Recruitment of Endophilin to Clathrin-Coated Pit Necks Is Required for Efficient Vesicle Uncoating after Fission

SummaryEndophilin is a membrane-binding protein with curvature-generating and -sensing properties that participates in clathrin-dependent endocytosis of synaptic vesicle membranes. Endophilin also binds the GTPase dynamin and the phosphoinositide phosphatase synaptojanin and is thought to coordinate constriction of coated pits with membrane fission (via dynamin) and subsequent uncoating (via synaptojanin). We show that although synaptojanin is recruited by endophilin at bud necks before fission, the knockout of all three mouse endophilins results in the accumulation of clathrin-coated vesicles, but not of clathrin-coated pits, at synapses. The absence of endophilin impairs but does not abolish synaptic transmission and results in perinatal lethality, whereas partial endophilin absence causes severe neurological defects, including epilepsy and neurodegeneration. Our data support a model in which endophilin recruitment to coated pit necks, because of its curvature-sensing properties, primes vesicle buds for subsequent uncoating after membrane fission, without being critically required for the fission reaction itself

The Character of Surface Archaeological Deposits and Its Influence on Survey Accuracy

Survey is one of the primary methods of data collection in archaeology today. Survey data often constitute the sole conserved record of the prehistoric use of an area and are used as the foundation for culture historical, demographic, and economic reconstructions. Given the fundamental nature of survey data in relation to other archaeological pursuits, identification of biases inherent in this type of data are important and have been the subject of a number of stimulating studies. Analyses reported here focus on the accuracy of results produced through intensive survey. Using data from several siteless surveys in the American West, the effects of artifact obtrusiveness, especially size, and artifact density on the survey accuracy are investigated. Implications for interpreting a biased archaeological document are addressed

Site Occupational History and Lithic Assemblage Structure: An Example from Southeast Utah

Recurrent patterns in the regional positioning of settlement systems over extended periods of time are the processes by which archaeological remains accumulate. These processes result in the differential use of portions of a landscape and therefore in different occupational histories among places. The purposes for which an archaeological site was used in the past and the number of separate uses of that site comprise its occupational history. It is this occupational history, rather than single episodes of behavior, which determines the content and structure of archaeological assemblages. However, neither assemblage composition nor the stratigraphic record of depositional events are direct evidence for the use histories of places.The spatial properties of surface artifact scatters from southeastern Utah are employed to identify the use histories of archaeological distributions. Ethnoarchaeologically documented patterns of space use provide clues to the use histories of places on several levels of site structure -- the spatial attributes of artifact and feature distributions. These levels include activity areas and their composites, and debris distributions formed by entire occupations. Based on patterned variation in the sizes of ethnographically documented occupations, patterns of space use obtained with archaeological scatters are interpreted as representing single and multiple activity episodes. Assemblage structure -- the associations and correlations of assemblage contents -- of functionally different occupations and of archaeological distributions, which result from the repetitive use of locations and facilities, is modeled with size/diversity relationships. Functionally different tool roles for lithic implements are also offered. Models of tool roles are applied to assemblages inferred to result from single and multiple activity episodes and are contrasted within apparent tool associations.The variable content and spatial structure of surface artifact scatters is attributed to different site use histories. Special-purpose, residential and multiple occupations are interpreted from analyses of tool roles. Assemblage size/diversity relationships and variation in flake morphology are used as independent avenues of inquiry with which to evaluate these interpretations. Identifying assemblages which result from single special-purpose strategies and those which are generated in the context of reuse of places, and are thus mixtures of debris from many separate functions, is seen as a prerequisite for understanding the spatial and temporal patterns characteristic of assemblages within a region. Dissertation, Department of Anthropology, University of New Mexico