Isolation of DNTNP, which encodes a potential nuclear protein that is expressed in the developing, dorsal neural tube

We have performed a screen to identify genes expressed in a functionally significant anatomic region of the vertebrate dorsal neural tube, the dorsomedial roof of the third ventricle (DMRTV). The DMRTV includes the primordia of a series of circumventricular organs. The screen searched for genes preferentially expressed in the DMRTV of stage 18-25 chicken embryos, relative to their telencephala and ventral diencephalon. Through this screen, we have cloned a series of genes strongly expressed in the dorsal but not ventral neural tube. We describe here the first of these genes, DNTNP (dorsal neural tube nuclear protein). DNTNP is highly expressed in the dorsal regions of the diencephalon, the midbrain, the hindbrain, and the spinal neural tube in the chicken stage 18 embryo. Expression is also observed in the telencephalon, the branchial arches, the heart, and somites, but is absent from the presomitic mesoderm. The amino acid sequence of DNTNP reveals that it belongs to an uncharacterized protein family with at least two additional members. All the members of this family possess a basic region reminiscent of a nuclear localization signal (NLS). We demonstrate that the putative NLS of DNTNP can indeed direct nuclear localization of green fluorescent protein (GFP). The dorsal localization of DNTNP in the early embryonic central nervous system suggests roles for this molecule in specifying dorsal cell fates within the neural tube.