scholarly journals Persistence of Mhc Heterozygosity in Homozygous Clonal Killifish, Rivulus marmoratus: Implications for the Origin of Hermaphroditism

Genetics ◽  
2002 ◽  
Vol 162 (4) ◽  
pp. 1791-1803
Author(s):  
Akie Sato ◽  
Yoko Satta ◽  
Felipe Figueroa ◽  
Werner E Mayer ◽  
Zofia Zaleska-Rutczynska ◽  
...  
Keyword(s):  
Genetic Distances ◽  
Gene Duplications ◽  
Neotropical Fish ◽  
The Bahamas ◽  
Rivulus Marmoratus ◽  
Allelic Lineages ◽  
Histocompatibility Complex ◽  
Different Populations ◽  
Shed Light ◽  
Mhc Alleles

Abstract The mangrove killifish Rivulus marmoratus, a neotropical fish in the order Cyprinodontiformes, is the only known obligatorily selfing, synchronous hermaphroditic vertebrate. To shed light on its population structure and the origin of hermaphroditism, major histocompatibility complex (Mhc) class I genes of the killifish from seven different localities in Florida, Belize, and the Bahamas were cloned and sequenced. Thirteen loci and their alleles were identified and classified into eight groups. The loci apparently arose ∼20 million years ago (MYA) by gene duplications from a single common progenitor in the ancestors of R. marmoratus and its closest relatives. Distinct loci were found to be restricted to different populations and different individuals in the same population. Up to 44% of the fish were heterozygotes at Mhc loci, as compared to near homozygosity at non-Mhc loci. Large genetic distances between some of the Mhc alleles revealed the presence of ancestral allelic lineages. Computer simulation designed to explain these findings indicated that selfing is incomplete in R. marmoratus populations, that Mhc allelic lineages must have diverged before the onset of selfing, and that the hermaphroditism arose in a population containing multiple ancestral Mhc lineages. A model is proposed in which hermaphroditism arose stage-wise by mutations, each of which spread through the entire population and was fixed independently in the emerging clones.

MHC polymorphism and parasites

1994 ◽  
Vol 346 (1317) ◽  
pp. 351-358 ◽  
Keyword(s):  
Human Leucocyte Antigen ◽  
Genetic Distances ◽  
Major Influence ◽  
Entire Body ◽  
Sequence Motifs ◽  
Short Sequence ◽  
Allelic Lineages ◽  
Body Of Knowledge ◽  
Histocompatibility Complex ◽  
Mhc Polymorphism

The major histocompatibility complex (MHC) polymorphism is marked by the existence of allelic lineages that are extremely old, having been passed from one species to another in an evolutionary line of descent. Each species has several of these lineages and many of their more recent derivatives, the actual alleles. The lineages are separated by large genetic distances and are characterized by the presence of short sequence motifs which, at the protein level, have remained virtually unaltered for over 40 million years. Several explanations for the mhc polymorphism have been proposed. We argue that the only one consistent with the entire body of knowledge about the MHC is an explanation based on the immune response to parasites. Furthermore, we propose that parasites coevolving with their hosts have had a major influence on MHC polymorphism, whereas parasites that switched hosts recently and became very virulent have had little effect. The latter category includes micro- and macroparasites responsible for the major human infectious diseases. This hypothesis explains why no convincing association between human leucocyte antigen ( HLA ) alleles and resistance to infectious disease can thus far be documented, and indicates the direction in which the search for such associations should be taken.

scholarly journals Bioinformatics Analysis of Allele Frequencies and Expression Patterns of ACE2, TMPRSS2 and FURIN in Different Populations and Susceptibility to SARS-CoV-2

Genes ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 1041
Author(s):  
Mohammad Tarek ◽  
Hana Abdelzaher ◽  
Firas Kobeissy ◽  
Hassan A. N. El-Fawal ◽  
Mohammed M. Salama ◽  
...  
Keyword(s):  
Immune Response ◽  
Genetic Factors ◽  
Bioinformatics Analysis ◽  
Expression Patterns ◽  
Spike Protein ◽  
Target Cells ◽  
Health Crisis ◽  
Expression Levels ◽  
Different Populations ◽  
Shed Light

