Examination of phosducin gene

光导蛋白通过cAMP依赖的蛋白激酶A与转导蛋白β亚基(1)相互作用来抑制光传导信号，但光导蛋白不抑制光传导信号(2)(3)的起始。经Southern blotting分析，该基因可能具有基因家族(4)，定位于Usher综合征II型(5)、(6)的致病基因座附近。我们用聚合酶链式反应产生的大鼠视网膜cDNAs的探针筛选牛的cDNA库。我们克隆了一个基因，该基因被认为是与Miles和他的同事所报道的大鼠的类磷蛋白类似的蛋白(7)。该基因通过选择性剪接产生异构体，有趣的是，其中一种形式在大鼠视网膜中广泛表达。我们构建了获得突变的光滑蛋白基因的转基因小鼠，其第73位氨基酸的异亮氨酸取代了丝氨酸。光刺激后转基因小鼠视网膜电流图b波的恢复率为光适应正常对照小鼠的50%。转基因小鼠在暗适应条件下也有50%的恢复。光镜和电子显微镜检查显示，光感受器细胞在出生后早期出现正常形态，但外节和外核层的长度逐渐缩短。免疫组织化学研究显示，在杏仁连合体或上丘也观察到免疫染色。

Phosducin inhibit phototransduction signal by interacting with transducin betagamma-subunit (1) by cAMP-dependent protein kinase A,but phosducin does not inhibit the initial onset of phototransduction signal (2) (3). The gene was suspected to have gene family from the Southern blotting analysis (4) and was located close to the disease locus of usher syndrome type II (5), (6). We screened the bovine cDNA library using the probe, which was generated the rat retina cDNA by polymerase chain reaction. We cloned a gene, which was considered bovine phosducin like protein as that of rat phosducin like protein reported by Miles and coworkers (7). The gene produced isoforms by alternative splicing and interestingly, one of the form was extensively expressed in the rat retina.We constracted transgenic mice harvaring mutant phosducin gene, which had isoleucin instead of serin at amino acid 73. The transgenic mice showed 50% recovery of the b-wave of electroretinogram after light stimulation as that of normal control mice under light adaptation. The transgenic mice also showed 50% recovery under dark adaptation. We speculated that phosducin may play an important role for the photoreceptor adaptation.Microscopic and electronmicroscopic examination revealed that photoreceptor cells show normal appearance at the early post natal days, but gradually decreased the length of the outer segment and outer nuclear layr.Immunohistochemical study revealed that immunostaining was also observed at habenula commissura amygdala or superiorcolliculus.