Molecular cloning and transfection studies of M6b-2, a novel splice variant of a member of the PLP-DM20/M6 gene family

Abstract

The present study documents the nucleic acid and deduced amino acid sequence of M6b-2, a novel splice variant of the M6b gene, which belongs to the PLP-DM20/M6 gene family. M6b-2 differs from the previously published M6b by a novel 40-amino acid insertion which is characterised by a high proline content, two casein kinase, and one tyrosine kinase consensus sequences. M6b-2 mRNA is enriched in perinatal central nervous system (CNS), and although it declines during development, it does persist into adulthood. Transient transfection studies coupled to secondary structure and hydrophobicity analysis suggest that the novel polypeptide in M6b-2 lies at the cytoplasmic face of the plasma membrane. It is therefore possible that the function(s) of M6b-2 may be regulated intracellularly by phosphorylation during CNS development.

Glial‐defined rhombomere boundaries in developing Xenopus hindbrain

“…They are closely related in primary sequences and have common topologic features, including four transmembrane domains separated by hydrophilic sequences. In rodents, DM␥/M6b appears to be expressed in neuronal cells with many alternative spliced variants (Vouyiouklis et al, 1998). The expression pattern is different amongst vertebrate species (Kitagawa et al, 1993;Yan et al, 1996), and we found no evidence of expression of this protein in Xenopus neurons.…”

Rhombex-29, a novel gene of the PLP/DM20-M6 family cloned from rat medulla oblongata by differential display

“…In the CNS, rat Rhombex-29 mRNA is concentrated much more heavily in the VMS than in the cerebral cortex and cerebellum. Ontogenetically, expression of rat Rhombex-29 mRNA appears by E20 and steadily increases after birth, which is consistent with the findings that the relative quantity of mouse M6b mRNA remains constant as the brain develops (Vouyiouklis et al, 1998).…”

“…Surprisingly, the primary structure of rat Rhombex-29 protein is homologous to that of the major CNS myelin protein family PLP/DM20-M6. The hydrophobicity profile showed that rat Rhombex-29 protein has the four-transmembranedomain arrangement typical of PLP/DM20-M6 family members (Popot et al, 1991;Kitagawa et al, 1993;Yan et al, 1993;Gow et al, 1997;Vouyiouklis et al, 1998; Yoshida et al, 1999). Within the PLP/DM20-M6 family, the primary structure of rat Rhombex-29 corresponded to an intermediate type between mouse M6b and shark DM␥, because the phylogenic tree of PLP/DM20-M6 family members indicates that rat Rhombex-29 is an intermediate type between shark DM␥ and mouse M6b.…”