Expression of PAX2 gene during human development.

The expression of human paired-box-containing PAX2 gene was examined in 7 human conceptuses 6 to 9 weeks old by in situ hybridization. The embryos were collected after legal abortions, embedded in paraffin, serially cut in transversal direction and treated with S35 labeled probe for PAX2. In the neural tube of 6-week embryos, PAX2 was expressed in the outer part of the ventricular zone on both sides of the sulcus limitans. At later stages, it was expressed in the intermediate zone of the spinal cord, both in alar and basal plates except in the region of motor neuroblasts. In the brain, expression of PAX2 extended from mesencephalic-rhombencephalic border along the entire rhombencephalon in a manner similar to that described for the spinal cord. Expression of PAX2 gene in the eye was seen in the optic cup and stalk, and later in the optic disc and nerve. In the ear, expression was restricted to the part of the otic vesicle flanking the neural tube and later to the utricle and cochlea. Expression of PAX2 was observed in developing kidneys as well. During human development PAX2 has a spatially restricted expression along the compartmental boundaries of the neural tube, and within developing eye, ear and kidneys. Differentiation of those organs seems to be mediated by PAX2 gene at the defined stages of human development.