Bio

Honors & Awards


  • National Researcher Candidate, Mexico?s National Researchers System (SNI) CONACyT (2020)
  • Postdoctoral Fellowship, CONACyT Mexico (2019)

Professional Education


  • PhD, CINVESTAV - IPN Mexico, Molecular Biomedicine (2018)
  • MSc, CINVESTAV - IPN Mexico, Molecular Biomedicine (2014)
  • Bachelor, Universidad Nacional Autonoma de Mexico, Pharmaceutical Biological Chemistry (2012)

Stanford Advisors


Publications

All Publications


  • Entamoeba stage conversion: progress and new insights. Current opinion in microbiology Manna, D., Ehrenkaufer, G. M., Lozano-Amado, D., Singh, U. 2020; 58: 62?68

    Abstract

    Entamoeba histolytica, an anaerobic protozoan, is an important global health problem. This parasite has a biphasic life cycle consisting of a dormant cyst stage which is environmentally resistant and transmits the infection, and the proliferative trophozoite stage which is motile and causes invasive disease. The stage conversion process remains poorly understood despite being central to amoebic biology. In this review, we will highlight recent progress in our understanding of Entamoeba stage conversion including dissecting transcriptome analysis in development, characterization of transcriptional networks, demonstration of epigenetic regulation, and role of small molecules that regulate Entamoeba development.

    View details for DOI 10.1016/j.mib.2020.09.005

    View details for PubMedID 33032142

  • The NAD+ Responsive Transcription Factor ERM-BP Functions Downstream of Cellular Aggregation and Is an Early Regulator of Development and Heat Shock Response in Entamoeba. Frontiers in cellular and infection microbiology Manna, D., Lozano-Amado, D., Ehrenkaufer, G., Singh, U. 2020; 10: 363

    Abstract

    Entamoeba histolytica is a protozoan parasite and a major cause of dysentery and diarrheal disease in developing countries. Disease transmission from one host to another occurs via cysts which can survive in environmental extremes and are transmitted through contaminated food and water. Recent studies in our lab identified a novel transcription factor, Encystation Regulatory Motif- Binding Protein (ERM-BP), which is responsive to NAD+ and has an important role in encystation. The key residues important for ERM-BP function were demonstrated in vitro using recombinant protein. In this study we demonstrate the in vivo functional consequences of mutations in key domains and their impact on Entamoeba encystation. Our results show that mutations in the DNA binding domain (ERM-BP-DBM) and in the nicotinamidase domain (ERM-BP-C198A) lead to protein mis-localization in both trophozoites and cysts and significantly reduce encystation efficiency. Additionally, we showed that silencing of ERM-BP significantly decreased the size and number of multi-nucleated giant cells (MGC) that form during encystation, indicating that ERM-BP functions upstream of the cellular aggregation that precedes stage conversion. Dissection of epistatic interactions between ERM-BP and a second encystation-related transcription factor, NF-Y revealed that ERM-BP is upstream of NF-Y in controlling the developmental cascade and appears to be one of the earliest regulators of development identified to date in Entamoeba. We also demonstrated that ERM-BP is upregulated during heat stress in Entamoeba, another condition which increases intracellular NAD+ levels and that overexpression of ERM-BP makes E. histolytica and E. invadens parasites more resistant to heat stress. Overexpression of ERM-BP in E. histolytica also induced the formation of cyst-like quadrinucleated cells and formation of MGCs. Overall, our work has identified an important role of ERM-BP in Entamoeba stress response and links an NAD+-responsive transcription factor to both development and heat shock response. Characterization of stress and developmental cascades are important avenues to investigate for Entamoeba, an important human parasitic pathogen.

    View details for DOI 10.3389/fcimb.2020.00363

    View details for PubMedID 32766170

    View details for PubMedCentralID PMC7379229

  • A class I histone deacetylase is implicated in the encystation of Entamoeba invadens. International journal for parasitology Lozano-Amado, D., Ávila-López, P. A., Hernández-Montes, G., Briseńo-Díaz, P., Vargas, M., Lopez-Rubio, J. J., Carrero, J. C., Hernández-Rivas, R. 2020

