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Smith G, Manzano-Marín A, Reyes-Prieto M, Antunes CSR, Ashworth V, Goselle ON, Jan AAA, Moya A, Latorre A, Perotti MA, Braig HR. Human follicular mites: Ectoparasites becoming symbionts. Mol Biol Evol 2022; 39:msac125. [PMID: 35724423 PMCID: PMC9218549 DOI: 10.1093/molbev/msac125] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Revised: 05/23/2022] [Accepted: 05/31/2022] [Indexed: 12/13/2022] Open
Abstract
Most humans carry mites in the hair follicles of their skin for their entire lives. Follicular mites are the only metazoans tha continuously live on humans. We propose that Demodex folliculorum (Acari) represents a transitional stage from a host-injuring obligate parasite to an obligate symbiont. Here, we describe the profound impact of this transition on the genome and physiology of the mite. Genome sequencing revealed that the permanent host association of D. folliculorum led to an extensive genome reduction through relaxed selection and genetic drift, resulting in the smallest number of protein-coding genes yet identified among panarthropods. Confocal microscopy revealed that this gene loss coincided with an extreme reduction in the number of cells. Single uninucleate muscle cells are sufficient to operate each of the three segments that form each walking leg. While it has been assumed that the reduction of the cell number in parasites starts early in development, we identified a greater total number of cells in the last developmental stage (nymph) than in the terminal adult stage, suggesting that reduction starts at the adult or ultimate stage of development. This is the first evolutionary step in an arthropod species adopting a reductive, parasitic or endosymbiotic lifestyle. Somatic nuclei show underreplication at the diploid stage. Novel eye structures or photoreceptors as well as a unique human host melatonin-guided day/night rhythm are proposed for the first time. The loss of DNA repair genes coupled with extreme endogamy might have set this mite species on an evolutionary dead-end trajectory.
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Affiliation(s)
- Gilbert Smith
- School of Natural Sciences, Bangor University, Bangor, Wales, United Kingdom
| | - Alejandro Manzano-Marín
- Centre for Microbiology and Environmental Systems Science (CMESS), University of Vienna, Vienna, Austria
| | - Mariana Reyes-Prieto
- Institute of Integrative Systems Biology (I2Sysbio), Universitat de València and Spanish Research Council (CSIC), València, Spain
- Foundation for the Promotion of Health and Biomedical Research of the Valencian Community (FISABIO), València, Spain
| | | | - Victoria Ashworth
- School of Natural Sciences, Bangor University, Bangor, Wales, United Kingdom
| | - Obed Nanjul Goselle
- School of Natural Sciences, Bangor University, Bangor, Wales, United Kingdom
| | | | - Andrés Moya
- Institute of Integrative Systems Biology (I2Sysbio), Universitat de València and Spanish Research Council (CSIC), València, Spain
- Foundation for the Promotion of Health and Biomedical Research of the Valencian Community (FISABIO), València, Spain
- Center for Networked Biomedical Research in Epidemiology and Public Health (CIBEResp), Madrid, Spain
| | - Amparo Latorre
- Institute of Integrative Systems Biology (I2Sysbio), Universitat de València and Spanish Research Council (CSIC), València, Spain
- Foundation for the Promotion of Health and Biomedical Research of the Valencian Community (FISABIO), València, Spain
- Center for Networked Biomedical Research in Epidemiology and Public Health (CIBEResp), Madrid, Spain
| | - M Alejandra Perotti
- School of Biological Sciences, University of Reading, Reading, United Kingdom
| | - Henk R Braig
- School of Natural Sciences, Bangor University, Bangor, Wales, United Kingdom
- Institute and Museum of Natural Sciences, National University of San Juan, San Juan, Argentina
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Ferrández-Roldán A, Martí-Solans J, Cañestro C, Albalat R. Oikopleura dioica: An Emergent Chordate Model to Study the Impact of Gene Loss on the Evolution of the Mechanisms of Development. Results Probl Cell Differ 2019; 68:63-105. [PMID: 31598853 DOI: 10.1007/978-3-030-23459-1_4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The urochordate Oikopleura dioica is emerging as a nonclassical animal model in the field of evolutionary developmental biology (a.k.a. evo-devo) especially attractive for investigating the impact of gene loss on the evolution of mechanisms of development. This is because this organism fulfills the requirements of an animal model (i.e., has a simple and accessible morphology, a short generation time and life span, and affordable culture in the laboratory and amenable experimental manipulation), but also because O. dioica occupies a key phylogenetic position to understand the diversification and origin of our own phylum, the chordates. During its evolution, O. dioica genome has suffered a drastic process of compaction, becoming the smallest known chordate genome, a process that has been accompanied by exacerbating amount of gene losses. Interestingly, however, despite the extensive gene losses, including entire regulatory pathways essential for the embryonic development of other chordates, O. dioica retains the typical chordate body plan. This unexpected situation led to the formulation of the so-called inverse paradox of evo-devo, that is, when a genetic diversity is able to maintain a phenotypic unity. This chapter reviews the biological features of O. dioica as a model animal, along with the current data on the evolution of its genes and genome. We pay special attention to the numerous examples of gene losses that have taken place during the evolution of this unique animal model, which is helping us to understand to which the limits of evo-devo can be pushed off.
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Affiliation(s)
- Alfonso Ferrández-Roldán
- Facultat de Biologia, Departament de Genètica, Microbiologia i Estadística and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Catalonia, Spain
| | - Josep Martí-Solans
- Facultat de Biologia, Departament de Genètica, Microbiologia i Estadística and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Catalonia, Spain
| | - Cristian Cañestro
- Facultat de Biologia, Departament de Genètica, Microbiologia i Estadística and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Catalonia, Spain
| | - Ricard Albalat
- Facultat de Biologia, Departament de Genètica, Microbiologia i Estadística and Institut de Recerca de la Biodiversitat (IRBio), Universitat de Barcelona, Barcelona, Catalonia, Spain.
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