foxj1a and foxj1b expression in ciliated cell types at different developmental stages. (A and B) foxj1a is uniformly expressed in precursors to the kidney and spinal cord at the 12-somite stage, as well as in Kupffer’s vesicle (arrowhead). (C) At 24, hpf foxj1a is expressed throughout the spinal cord (arrow) and in all cells of the paired pronephric ducts (arrowhead). (D) By 48 hpf, foxj1a is down-regulated in singly ciliated cells of the pronephros but is maintained in a “salt-and-pepper” pattern in tubule cells, consistent with expression in multiciliated cells. (E) At 48 hpf, expression is also observed in the olfactory placode (arrowhead) and brain ventricular system (arrow). (F) Spinal cord is positive for foxj1a at 48 hpf. (G and H) foxj1b is expressed in developing otic placodes (arrowheads) at the 12-somite stage, and (I) in pronephric multiciliated cells (arrowhead) at 48 hpf. Note that foxj1b expression is seen only at the most distal tip of the spinal cord (arrow).