The invention provides a method for modulating gene expression by contacting a cellular system with a double-stranded ribonucleic acid molecule capable of associating with a regulatory machinery that controls transcription of one or more genes, wherein the association results in altered expression of the one or more genes. The invention is further directed to method for directing the differentiation of neuronal stem cells into neurons by contacting a cellular system with a double-stranded ribonucleic acid molecule capable of associating with a regulatory machinery that controls transcription of one or more genes involved in neuronal differentiation and directing the transcription of the one or more genes. In related embodiments, the invention provides particular compositions of double-stranded ribonucleic acid molecules as well as therapeutic and screening applications of the invention.
