Department Medical Genetics, University of Calgary, Calgary, Alberta, Canada.
Adv Exp Med Biol. 2010;664:549-58. doi: 10.1007/978-1-4419-1399-9_63.
Mutations in CACNA1F, which encodes the Ca(v)1.4 subunit of a voltage-gated L-type calcium channel, cause X-linked incomplete congenital stationary night blindness (CSNB2), a condition of defective retinal neurotransmission which results in night blindness, reduced visual acuity, and diminished ERG b-wave. We have characterized two putative murine CSNB2 models: an engineered null-mutant, with a stop codon (G305X); and a spontaneous mutant with an ETn insertion in intron 2 of Cacna1f (nob2).
Cacna1f ( G305X ): Adults were characterized by visual function (photopic optokinetic response, OKR); gene expression (microarray) and by cell death (TUNEL) and synaptic development (TEM). Cacna1f ( nob2 ): Adults were characterized by properties of Cacna1f mRNA (cloning and sequencing) and expressed protein (immunoblotting, electrophysiology, filamin [cytoskeletal protein] binding), and OKR.
The null mutation in Cacna1f ( G305X ) mice caused loss of cone cell ribbons, failure of OPL synaptogenesis, ERG b-wave and absence of OKR. In Cacna1f ( nob2 ) mice alternative ETn splicing produced ~90% Cacna1f mRNA having a stop codon, but ~10% mRNA encoding a complete polypeptide. Cacna1f ( nob2 ) mice had normal OKR, and alternatively-spliced complete protein had WT channel properties, but alternative ETn splicing abolished N-terminal protein binding to filamin.
Ca(v)1.4 plays a key role in photoreceptor synaptogenesis and synaptic function in mouse retina. Cacna1f ( G305X ) is a true knockout model for human CSNB2, with prominent defects in cone and rod function. Cacna1f ( nob2 ) is an incomplete knockout model for CSNB2, because alternative splicing in an ETn element leads to some full-length Ca(v)1.4 protein, and some cones surviving to drive photopic visual responses.
CACNA1F 基因突变导致电压门控 L 型钙通道的 Ca(v)1.4 亚基，引起 X 连锁不完全先天性静止性夜盲症（CSNB2），这种疾病的视网膜神经传递缺陷导致夜盲症、视力下降和 ERG b 波减少。我们已经描述了两种假定的鼠 CSNB2 模型：一种是工程缺失突变，具有终止密码子（G305X）；另一种是自发突变，在内含子 2 中具有 ETn 插入（nob2）的 Cacna1f。
Cacna1f（G305X）：通过视觉功能（光觉视动反应，OKR）；基因表达（微阵列）和细胞死亡（TUNEL）和突触发育（TEM）来描述成年个体。Cacna1f（nob2）：通过克隆和测序）和表达蛋白（免疫印迹、电生理学、细丝蛋白[细胞骨架蛋白]结合）以及 OKR 来描述成年个体。
Cacna1f（G305X）小鼠中的缺失突变导致锥体细胞带丢失，外核层突触发生失败，ERG b 波缺失和 OKR 缺失。在 Cacna1f（nob2）小鼠中，替代 ETn 剪接产生约 90%的 Cacna1f mRNA 具有终止密码子，但约 10%的 mRNA 编码完整多肽。Cacna1f（nob2）小鼠具有正常的 OKR，并且替代剪接的完整蛋白具有 WT 通道特性，但替代 ETn 剪接消除了 N 端蛋白与细丝蛋白的结合。
Ca(v)1.4 在小鼠视网膜中感光细胞突触发生和突触功能中起着关键作用。Cacna1f（G305X）是人类 CSNB2 的真正敲除模型，在锥体和杆体细胞功能中存在明显缺陷。Cacna1f（nob2）是 CSNB2 的不完全敲除模型，因为 ETn 元件中的替代剪接导致一些全长 Ca(v)1.4 蛋白和一些存活的锥体来驱动光觉视觉反应。
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