Expression of Glia Maturation Factor β mRNA and Protein in Rat Organs and Cells

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Abstract
Rat glia maturation factor β (GMF-β) cDNA was obtained by reverse transcription of rat brain mRNA followed by polymerase chain reaction amplification, using primers from the human sequence. The deduced amino acid sequence of rat GMF-β differed from the human counterpart in only three places: His27 in place of Asn, Val51 in place of Ile, and Leu93 in place of Val. The high degree of evolutionary conservation suggests that GMF-β plays an essential role in animal cell physiology. The expression of GMF-β mRNA in the rat was studied by the northern blot technique, using a rat cRNA probe corresponding to the entire coding region. GMF-β mRNA was predominantly expressed in the brain and spinal cord, although trace levels were found in other organs, including testis and ovary. In the brain GMF-β mRNA was detectable at as early as embryonic day 10, and persisted through as late as postnatal month 14, with minor variations in between. On the other hand, GMF-β protein exhibited more obvious developmental changes, with its level increasing slowly prenatally and plateauing at 1 week after birth. GMF-β mRNA and protein were also observed in several cultured cells. Some cells of neural origin contained higher levels of GMF-β protein compared with cells derived from other sources. Through demonstration of mRNA and confirmation by immunoblotting, we conclude that GMF-β is synthesized by rat organs and that GMF-β is predominantly a brain protein.