Myelin development in the peripheral nervous system of Trachemys scripta

The upregulation of orthologous myelin genes in the turtle PNS supports the idea that these components are conserved, although their timing, regulation, or network structure may differ across tetrapods. We based our inference of conservation on orthology and the coordinated expression of key myelin genes (e.g., ErbB2, Mag, Mpz, Mbp, Pmp22) in T. scripta. TEM analysis of turtle sciatic nerves shows myelin rings in a few axons starting at stage 21, increasing significantly by stage 24, and becoming prominent in most axons of the adult nerve.

Furthermore, antibodies against MPZ, DRP2, and Kv1.1 indicate that T. scripta adult peripheral nerves at various axial levels contain myelin segments with structures consistent with appositions and Schmidt-Lanterman incisures. Overall, this is the first study of PNS myelin development in a reptile, demonstrating that myelination is a highly conserved process in vertebrates.