FOXN1 homozygous mutation associated with anencephaly and severe neural tube defect in human athymic Nude/SCID fetus.

The forkhead, Fox, gene family comprises a diverse group of 'winged-helix' transcription factors that play important roles in development, metabolism, cancer and aging. Recently, several forkhead genes have been demonstrated to play critical roles in lymphocyte development and effector functions. Alterations of the FOXN1 gene in both mice and humans result in a severe combined immunodeficiency caused by an intrinsic defect of the thymus associated with congenital alopecia (Nude/severe combined immunodeficiency phenotype). FOXN1 is a member of the class of proteins involved in the development and differentiation of the central nervous system. We identified a human fetus homozygous for a mutation in FOXN1 gene who lacked the thymus and also had abnormal skin, anencephaly and spina bifida. Moreover, we found that FOXN1 gene is expressed in mouse developing choroid plexus. These observations suggest that FOXN1 may be involved in neurulation in humans.