CEREBRIN-50, A HUMAN CEREBROSPINAL-FLUID PROTEIN WHOSE MESSENGER-RNA IS PRESENT IN MULTIPLE TISSUES BUT PREDOMINANTLY EXPRESSED IN THE LYMPHOBLASTOID-CELLS AND THE BRAIN

A full-length cDNA of 2295 bp coding for a human cerebrospinal fluid p rotein, designated cerebrin-50, has been isolated from a human brain c DNA expression library. Nucleotide sequence analysis of this cDNA reve aled that it codes for a 435 amino acid polypeptide which starts with an ATG initiation codon from the 5'-end and ends with a TGA terminatio n codon with a calculated molecular weight of 51,484 daltons. A 10-ami no acid peptide of NH2-SGDLETRYWG based on the deduced amino acid sequ ence of the cerebrin-50 cDNA was synthesized, conjugated to bovine ser um albumin and was used to raise a monospecific polyclonal antibody in a rabbit. Immunoblot analysis using this antibody indicated the prese nce of a 52 kD protein in the human cerebrospinal fluid, brain cytosol , T lymphoblastoid cell-conditioned medium, and human serum; it is als o noted that the concentration of this 52 kD protein is several order of magnitude higher in the cerebrospinal fluid than in other biologica l fluids. The presence of its mRNA in the brain, T lymphoblastoid cell s, spleen, liver, and testis was confirmed by sequential use of revers e-transcription and polymerase chain reaction (RT-PCR). Preliminary an alysis by quantitative RT-PGR has noted that the expression of the cer ebrin-50 mRNA is higher in the lymphoblastoid cells and brain than the spleen, liver, and testis.