Can gene therapy expand sensory capacity in the adult?

成人神经系统的可塑性有多大？动物的行为是否可以通过将编码光敏蛋白的基因传递到视网膜中适当的神经元来改变？如果这个问题的答案是肯定的，这意味着神经系统有足够的可塑性，可以重塑成年人的神经回路，从而改变行为。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的影响，它将为人类疾病的基因治疗开辟新的前景，我将允许我们创建一个模型系统来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染色体上有一个单一的视觉色素基因。然而，三个等位基因发生在这个基因座，每个等位基因编码光谱不同的色素。这三个等位基因对应于L和M色素基因，它们是人类红-绿色觉的基础，猴子有一条X染色体，因此是人类男性中常见的一种遗传性红-绿色觉缺陷的模型。人类的这种色觉丧失是由于X染色体上除了一个视觉色素基因之外的所有视觉色素基因缺失引起的。为了拥有正常的三色视觉，男性必须至少有一个L和一个M色素基因。在X连锁色素基因位点上杂合的雌性松鼠猴具有与人类相似的三色色觉。因此，建立三色色觉所必需的神经回路存在于这个物种中，并且当发育过程中存在第三个视觉色素基因时，明显地被利用。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，在成年雄性松鼠猴视网膜上增加第三种视锥细胞类型。三种视锥类型将是雄性松鼠猴视网膜的内源性S和M视锥，加上用rAAV病毒转导并表达人L色素的M克隆。我们将在视网膜下注射之前和之后监测色觉行为，以确定动物的色觉是否从二色视觉变为三色视觉。

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.