Acts as a transcriptional activator by binding to an A/T-rich sequence, the FLAT element, in the insulin gene promoter. Required for development of the roof plate and, in turn, for specification of dorsal cell fates in the CNS and developing vertebrae (By similarity). Isoform 1 is expressed in many tissues. Not found in heart, liver, spleen and testis. Relatively highly expressed in fetal brain. Isoform LMX1A-4AB is expressed in testis. The disease is caused by variants affecting the gene represented in this entry.