the one that is found in mice (they are 92% identical at amino acid level, this enabling the scientists to study its structure. There are other CAM proteins like Ng-CAM (found in chicken) which has lower similarities to the human one (they are 40% identical at the amino acid level). The comparative of the sequences from human, mouse, chick and Drosophila and its good conservation, indicates that the L1 immunoglobulin domain 2 and fibronectin type III domain 2 probably are functionally important. Function L1 is an important protein for the development of the nervous system affecting both cell adhesion and motility. Cell adhesion L1 has a static function as a cell adhesion molecule which connects different cells. It is involved in the adhesion between neurons and in the growth and association of neurites called neurite fasciculation. Cell motility Motility promoting functions are related to the regulation of the movement of nerve cells during neural development. L1 is present in developing neurons and plays an important role in guiding new neurons into the correct positions and helping axons grow and make connections with other neurons. L1 is also involved in synaptic plasticity, which is the ability of synapses to strengthen or weaken, and it also plays a role in regeneration after trauma. Some studies have proved that L1 has a role in tumor growth, tumor cell invasion, metastasis of melanoma, ovarian and colon cancer due to an overexpression of the protein L1 that improves cell motion of the malignant cells. The domains of this protein promote homophilic interactions, where adhesion molecules on one cell interact with identical molecules on the other cell. And also heterophilic interactions, where an adhesion molecule on one cell works as a receptor that connects with a different molecule on the other cell. These interactions promote cell adhesion and regulation of signal transduction. In addition, L1 participates in myelination processes, which are involved in the proliferation of myelin through the nervous system (specifically the progressive myelination of nerve axon fibers), by mediating the elongation of Schwann cells along the axon. Nervous system L1 is involved in neuron-neuron adhesion, neurite fasciculation, outgrowth of neurites, cerebellar granule cell migration, neurite outgrowth on Schwann cells and interactions among epithelial cells of intestinal crypts. As a consequence, mutations in the L1CAM gene cause the Nervous System to malfunction. The main disorders linked to this mutation are known by the acronym CRASH