SIM1 and SIM2 genes are Drosophila single-minded (sim) gene homologs. The Drosophila sim gene encodes a transcription factor that is a master regulator of fruit fly neurogenesis. SIM2 maps within the so-called Down syndrome chromosomal region. Based on the mapping position, its potential function as transcriptional repressor and similarity to Drosophila sim, it is proposed that SIM2 may contribute to some specific Down syndrome phenotypes [provided by RefSeq, Jul 2008].