Required for early specification of the kidney glomus, lying upstream of wt1 in the pathway controlling glomus differentiation. The balance in levels and expression patterns of binding partners such as lhx1/lim-1 influences differentiation into glomus or tubule derivatives. Involved in specification of serotonergic neurons. Shows a temporal expression pattern in three main areas: neural, kidney and limbs. From stage 13 onwards, expressed in regions of the nervous system including the placodes and otic vesicles, eye, specific sets of neurons, and in discreet regions of the neural tube. From stage 13, also expressed in the presumptive pronephros, and from stage 27 expression is predominant in the capsule of the pronephric glomus. Also expressed in the developing forelimbs and hindlimbs. In metamorphosing tadpoles, expressed in the eye, brain, muscle and mesonephric kidney. Expressed zygotically from stage 10.5. Expression is elevated between stages 12.5 and 14, and continues throughout neurulae, tailbud and swimming tadpole stages. By activin; retinoic acid (RA) inhibits this up-regulation. Expression in neurons is regulated by calcium (Ca2+) activity: the lower the activity, the larger the number of neurons showing expression.