuronal staining was not diminished in ad ult animals. We have identified multiple populations of developing oli godendrocytes in the rat spinal cord. Oligodendrocytes (or precursors) in the presumptive white matter at E20 are elongated, radially orient ed cells. Some are amphoterin(+) and Rip(-), while others are positive for both antigens. At the same age, a small number of process-bearing Rip(+) cells are present in the grey matter. These morphologically an d antigenically defined populations of cells could reflect different o ligodendrocyte lineages, developmental stages, or different responses to environmental cues. While the function of amphoterin is unknown, th e finding that amphoterin is expressed in numerous oligodendrocytes fr om late embryonic development suggests that amphoterin expression may be important in the early stages of oligodendrocyte maturation. The on set of amphoterin expression, prior to the expression of myelin-specif ic antigens, makes amphoterin a useful marker for studying oligodendro cyte development.