NRL, a bZIP transcription factor of the Maf subfamily, interacts with the h
omeodomain protein CRX and synergistically regulates rhodopsin expression.
Here we report that six isoforms of NRL (29-35 kDa) are generated by phosph
orylation and expressed specifically in the mammalian retina. The anti-NRL
antibody also crossreacts with a cytosolic 45-kDa protein, which is detecte
d in neuronal tissues but is not encoded by the NRL gene. In both human ret
inal cell cultures and sections of fetal and adult human retina, NRL is pre
sent in the nuclei of developing and mature rods but not cones. We propose
that NRL regulates rod photoreceptor-specific gene expression and is involv
ed in rod differentiation.