LIS1 Association With Dynactin is Required for Nuclear Motility and Genomic Union in the Fertilized Mammalian Oocyte Christopher Payne, 1,2 Justin C. St. John, 3 Joa ˜ o Ramalho-Santos, 2,4 and Gerald Schatten 2 * 1 Program in Molecular and Cellular Biosciences, Department of Cell and Developmental Biology, Oregon Health and Science University, Portland 2 Pittsburgh Development Center, Magee-Womens Research Institute, Departments of Obstetrics, Gynecology and Reproductive Sciences, and Cell Biology and Physiology, University of Pittsburgh School of Medicine Pittsburgh, Pennsylvania 3 Reproductive Biology and Genetics Group, Department of Medicine, University of Birmingham, Birmingham, United Kingdom 4 Center for Neuroscience and Cell Biology, Department of Zoology, University of Coimbra, Coimbra, Portugal Mutations in the human LIS1 gene cause the devastating brain disorder lissencephaly. LIS1 also regulates microtubule dynamics; it interacts with the molecular motor cytoplasmic dynein and its cofactor dynactin, and is necessary for neuronal migration. Recently, LIS1 has been suggested to mediate pronuclear migration during fertiliza- tion. Here we use rhesus monkey and bovine oocytes, as well as pronucleate-stage bovine zygotes, to determine: Lis1 RNA expression using reverse transcription- polymerase chain reaction; LIS1 protein association with dynactin using immunopre- cipitation, Western blot analysis, and immunocytochemistry; and LIS1 function in mediating genomic union using antibody transfection. We find that Lis1 RNA ex- pression increases during fertilization, that LIS1 and dynactin subunit p150/ Glued co-immunoprecipitate and co-localize to pronuclear surfaces, and that anti-LIS1 antibodies transfected into zygotes dramatically inhibit pronuclear migration and apposition. LIS1 is, therefore, essential to mediate genomic union in a process that involves the dynein-dynactin complex. These results shed light on an additional role for LIS1 and raise implications for human reproduction. Cell Motil. Cytoskeleton 56: 245–251, 2003. © 2003 Wiley-Liss, Inc. Key words: nuclear movement; microtubules, molecular motor; fertilization; LIS1 inhibition INTRODUCTION Human type I lissencephaly is a severe brain disorder caused by the failure of neurons to migrate from the paraventricular zone to the cerebral cortex during development [Dobyns et al., 1993]. This results in disorganized cortical layers and reduced gyri, in- ducing epilepsy and severe mental retardation with death at an early age. Haplo-insufficiency of the Lis1 gene product leads to both isolated lissencephaly se- quence (ILS) and Miller-Dieker Syndrome (MDS), which together comprise a majority of cases seen in the clinic [Lo Nigro et al., 1997]. Whereas total loss of Lis1 is embryonic lethal, heterozygous mutations gen- erated in mice result in neuronal migration defects [Hirotsune et al., 1998]. The LIS1 protein, also a subunit of platelet-activating factor acetylhydrolase Contract grant sponsor: Fundac ¸a ˜o para a Cie ˆncia e Tecnologia (FCT), Portugal; Contract grant number: POCTI/ESP/38049/2001; Contract grant sponsor: NIH. *Correspondence to: Gerald Schatten, Pittsburgh Development Center, Magee-Womens Research Institute, Departments of Obstetrics, Gyne- cology and Reproductive Sciences, and Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213. E-mail: gschatten@magee.edu Received 23 April 2003; accepted 10 September Cell Motility and the Cytoskeleton 56:245–251 (2003) © 2003 Wiley-Liss, Inc.