Embryonic differentiation is mediated in part by determinants asymmetrically distributed in the cytoplasm of the egg. The vegetal region of frog eggs appears to contain at least four sets of determinants, those specifying: mesoderm, endoderm, the dorsal axial structures and the germ cell lineage. Localized maternal mRNAs are a rare class of RNAs that can code for determinants. The mechanism through which the spatial distribution of RNAs is established and maintained is unknown and represents a central problem in both cell and developmental biology. Modern and classical studies have suggested that the cytoskeleton plays an important role. Recently, we have isolated two novel Xenopus cytoskeletal associated transcripts in oocytes that are localized to the vegetal pole (XCAT-2 and XCAT-3). Remarkably, XCAT-2 is homologous to manos, the posterior determinant in Drosophila. In this proposal experiments are outlined to: (1) study the spatial and temporal expression of XCAT-2 and XCAT-3 during normal development. (2) characterize the XCAT-2 and XCAT-3 protein products and examine their function in early development. (3) determine the RNA localization signal and protein binding components involved in XCAT-2 and XCAT-3 localization. The general strategy will be to establish how the XCATs are inherited during embryogenesis by RNA blot and in situ hybridization studies. Mis- expression and non-expression of XCAT-2 and XCAT-3 proteins in the oocyte, embryo, and animal caps will be used to characterize their possible functions in development. Microinjection studies of XCAT-2 and XCAT-3 mutant constructs will allow us to identify the RNA sequences required for localization and to assess the function of associated proteins. By studying localized maternal RNAs and their relationship to the cytoskeleton, we hope to understand how molecular polarity is established in the oocyte and how it directs regional specification of the early embryo.

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National Institute of General Medical Sciences (NIGMS)
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Cellular Biology and Physiology Subcommittee 1 (CBY)
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University of Miami School of Medicine
Anatomy/Cell Biology
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Mei, Wenyan; Jin, Zhigang; Lai, Fangfang et al. (2013) Maternal Dead-End1 is required for vegetal cortical microtubule assembly during Xenopus axis specification. Development 140:2334-44
Lai, Fangfang; Singh, Amar; King, Mary Lou (2012) Xenopus Nanos1 is required to prevent endoderm gene expression and apoptosis in primordial germ cells. Development 139:1476-86
Luo, Xueting; Nerlick, Steve; An, Weijun et al. (2011) Xenopus germline nanos1 is translationally repressed by a novel structure-based mechanism. Development 138:589-98
Lai, Fangfang; Zhou, Yi; Luo, Xueting et al. (2011) Nanos1 functions as a translational repressor in the Xenopus germline. Mech Dev 128:153-63
Venkatarama, Thiagarajan; Lai, Fangfang; Luo, Xueting et al. (2010) Repression of zygotic gene expression in the Xenopus germline. Development 137:651-60
Rodrigues, Claudia O; Nerlick, Steve T; White, Elsie L et al. (2008) A Myc-Slug (Snail2)/Twist regulatory circuit directs vascular development. Development 135:1903-11
Song, Hye-Won; Cauffman, Karen; Chan, Agnes P et al. (2007) Hermes RNA-binding protein targets RNAs-encoding proteins involved in meiotic maturation, early cleavage, and germline development. Differentiation 75:519-28
Lewis, Raymond A; Mowry, Kimberly L (2007) Ribonucleoprotein remodeling during RNA localization. Differentiation 75:507-18
King, Mary Lou; Messitt, Timothy J; Mowry, Kimberly L (2005) Putting RNAs in the right place at the right time: RNA localization in the frog oocyte. Biol Cell 97:19-33
Machado, Rachel J; Moore, Wendy; Hames, Richard et al. (2005) Xenopus Xpat protein is a major component of germ plasm and may function in its organisation and positioning. Dev Biol 287:289-300

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