TY  - JOUR
A1  - Andreska, Thomas
A1  - Aufmkolk, Sarah
A1  - Sauer, Markus
A1  - Blum, Robert
T1  - High abundance of BDNF within glutamatergic presynapses of cultured hippocampal neurons
JF  - Frontiers in Cellular Neuroscience
N2  - In the mammalian brain, the neurotrophin brain-derived neurotrophic factor (BDNF) has emerged as a key factor for synaptic refinement, plasticity and learning. Although BDNF-induced signaling cascades are well known, the spatial aspects of the synaptic BDNF localization remained unclear. Recent data provide strong evidence for an exclusive presynaptic location and anterograde secretion of endogenous BDNF at synapses of the hippocampal circuit. In contrast, various studies using BDNF overexpression in cultured hippocampal neurons support the idea that postsynaptic elements and other dendritic structures are the preferential sites of BDNF localization and release. In this study we used rigorously tested anti-BDNF antibodies and achieved a dense labeling of endogenous BDNF close to synapses. Confocal microscopy showed natural BDNF close to many, but not all glutamatergic synapses, while neither GABAergic synapses nor postsynaptic structures carried a typical synaptic BDNF label. To visualize the BDNF distribution within the fine structure of synapses, we implemented super resolution fluorescence imaging by direct stochastic optical reconstruction microscopy (dSTORM). Two-color dSTORM images of neurites were acquired with a spatial resolution of ~20 nm. At this resolution, the synaptic scaffold proteins Bassoon and Homer exhibit hallmarks of mature synapses and form juxtaposed bars, separated by a synaptic cleft. BDNF imaging signals form granule-like clusters with a mean size of ~60 nm and are preferentially found within the fine structure of the glutamatergic presynapse. Individual glutamatergic presynapses carried up to 90% of the synaptic BDNF immunoreactivity, and only a minor fraction of BDNF molecules was found close to the postsynaptic bars. Our data proof that hippocampal neurons are able to enrich and store high amounts of BDNF in small granules within the mature glutamatergic presynapse, at a principle site of synaptic plasticity.
KW  - hippocampal neurons
KW  - synapse structure
KW  - presynapse
KW  - synaptic localization
KW  - BDNF
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-119793
SN  - 1662-5102
VL  - 8
IS  - 107
ER  - 
TY  - JOUR
A1  - Proppert, Sven
A1  - Wolter, Steve
A1  - Holm, Thorge
A1  - Klein, Theresa
A1  - van de Linde, Sebastian
A1  - Sauer, Markus
T1  - Cubic B-spline calibration for 3D super-resolution measurements using astigmatic imaging
JF  - Optics Express
N2  - In recent years three-dimensional (3D) super-resolution fluorescence imaging by single-molecule localization (localization microscopy) has gained considerable interest because of its simple implementation and high optical resolution. Astigmatic and biplane imaging are experimentally simple methods to engineer a 3D-specific point spread function (PSF), but existing evaluation methods have proven problematic in practical application. Here we introduce the use of cubic B-splines to model the relationship of axial position and PSF width in the above mentioned approaches and compare the performance with existing methods. We show that cubic B-splines are the first method that can combine precision, accuracy and simplicity.
KW  - three-dimensional microscopy
KW  - fluorescence microscopy
KW  - medical and biological imaging
KW  - superresolution
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-119730
SN  - 1094-4087
VL  - 22
IS  - 9
ER  -