Approximately 70% of embryos expressing SV40\ST^{Scer\UAS.P\T.T:Zzzz\FLAG} under the control of Scer\GAL4^{nos.UTR.T:Hsim\VP16} fail to hatch, with most embryos failing to progress beyond the early syncytial and blastoderm cleavage cycles of embryogenesis.

Expression of SV40\ST^{Scer\UAS.P\T.T:Zzzz\FLAG} under the control of Scer\GAL4^{nos.UTR.T:Hsim\VP16} causes centrosome overduplication by the first mitotic cycle in embryos, and also causes other spindle assembly defects, including a failure to organise or maintain chromosomes within the spindle. The extra centrosomes are often free and not associated with a mitotic spindle. During cleavage stage divisions, larger astral microtubules containing longer microtubules than normal are seen. Actin frequently fails to assemble into cleavage furrows, but instead organises into clumps near the centrosomes.

The cleavage cycles retain synchrony and progress on a similar timescale as control embryos in embryos expressing SV40\ST^{Scer\UAS.P\T.T:Zzzz\FLAG} under the control of Scer\GAL4^{nos.UTR.T:Hsim\VP16}, but some nuclei fail to complete cleavage, causing daughter chromosomes to collapse back together after anaphase and producing polyploid nuclei associated with four centrosomes that fail to enter the next cleavage cycle.