ISOLATION AND CHARACTERIZATION OF A CDNA-ENCODING THE ZEBRA FINCH MYELIN PROTEOLIPID PROTEIN

A cDNA was isolated from a zebra finch telencephalon cDNA library that encodes the myelin proteolipid protein. The clone was 2874 nucleotide s long containing an open reading frame of 831 nucleotides that encode d a 277 amino acid myelin proteolipid protein. The 5'-and 3' untransla ted regions were 112 and 1931 nucleotides, respectively. In Northern b lots the clone hybridized to 3 bands of 3.5, 2.4 and 1.5 Kb in mouse b rain RNA, but to only a single band of 3.0 kb in zebra finch brain RNA , suggesting the lack of alternative polyadenylation sites within the 3' untranslated region of the zebra finch PLP mRNAs. There was a small degree of homology between the zebra finch and chicken PLP 5' untrans lated regions, but relatively little homology of the 5' untranslated r egions of the zebra finch PLP cDNA clone with the homologous regions o f PLP cDNAs of many mammalian species. Except for a small stretch of c onsiderable homology, there was little overall homology with the 3' un translated regions of mammalian PLP mRNAs. Approximately 10% (i.e. 28) of the amino acids in the zebra finch PLP differed from mammalian PLP , with most of these changes located within exon 3. There were 16 amin o acid changes between zebra finch and chicken, suggesting that greate r sequence variation in PLP structure is tolerated among avian species than among mammalian species.