MYCN

At least 36 mutations involving the MYCN gene have been found to cause Feingold syndrome type 1. This developmental disorder is characterized by abnormalities of the fingers and toes, particularly shortening of the second and fifth fingers (brachymesophalangy). Other common features include a blockage in part of the digestive system (gastrointestinal atresia), an unusually small head size (microcephaly) and learning disabilities. Most of these mutations lead to a premature stop signal in the instructions for making the protein. In some cases of Feingold syndrome type 1, the entire MYCN gene is deleted. These genetic changes prevent one copy of the gene in each cell from producing any functional MYCN protein. As a result, only half the normal amount of this protein is available to control the activity of specific genes during development. It is unclear how a reduced amount of the MYCN protein causes the varied features of Feingold syndrome type 1.

Some gene mutations are acquired during a person's lifetime and are present only in certain cells. These changes, which are not inherited, are called somatic mutations. Somatic mutations sometimes occur when DNA makes a copy of itself (replicates) in preparation for cell division. Errors in the replication process can result in one or more extra copies of a gene within a cell. The presence of extra copies of certain genes, known as gene amplification, can underlie the formation and growth of tumor cells. For example, amplification of the MYCN gene is found in about 25 percent of neuroblastomas. Neuroblastoma is a type of cancerous tumor that arises in developing nerve cells. The number of copies of the MYCN gene varies widely among these tumors but is typically between 50 and 100. Amplification of the MYCN gene is associated with a severe form of neuroblastoma. It is unknown how amplification of this gene contributes to the aggressiveness of neuroblastoma.

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