Isolation of single circulating trophoblasts from maternal circulation for noninvasive fetal copy number variant profiling

OBJECTIVE

To develop a multi-step workflow for the isolation of circulating extravillous trophoblasts (cEVTs) by describing the key steps enabling a semi-automated process, including a proprietary algorithm for fetal cell origin genetic confirmation and copy number variant (CNV) detection.

METHODS

Determination of the limit of detection (LoD) for submicroscopic CNV was performed by serial experiments with genomic DNA and single cells from Coriell cell line biobank with known imbalances of different sizes. A pregnancy population of 372 women was prospectively enrolled and blindly analyzed to evaluate the current workflow.

RESULTS

An LoD of 800 Kb was demonstrated with Coriell cell lines. This level of resolution was confirmed in the clinical cohort with the identification of a pathogenic CNV of 800 Kb, also detected by chromosomal microarray. The mean number of recovered cEVTs was 3.5 cells per sample with a significant reverse linear trend between gestational age and cEVT recovery rate and number of recovered cEVTs. In twin pregnanices, evaluation of zygosity, fetal sex and copy number profiling was performed in each individual cell.

CONCLUSION

Our semi-automated methodology for the isolation and single-cell analysis of cEVTS supports the feasibility of a cell-based noninvasive prenatal test for fetal genomic profiling.

Abstract 5385: Standardization and automation of volume reduction procedure for circulating tumor cells and rare cell workflows with VRNxT technology

Tumor heterogeneity is a hallmark of cancer and a major driving force for tumor progression, and emergence of resistance to cancer therapy. Single-cell studies have greatly contributed to unravelling tumour heterogeneity but wider adoption has been prevented by technical challenges. Isolation and analysis of single circulating tumor cells (CTCs) offer a unique minimally invasive approach to characterize and monitor dynamic changes in tumor heterogeneity at the genomic level. Standardization and reproducibility of the workflows are mandatory for translating CTC-based assays to the clinic and meet the regulatory requirements to enter routine practice. Recently, we and other groups have demonstrated the applicability of the CellSearch®/DEPArray™/ Ampli1™ workflow for the enumeration, isolation and molecular characterization of single CTCs. This workflow combines the high sensitivity and specificity of the CellSearch platform for CTC detection and enrichment with the DEPArray technology, which ensures a precise and accurate image-based isolation of single CTCs, 100% pure. Here, we validate the VRNxT™, an innovative technology that further harmonizes the CellSearch/DEPArray workflow by automating the volume reduction steps. The working principle of VRNxT instrument uses centrifugal forces to reduce the sample volume, eliminating the use of pipettes in washing steps and consequently, the risk of cell loss. Precision and accuracy of VRNxT were tested by comparing automatic and manual volume reduction (VR) procedures in a typical workflow. Briefly, after single cell isolation with the DEPArray, standard sample preparation for whole genome amplification analysis were carried out by four different skilled operators and compared to automatic VRNxT procedure. Each operator sorted 90 single CTCs using DEPArray and then performed manual VR in order to obtain a final volume of about 2 µl, compatible with the whole genome amplification procedure. Significant differences were observed in the volume reduction procedure performed by operators (2.65±0.79; 1.16±0.50; 1.26±0.96; 1.58±0.67, respectively). Conversely, VRNxT exhibited a higher reproducibility of data (1.82 µl±0.23 SD), by eliminating the user-dependent variability. Moreover, automatic VR exponentially reduced the time required to VR (about 30 minutes compared to 218 minutes of manual VR, for 96 single cell recoveries), and minimized single cell loss with a success rate never achieved so far (100% respect to 92.8% manual VR). VRNxT is thus an easy-to-use technology, that minimizes the variability and error rate in rare cell workflow and consequently reduces user-dependent variability and improve standardization. VRNxT technology coupled to CellSearch, DEPArray and Ampli1, offers an effective solution for a streamlined liquid biopsy workflow to characterize and monitor tumor heterogeneity.

Citation Format: Mariano Di Trapani, Alex Calanca, Fabrizio Alberti, Gianpiero Parisi, Valeria Stivani, Chiara Maranta, Francesca Dattolo, Francesco Grasso, Michele Ricci, Alex Marchi, Gianni Medoro. Standardization and automation of volume reduction procedure for circulating tumor cells and rare cell workflows with VRNxT technology [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5385.

The cold way for glutathione biosynthesis in the psychrophile Pseudoalteromonas haloplanktis. Redundancy and reaction rates

In the psychrophileP. haloplanktisGSH is formed in two consecutive steps coupled to ATP hydrolysis. Differently from other sources, two redundant γ-glutamyl cysteine ligases catalyse first step; overall GSH biosynthesis is rate-limited by second step.

Rate and extent of early axonal degeneration of the human facial nerve

Electrophysiologic and histologic studies on a severed human facial nerve have shown that 1) response to stimulation by electroneuronography was lost on the sixth day following injury, 2) wallerian degeneration progressed in a nonuniform "front," leaving some of the distal stump axons still viable and responsive to intraoperative stimulation 2 days following injury, and 3) the extent of proximal retrograde degeneration was far greater than to the next node of Ranvier. These findings are discussed in light of the current knowledge regarding peripheral nerve degeneration, and explanations are suggested.