The virus responsible for the COVID-19 global health crisis, SARS-CoV-2, has been shown to utilize the ACE2 protein as an entry point to its target cells. The virus has been shown to rely on the actions of TMPRSS2 (a serine protease), as well as FURIN (a peptidase), for the critical priming of its spike protein. It has been postulated that variations in the sequence and expression of SARS-CoV-2’s receptor (ACE2) and the two priming proteases (TMPRSS2 and FURIN) may be critical in contributing to SARS-CoV-2 infectivity. This study aims to examine the different expression levels of FURIN in various tissues and age ranges in light of ACE2 and TMPRSS2 expression levels using the LungMAP database. Furthermore, we retrieved expression quantitative trait loci (eQTLs) of the three genes and their annotation. We analyzed the frequency of the retrieved variants in data from various populations and compared it to the Egyptian population. We highlight FURIN’s potential interplay with the immune response to SARS-CoV-2 and showcase a myriad of variants of the three genes that are differentially expressed across populations. Our findings provide insights into potential genetic factors that impact SARS-CoV-2 infectivity in different populations and shed light on the varying expression patterns of FURIN.

scholarly journals Gene duplications in the TL region of the mouse major histocompatibility complex.

1985 ◽  
Vol 4 (6) ◽  
pp. 1431-1434 ◽  
Author(s):  
U. Hammerling ◽  
H. Ronne ◽  
E. Widmark ◽  
B. Servenius ◽  
M. Denaro ◽  
...  
Keyword(s):  
Major Histocompatibility Complex ◽  
Gene Duplications ◽  
Major Histocompatibility ◽  
Mouse Major Histocompatibility Complex ◽  
Histocompatibility Complex

Multiple sclerosis: MHC associations and therapeutic implications

2005 ◽  
Vol 7 (3) ◽  
pp. 1-17 ◽  
Author(s):  
Samantha Holmes ◽  
Manuel A. Friese ◽  
Christian Siebold ◽  
E. Yvonne Jones ◽  
John Bell ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Major Histocompatibility Complex ◽  
T Cell Receptors ◽  
Molecular Basis ◽  
Structural Studies ◽  
Specific Level ◽  
Therapeutic Implications ◽  
Mhc Molecules ◽  
Histocompatibility Complex ◽  
Mhc Alleles

Multiple sclerosis (MS) is an autoimmune disease with an important genetic component. The strongest genetic association is with the major histocompatibility complex (MHC) region. Several MHC alleles predispose to the disease, the most prominent of which are certain alleles in the HLA-DR2 haplotype. Functional and structural studies have helped to explain the molecular basis of these associations. Although there is currently no curative treatment for MS, an increased understanding of the disease has aided the design of immunotherapies that act on the immune system more specifically than the longstanding drugs. Many of these therapies work at the antigen-specific level, disrupting the interaction between T-cell receptors and MHC molecules that leads to disease.

scholarly journals AFLP MARKER IN GENETIC DIVERSITYASSESSMENT OF FIG (Ficus carica L.) POPULATIONS IN KURDISTAN REGION – IRAQ.

2021 ◽  
Vol 52 (4) ◽  
pp. 859-867
Author(s):  
Hussein & Jubrael
Keyword(s):  
Genetic Similarity ◽  
Genetic Relatedness ◽  
Aflp Marker ◽  
Genetic Distances ◽  
Similarity Coefficient ◽  
Kurdistan Region ◽  
Aflp Data ◽  
Different Populations ◽  
Cultivar Improvement ◽  
Similarity Matrices

In this study, the genetic relatedness of 12 cultivars of fig from different populations in Kurdistan region- Iraq were analyzed using eleven AFLP primers pairs combinations by using the technology of molecular analysis the DNA. Genetic similarity matrices were produced for the AFLP data to calculate genetic distances among their cultivars. Genetic similarity coefficient ranged from 0.1261 to 0.3905. The lowest genetic similarity was observed between Kola and Gala Zard (0.1261). The Hejeera Rash and Shela cultivars were most similar ones with a coefficient of 0.3905. Clustering based on AFLP data for the 12 fig cultivars was identified at the 0.32 similarity level. In the developed dendogram two main groups were found, the first one combined Ketek and Shela together, while the second group contained two sub group Shingaly and Benatty combined together, while in the other sub group cluster three other sub-group were identified. The results of this study may help in the formulation of appropriate strategies for conservation and cultivar improvement in figs, for which limited knowledge of the genetic diversity is available.

