geneBasis: an iterative approach for unsupervised selection of targeted gene panels from scRNA-seq.

Funder: European Molecular Biology Laboratory (EMBL) (4843)scRNA-seq datasets are increasingly used to identify gene panels that can be probed using alternative technologies, such as spatial transcriptomics, where choosing the best subset of genes is vital. Existing methods are limited by a reliance on pre-existing cell type labels or by difficulties in identifying markers of rare cells. We introduce an iterative approach, geneBasis, for selecting an optimal gene panel, where each newly added gene captures the maximum distance between the true manifold and the manifold constructed using the currently selected gene panel. Our approach outperforms existing strategies and can resolve cell types and subtle cell state differences

mtDNA dynamics are a driving force of cell-to-cell heterogeneity in Saccharomyces cerevisiae

Isogenic cells exhibit a large degree of cell-to-cell heterogeneity in proliferation, with a subpopulation of cells growing at a substantially lower rate. We conducted a high throughput microscopy screen to determine the proliferation distributions for a collection of wild isolates and 1592 single gene deletions in S. cerevisiae. We found that mitochondrial impairment is a primary cause of slow growth within an isogenic population and that high mitochondrial membrane potential is predictive of reduced growth and respiratory deficiency. We showed that respiratory deficiency can be recovered and that temporary respiratory deficiency is a common trait present in many genetic backgrounds. We developed a mathematical model that predicts the dynamics of the respiratory capacity of single cells within a population as a function of mtDNA state. Finally, we showed that growth in the antifungal agent fluconazole enriches for temporarily respiratory deficient cells, suggesting that this phenotype may be a form of bet-hedging in which a slow growing drug-resistant respiratory deficient cell with low mtDNA content can produce progeny with fast growth and fully functioning mitochondria.Les cèl·lules isogèniques mostren un gran grau d' heterogenietat cel·lular en la seva taxa de proliferació, amb una subpoblació de cèl·lules creixent de manera substancialment lenta. Hem realitzat un assaig de microsopia d’alt rendiment (high-throughput) i hem determinat les distribucions de proliferació d'un conjunt de més de 1590 delecions de gens individuals i de soques wild type de Saccharomyces cerevisiae. Hem trobat que la disfunció mitocondrial és una causa primària del creixement lent dins d'una població isogènica i hem observat que un potencial alt de la membrana mitocondrial ens permet predir la reducció del creixement i la deficiència respiratòria. Hem mostrat que aquesta reducció es pot revertir en determinades circumstàncies i que la deficiència respiratòria temporal és un tret comú en moltes soques. També hem relacionat la dinàmica de la capacitat respiratòria d'una cèl·lula amb l’estat del seu ADN mitocondrial. Finalment, hem mostrat que el creixement en presència d'agents antifúngics augmenta el nombre de cèl·lules amb deficiència temporal respiratòria, suggerint que aquest fenotip pot ser una forma de protecció (subpoblació resistent als fàrmacs amb ADN mitocondrial intacte).Programa de doctorat en Biomedicin

Single cell functional genomics reveals the importance of mitochondria in cell-to-cell phenotypic variation

Mutations frequently have outcomes that differ across individuals, even when these individuals are genetically identical and share a common environment. Moreover, individual microbial and mammalian cells can vary substantially in their proliferation rates, stress tolerance, and drug resistance, with important implications for the treatment of infections and cancer. To investigate the causes of cell-to-cell variation in proliferation, we used a high-throughput automated microscopy assay to quantify the impact of deleting >1500 genes in yeast. Mutations affecting mitochondria were particularly variable in their outcome. In both mutant and wild-type cells mitochondrial membrane potential - but not amount - varied substantially across individual cells and predicted cell-to-cell variation in proliferation, mutation outcome, stress tolerance, and resistance to a clinically used anti-fungal drug. These results suggest an important role for cell-to-cell variation in the state of an organelle in single cell phenotypic variation.Work in the lab of BL was supported by a European Research Council Consolidator grant (616434), the Spanish Ministry of Economy and Competitiveness (BFU2017-89488-P and SEV-2012–0208), the AXA Research Fund, the Bettencourt Schueller Foundation, Agència de Gestió d’Ajuts Universitaris i de Recerca (AGAUR SGR 1322), the EMBL Partnership, and the Generalitat/CERCA program. Work in the lab of LBC was supported by MINECO (BFU2015-68351-P) and AGAUR (2014 SGR 0974) and the Unidad de Excelencia Maria de Maeztu (MDM-2014–0370)

