Maternal phosphatase inhibitor-2 is required for proper chromosome segregation and mitotic synchrony during Drosophila embryogenesis.
Protein phosphatase-1 (PP1) is a major Ser/Thr phosphatase conserved among all eukaryotes, present as the essential GLC7 gene in yeast. Inhibitor-2 (I-2) is an ancient PP1 regulator, named GLC8 in yeast, but its in vivo function is unknown. Unlike mammals with multiple I-2 genes, in Drosophila there is a single I-2 gene, and here we describe its maternally derived expression and required function during embryogenesis. During oogenesis, germline expression of I-2 results in the accumulation of RNA and abundant protein in unfertilized eggs; in embryos, the endogenous I-2 protein concentrates around condensed chromosomes during mitosis and also surrounds interphase nuclei. An I-2 loss-of-function genotype is associated with a maternal-effect phenotype that results in drastically reduced progeny viability, as measured by reduced embryonic hatch rates and larval lethality. Embryos derived from I-2 mutant mothers show faulty chromosome segregation and loss of mitotic synchrony in cleavage-stage embryos, patchy loss of nuclei in syncytial blastoderms, and cuticular pattern defects in late-stage embryos. Transgenic expression of wild-type I-2 in mutant mothers gives dose-dependent rescue of the maternal effect on embryo hatch rate. We propose that I-2 is required for proper chromosome segregation during Drosophila embryogenesis through the coordinated regulation of PP1 and Aurora B.
Wang
Weiping
W
Center for Cell Signaling and Department of Microbiology, School of Medicine, University of Virginia, Charlottesville, Virginia 22908, USA.
Cronmiller
Claire
C
Brautigan
David L
DL
D000818:Animals; D064127:Aurora Kinases; D020090:Chromosome Segregation / Q000235:genetics / Q000502:physiology*; D004331:Drosophila melanogaster / Q000196:embryology* / Q000201:enzymology* / Q000235:genetics; D004625:Embryo, Nonmammalian; D018507:Gene Expression Regulation, Developmental; D008938:Mitosis; D054645:Protein Phosphatase 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D000097847:Protein Phosphatase Inhibitory Proteins
D064127:Aurora Kinases; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases; D011506:Proteins; C024833:protein phosphatase inhibitor-2; D000097847:Protein Phosphatase Inhibitory Proteins