CDNA SEQUENCE AND DIFFERENTIAL MESSENGER-RNA REGULATION OF 2 FORMS OFGLIAL-CELL LINE-DERIVED NEUROTROPHIC FACTOR IN SCHWANN-CELLS AND RAT SKELETAL-MUSCLE

Total RNA from rat Schwann cells grown in culture and adult rat skelet al muscle was reverse transcribed, amplified for glial cell line-deriv ed neurotrophic factor (GDNF) messenger RNA (mRNA) using the polymeras e chain reaction (PCR), and the PCR products sequenced. Two forms of G DNF were detected in the PCR step, one of a predicted size (GDNF(633)) and a second smaller form missing a 78-base pair sequence (GDNF(555)) . Sequence analysis demonstrated that GDNF(633) is similar to the publ ished sequence of GDNF differing only at three nucleotides, Southern a nd Northern blot analyses reveal that the two forms are probably deriv ed from a single RNA species that is alternatively spliced. Interestin gly, GDNF(633) mRNA was found to be selectively upregulated in denerva ted rat skeletal muscle at 1-2 weeks following axotomy, providing evid ence that the innervation status of the muscle may determine the expre ssion profile of the two alternately spliced forms. Given these findin gs, we suggest that GDNF may function as a target-derived trophic fact or for neuronal populations innervating skeletal muscle, including sen sory neurons and spinal cord motoneurons. (C) 1995 Academic Press, Inc .