Microphthalmia-associated transcription factor (MITF) is a transcription factor 
with a basic-helix-loop-helix-leucine zipper (bHLHZip) structure. Mutations of 
the MITF gene cause a variety of phenotypes, most notably in pigmented cells, in 
several species. In humans, haploinsufficiency of MITF causes Waardenburg 
syndrome type 2, while a dominant-negative mutation causes Tietz syndrome. Four 
isoforms have been cloned so far: MITF-M is the most abundant and is expressed 
in neural-crest-derived melanocytes; MITF-A is expressed in various cultured 
cells including retinal pigment epithelium (RPE) and enriched in RPE of 
embryonal and developing eyes; MITF-H are expressed in many types of cultured 
cells and in the heart tissue; MITF-C is expressed in many types of cultured 
cells, but not in melanocytes. Many growth factor signaling pathways have been 
implicated for regulation of MITF at both protein and promoter levels. Most 
notably, Steel factor/c-Kit signaling pathway was linked to phosphorylation of 
MITF at Ser73 and Ser409 through activation of MAP kinase and RSK-1, 
respectively. Phosphorylation of MITF is also conducted at Ser298 through 
GSK3beta, although the signaling pathway for this event still remains to be 
elucidated. IGF-1 and HGF/SF pathways may merge with the c-Kit signaling 
pathway. WNT and MSH signaling pathways regulate MITF positively at the promoter 
level. Endothelins may regulate MITF at the protein and promoter levels. MITF is 
involved in the differentiation, growth and survival of pigment cells, employing 
a number of signaling pathways.