First expressed in developing facial cartilage in early tailbud embryos, with expression localized to the basihyobranchial, palatoquadrate and possibly Meckel's cartilages. Shortly after, a second area of expression is seen in the musculature of the anterior gut. During late embryogenesis, gut expression extends into hindgut tissues. In adults, expressed at a high level in the kidney, pancreas, spleen and stomach and at a slightly lower level in the intestine, skeletal muscle and tongue. Adult heart, liver and lung show little or no expression. First expressed during late neurula stage (stage 18). Levels increase slowly up to the tailbud stage (stage 28), then increase sharply before remaining approximately constant through the remaining tailbud and tadpole stages (stages 30-44). By foxf1-B. Belongs to the NK-3 homeobox family.