The Lim gene family is a subfamily of homeobox genes. The homeobox genes are essential in organizing the body plan of an organism and all contain the same conserved homeodomain of amino acids.Evidence that Lim-1 is essential to a developing organism is its conservation throughout evolution and presence in a variety of organisms.The Lim-1 gene encodes a transcription factor which binds to the DNA of specific genes and functions to produce the needed gene product for development of the organism. Lim-1 is important during early molecular development and is required in both primitive streak-derived tissue and visceral endoderm of the early embryo for development of a head. Studies done using mutant organisms without the Lim gene results in organisms that develop no head structure at all support the essential role of the Lim-1 gene in formation of the head. This gene has also been shown to play a crucial role in the formation of the female reproductive tract.The gene is expressed in the developing Müllerian duct of females, and when the gene is knocked out no reproductive tract forms. Recent studies have shown that Lim-1 mutations may be one cause of the Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome. MRKH is characterized by defective development, or absence, of the uterus and upper part of the vagina in women with normal ovaries and karyotype.