Single cell functional genomics reveals the importance of mitochondria in cell-to-cell phenotypic variation

Mutations frequently have outcomes that differ across individuals, even when these individuals are genetically identical and share a common environment. Moreover, individual microbial and mammalian cells can vary substantially in their proliferation rates, stress tolerance, and drug resistance, with important implications for the treatment of infections and cancer. To investigate the causes of cell-to-cell variation in proliferation, we used a high-throughput automated microscopy assay to quantify the impact of deleting >1500 genes in yeast. Mutations affecting mitochondria were particularly variable in their outcome. In both mutant and wild-type cells mitochondrial membrane potential - but not amount - varied substantially across individual cells and predicted cell-to-cell variation in proliferation, mutation outcome, stress tolerance, and resistance to a clinically used anti-fungal drug. These results suggest an important role for cell-to-cell variation in the state of an organelle in single cell phenotypic variation.Work in the lab of BL was supported by a European Research Council Consolidator grant (616434), the Spanish Ministry of Economy and Competitiveness (BFU2017-89488-P and SEV-2012–0208), the AXA Research Fund, the Bettencourt Schueller Foundation, Agència de Gestió d’Ajuts Universitaris i de Recerca (AGAUR SGR 1322), the EMBL Partnership, and the Generalitat/CERCA program. Work in the lab of LBC was supported by MINECO (BFU2015-68351-P) and AGAUR (2014 SGR 0974) and the Unidad de Excelencia Maria de Maeztu (MDM-2014–0370)

geneBasis: an iterative approach for unsupervised selection of targeted gene panels from scRNA-seq.

scRNA-seq datasets are increasingly used to identify gene panels that can be probed using alternative technologies, such as spatial transcriptomics, where choosing the best subset of genes is vital. Existing methods are limited by a reliance on pre-existing cell type labels or by difficulties in identifying markers of rare cells. We introduce an iterative approach, geneBasis, for selecting an optimal gene panel, where each newly added gene captures the maximum distance between the true manifold and the manifold constructed using the currently selected gene panel. Our approach outperforms existing strategies and can resolve cell types and subtle cell state differences

Budding yeast complete DNA synthesis after chromosome segregation begins

To faithfully transmit genetic information, cells must replicate their entire genome before division. This is thought to be ensured by the temporal separation of replication and chromosome segregation. Here we show that in 20-40% of unperturbed yeast cells, DNA synthesis continues during anaphase, late in mitosis. High cyclin-Cdk activity inhibits DNA synthesis in metaphase, and the decrease in cyclin-Cdk activity during mitotic exit allows DNA synthesis to finish at subtelomeric and some difficult-to-replicate regions. DNA synthesis during late mitosis correlates with elevated mutation rates at subtelomeric regions, including copy number variation. Thus, yeast cells temporally overlap DNA synthesis and chromosome segregation during normal growth, possibly allowing cells to maximize population-level growth rate while simultaneously exploring greater genetic space.This study was supported by Ministerio de Economía y Competitividad (MINECO) (BFU2015-68351-P) and AGAUR (2014SGR0974 & 2017SGR1054) grants to L.B.C. and the Unidad de Excelencia María de Maeztu, funded by the MINECO (MDM-2014-0370); the European Research Council (ERC) Starting Grant 2010-St-20091118 to Ma.M., the Spanish Ministry of Economy and Competitiveness, ‘Centro de Excelencia Severo Ochoa 2013–2017’, SEV- 2012-0208 to the CRG and the grant ANR-10-LABX-0030-INRT, which is a French State fund managed by the Agence Nationale de la Recherche under the frame programme Investissements d’Avenir ANR-10-IDEX-0002-02 to the IGBMC