Imprecise excision of P{EP}RecQ4G7470 results in an insert of approximately 3.5kb remaining at the original site and a deletion of 3200bp from the nucleotide 43bp upstream of the translation initiation codon to nucleotide 3174bp downstream of the translation initiation codon of RecQ4.
RecQ419 homozygotes survive through embryogenesis to the larval stage. Although they have no apparent defect when they hatch, they stop growing and begin to show an apparent growth retardation, and decreased survival 3 days after egg deposition. RecQ419 heterozygotes exhibit normal growth and viability; 90% of the larvae develop into pupae 9 days after egg-laying, and 83% develop into adults 12 days after egg laying. In contrast, about 13 days after egg laying, all the homozygous RecQ419 larvae eventually die. According to the morphology of the mouth hook apparatus, nearly all of the dead larvae are arrested in the first instar.
Mosaic analysis in the wing discs reveals that homozygous RecQ419 mutant cells cannot proliferate.
Salivary glands of RecQ419 mutants are dramatically reduced in size compared with those of their heterozygous siblings. Since endoreplication serves to increase nuclear and cellular size in salivary gland cells, the lower DNA content and smaller nuclear size suggest that endoreplication is arrested in salivary glands in RecQ419 mutants. The same can be said for the fat body. In mutant salivary glands, no more than 4 cells are observed at imaginal ring sites, in contrast to more than 100 cells for heterozygous siblings.
The overall size of the homozygous RecQ419 mutant brain is smaller than in the heterozygous sibling, consistent with the observation that mutant larvae begin to show lagged growth 3 days after egg deposition. BrdU incorporation in the mutant brain is severely reduced compared with the heterozygous control. Quantification of the BrdU labeling signals reveals that DNA synthesis in the RecQ419 mutant is less than 1% of that in the heterozygous sibling.
Metaphase plates are not observed in RecQ419 mutant brain tissue, and 0.34% of nuclei exhibit fragmented, condensed chromosomes (compared to 0.04% in controls).
Although RecQ419 homozygous animals exhibit fragmentation of chromosomes, dramatically reduced mitotic index, and impeded DNA endoreplication and diploid cell DNA replication.
RecQ419 is rescued by RecQ4Tag:V5
RecQ419 is not rescued by RecQ4K898N.Tag:V5
