DEVELOPMENTAL EXPRESSION OF MESSENGER-RNA LEVELS OF THE ALPHA-SUBUNITOF THE GTP-BINDING PROTEIN, G(Z), IN THE MOUSE NERVOUS-SYSTEM

There has been recent evidence that G(z) may play a role in the transm ission of the neurotrophic signal from nerve terminals to the cell bod ies [Johanson, S.O., Crouch, M.F., Hendry, I.A., Signal transduction f rom membrane to nucleus: the special case for neurons, Neurochem. Res. 21 (1996) 779-785]. We examined the developmental expression of the ( y subunit of G(z) (G(z alpha)) in the peripheral and central nervous s ystems of the mouse. Our laboratory has developed a quantitative rever se transcription-polymerase chain reaction (RT-PCR) for G(z alpha) whi ch makes use of a fragment of the PCR product shortened by 107 base pa irs creating a standard which mimics the original RNA. Serial dilution s of the mouse RNA with a constant concentration of mimic RNA were mad e and the point where equal amounts of product are formed allows accur ate measurement of G(z alpha) mRNA in the tissue. We have demonstrated that in the developing mouse superior cervical ganglion (SCG), dorsal root ganglion (DRG) and trigeminal ganglion the expression of G(z alp ha) mRNA is highest perinatally. From 3 weeks of age, in all tissues w ith the exception of the SCG, G(z alpha) mRNA levels fall to lower lev els in the adult animal. The developmental pattern of expression of G( z alpha) in both the cerebellum and the brain differs from the periphe ral nervous system. In the cerebellum G(z alpha) mRNA expression is hi ghest around birth and in the brain it is highest around third postnat al week and then the levels decline as adulthood is approached. These results suggest that the highest level of G(z alpha) mRNA is expressed at the time when target tissue innervation is occurring. This further strengthens the hypothesis that G(z alpha) is important in the transf er of information from target tissues to the innervating nerve cells. (C) 1998 Elsevier Science B.V.