Dopaminergic (DA) signaling governs the control of complex behaviors, and its deregulation has been implicated in a wide range of diseases. Here we demonstrate that inactivation of the Fto gene, encoding a nucleic acid demethylase, impairs dopamine receptor type 2 (D2R) and type 3 (D3R) (collectively, 'D2-like receptor')-dependent control of neuronal activity and behavioral responses. Conventional and DA neuron-specific Fto knockout mice show attenuated activation of G protein-coupled inwardly-rectifying potassium (GIRK) channel conductance by cocaine and quinpirole. Impaired D2-like receptor-mediated autoinhibition results in attenuated quinpirole-mediated reduction of locomotion and an enhanced sensitivity to the locomotor- and reward-stimulatory actions of cocaine. Analysis of global N(6)-methyladenosine (m(6)A) modification of mRNAs using methylated RNA immunoprecipitation coupled with next-generation sequencing in the midbrain and striatum of Fto-deficient mice revealed increased adenosine methylation in a subset of mRNAs important for neuronal signaling, including many in the DA signaling pathway. Several proteins encoded by these mRNAs had altered expression levels. Collectively, FTO regulates the demethylation of specific mRNAs in vivo, and this activity relates to the control of DA transmission.

The use of in vitro preparations of human skin to study percutaneous absorption is widespread. Yet, up to the present time, little has been done to systematically validate this model and demonstrate the extent to which it mimicks in vivo absorption. In this study, the permeability of 12 organic compounds has been evaluated in excised skin and the results compared to those obtained previously by others in living man. With special emphasis being given here to duplicating in vivo conditions, it was possible to demonstrate an excellent qualitative agreement between the two methods. In all cases, the absorption pattern determined in vitro rather precisely paralleled the pattern which was obtained in vivo. Quantitative agreement between the two sets of data was less than perfect, although the in vitro method adequately distinguished compounds of low permeability from those of high permeability and ranked then in approximately the same order found in vivo. This systematic comparison of in vitro with in vivo data was clearly shown how accurately in vitro absorption studies can reflect the living state.

Hypotrichosis simplex is a group of nonsyndromic human alopecias. We mapped an autosomal recessive form of this disorder to chromosome 13q14.11-13q21.33, and identified homozygous truncating mutations in P2RY5, which encodes an orphan G protein-coupled receptor. Furthermore, we identified oleoyl-L-alpha-lysophosphatidic acid (LPA), a bioactive lipid, as a ligand for P2Y5 in reporter gene and radioligand binding experiments. Homology and studies of signaling transduction pathways suggest that P2Y5 is a member of a subgroup of LPA receptors, which also includes LPA4 and LPA5. Our study is the first to implicate a G protein-coupled receptor as essential for and specific to the maintenance of human hair growth. This finding may provide opportunities for new therapeutic approaches to the treatment of hair loss in humans.

Piwi proteins and their associated Piwi-interacting RNAs (piRNAs) are implicated in transposon silencing in the mouse germ line. There is currently little information on additional proteins in the murine Piwi complex and how they might regulate the entry of transcripts that accumulate as piRNAs in the Piwi ribonucleoprotein (piRNP). We isolated Mili-containing complexes from adult mouse testes and identified Tudor domain-containing protein-1 (Tdrd1) as a factor specifically associated with the Mili piRNP throughout spermatogenesis. Complex formation is promoted by the recognition of symmetrically dimethylated arginines at the N terminus of Mili by the tudor domains of Tdrd1. Similar to a Mili mutant, mice lacking Tdrd1 show derepression of L1 transposons accompanied by a loss of DNA methylation at their regulatory elements and delocalization of Miwi2 from the nucleus to the cytoplasm. Finally, we show that Mili piRNPs devoid of Tdrd1 accept the entry of abundant cellular transcripts into the piRNA pathway and accumulate piRNAs with a profile that is drastically different from that of the wild type. Our data suggest that Tdrd1 ensures the entry of correct transcripts into the normal piRNA pool.

Precise control of mitochondrial DNA gene expression is critical for regulation of oxidative phosphorylation capacity in mammals. The MTERF protein family plays a key role in this process, and its members have been implicated in regulation of transcription initiation and site-specific transcription termination. We now demonstrate that a member of this family, MTERF4, directly controls mitochondrial ribosomal biogenesis and translation. MTERF4 forms a stoichiometric complex with the ribosomal RNA methyltransferase NSUN4 and is necessary for recruitment of this factor to the large ribosomal subunit. Loss of MTERF4 leads to defective ribosomal assembly and a drastic reduction in translation. Our results thus show that MTERF4 is an important regulator of translation in mammalian mitochondria.

In mammalian cells, actin dynamics is tightly controlled through small GTPases of the Rho family, WASP/Scar proteins and the Arp2/3 complex. We employed Cre/loxP-mediated gene targeting to disrupt the ubiquitously expressed N-WASP in the mouse germline, which led to embryonic lethality. To elucidate the role of N-WASP at the cellular level, we immortalized embryonic fibroblasts and selected various N-WASPdefective cell lines. These fibroblasts showed no apparent morphological alterations and were highly responsive to the induction of filopodia, but failed to support the motility of Shigella flexneri. In addition, enteropathogenic Escherichia coli were incapable of inducing the formation of actin pedestals in N-WASP-defective cells. Our results prove the essential role of this protein for actin cytoskeletal changes induced by these bacterial pathogens in vivo and in addition show for the first time that N-WASP is dispensible for filopodia formation.

Gephyrin is a bi-functional modular protein involved in molybdenum cofactor biosynthesis and in postsynaptic clustering of inhibitory glycine receptors (GlyRs). Here, we show that full-length gephyrin is a trimer and that its proteolysis in vitro causes the spontaneous dimerization of its C-terminal region (gephyrin-E), which binds a GlyR b-subunit-derived peptide with high and low affinity. The crystal structure of the tetra-domain gephyrin-E in complex with the b-peptide bound to domain IV indicates how membrane-embedded GlyRs may interact with subsynaptic gephyrin. In vitro, trimeric full-length gephyrin forms a network upon lowering the pH, and this process can be reversed to produce stable full-length dimeric gephyrin. Our data suggest a mechanism by which induced conformational transitions of trimeric gephyrin may generate a reversible postsynaptic scaffold for GlyR recruitment, which allows for dynamic receptor movement in and out of postsynaptic GlyR clusters, and thus for synaptic plasticity.

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