Anchialine adjustments: an updated phylogeny and classification for the family Barbouriidae Christoffersen, 1987 (Decapoda: Caridea)

2020 ◽  
Vol 40 (4) ◽  
pp. 401-411 ◽  
Author(s):  
Robert E Ditter ◽  
Luis M Mejía-Ortíz ◽  
Heather D Bracken-Grissom
Keyword(s):  
Phylogenetic Analyses ◽  
Nuclear Gene ◽  
Morphological Characters ◽  
Molecular Data ◽  
Genetic Distances ◽  
Evolutionary Relationships ◽  
The Bahamas ◽  
16S Gene ◽  
Dichotomous Key ◽  
The Family

Abstract Barbouriidae Christoffersen, 1987 is a family comprised of 4 genera and 11 species of enigmatic shrimps restricted to anchialine or marine caves whose evolutionary history and relationships remain elusive. We investigated the evolutionary relationships among members of Barbouriidae with the inclusion of four genera and nine species, and newly collected material from Belize, the Bahamas, and the Yucatán Peninsula, Mexico. Phylogenetic analyses based on seven mitochondrial and nuclear gene regions and genetic distances calculated using partial 16S gene regions have identified a need to revisit the relationships and classification within Barbouriidae. More specifically, we find evidence to suggest Janicea Manning & Hart, 1984 as a junior synonym of Parhippolyte Borradaile, 1900, B. yanezi Mejía, Zarza & López, 2008 as a synonym of Barbouria cubensis (von Martens, 1872), and define two new subfamilies, Calliasmatinae Holthuis, 1973 and Barbouriinae Christoffersen, 1987. Included is a dichotomous key for the species of Barbouriidae that summarizes previous literature and includes new morphological characters. Our findings shed light on existing inaccuracies and gaps in molecular data from barbouriids. We also provide further clarity into evolutionary relationships among genera of Barbouriidae and their allies, suggesting phylogeographic divisions within the family. Our findings suggest an early Atlantic-Pacific divide among genera originating from a shallow-water reef ancestor.

Cytogenetic analysis of a self-fertilizing fish, Rivulus marmoratus: remarkable chromosomal constancy over a vast geographic range

Genome ◽  
1997 ◽  
Vol 40 (6) ◽  
pp. 945-949 ◽  
Author(s):  
L. Sola ◽  
M. Marzovillo ◽  
A. R. Rossi ◽  
E. Gornung ◽  
S. Bressanello ◽  
...  
Keyword(s):  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Natural Populations ◽  
Chromosome Complement ◽  
Nucleolar Organizer ◽  
Geographic Range ◽  
Molecular Techniques ◽  
Clonal Variation ◽  
The Bahamas ◽  
Rivulus Marmoratus

The aplocheiloid killifish Rivulus marmoratus is the only known self-fertilizing hermaphroditic vertebrate. Most natural populations consist almost entirely of hermaphrodites and comprise arrays of homozygous clones. However, in almost all populations thus far studied, clonal variation, as detected with molecular techniques, is very high. A karyological survey was carried out on specimens from Brazil, the Bahamas, Belize, and Florida (4 locales) by C-banding, silver staining, and fluorescent staining. The chromosome complement of R. marmoratus is surprisingly uniform over its vast geographic range, in terms of both chromosome number and morphology, heterochromatin distribution and composition, and nucleolar organizer region (NOR) distribution. The short arms of chromosome pair 15, where NORs are located, showed the only variation detected in this study: those of pattern A were consistently shorter than those of pattern B; moreover, the latter show positive heteropycnosis with Giemsa staining. The present data demonstrate that chromosomal variation is not a significant part of the clonal divergence in this species, even though its breeding system, by forming homozygotes for new rearrangements almost immediately, should make that variation easier to detect. The high chromosomal homogeneity is discussed in the light of the peculiar natural history of the species.Key words: hermaphrodite killifish, chromosomes, NORs, heterochromatin.

