Performances of rapid and connected salivary RT-LAMP diagnostic test for SARS-CoV-2 infection in ambulatory screening

In the context of social events reopening and economic relaunch, sanitary surveillance of SARS-CoV-2 infection is still required. Here, we evaluated the diagnostic performances of a rapid, extraction-free and connected reverse-transcription loop-mediated isothermal amplification (RT-LAMP) assay on saliva. Nasopharyngeal (NP) swabs and saliva from 443 outpatients were collected simultaneously and tested by reverse-transcription quantitative PCR (RT-qPCR) as reference standard test. Seventy-one individuals (16.0%) were positive by NP and/or salivary RT-qPCR. Sensitivity and specificity of salivary RT-LAMP were 85.9% (95%CI 77.8–94.0%) and 99.5% (98.7–100%), respectively. Performances were similar for symptomatic and asymptomatic participants. Moreover, SARS-CoV-2 genetic variants were analyzed and no dominant mutation in RT-LAMP primer region was observed during the period of the study. We demonstrated that this RT-LAMP test on self-collected saliva is reliable for SARS-CoV-2 detection. This simple connected test with optional automatic results transfer to health authorities is unique and opens the way to secure professional and social events in actual context of economics restart.

Simple, sensitive and robust chicken specific sexing assays, compliant with large scale analysis

Chicken meat and eggs are important sources of food for the world population. The significant increase in food demand has pushed the food industry toward a rapid non-expensive production which in turn raises ethical issues. How chicken are cultivated and processed in food industry is no longer acceptable. Ethical and economical concerns emerging from chicken culling need to be solved in the near future. Indeed, in egg production industry, male chicken are killed at the age of 1-day post-hatching since they are not egg producers. A number of laboratory all over the world are looking for innovative non-invasive sexing methods to determine the sex of chicken in the early stages of the development before hatching. It will allow males' chicken elimination before the pain-feeling stages. In order to evaluate the efficiency of these methods, the scientific community need a reliable, easy to use and cost-effective in-ovo invasive sexing method. In this report, we developed two new invasive assays based on PCR and Q-PCR techniques respectively, which fulfil the above mentioned requirements. In the same line with other groups, we exploited the differences betweed males (ZZ) and females (ZW) chicken sexual chromosomes. We identified two genes, SWIM and Xho-I, on chromosome W and DMRT gene on chromosome Z allowing a clear discrimination between the two sexes using PCR and qPCR respectively. These two new genomic markers and their corresponding methods not only increase the accuracy but also reduce time and cost of the test compared to previously developed sexing methods. Depending on the technology available in the lab, one can choose between the two techniques requiring different machines and expertise.

SKAP, an outer kinetochore protein, is required for mouse germ cell development

In sexually reproducing organisms, accurate gametogenesis is crucial for the transmission of genetic material from one generation to the next. This requires the faithful segregation of chromosomes during mitotic and meiotic divisions. One of the main players in this process is the kinetochore, a large multi-protein complex that forms at the interface of centromeres and microtubules. Here, we analyzed the expression profile and function of small kinetochore-associated protein (SKAP) in the mouse. We found that two distinct SKAP isoforms are specifically expressed in the germline: a smaller isoform, which is detected in spermatogonia and spermatocytes and localized in the outer mitotic and meiotic kinetochores from metaphase to telophase, and a larger isoform, which is expressed in the cytoplasm of elongating spermatids. We generated SKAP-deficient mice and found that testis size and sperm production were severely reduced in mutant males. This phenotype was partially caused by defects during spermatogonia proliferation before entry into meiosis. We conclude that mouse SKAP, while being dispensable for somatic cell divisions, has an important role in the successful outcome of male gametogenesis. In germ cells, analogous to what has been suggested in studies using immortalized cells, SKAP most likely stabilizes the interaction between kinetochores and microtubules, where it might be needed as an extra safeguard to ensure the correct segregation of mitotic and meiotic chromosomes.

Natural Loss of Mps1 Kinase in Nematodes Uncovers a Role for Polo-like Kinase 1 in Spindle Checkpoint Initiation

The spindle checkpoint safeguards against chromosome loss during cell division by preventing anaphase onset until all chromosomes are attached to spindle microtubules. Checkpoint signal is generated at kinetochores, the primary attachment site on chromosomes for spindle microtubules. Mps1 kinase initiates checkpoint signaling by phosphorylating the kinetochore-localized scaffold protein Knl1 to create phospho-docking sites for Bub1/Bub3. Mps1 is widely conserved but is surprisingly absent in many nematode species. Here, we show that PLK-1, which targets a substrate motif similar to that of Mps1, functionally substitutes for Mps1 in C. elegans by phosphorylating KNL-1 to direct BUB-1/BUB-3 kinetochore recruitment. This finding led us to re-examine checkpoint initiation in human cells, where we found that Plk1 co-inhibition significantly reduced Knl1 phosphorylation and Bub1 kinetochore recruitment relative to Mps1 inhibition alone. Thus, the finding that PLK-1 functionally substitutes for Mps1 in checkpoint initiation in C. elegans uncovered a role for Plk1 in species that have Mps1.

