piRNAs and Aubergine cooperate with Wispy poly(A) polymerase to stabilize mRNAs in the germ plasm

Piwi-interacting RNAs (piRNAs) and PIWI proteins play a crucial role in germ cells by repressing transposable elements and regulating gene expression. In Drosophila, maternal piRNAs are loaded into the embryo mostly bound to the PIWI protein Aubergine (Aub). Aub targets maternal mRNAs through incomplete base-pairing with piRNAs and can induce their destabilization in the somatic part of the embryo. Paradoxically, these Aub-dependent unstable mRNAs encode germ cell determinants that are selectively stabilized in the germ plasm. Here we show that piRNAs and Aub actively protect germ cell mRNAs in the germ plasm. Aub directly interacts with the germline-specific poly(A) polymerase Wispy, thus leading to mRNA polyadenylation and stabilization in the germ plasm. These results reveal a role for piRNAs in mRNA stabilization and identify Aub as an interactor of Wispy for mRNA polyadenylation. They further highlight the role of Aub and piRNAs in embryonic patterning through two opposite functions

Animal spirits in cash-in-advance economies

The possibility of indeterminacy and sunspot fluctuations in dynamic rational expectations models has been often questioned on empirical grounds, for such models are widely believed to rely on implausibly high degrees of increasing returns to scale and/or other controversial calibrations of economic fundamentals. In this paper, we study the occurrence of such phenomena in a standard (one-sector) optimal growth model with endogenous labor supply and a partial cash-in-ad vanee constraint on consumption purchases. We show that, under standard preferences and constant returns to scale in production, indeterminacy typically prevails for an arbitrarily small amplitude of the liquidity constraint. We also analyze the cyclical properties of the model submitted to technological and beliefs disturbances and observe that it performs as well as comparable indeterminate models in the literature

Alfred Marshall and Fran\ue7ois Perroux: the neglected liaison

The richness Fran\ue7ois Perroux\u2019s economic theories have allowed the literature to highlight several connections between him and other authors. Among the names mentioned in the literature, one economist is conspicuous by his absence: Alfred Marshall. However, the relations between Marshall and Perroux are manifold and are far from accidental: not only because Perroux was a careful reader of Marshall but also and moreover because they both have an important common ground, which affected their perspectives. The main aim of this paper is to inquire into the aspects that characterise Marshall\u2019s and Perroux\u2019s approaches, stressing their affinities and underlining their common roots