OPL - A ZINC-FINGER PROTEIN THAT REGULATES NEURAL DETERMINATION AND PATTERNING IN XENOPUS

In order to study the mechanism of neural patterning in Xenopus, we us ed subtractive cloning to isolate genes activated early during this pr ocess, One gene isolated was opl, (odd-paired-like) that resembles the Drosophila pair-rule gene odd-paired and encodes a zinc finger protei n that is a member of the Zic gene family. At the onset of gastrulatio n, opl is expressed throughout the presumptive neural plate, indicatin g that neural determination has begun at this stage while, by neurula, opl expression is restricted to the dorsal neural tube and neural cre st. opl encodes a transcriptional activator, with a carboxy terminal r egulatory domain, which when removed increases opl activity. opl both sensitizes animal cap ectoderm to the neural inducer noggin and alters the spectrum of genes induced by noggin, allowing activation of the m idbrain marker engrailed. Consistent with the later dorsal neural expr ession of opl, the activated form of opl is able to induce neural cres t and dorsal neural tube markers both in animal caps and whole embryos . In ventral ectoderm, opl induces formation of loose cell aggregates that may indicate neural crest precursor cells. Aggregates do not expr ess an epidermal marker, indicating that opl suppresses ventral fates. Together, these data suggest that opl may mediate neural competence a nd may be involved in activation of midbrain, dorsal neural and neural crest fates.