A Bub1-Mad1 interaction targets the Mad1-Mad2 complex to unattached kinetochores to initiate the spindle checkpoint

A Bub1–Mad1 interaction targets the Mad1–Mad2 complex to unattached kinetochores to initiate the spindle checkpoint.

Recruitment of Mad1–Mad2 complexes to unattached kinetochores is a central event in spindle checkpoint signaling. Despite its importance, the mechanism that recruits Mad1–Mad2 to kinetochores is unclear. In this paper, we show that MAD-1 interacts with BUB-1 in Caenorhabditis elegans. Mutagenesis identified specific residues in a segment of the MAD-1 coiled coil that mediate the BUB-1 interaction. In addition to unattached kinetochores, MAD-1 localized between separating meiotic chromosomes and to the nuclear periphery. Mutations in the MAD-1 coiled coil that selectively disrupt interaction with BUB-1 eliminated MAD-1 localization to unattached kinetochores and between meiotic chromosomes, both of which require BUB-1, and abrogated checkpoint signaling. The identified MAD-1 coiled-coil segment interacted with a C-terminal region of BUB-1 that contains its kinase domain, and mutations in this region prevented MAD-1 kinetochore targeting independently of kinase activity. These results delineate an interaction between BUB-1 and MAD-1 that targets MAD-1–MAD-2 complexes to kinetochores and is essential for spindle checkpoint signaling.

Microtubule binding by KNL-1 contributes to spindle checkpoint silencing at the kinetochore

A microtubule-binding site in the extreme N terminus of KNL-1 is dispensable for load-bearing attachments but participates in checkpoint silencing at the kinetochore.

Accurate chromosome segregation requires coordination between microtubule attachment and spindle checkpoint signaling at the kinetochore. The kinetochore-localized KMN (KNL-1/Mis12 complex/Ndc80 complex) network, which mediates microtubule attachment and scaffolds checkpoint signaling, harbors two distinct microtubule-binding activities: the load-bearing activity of the Ndc80 complex and a less well-understood activity in KNL-1. In this paper, we show that KNL-1 microtubule-binding and -bundling activity resides in its extreme N terminus. Selective perturbation of KNL-1 microtubule binding in Caenorhabditis elegans embryos revealed that this activity is dispensable for both load-bearing attachment formation and checkpoint activation but plays a role in checkpoint silencing at the kinetochore. Perturbation of both microtubule binding and protein phosphatase 1 docking at the KNL-1 N terminus additively affected checkpoint silencing, indicating that, despite their proximity in KNL-1, these two activities make independent contributions. We propose that microtubule binding by KNL-1 functions in checkpoint silencing by sensing microtubules attached to kinetochores and relaying their presence to eliminate generation of the checkpoint signal.

MacMARCKS interacts with the metabotropic glutamate receptor type 7 and modulates G protein-mediated constitutive inhibition of calcium channels

We have previously shown that the interaction of Ca2+/calmodulin with the metabotropic glutamate receptor type 7 (mGluR7) promotes the G-protein-mediated inhibition of voltage-sensitive Ca2+ channels (VSCCs) seen upon agonist activation. Here, we performed a yeast two-hybrid screen of a new-born rat brain cDNA library using the cytoplasmic C-terminal tail of mGluR7 as bait and identified macrophage myristoylated alanine-rich c-kinase substrate (MacMARCKS) as a binding protein. The interaction was confirmed in vitro and in vivo by pull-down assays, immunoprecipitation, and colocalization of mGluR7 and MacMARCKS in transfected HEK293 cells and cultured cerebellar granule cells. Binding of MacMARCKS to mGluR7 was antagonized by Ca2+/calmodulin. In neurons, cotransfection of MacMARCKS with mGluR7, but not mGluR7 mutants unable to bind MacMARCKS, reduced the G-protein-mediated tonic inhibition of VSCCs in the absence of mGluR7 agonist. These results suggest that competitive interactions of Ca2+/calmodulin and MacMARCKS with mGluR7 control the tonic inhibition of VSCCs by G-proteins.

ASAP, a human microtubule-associated protein required for bipolar spindle assembly and cytokinesis

We have identified a unique human microtubule-associated protein (MAP) named ASAP for ASter-Associated Protein. ASAP localizes to microtubules in interphase, associates with the mitotic spindle during mitosis, localizes to the central body during cytokinesis and directly binds to purified microtubules by its COOH-terminal domain. Overexpression of ASAP induces profound bundling of cytoplasmic microtubules in interphase cells and aberrant monopolar spindles in mitosis. Depletion of ASAP by RNA interference results in severe mitotic defects: it provokes aberrant mitotic spindle, delays mitotic progression, and leads to defective cytokinesis or cell death. These results suggest a crucial role for ASAP in the organization of the bipolar mitotic spindle, mitosis progression, and cytokinesis and define ASAP as a key factor for proper spindle assembly.