    Abstract

    Epigenetic mechanisms such as histone acetylation and deacetylation participate in regulation of the genes involved in encystation of Entamoeba invadens. However, the histones and target residues involved, and whether the acetylation and deacetylation of the histones leads to the regulation of gene expression associated with the encystation of this parasite, remain unknown. In this study, we found that E. invadens histone H4 is acetylated in both stages of the parasite and is more highly acetylated during the trophozoite stage than in the cyst. Histone hyperacetylation induced by Trichostatin A negatively affects the encystation of E. invadens, and this inhibition is associated with the downregulation of the expression of genes implicated in the synthesis of chitin, polyamines, gamma-aminobutyric acid pathways and cyst wall proteins, all of which are important in the formation of cysts. Finally, in silico analysis and activity assays suggest that a class I histone deacetylase (EiHDAC3) could be involved in control of the expression of a subset of genes that are important in several pathways during encystation. Therefore, the identification of enzymes that acetylate and/or deacetylate histones that control encystation in E. invadens could be a promising therapeutic target for preventing transmission of other amoebic parasites such as E. histolytica, the causative agent of amoebiasis in humans.

    View details for DOI 10.1016/j.ijpara.2020.05.014

    View details for PubMedID 32822677

  • Clipped histone H3 is integrated into nucleosomes of DNA replication genes in the human malaria parasite Plasmodium falciparum. EMBO reports Herrera-Solorio, A. M., Vembar, S. S., MacPherson, C. R., Lozano-Amado, D., Meza, G. R., Xoconostle-Cazares, B., Martins, R. M., Chen, P., Vargas, M., Scherf, A., Hernández-Rivas, R. 2019; 20 (4)

    Abstract

    Post-translational modifications of histone H3 N-terminal tails are key epigenetic regulators of virulence gene expression and sexual commitment in the human malaria parasite Plasmodium falciparum Here, we identify proteolytic clipping of the N-terminal tail of nucleosome-associated histone H3 at amino acid position 21 as a new chromatin modification. A cathepsin C-like proteolytic clipping activity is observed in nuclear parasite extracts. Notably, an ectopically expressed version of clipped histone H3, PfH3p-HA, is targeted to the nucleus and integrates into mononucleosomes. Furthermore, chromatin immunoprecipitation and next-generation sequencing analysis identified PfH3p-HA as being highly enriched in the upstream region of six genes that play a key role in DNA replication and repair: In these genes, PfH3p-HA demarcates a specific 1.5 kb chromatin island adjacent to the open reading frame. Our results indicate that, in P. falciparum, the process of histone clipping may precede chromatin integration hinting at preferential targeting of pre-assembled PfH3p-containing nucleosomes to specific genomic regions. The discovery of a protease-directed mode of chromatin organization in P. falciparum opens up new avenues to develop new anti-malarials.

    View details for DOI 10.15252/embr.201846331

    View details for PubMedID 30833341

    View details for PubMedCentralID PMC6446197

  • PfAP2Tel, harbouring a non-canonical DNA-binding AP2 domain, binds to Plasmodium falciparum telomeres. Cellular microbiology Sierra-Miranda, M., Vembar, S. S., Delgadillo, D. M., Ávila-López, P. A., Herrera-Solorio, A. M., Lozano Amado, D., Vargas, M., Hernandez-Rivas, R. 2017; 19 (9)

    Abstract

    The telomeres of the malaria parasite Plasmodium falciparum are essential not only for chromosome end maintenance during blood stage development in humans but also to generate genetic diversity by facilitating homologous recombination of subtelomeric, multigene virulence families such as var and rifin. However, other than the telomerase PfTERT, proteins that act at P. falciparum telomeres are poorly characterised. To isolate components that bind to telomeres, we performed oligonucleotide pulldowns and electromobility shift assays with a telomeric DNA probe and identified a non-canonical member of the ApiAP2 family of transcription factors, PfAP2Tel (encoded by PF3D7_0622900), as a component of the P. falciparum telomere-binding protein complex. PfAP2Tel is expressed throughout the intra-erythrocytic life cycle and localises to the nuclear periphery, co-localising with telomeric clusters. Furthermore, EMSAs using the recombinant protein demonstrated direct binding of PfAP2Tel to telomeric repeats in vitro, while genome-wide chromatin immunoprecipitation followed by next generation sequencing corroborated the high specificity of this protein to telomeric ends of all 14 chromosomes in vivo. Taken together, our data describe a novel function for ApiAP2 proteins at chromosome ends and open new avenues to study the molecular machinery that regulates telomere function in P. falciparum.

