It should be emphasized that four of the five S1P receptors (S1PR1, S1PR2, S1PR3, S1PR5) are expressed in both cell types—astrocytes and oligodendrocytes [139]—and increased levels of S1PR1 and S1PR3 have also been reported in MS lesions [30,140,141]. The gene discussed is S1PR1; the disease is myeloid sarcoma.