scholarly journals Associations between malaria and MHC genes in a migratory songbird

2005 ◽  
Vol 272 (1571) ◽  
pp. 1511-1518 ◽  
Author(s):  
Helena Westerdahl ◽  
Jonas Waldenström ◽  
Bengt Hansson ◽  
Dennis Hasselquist ◽  
Torbjörn von Schantz ◽  
...  
Keyword(s):  
Positive Association ◽  
Malaria Parasites ◽  
Mhc Genes ◽  
Long Term Study ◽  
Histocompatibility Complex ◽  
Study Population ◽  
Migratory Songbird ◽  
Avian Populations ◽  
Mhc Alleles

Malaria parasites are a widespread and species-rich group infecting many wild populations of mammals, birds and reptiles. Studies on humans have demonstrated that genetic factors play a key role in the susceptibility and outcome of malaria infections. Until the present study, it has not been examined whether genetic variation in hosts is important for the outcome of malaria infections in natural avian populations. We investigated associations between major histocompatibility complex (MHC) genes and prevalence of three different avian malaria parasites ( Haemoproteus payevskyi (GRW1), Plasmodium sp. (GRW2) and Plasmodium sp. (GRW4)) in a long-term study of great reed warblers Acrocephalus arundinaceus . We hypothesized that the MHC genes could either give full protection against a malaria infection, or confer protection against lethal malaria and direct the infection towards being milder. We found a positive association between numbers of MHC class I alleles (a measure of level of heterozygosity) and prevalence of the GRW2 parasite, suggesting the latter scenario. There was also a positive association between a specific MHC allele (B4b), previously shown to be under frequency-dependent selection in the study population, and prevalence of GRW2. These associations suggest that individuals carrying either a large number of MHC alleles or a specific MHC allele are protected against lethal malaria infections.

Metacercarial polymorphism and genetic variation of Paragonimus heterotremus (Digenea: Paragonimidae), and a re-appraisal of the taxonomic status of Paragonimus pseudoheterotremus

2013 ◽  
Vol 89 (2) ◽  
pp. 182-188 ◽  
Author(s):  
P.N. Doanh ◽  
U. Thaenkham ◽  
P.T. An ◽  
H.V. Hien ◽  
Y. Horii ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Taxonomic Status ◽  
Haplotype Network ◽  
Genetic Distances ◽  
Maximum Diameter ◽  
Molecular Characteristics ◽  
Extensive Collection ◽  
Different Populations ◽  
A New Species ◽  
India And China

AbstractParagonimus heterotremus, which is an important pathogen for human paragonimiasis in Asia, is recognized as having the smallest metacercariae (maximum diameter < 300 μm) of any previously reported Paragonimus species. Recently, P. pseudoheterotremus has been described from Thailand as a new species having metacercariae (about 200 μm) slightly smaller than those of Thai P. heterotremus. In fact, the small size of P. pseudoheterotremus metacercariae is compatible with those of P. heterotremus from India and China. In this study in Vietnam, we found variably sized small metacercariae which are expected to consist of both P. heterotremus and P. pseudoheterotremus. Contrary to expectation, the adult flukes obtained by separate infection of experimental cats with different sized metacercariae were all identified as P. heterotremus, using both morphological and molecular characteristics. The molecular analyses of an extensive collection of P. heterotremus/P. pseudoheterotremus isolates from Asian countries also indicated that genetic distances between different populations of P. heterotremus are even larger than that between P. pseudoheterotremus and P. heterotremus. The haplotype network showed that all P. heterotremus and P. pseudoheterotremus isolates formed a P. heterotremus complex consisting of three groups with strong geographical origins. In addition, the Indian P. heterotremus group is the root of the other P. heterotremus and P. pseudoheterotremus populations. Based on the observed metacercarial polymorphisms and genetic variation in P. heterotremus,P. pseudoheterotremus should be considered a geographically isolated population of the P. heterotremus complex.

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