    View details for DOI 10.1111/cmi.12742

    View details for PubMedID 28376558

  • A new nucleocytoplasmic RhoGAP protein contributes to control the pathogenicity of Entamoeba histolytica by regulating EhRacC and EhRacD activity. Cellular microbiology Hernandez-Flores, A., Almaraz-Barrera, M. d., Lozano-Amado, D., Correa-Basurto, J., Rojo-Dominguez, A., Luna-Rivera, E., Schnoor, M., Guillen, N., Hernandez-Rivas, R., Vargas, M. 2016; 18 (11): 1653?72

    Abstract

    Small GTPases are signalling molecules that regulate important cellular processes. GTPases are deactivated by GTPase-activating proteins (GAPs). While human GAPs have been intensively studied, no GAP has yet been characterized in Entamoeba histolytica. In this study, we identified and characterized a novel nucleocytoplasmic RhoGAP in E.?histolytica termed EhRhoGAPnc. In silico analyses of the domain structure revealed a previously undescribed peptide region within the carboxy-terminal region of EhRhoGAPnc capable of interacting with phosphatidic acid and phosphatidylinositol 3,5-bisphosphate. The full structural GAP domain showed increase GAP activity compared with the minimum region able to display GAP activity, as analysed both by experimental assays and molecular dynamics simulations. Furthermore, we identified amino acid residues that promote interactions between EhRhoGAPnc and its target GTPases EhRacC and EhRacD. Immunofluorescence studies revealed that EhRhoGAPnc colocalized with EhRacC and EhRacD during uroid formation but not during erythrophagocytosis. Interestingly, during erythrophagocytosis of red blood cells, EhRhoGAPnc colocalized with phosphatidic acid and phosphatidylinositol 3,5-bisphosphate. Overexpression of EhRhoGAPnc in E.?histolytica led to inhibition of actin adhesion plate formation, migration, adhesion of E.?histolytica to MDCK cells and consequently to an impairment of the cytopathic activity.

    View details for DOI 10.1111/cmi.12603

    View details for PubMedID 27107405

  • Identification of repressive and active epigenetic marks and nuclear bodies in Entamoeba histolytica. Parasites & vectors Lozano-Amado, D., Herrera-Solorio, A. M., Valdés, J., Alemán-Lazarini, L., Almaraz-Barrera, M. d., Luna-Rivera, E., Vargas, M., Hernández-Rivas, R. 2016; 9: 19

    Abstract

    In human hosts, Entamoeba histolytica cysts can develop into trophozoites, suggesting that the life cycle of this parasite are regulated by changes in gene expression. To date, some evidence has suggested that epigenetic mechanisms such as DNA methylation and histone modification are involved in the regulation of gene expression in Entamoeba. Some post-translational modifications (PTMs) at the N-terminus of E. histolytica's histones have been reported experimentally, including tri-methylation in the lysine 4 of histone H3 (H3K4me3) and dimethylation in the lysine 27 of histone H3 (H3K27me2), dimethylation of arginine 3 (H4R3me2) and the indirect acetylation of histone H4 in the N-terminal region. However, it is not known which residues of histone H4 are subject to acetylation and/or methylation or where in the nucleus these epigenetic marks are located.Histones from trophozoites of E. histolytica were obtained and analyzed by LC-MS/MS. WB assays were performed using antibodies against epigenetic marks (acetylated lysines and methylated arginines). Immunofluorescence assays (IFA) were carried out to determine the distribution of PTMs and the localization of DNA methylation as a heterochromatin marker. Nuclear bodies such as the nucleolus were identified by using antibodies against fibrillarin and nucleolin and speckles by using anti-PRP6 antibody.Some new PTMs in histone H4 of E. histolytica, such as the acetylation of lysines 5, 8, 12 and 16 and the monomethylation of arginine 3, were identified by WB. IFA demonstrated that some marks are associated with transcriptional activity (such as acetylation and/or methylation) and that these marks are distributed throughout the E. histolytica nucleus. Staining with antibodies against anti-pan-acetylated lysine H4 histone and 5-methyl cytosine showed that the activation and transcriptional repression marks converge. Additionally, two nuclear bodies, the nucleolus and speckles, were identified in this parasite.This study provides the first evidence that the nucleus of E. histolytica is not compartmentalized and contains two nuclear bodies, the nucleolus and speckles, the latter of which was not identified previously. The challenge is now to understand how these epigenetic marks and nuclear bodies work together to regulate gene expression in E. histolytica.

    View details for DOI 10.1186/s13071-016-1298-7

    View details for PubMedID 26767976

    View details for PubMedCentralID PMC4712492

Footer Links:

Stanford Medicine Resources: