A proteolipid protein gene family: expression in sharks and rays and possible evolution from an ancestral gene encoding a pore-forming polypeptide.
The myelin proteolipid proteins (PLP and DM20) are believed to act as "adhesive struts" in the extracellular apposition of the CNS myelin sheath. These proteins have been considered late evolutionary developments, which arose de novo in the antecedents of early tetrapods. However, PCR primed with degenerate oligonucleotides corresponding to common segments of rat PLP/DM20 revealed three novel mRNAs in the brains of two elasmobranchs. These mRNAs are closely related to each other and to mammalian DM20, but lack the sequence that distinguishes PLP from DM20. We term the novel proteolipid proteins DM alpha, DM beta, and DM gamma. At least DM alpha and DM gamma are highly expressed in white matter in myelinating shark brain. The DMs not only are highly homologous to each other, but also contain regions bearing similarities with segments of channel-forming regions of the nicotinic acetylcholine receptor and the glutamate receptor macromolecular complexes. Significantly, we find that across these segments, DM alpha and DM gamma are more similar to the channel proteins than the two channel proteins are to each other.
Brookdale Center for Molecular Biology, Mount Sinai School of Medicine, New York, New York 10029.
K
K
Kitagawa
M P
MP
Sinoway
C
C
Yang
R M
RM
Gould
D R
DR
Colman
D000595:Amino Acid Sequence; D000818:Animals; D001059:Apoproteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D005075:Biological Evolution; D001921:Brain / Q000378:metabolism; D003001:Cloning, Molecular; D015870:Gene Expression; D005796:Genes; D008969:Molecular Sequence Data; D009185:Myelin Proteins / Q000235:genetics* / Q000378:metabolism; D018991:Myelin Proteolipid Protein / Q000235:genetics* / Q000378:metabolism; D009419:Nerve Tissue Proteins; D015345:Oligonucleotide Probes / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats / Q000235:genetics; D012754:Sharks / Q000235:genetics*; D012860:Skates, Fish / Q000235:genetics*; D014101:Torpedo
D001059:Apoproteins; D009185:Myelin Proteins; D018991:Myelin Proteolipid Protein; D009419:Nerve Tissue Proteins; D015345:Oligonucleotide Probes; C489071:Plp1 protein, rat; D012333:RNA, Messenger