Rod bipolar cells and horizontal cells form displaced synaptic contacts with rods in the outer nuclear layer of the nob2 retina
Rod bipolar cells and horizontal cells form displaced synaptic contacts with rods in the outer nuclear layer of the nob2 retina
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DOI：
10.1002/cne.21188
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发表时间：
2007-01-10
影响因子：
2.5
通讯作者：
Morgans, Catherine W.
中科院分区：
文献类型：
--
作者：
Bayley, Philippa R.;Morgans, Catherine W.
Nob2小鼠携带CacNA1f基因的零突变，该基因编码L型钙通道的致孔亚单位Ca(V)1.4。这些小鼠视网膜电波b波的丢失表明光感受器和视网膜二级神经元之间的传递严重减少，并支持光感受器带状突触上的钙通道的中心作用，它被定位到该通道上。在这里，我们发现Cav1.4的缺失导致视杆双极细胞树突和水平细胞突起异常地生长到nob2视网膜的外核层(ONL)，并与视杆感光细胞形成异位突触接触。异位接触主要在杆状和杆状双极细胞之间，水平细胞突起也存在于某些部位。异位接触包含截然相反的突触前和突触后的特化，尽管有畸形的突触带。视锥感受器终末不参与ONL的异位接触。在视网膜发育过程中，异位接触出现在睁开眼睛后的几天，在出生后的后期逐渐深入ONL。异位接触发生在杆状双极细胞树突的顶端，较少与水平细胞突起的顶端相关，这与成体的表型一致。在ONL发育过程中，突触前和突触后标记的相对出现提示了异位突触接触的形成机制，这种机制是由视杆感光终末的收缩和视杆双极细胞树突突起的生长所驱动的。
The nob2 mouse carries a null mutation in the Cacna1f gene, which encodes the pore-forming subunit of the L-type calcium channel, Ca(v)1.4. The loss of the electroretinogram b-wave in these mice suggests a severe reduction in transmission between photoreceptors and second-order neurons in the retina and supports a central role for the Ca(v)1.4 calcium channel at photoreceptor ribbon synapses, to which it has been localized. Here we show that the loss of Cav1.4 leads to the aberrant outgrowth of rod bipolar cell dendrites and horizontal cell processes into the outer nuclear layer (ONL) of the nob2 retina and to the formation of ectopic synaptic contacts with rod photoreceptors in the ONL. Ectopic contacts are predominantly between rods and rod bipolar cells, with horizontal cell processes also present at some sites. Ectopic contacts contain apposed pre- and postsynaptic specializations, albeit with malformed synaptic ribbons. Cone photoreceptor terminals do not participate in ectopic contacts in the ONL. During retinal development, ectopic contacts appear in the days after eye opening, appearing progressively farther into the ONL at later postnatal stages. Ectopic contacts develop at the tips of rod bipolar cell dendrites and are less frequently associated with the tips of horizontal cell processes, consistent with the adult phenotype. The relative occurrence of pre- and postsynaptic markers in the ONL during development suggests a mechanism for the formation of ectopic synaptic contacts that is driven by the retraction of rod photoreceptor terminals and neurite outgrowth by rod bipolar cell dendrites.