Overexpression of HuD accelerates neurite outgrowth and increases GAP-43 mRNA expression in cortical neurons and retinoic acid-induced embryonic stemcells in vitro
Kd. Anderson et al., Overexpression of HuD accelerates neurite outgrowth and increases GAP-43 mRNA expression in cortical neurons and retinoic acid-induced embryonic stemcells in vitro, EXP NEUROL, 168(2), 2001, pp. 250-258
The neuron-specific RNA-binding protein HuD binds to a U-rich regulatory el
ement of the 3 ' untranslated region (3 ' UTR) of the GrAP-43 mRNA and stab
ilizes the mRNA, We have previously shown that overexpression of HuD in PC1
2 cells increases GAP-43 protein expression and induces the spontaneous for
mation of multiple neurites (K, D, Anderson et al, 2000, J, Neurochem, 75:
1103-1114). In this study, we examined the effects of HuD overexpression on
the initial stages of neurite outgrowth and on GAP-43 gene expression usin
g two in vitro systems: E19 rat cortical neurons and retinoic acid (RA)-ind
uced embryonic stem (ES) cells. Normal neurite outgrowth of cortical neuron
s in vitro occurs over a 3-day period with a concomitant increase in GAP-43
and HuD expression. Cortical cells were infected with a replication-defici
ent HSV-1 vector containing the HuD cDNA in the sense orientation (HSV-HuD)
. Overexpression of HuD accelerated the formation of neurites, Immunocytoch
emical analysis showed that excess HuD resulted in a threefold increase in
the number of GAP-43-positive cells undergoing morphological differentiatio
n after 24 h of treatment. Using in situ hybridization, we found that the i
ncreased HuD expression resulted in a twofold increase in the levels of GAP
-43 mRNA Similarly, overexpression of HuD in RA-induced embryonic stem cell
s was found to increase the number of GAP-43-positive cells undergoing proc
ess outgrowth. In conclusion, our results demonstrate that HuD functions in
the initiation of neurite outgrowth in a manner due, at least in part, to
its regulation of GAP-43 expression. (C) 2001 Academic Press.