LARGE-SCALE chemical mutagenesis screens in zebrafish have led to the
isolation of thousands of lethal mutations in genes that are essential
for embryonic development(1,2). However, the cloning of these mutated
genes is difficult at present as it requires positional cloning metho
ds, In Drosophila, chemical mutagenesis screens were complemented with
P-element insertional mutagenesis which facilitated the cloning of ma
ny genes that had been identified by chemical lesions(3,4). To facilit
ate the cloning of vertebrate genes that are important during embryoge
nesis, we have developed an insertional mutagenesis strategy in zebraf
ish using a retroviral vector, Here, in a pilot screen of 217 proviral
insertions, we obtained three insertional mutants with embryonic leth
al phenotypes, and identified two of the disrupted genes, One of these
, no arches, is essential for normal pharyngeal arch development, and
is homologous to the recently characterized Drosophila zinc-finger gen
e, clipper, which encodes a novel type of ribonuclease(5). As it is ea
sy to generate tens to hundreds of thousands of proviral transgenes in
zebrafish(6), it should now be possible to use this screening method
to mutate and then rapidly clone a large number of genes affecting ver
tebrate developmental and cellular processes.