Identification and characterisation of the gene TWIST NEIGHBOR (TWISTNB) located in the microdeletion syndrome 7p21 region.

We have characterised a 2.4-Mb genomic sequence of a smallest region of overlap (SRO) deleted in the human microdeletion syndrome 7p21 by in silico analysis. Patients harbouring this minimal deletion present in addition to the clinical features of Saethre-Chotzen syndrome (MIM 101400) a distinct learning disability. This genomic region shows a very low gene content. Besides the transcription factor gene TWIST, the Histone Deacetylase 9 (HDAC9), Sorting Nexin 13 (SNX13) and an evolutionarily conserved bHLH transcription factor gene Nephew of Atonal 3 (HNATO3) have been detected previously. Here we describe the localisation and characterisation of the TWIST NEIGHBOR (TWISTNB) gene. Comparison of the predicted proteins of human TWISTNB and mouse Twistnb shows a high degree of conservation. Northern blot analysis of human fetal and adult tissues shows ubiquitous expression in all tissues tested.