Behavior of Schwann cells from Trembler mouse unmyelinated fibers transplanted into myelinated nerves

Abstract

In the peripheral nerves of Trembler mice, Schwann cells produce little or no myelin and continue to multiply beyond the normal neonatal period. However, in the unmyelinated (Remak) fibers of these mutants, Schwann cell morphology and multiplication are normal. To determine if such phenotypically normal Schwann cells would show the Trembler abnormalities when challenged to form myelin in nerve grafts, an unmyelinated nerve, the cervical sympathetic trunk, was transplanted into the richly myelinated sural nerve in a series of normal host animals. Two months after transplantation, regenerated grafts, composed of normal host axons and Trembler cervical sympathetic trunk Schwann cells, showed the characteristic Trembler abnormalities of myelination and multiplication whereas Schwann cells from normal cervical sympathetic trunks myelinated the host axons normally. Thus, the Trembler mutation appears to affect Schwann cell differentiation at a specific phase, the formation of myelin. This primary expression of the Schwann cell abnormality initiates a cycle of secondary effects that include demyelination, Schwann cell multiplication, and attempted remyelination.