The present invention relates to novel isolated siRNAs comprising a sense RNA strand and a complementary antisense RNA strand which together form an RNA duplex, characterized in that the sense RNA strand comprises a sequence which has at most one nucleotide that is distinct in relation to a fragment of 14 to 30 contiguous nucleotides of the nucleotide sequence of exon F of the gene encoding the myosin Va protein, and also to compositions comprising at least one such siRNA, and to the use of at least one such siRNA as a cosmetic or therapeutic agent for skin depigmentation.