Holm Pontus C, Rodríguez Francisco J, Kresse Adelheid, Canals Josep M, Silos-Santiago Inmaculada, Arenas Ernest
Department of Medical Biochemistry and Biophysics, Laboratory of Molecular Neurobiology, Karolinska Institutet, Stockholm S-171 77, Sweden.
Development. 2003 Aug;130(15):3535-45. doi: 10.1242/dev.00565.
The role of glial cell-line derived neurotrophic factor (GDNF) and neurotrophins in the development of locus coeruleus noradrenergic neurons was evaluated. We found that two neurotrophic factors previously reported to prevent the degeneration of lesioned adult central noradrenergic neurons, GDNF and neurotrophin 3 (NT3), do not play significant roles in the prenatal development of locus coeruleus noradrenergic neurons, as demonstrated by: (1) the lack of alterations in double Gdnf/Nt3 null mutant mice; and (2) the lack of survival-promoting effects of GDNF and/or NT3 in rat E13.5 primary cultures. In contrast, null mutant mice for TrkB, the tyrosine kinase receptor for brain-derived neurotrophic factor and neurotrophin 4, displayed a clear loss of locus coeruleus noradrenergic neurons. In accordance with this, treatment of rat E13.5 primary cultures with TrkB ligands prevented the early loss of noradrenergic neurons and maintained their survival for up to 6 days in vitro. Moreover, an additional 5-10-fold increase in the number of tyrosine hydroxylase positive noradrenergic neurons was detected after 12 hours in culture. This second effect of TrkB ligands involved neither proliferation nor survival, because the number of BrdU- or TUNEL-positive noradrenergic neurons did not change and the effect was elicited by delayed administration of either factor. Because TrkB ligands increased the number of tyrosine hydroxylase-positive cells expressing Phox2a, a paired homeodomain protein required for the development of locus coeruleus noradrenergic neurons, but did not affect the number of Phox2a-positive tyrosine hydroxylase-negative cells, our results suggest that the second effect of TrkB ligands may involve promoting or inducing a noradrenergic phenotype. In summary, our findings suggest that, unlike NT3 and GDNF, TrkB ligands are required and sufficient to promote the development of central noradrenergic neurons.
评估了胶质细胞源性神经营养因子（GDNF）和神经营养因子在蓝斑去甲肾上腺素能神经元发育中的作用。我们发现，先前报道的两种可预防成年受损中枢去甲肾上腺素能神经元变性的神经营养因子，即GDNF和神经营养因子3（NT3），在蓝斑去甲肾上腺素能神经元的产前发育中并不起重要作用，这表现为：（1）双Gdnf/Nt3基因敲除突变小鼠未出现改变；（2）GDNF和/或NT3对大鼠E13.5原代培养物无促存活作用。相比之下，脑源性神经营养因子和神经营养因子4的酪氨酸激酶受体TrkB的基因敲除突变小鼠，蓝斑去甲肾上腺素能神经元明显缺失。与此一致的是，用TrkB配体处理大鼠E13.5原代培养物可防止去甲肾上腺素能神经元的早期缺失，并使其在体外存活长达6天。此外，培养12小时后，酪氨酸羟化酶阳性的去甲肾上腺素能神经元数量额外增加了5 - 10倍。TrkB配体的这第二种作用既不涉及增殖也不涉及存活，因为BrdU或TUNEL阳性的去甲肾上腺素能神经元数量没有变化，且该作用是由两种因子的延迟给药引发的。由于TrkB配体增加了表达Phox2a的酪氨酸羟化酶阳性细胞的数量，Phox2a是蓝斑去甲肾上腺素能神经元发育所需的一种配对同源结构域蛋白，但不影响Phox2a阳性的酪氨酸羟化酶阴性细胞的数量，我们的结果表明TrkB配体的第二种作用可能涉及促进或诱导去甲肾上腺素能表型。总之，我们的研究结果表明，与NT3和GDNF不同，TrkB配体对于促进中枢去甲肾上腺素能神经元的发育是必需且充分的。
