This polarity is specified by intrinsic and extracellular signals that allow neurons to determine axon and dendrite fate during development.
In acrosome-deficient round spermatids of hrb−/− and gopc−/− mice, H1T2 localization is not altered, indicating that proper acrosome development is not required for specifying nuclear polarity.
The ability of higher vertebrate embryos to retain a regulative model of development until such a late stage strongly suggests that localisation of maternally inherited determinants is not an essential component of the mechanisms specifying embryo polarity (Stern and Downs, 2012).
Operationally, the tree reconstruction algorithm finds the shortest unrooted tree(s) without specifying character polarity and then roots the tree(s) by invoking a hypothetical ancestor defined by ancestral character states and selecting the rooted topology that minimizes overall tree length (see Methods).
Here we take advantage of these observations to design a molecular screen for new genes involved in the earliest stages of specifying embryo polarity; together with bioinformatic analysis and embryological experiments we identify the transcription factor Pitx2 as a direct and essential regulator of cVg1 expression both during normal development and in embryonic regulation (induced twinning).
Asymmetric cell divisions combine cell division with fate specification and one general model of how this is achieved was proposed already decades ago: During interphase, the cell polarity axis is specified, followed by orientation of the spindle along the polarity axis and segregation of fate determinants along the polarity axis during mitosis.
Whist well-formulated inclusion and exclusion criteria strengthen the aims and overall findings, they also limit the ability to confer associations between studies on cognitive functioning in juvenile bipolar disorder, first-episode affective disorders and in first-episode bipolar disorders when episode polarity was not specified.
In Par-mediated polarity, upstream components specify the location and activity of aPKC.
Among many other roles in Drosophila, wg functions as a segment polarity gene to specify and maintain boundaries and cell fates across the primary segmental units or parasegments [ 3, 9, 26- 29].
The Toll (also known as Toll-1) gene was originally isolated for its role in specifying dorso-ventral polarity of the Drosophila embryo [14].
