Cyclotosaurus cf. PosthumusFraas (Capitosauridae,Stereospondyli) from the Huai Hin Lat Formation (Upper Triassic), Northeastern Thailand: With a note on capitosaurid biogeography

Part of a large capitosaurid skull, similar to that of Cyclotosaurus posthumus from the Upper Triassic of Germany, has been discovered in the upper part of the Huai Hin Lat Formation near Chulabhorn (Nam Phrom) Dam. This discovery is consistent with the presumed Norian age of this formation. Although the phylogeny of the Capitosauridae is still unclear, the group of Upper Triassic Cyclotosaurus species to which C. posthumus belongs is monophyletic and seems to be known only from Laurasia or Northwestern Gondwana (Morocco). The occurrence of C. cf. posthumus in Thailand is consistent with the hypothesis previously put forward, that this part of Southeast Asia was bound to Laurasia in Mesozoic times.     

Les vertébrés dévoniens de l'Iran central I: Dipneustes

The dipnoan dental plates discovered in the Frasnian of the Kerman region (Central Iran) are referred to the genera Rhinodipterus, ? Dipterus and ? Chirodipterus. The new taxon Iranorhynchus seyedemamii n. g., n. sp. is erected for a peculiar lower jaw with an elongate, spatula-shaped symphysial region, and with all the ventral and lateral dermal bones fused into a continuous exoskeleton. Furthermore, this lower jaw possesses a well-developed system of symphysial tubuli which is related to the bottle-shaped cavities of the exoskeleton (pore-canal system). A snout fragment from a large dipnoan is provisionnally referred to a rhynchodipterid.     

The tail of the Ordovician fish Sacabambaspis

The tail of the earliest known articulated fully skeletonized vertebrate, the arandaspid Sacabambaspis from the Ordovician of Bolivia, is redescribed on the basis of further preparation of the only specimen in which it is most extensively preserved. The first, but soon discarded, reconstruction, which assumed the presence of a long horizontal notochordal lobe separating equal sized dorsal and ventral fin webs, appears to have considerable merit. Although the ventral web is significantly smaller than the dorsal one, the presence of a very long notochordal lobe bearing a small terminal web is confirmed. The discrepancy in the size of the ventral and dorsal webs rather suggests that the tail was hypocercal, a condition that would better accord with the caudal morphology of the living agnathans and the other jawless stem gnathostomes.     

Scale-dependent effects of landscape context on urban bee diversity

Journal of Insect Conservation - As urbanization continues throughout much of the world, there is great interest in better understanding the value of urban and residential environments to...     

Nef-induced CD4 downregulation: a diacidic sequence in human immunodeficiency virus type 1 Nef does not function as a protein sorting motif through direct binding to beta-COP

The Nef protein from the human immunodeficiency virus (HIV) induces CD4 cell surface downregulation by interfering with the endocytic machinery. It has been recently proposed that binding of HIV type 1 Nef to the beta subunit of COPI coatomers participated in the Nef-induced CD4 downregulation through recognition of a novel diacidic motif found in the C-terminal disordered loop of Nef (V. Piguet, F. Gu, M. Foti, N. Demaurex, J. Gruenberg, J. L. Carpentier, and D. Trono, Cell 97:63-73, 1999). We have mutated the glutamate residues which formed this motif in order to document this observation. Surprisingly, mutation of the diacidic sequence of Nef did not significantly affect its ability (i) to interact with beta-COP, (ii) to downregulate CD4 cell surface expression, and (iii) to address an integral resident membrane protein containing Nef as the cytoplasmic domain to the endocytic pathway. Our results indicate that these acidic residues are not involved in the connection of Nef with the endocytic machinery through binding to beta-COP. Additional studies are thus required to characterize the residues of Nef involved in the binding to beta-COP and to evaluate the contribution of this interaction to the Nef-induced perturbations of membrane trafficking.     

Jaw transformation with gain of symmetry after Dlx5/Dlx6 inactivation: Mirror of the past?

In modern vertebrates upper and lower jaws are morphologically different. Both develop from the mandibular arch, which is colonized mostly by Hox-free neural crest cells. Here we show that simultaneous inactivation of the murine homeobox genes Dlx5 and Dlx6 results in the transformation of the lower jaw into an upper jaw and in symmetry of the snout. This is the first homeotic-like transformation found in this Hox-free region after gene inactivation. A suggestive parallel comes from the paleontological record, which shows that in primitive vertebrates both jaws are essentially mirror images of each other. Our finding supports the notion that Dlx genes are homeotic genes associated with morphological novelty in the vertebrate lineage.     

Two independent regions of HIV-1 Nef are required for connection with the endocytic pathway through binding to the mu 1 chain of AP1 complex

The Nef protein from the human immunodeficiency virus (HIV) induces down-regulation of the CD4 and major histocompatibility complex class I molecules from the cell surface by interfering with the endocytic machinery. This work focuses on the interaction of HIV-1 Nef with the mu 1 chain of adaptor protein type 1 (AP1) complex and its contribution to the Nef-induced alterations of membrane trafficking. Two independent regions surrounding a disordered loop located in the C-terminal part of Nef are involved in mu 1 binding. Each region can separately interact with mu 1, and simultaneous point mutations within both regions are needed to abolish binding. We used CD8 chimeras in which the cytoplasmic tail was replaced by Nef mutants to show that these mu 1-binding sites contain determinants required to induce CD4 down-regulation and to target the chimera to the endocytic pathway by promoting AP1 complex recruitment. Ultrastructural analysis revealed that the CD8-Nef chimera provokes morphological alterations of the endosomal compartments and co-localizes with AP1 complexes. These data indicate that the recruitment by Nef of AP1 via binding to mu 1 participates in the connection of Nef with the endocytic pathway.     

HIV-2 and SIV nef proteins target different Src family SH3 domains than does HIV-1 Nef because of a triple amino acid substitution

The nef gene is required for optimal viral spread of human and simian immunodeficiency viruses. However, the molecular mechanisms underlying the action of the Nef proteins may not be identical for all viral families. Here we investigate the interaction between the Nef protein of human and simian immunodeficiency viruses and SH3 domains from Src family kinases. Using the yeast two-hybrid system and immunoblotting we show that, in contrast to HIV-1 Nef, SIV and HIV-2 Nef poorly interact with Hck SH3 but bind to Src and Fyn SH3 domains. The molecular basis of these differences in SH3 targeting was revealed by sequence analysis and homology modeling of the putative SH3-Nef structures. Three amino acids (Trp-113, Thr-117, and Gln-118) that localize in a "hydrophobic pocket" implicated in SH3 binding of HIV-1 Nef, are systematically substituted in SIV/HIV-2 alleles (by Tyr, Glu, and Glu, respectively). We demonstrate that site-directed mutagenesis of these residues in SIV(mac239) Nef suffices to restore Hck SH3 binding and co-immunoprecipitation with full-length Hck from transfected cells. Our findings identify fundamental mechanistic differences in targeting of Src family kinases by HIV and SIV Nef. The herein described mechanism of SH3 selection by Nef via a "pocket" proximal to the canonical proline-rich motif may be a common feature for SH3 recognition by their natural ligands.