[Functional analysis of autism-associated NRXN1β gene promoter]

Neurexins are neuron-specific synaptic proteins, and abnormal structure of Neurexin1β is closely associated with autism. To characterize the minimal promoter of autism-associated NRXN1β gene and identify functional elements regulating its transcription, luciferase reporter plasmids containing different regulatory regions upstream of NRXN1β gene were constructed. After transfecting HEK293 cells with these plasmids, the minimal promoter region of NRXN1β gene was determined by detecting the transcriptional activity of luciferase reporter genes while the corresponding functional elements that significantly enhance or inhibit the activity of reporter genes were further screened out. To identify cis-acting elements, continuous nucleotide mutation within the functional regions and adjacent DNA sequences were generated using site-directed mutagenesis techniques and then transcriptional regulatory elements in corresponding regions were analyzed using transcription factor binding prediction tool. Our results showed for the first time that the minimal promoter region of human NRXN1β gene is located between positions -88 and +156 (-88/+156); two regions -88/-73 and +156/+149 enhance while the region +229/+419 inhibits promoter activity. The region -84/-63 significantly enhances promoter activity as cis-acting elements, suggesting the presence of DBP and ABF1 transcription factor binding sites in this region.