NK2 genes ( gene cluster in humans) encode for homeodomain-containing transcription factors that are conserved along the phylogeny. According to the most detailed classifications, vertebrate genes are classified into two distinct families, and . The former is constituted by and genes which are homologous to the gene; the latter includes and genes, which are homologous to the gene. Conservation of these genes is not only related to molecular structure and expression, but also to biological functions. In and vertebrates, NK2 genes share roles in the development of ventral regions of the central nervous system. In vertebrates, genes have a relevant role in the development of several other organs such as the thyroid, lung, and pancreas. Loss-of-function mutations in and are the monogenic cause of the brain-lung-thyroid syndrome and neonatal diabetes, respectively. Alterations in and genes may play a role in multifactorial diseases, autism spectrum disorder, and neural tube defects, respectively. , , and are expressed in various cancer types as either oncogenes or tumor suppressor genes. Several data indicate that evaluation of their expression in tumors has diagnostic and/or prognostic value.