Methods and agents for suppressing expression of a
mutant allele of a
gene and providing a replacement
nucleic acid are provided. The methods of the invention provide suppression effectors such as, for example, antisense nucleic acids, ribozymes, or RNAi, that bind to the
gene or its
RNA. The invention further provides for the introduction of a replacement
nucleic acid with modified sequences such that the replacement
nucleic acid is protected from suppression by the suppression
effector. The replacement nucleic acid is modified at degenerate wobble positions in the target region of the suppression
effector and thereby is not suppressed by the suppression
effector. In addition, by altering wobble positions, the replacement nucleic acid can still
encode a
wild type gene product. The invention has the
advantage that the same suppression strategy could be used to suppress, in principle, many mutations in a gene. Also disclosed is a transgenic mouse that expresses human
rhodopsin (modified replacement gene) and a transgenic mouse that expresses a suppression effector targeting
rhodopsin. Also disclosed in intraocular administration of siRNA.