Oct-6 (SCIP Tst-1) is expressed in Schwann cell precursors, embryonic Schwann cells, and postnatal myelinating Schwann cells: Comparison with Oct-1, Krox-20, and Pax-3

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Abstract
The POU domain transcription factor Oct-6 (SCIP/ Tst-1) is likely to control important stages of Schwann cell development, including the initiation of myelination around birth. Here, we use immunocytochemical and reverse transcriptase-polymerase chain reaction techniques to examine Oct-6 earlier in nerve development, to test the idea that Oct-6 has an additional role in Schwann cell precursors or early embryonic Schwann cells, a possibility raised by previous studies on transgenic mice. Consistent with this, we find low but unambiguous levels of Oct-6 mRNA and protein in Schwann cell precursors of mouse and rat (nerves from 12- and 14-day-old embryos, respectively), with expression levels gradually increasing during early Schwann cell development and towards birth. Unexpectedly, Oct-6 immunoreactivity is clearly present in nuclei of most myelinating cells at least as late as postnatal day 12. Furthermore, many nonmyelinating Schwann cells express Oct-6 in adult life. A comparison of Oct-6 mRNA with other Schwann cell transcription factors—namely, Oct-1, Krox-20, and Pax-3—reveals that each factor exhibits strong developmental regulation and a unique expression pattern in embryonic nerves. Therefore, they are likely to play distinct regulatory roles in early development of the Schwann cell lineage.