LMX1A belongs to the LIM-homeodomain family. Members of this family are known to be important for pattern formation during development. LMX1A functions in the nucleus as a transcriptional activator to the insulin gene promoter. In the developing embryo, LMX1A is expressed along the neuraxis and leads to the development of the roof plate of the vertebrae. Two isoforms of LMX1A exist due to alternative splicing. Isoform 1 represents the full length protein and is expressed in many tissues including fetal brain, but is absent in heart, liver, spleen and testis. The second isoform, designated LMX1A-4AB, lacks amino acids 1-249 and is expressed in testis.