Jonakait G M, Luskin M B, Ni L
Department of Biological Sciences, Rutgers University/Newark, New Jersey 07102, USA.
J Neurobiol. 1998 Nov 15;37(3):405-12. doi: 10.1002/(sici)1097-4695(19981115)37:3<405::aid-neu6>3.0.co;2-6.
Transforming growth factor-alpha (TGF-alpha), a member of the epidermal growth factor (EGF) family, binds to the EGF-receptor (EGF-R). The early expression and widespread distribution of TGF-alpha and EGF-R in the developing central nervous system (CNS) suggest that TGF-alpha may play a role in the developing CNS. To study possible effects of TGF-alpha on cholinergic differentiation in the basal forebrain, we cultured septal nuclei with adjacent basal forebrain from embryonic rat brain in the presence and absence of TGF-alpha. At the highest dose of TGF-alpha used (100 ng/mL), activity of choline acetyltransferase (ChAT; EC 2.3.1.6) and the number of cholinergic neurons doubled. However, because protein levels tripled, specific ChAT activity actually declined. To determine the mechanism accounting for the increase in ChAT, we labeled dividing precursors present in the cultures with a replication-deficient retrovirus expressing beta-galactosidase in the presence and absence of TGF-alpha. By staining the cultures for both LacZ and ChAT, we determined that the precursor population expanded in size (individually labeled clones contained more cells), but the percentage of cholinergic neurons present in the clones was unchanged. Therefore, while TGF-alpha expands the precursor pool, it does not promote cholinergic differentiation. Interleukin-9, included to prompt neuronal differentiation, did not by itself increase ChAT activity, nor did it enhance the action of TGF-alpha. This was true even when basic fibroblast growth factor was included.
转化生长因子-α（TGF-α）是表皮生长因子（EGF）家族的一员，可与EGF受体（EGF-R）结合。TGF-α和EGF-R在发育中的中枢神经系统（CNS）中早期表达且分布广泛，这表明TGF-α可能在CNS发育中发挥作用。为了研究TGF-α对基底前脑胆碱能分化的可能影响，我们在有和没有TGF-α的情况下，培养了来自胚胎大鼠脑的隔核与相邻基底前脑。在所使用的最高剂量的TGF-α（100 ng/mL）下，胆碱乙酰转移酶（ChAT；EC 2.3.1.6）的活性和胆碱能神经元的数量增加了一倍。然而，由于蛋白质水平增加了两倍，ChAT的比活性实际上下降了。为了确定ChAT增加的机制，我们在有和没有TGF-α的情况下，用一种表达β-半乳糖苷酶的复制缺陷型逆转录病毒标记培养物中存在的分裂前体。通过对培养物进行LacZ和ChAT染色，我们确定前体群体的大小增加了（单个标记的克隆包含更多细胞），但克隆中胆碱能神经元的百分比没有变化。因此，虽然TGF-α扩大了前体池，但它并不促进胆碱能分化。为促进神经元分化而加入的白细胞介素-9本身并没有增加ChAT活性，也没有增强TGF-α的作用。即使加入碱性成纤维细胞生长因子，情况也是如此。
