Can gene therapy expand sensory capacity in the adult?

成人神经系统的可塑性有多大？动物的行为可以通过向视网膜中适当的神经元传递编码光敏蛋白的基因来改变吗？如果这个问题的答案是肯定的，这意味着神经系统具有足够的可塑性，可以重塑成人的神经回路，从而导致行为的改变。如果这个问题的答案是肯定的，它将对我们对神经可塑性的理解产生巨大影响，它将为人类疾病的基因治疗打开新的前景，我将允许我们创建一个模型系统，直接探索神经回路建立和重塑的机制。大多数新大陆灵长类动物，包括松鼠猴，在X染色体上只有一个视觉色素基因。然而，在这个基因座上有三个等位基因，每个等位基因编码一种光谱上不同的色素。这三个等位基因对应于L和M色素基因，这两个基因是人类红绿视觉的基础，而猴子只有一条X染色体，因此是一种在人类男性中常见的遗传性红绿视觉缺陷的模型。人类这种形式的色觉丧失是由X染色体上除一个以外的所有视觉色素基因缺失引起的。要拥有正常的三色视觉，男性必须至少有一个L和Ne M色素基因。在X-连锁色素基因座位上杂合子的雌性松鼠猴子具有与人类相似的三色视觉。因此，建立三色色觉所需的神经回路在该物种中存在，当第三个视觉色素基因存在于发育过程中时，该神经回路显然被利用。我们建议，通过视网膜下注射携带人L视蛋白基因的重组腺相关病毒，在成年雄性松鼠猴的视网膜上增加第三种锥体类型。这三种视锥类型将是雄性松鼠猴视网膜的内源性S视锥和M视锥，以及转导了重组腺病毒病毒并表达人L色素的M克隆。我们将监测视网膜下注射前后的色觉行为，以确定动物的色觉是否从二色变为三色。

How plastic is the adult nervous system? Can an animal's behavior be changed by delivering a gene encoding a light sensitive protein to the appropriate neuron in the retina. If the answer to this question is yes, it means that the nervous systems is sufficiently plastic to allow remodeling of the adult neural circuitry to the extent that it would bring about a change in behavior. If the answer to this question is yes, it will have an enormous impact on our understanding of neural plasticity, it will open new vistas for gene therapy for human disease, and i will allow us to create a model system to directly probe the mechanisms by which neural circuits are established and remodeled. Most New World primates, including squirrel monkeys, have a single visual pigment gene on the X-chromosome. However, three alleles occur at this locus and each allele encodes a spectrally distinct pigment. The three alleles correspond to the L and M pigment genes that are the basis for red-green color vision in humans, and the monkeys have a single X- chromosome, and thus are a model for a form of inherited red-green color vision deficiency common among human males. This form of color vision loss in humans is caused by deletion of all but one of the visual pigment genes on the X chromosome. To have normal, trichromatic color vision, male humans must have at least one L and ne M pigment gene. Female squirrel monkeys who are heterozygous at the X-linked pigment gene locus have trichromatic color vision similar to that of humans. Thus, the neural circuitry necessary to establish trichromatic color vision is present in this species, and is clearly utilized when a third visual pigment gene is present during development. We propose to add, by subretinal injection of recombinant adeno-associated virus carrying a human L opsin gene, a third cone type to the adult male squirrel monkey retina. The three cone types will be the endogenous S and M cones of the male squirrel monkey retina, plus M clones transduced with the rAAV virus and expressing a human L pigment. We will monitor color vision behavior both before and after subretinal injection to determine whether the animal's color vision changes from dichromatic to trichromatic.