Biology subjects

Wittwer, C.

Publications and source records attributed to Wittwer, C..

3 recordsLinked to original sources

bioRxiv2022

Inositol pyrophosphate profiling reveals regulatory roles of IP6K2-dependent enhanced IP7 metabolism in enteric nervous system

Inositol pyrophosphates (PP-IPs) regulate diverse physiological processes; to better understand their functional roles, assessing their tissue-specific distribution is important. Here, we profiled PP-IP levels in mammalian organs using a novel HILIC-MS/MS protocol and discovered that the gastrointestinal tract (GIT) contained the highest levels of IP7 and its precursor IP6. Although their absolute levels in the GIT is diet-dependent, elevated IP7 metabolism still exists under dietary regimes devoid of exogenous IP7. Of the major GIT cells, enteric neurons selectively express the IP7-synthesizing enzyme IP6K2. IP6K2-knockout mice exhibited significantly impaired IP7 metabolism in the various organs including the proximal GIT. Additionally, HILIC-MS/MS analysis displayed that genetic ablation of IP6K2 significantly impaired IP7 metabolism in the gut and duodenal muscularis externa containing myenteric plexus. Whole transcriptome analysis of duodenal muscularis externa further suggested that IP6K2 inhibition induced the gene sets associated with mature neurons such as inhibitory, GABAergic and dopaminergic neurons, concomitantly with suppression of those for neural progenitor/stem cells and glial cells. In addition, IP6K2 inhibition explicitly affected transcript levels of certain genes modulating neuronal differentiation and functioning, implying critical roles of IP6K2-IP7 axis in developmental and functional regulation of enteric nervous system. These results collectively reveal an unexpected role of mammalian IP7--a highly active IP6K2-IP7 pathway is conducive to enteric nervous system.

molecular biology↗

bioRxiv2020

Analysis of Inositol Phosphate Metabolism by Capillary Electrophoresis Electrospray Ionization Mass Spectrometry (CE-ESI-MS)

The analysis of myo-inositol phosphates (InsPs) and myo-inositol pyrophosphates (PP-InsPs) is a daunting challenge due to the large number of possible isomers, the absence of a chromophore, the high charge density, the low abundance, and the instability of the esters and anhydrides. Given their importance in biology, an analytical approach to follow and understand this complex signaling hub is highly desirable. Here, capillary electrophoresis (CE) coupled to electrospray ionization mass spectrometry (ESI-MS) is implemented to analyze complex mixtures of InsPs and PP-InsPs with high sensitivity. Stable isotope labeled (SIL) internal standards allow for matrix-independent quantitative assignment. The method is validated in wild-type and knockout mammalian cell lines and in model organisms. SIL-CE-ESI-MS enables for the first time the accurate monitoring of InsPs and PP-InsPs arising from compartmentalized cellular synthesis pathways, by feeding cells with either [13C6]-myo-inositol or [13C6]-D-glucose. In doing so, we uncover that there must be unknown inositol synthesis pathways in mammals, highlighting the unique potential of this method to dissect inositol phosphate metabolism and signalling.

biochemistry↗

bioRxiv2017

Twenty-five species of frogs in a liter of water: eDNA survey for exploring tropical frog diversity

Rapid environmental change in highly biodiverse tropical regions demands efficient biomonitoring programs. While existing metrics of species diversity and community composition rely on encounter-based survey data, eDNA recently emerged as alternative approach. Costs and ecological value of eDNA-based methods have rarely been evaluated in tropical regions, where high species richness is accompanied by high functional diversity (e.g. the use of different microhabitats by different species and life-stages). We first tested whether estimation of tropical frogs community structure derived from eDNA data is compatible with expert field assessments. Next we evaluated whether eDNA is a financially viable solution for biodiversity monitoring in tropical regions. We applied eDNA metabarcoding to investigate frog species occurrence in five ponds in the Chiquitano dry forest region in Bolivia and compared our data with a simultaneous visual and audio encounter survey (VAES). We found that taxon lists and community structure generated with eDNA and VAES correspond closely, and most deviations are attributable to different species life histories. Cost efficiency of eDNA surveys was mostly influenced by the richness of local fauna and the number of surveyed sites: VAES may be less costly in low-diversity regions, but eDNA quickly becomes more cost-efficient in high-diversity regions with many sites sampled. The results highlight that eDNA is suitable for large-scale biodiversity surveys in high-diversity areas if life history is considered, and certain precautions in sampling, genetic analyses and data interpretation are taken. We anticipate that spatially extensive, standardized eDNA biodiversity surveys will quickly emerge in the future.

ecology↗