1
|
Abstract
Gamete fusion is the climax of fertilization in all sexually reproductive organisms, from unicellular fungi to humans. Similarly to other cell-cell fusion events, gamete fusion is mediated by specialized proteins, named fusogens, that overcome the energetic barriers during this process. In recent years, HAPLESS 2/GENERATIVE CELL-SPECIFIC 1 (HAP2/GCS1) was identified as the fusogen mediating sperm-egg fusion in flowering plants and protists, being both essential and sufficient for the membrane merger in some species. The identification of HAP2/GCS1 in invertebrates, opens the possibility that a similar fusogen may be used in vertebrate fertilization. HAP2/GCS1 proteins share a similar structure with two distinct families of exoplasmic fusogens: the somatic Fusion Family (FF) proteins discovered in nematodes, and class II viral glycoproteins (e.g., rubella and dengue viruses). Altogether, these fusogens form the Fusexin superfamily. While some attributes are shared among fusexins, for example the overall structure and the possibility of assembly into trimers, some other characteristics seem to be specific, such as the presence or not of hydrophobic loops or helices at the distal tip of the protein. Intriguingly, HAP2/GCS1 or other fusexins have neither been identified in vertebrates nor in fungi, raising the question of whether these genes were lost during evolution and were replaced by other fusion machinery or a significant divergence makes their identification difficult. Here, we discuss the biology of HAP2/GCS1, its involvement in gamete fusion and the structural, mechanistic and evolutionary relationships with other fusexins.
Collapse
Affiliation(s)
- Nicolas G Brukman
- Department of Biology, Technion- Israel Institute of Technology, Haifa, Israel
| | - Xiaohui Li
- Department of Biology, Technion- Israel Institute of Technology, Haifa, Israel
| | | |
Collapse
|
2
|
Abstract
Most, if not all the cellular requirements for fertilization and sexual reproduction arose early in evolution and are retained in extant lineages of single-celled organisms including a number of important model organism species. In recent years, work in two such species, the green alga, Chlamydomonas reinhardtii, and the free-living ciliate, Tetrahymena thermophila, have lent important new insights into the role of HAP2/GCS1 as a catalyst for gamete fusion in organisms ranging from protists to flowering plants and insects. Here we summarize the current state of knowledge around how mating types from these algal and ciliate systems recognize, adhere and fuse to one another, current gaps in our understanding of HAP2-mediated gamete fusion, and opportunities for applying what we know in practical terms, especially for the control of protozoan parasites.
Collapse
Affiliation(s)
- Jennifer F. Pinello
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, United States
| | - Theodore G. Clark
- Department of Microbiology and Immunology, Cornell University, Ithaca, NY, United States
| |
Collapse
|
3
|
Li D, Yu C, Guo J, Wang Y, Zhao Y, Wang L, Soe MT, Feng H, Kyaw MP, Sattabongkot J, Jiang L, Cui L, Zhu X, Cao Y. Plasmodium vivax HAP2/GCS1 gene exhibits limited genetic diversity among parasite isolates from the Greater Mekong Subregion. Parasit Vectors 2020; 13:175. [PMID: 32264948 PMCID: PMC7137254 DOI: 10.1186/s13071-020-04050-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Accepted: 03/28/2020] [Indexed: 12/02/2022] Open
Abstract
Background Antigens expressed in sexual stages of the malaria parasites are targets of transmission-blocking vaccines (TBVs). HAP2/GCS1, a TBV candidate, is critical for fertilization in Plasmodium. Here, the genetic diversity of PvHAP2 was studied in Plasmodium vivax parasite populations from the Greater Mekong Subregion (GMS). Methods Plasmodium vivax clinical isolates were collected in clinics from the China-Myanmar border region (135 samples), western Thailand (41 samples) and western Myanmar (51 samples). Near full-length Pvhap2 (nucleotides 13–2574) was amplified and sequenced from these isolates. Molecular evolution studies were conducted to evaluate the genetic diversity, selection and population differentiation. Results Sequencing of the pvhap2 gene for a total of 227 samples from the three P. vivax populations revealed limited genetic diversity of this gene in the GMS (π = 0.00036 ± 0.00003), with the highest π value observed in Myanmar (0.00053 ± 0.00009). Y133S was the dominant mutation in the China-Myanmar border (99.26%), Myanmar (100%) and Thailand (95.12%). Results of all neutrality tests were negative for all the three populations, suggesting the possible action of purifying selection. Codon-based tests identified specific codons which are under purifying or positive selections. Wright’s fixation index showed low to moderate genetic differentiation of P. vivax populations in the GMS, with FST ranging from 0.04077 to 0.24833, whereas high levels of genetic differentiation were detected between the China-Myanmar border and Iran populations (FST = 0.60266), and between Thailand and Iran populations (FST = 0.44161). A total of 20 haplotypes were identified, with H2 being the abundant haplotype in China-Myanmar border, Myanmar and Thailand populations. Epitope mapping prediction of Pvhap2 antigen showed that high-score B-cell epitopes are located in the S307-G324, L429-P453 and V623-D637 regions. The E317K and D637N mutations located within S307-G324 and V623-D637 epitopes slightly reduced the predicted score for potential epitopes. Conclusions The present study showed a very low level of genetic diversity of pvhap2 gene among P. vivax populations in the Greater Mekong Subregion. The relative conservation of pvhap2 supports further evaluation of a Pvhap2-based TBV.![]()
Collapse
Affiliation(s)
- Danni Li
- Department of Immunology, College of Basic Medical Science, China Medical University, Shenyang, 110122, Liaoning Province, People's Republic of China
| | - Chunyun Yu
- Department of Immunology, College of Basic Medical Science, China Medical University, Shenyang, 110122, Liaoning Province, People's Republic of China
| | - Jian Guo
- Department of Laboratory Medicine, Shanghai East Hospital, Tongji School of Medicine, Shanghai, People's Republic of China
| | - Yazhou Wang
- Department of Environmental Health, School of Public Health, China Medical University, Shenyang, 110122, Liaoning Province, People's Republic of China
| | - Yan Zhao
- Department of Immunology, College of Basic Medical Science, China Medical University, Shenyang, 110122, Liaoning Province, People's Republic of China
| | - Lin Wang
- Department of Immunology, College of Basic Medical Science, China Medical University, Shenyang, 110122, Liaoning Province, People's Republic of China
| | - Myat Thu Soe
- Myanmar Health Network Organization, Yangon, Myanmar
| | - Hui Feng
- Department of Immunology, College of Basic Medical Science, China Medical University, Shenyang, 110122, Liaoning Province, People's Republic of China
| | | | - Jetsumon Sattabongkot
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Lubin Jiang
- Unit of Human Parasite Molecular and Cell Biology, Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, People's Republic of China
| | - Liwang Cui
- Department of Internal Medicine, Morsani College of Medicine, University of South Florida, 3720 Spectrum Boulevard, Suite 304, Tampa, FL, 33612, USA
| | - Xiaotong Zhu
- Department of Immunology, College of Basic Medical Science, China Medical University, Shenyang, 110122, Liaoning Province, People's Republic of China.
| | - Yaming Cao
- Department of Immunology, College of Basic Medical Science, China Medical University, Shenyang, 110122, Liaoning Province, People's Republic of China.
| |
Collapse
|