FOXG1 (Forkhead Box G1) is located on the chromosome 14q12 (1 of the 46 that contain all of our genes and are inherited from our parents). The gene is responsible for regulating how much certain DNA sequences are expressed and how much proteins are made. The FOXG1 protein is highly expressed in the developing brain and is critical for early brain development. FOXG1 regulates a network of developmental genes. Although it mainly acts as a suppressor of certain gene expression, it can also play an activating role in certain aspects. This can be important for certain cell development of specialized and particular functions. Pathogenic FOXG1 mutations usually occur spontaneously, and result in the production of dysfunctional protein products. The majority of mutations lead to genes experiencing loss of function, while other mutations can be smaller and less severe (missense). In some cases, the gene itself can be deleted or duplicated.
Missense mutations generally lead to milder observed symptoms since some proteins are still functional. For example, patients with missense mutations more frequently reach motor milestones (sitting, walking) and have lower incidence of epilepsy compared to those with FOXG1 deletions. Thus, depending on the type of mutation, the FOXG1 phenotype can be variable in terms of severity and clinical features present.
FOXG1