The C-terminal pro-fibrillin-1 propeptide asprosin is described as white adipose tissue derived hormone that stimulates rapid hepatic glucose release and activates hunger-promoting hypothalamic neurons. Numerous studies proposed correlations of asprosin levels with clinical parameters. However, the enormous variability of reported serum and plasma asprosin levels illustrates the need for sensitive and reliable detection methods in clinical samples. Here we report on newly developed biochemical methods for asprosin concentration and detection in several body fluids including serum, plasma, saliva, breast milk, and urine. Since we found that glycosylation impacts human asprosin detection we analyzed its glycosylation profile. Employing a new sandwich ELISA revealed that serum and saliva asprosin correlate strongly, depend on biological sex, and feeding status. To investigate the contribution of connective tissue-derived asprosin to serum levels we screened two cohorts with described cartilage turnover. Serum asprosin correlated with COMP, a marker for cartilage degradation upon running exercise and after total hip replacement surgery. This together with our finding that asprosin is produced by primary human chondrocytes and expressed in human cartilage suggests a contribution of cartilage to serum asprosin. Furthermore, we determined asprosin levels in breast milk, and urine, for the first time, and propose saliva asprosin as an accessible clinical marker for future studies.

In this study, we describe the identification of a novel splice variant of TERF1/PIN2, one of the main components of the telomeric shelterin complex. This new splice variant is identical to TERF1, apart from a 30 amino acid internal insertion near to the C-terminus of TERF1. Based on genome comparison analyses and RNA expression data, we show that this splice variant is conserved among hominidae but absent from all other species. RNA expression and histological analyses show specific expression in human spermatogonial and hematopoietic stem cells (HSCs), while all other analyzed tissues lack the expression of this TERF1-isoform, hence the name TERF1-tsi (TERF1-tissue-specific-isoform). In addition, we could not detect any expression in primary human cells and established cancer cell lines. Immunohistochemistry results involving two new rabbit polyclonal antibodies, generated against TERF1-tsi specific peptides, indicate nuclear localization of TERF1-tsi in a subset of spermatogonial stem cells. In line with this observation, immunofluorescence analyzes in various cell lines consistently revealed that ectopic TERF1-tsi localizes to the cell nucleus, mainly but not exclusively at telomeres. In a first attempt to evaluate the impact of TERF1-tsi in the testis, we have tested its expression in normal testis samples versus matched tumor samples from the same patients. Both RT-PCR and IHC show a specific downregulation of TERF1-tsi in tumor samples while the expression of TERF1 and PIN2 remains unchanged.

The Cellular Thermal Shift Assay (CETSA) has emerged as a powerful tool for evaluating drug-target interactions in live cells, yet its application in ultra-high throughput screening (uHTS) has been limited by technical constraints. In this study, we present significant advancements in CETSA methodology, focusing on the development of an innovative isothermal CETSA platform for primary uHTS screen in 1536 well plates and a Gradient Peltier Device (GPD) for retesting hits in full melting curve CETSA. Our optimized isothermal CETSA allows for the evaluation of adherent cells in their physiological state, enhancing assay performance through a controlled thermal ramp-up instead of traditional heat shock methods and utilizing highly sensitive luminescence detection. The GPD enables all steps of a full melt curve CETSA to be conducted in one single flat bottom microtiter plate, improving data quality by reducing handling and pipetting steps and improving temperature control. We benchmarked both methods against an established fluorescence polarization assay using the androgen receptor as a model target. Results demonstrated a strong correlation between both CETSA methods and the fluorescence polarization assay, indicating the potential for identifying true binders while minimizing false positives. Our findings highlight the utility of this optimized CETSA platform for high throughput drug discovery, paving the way for more effective screening of true binders in live cells.