Lim1 transcription factor

Lim1 is a transcription factor in mice that prompts formation of head structures. It is derived from the anterior visceral endoderm, is in tissues formed by the primitive streak, and is required in both tissues for head formation. If a Lim1 gene mutation occurs, head development will be severely affected. If the Lim1 gene is not present in the embryo, the embryo will develop without a head. Lim1 is down regulated after embryonic day 7.5. Then, the Lim1 gene, with help from the anterior definitive mesoderm, goes to regulate sequential signaling from the anterior visceral endoderm. This signal regulation is necessary for head formation. Lim1 is a member of the LIM homeobox gene and encodes a 406 amino acid protein. Lim1 is expressed during embryogenesis to promote head formation. The Lim1 gene is also expressed in adult life, possibly to maintain a differentiated state in neural tissue of adults. During embryogenesis, Lim1 is expressed from the central nervous system (CNS) and the excretory system (primarily the kidney). In the CNS, it is expressed approximately 10 days after fertilization and patterns the forebrain, midbrain, hindbrain, and spinal cord regions. In the spinal cord Lim1 is expressed in dorsal and lateral parts but is not detected in the ventricular region.