scholarly journals Gene-rich X chromosomes implicate intragenomic conflict in the evolution of bizarre genetic systems

2020 ◽  
Author(s):  
Noelle Anderson ◽  
Kamil S. Jaron ◽  
Christina N. Hodson ◽  
Matthew B. Couger ◽  
Jan Ševčík ◽  
...  
Keyword(s):  
De Novo ◽  
Paternal Genome ◽  
X Chromosomes ◽  
General Role ◽  
Genetic Transmission ◽  
X Linkage ◽  
Intragenomic Conflict ◽  
Genetic Systems ◽  
High Degree ◽  
Male Heterogamety

AbstractHaplodiploidy and paternal genome elimination (HD/PGE) are common in animals, having evolved at least two dozen times. HD/PGE typically evolves from male heterogamety (i.e., systems with X chromosomes), however why X chromosomes are important for the evolution of HD/PGE remains debated. The Haploid Viability Hypothesis argues that X chromosomes promote the evolution of male haploidy by facilitating purging recessive deleterious mutations. The Intragenomic Conflict Hypothesis instead argues that X chromosomes promote the evolution of male haploidy due to conflicts with autosomes over sex ratios and transmission. To test these hypotheses, we studied lineages that combine germline PGE with XX/X0 sex determination (gPGE+X systems). Because the evolution of such systems involves changes in genetic transmission but not increases in male hemizygosity, a high degree of X linkage in these systems is predicted by the Intragenomic Conflict Hypothesis but not the Haploid Viability Hypothesis. Through de novo genome sequence, we compared the genomes of 7 species with gPGE+X systems and 10 related species with typical XX/XY or XX/X0 genetic systems. We find highly increased X-linkage in modern and ancestral genomes of gPGE+X species, with an estimated 30 times more X-linked genes than in non-gPGE+X relatives. These results suggest a general role for intragenomic conflict in the origins of PGE/HD. These findings are among the first empirical results supporting a role for intragenomic conflict in the evolution of novel genetic systems.

Cerebellotrigeminal Dermal Dysplasia (Gómez-López-Hernández Syndrome)

2018 ◽  
Vol 16 (05) ◽  
pp. 362-368 ◽  
Author(s):  
Federica Sullo ◽  
Agata Polizzi ◽  
Stefano Catanzaro ◽  
Selene Mantegna ◽  
Francesco Lacarrubba ◽  
...  
Keyword(s):  
De Novo ◽  
Chromosomal Rearrangements ◽  
Number Of Patients ◽  
Wide Range ◽  
Visual Problems ◽  
Neurodevelopmental Abnormalities ◽  
Clinical Triad ◽  
High Degree ◽  
Motor Handicap

Cerebellotrigeminal dermal (CTD) dysplasia is a rare neurocutaneous disorder characterized by a triad of symptoms: bilateral parieto-occipital alopecia, facial anesthesia in the trigeminal area, and rhombencephalosynapsis (RES), confirmed by cranial magnetic resonance imaging. CTD dysplasia is also known as Gómez-López-Hernández syndrome. So far, only 35 cases have been described with varying symptomatology. The etiology remains unknown. Either spontaneous dominant mutations or de novo chromosomal rearrangements have been proposed as possible explanations. In addition to its clinical triad of RES, parietal alopecia, and trigeminal anesthesia, CTD dysplasia is associated with a wide range of phenotypic and neurodevelopmental abnormalities.Treatment is symptomatic and includes physical rehabilitation, special education, dental care, and ocular protection against self-induced corneal trauma that causes ulcers and, later, corneal opacification. The prognosis is correlated to the mental development, motor handicap, corneal–facial anesthesia, and visual problems. Follow-up on a large number of patients with CTD dysplasia has never been reported and experience is limited to few cases to date. High degree of suspicion in a child presenting with characteristic alopecia and RES has a great importance in diagnosis of this syndrome.

scholarly journals Red queen's race: rapid evolutionary dynamics of an expanding family of meiotic drive factors and their hpRNA suppressors

2021 ◽  
Author(s):  
Jeffrey Vedanayagam ◽  
Ching-Jung Lin ◽  
Eric C. Lai
Keyword(s):  
Evolutionary Dynamics ◽  
Sex Chromosome ◽  
De Novo ◽  
Independent Set ◽  
Meiotic Drive ◽  
Sperm Chromatin ◽  
Arms Races ◽  
X Chromosomes ◽  
Selfish Genetic Elements ◽  
Satellite Repeats

Meiotic drivers are a class of selfish genetic elements that are widespread across eukaryotes. Their activities are often detrimental to organismal fitness and thus trigger drive suppression to ensure fair segregation during meiosis. Accordingly, their existence is frequently hidden in genomes, and their molecular functions are little known. Here, we trace evolutionary steps that generated the Dox meiotic drive system in Drosophila simulans (Dsim), which distorts male:female balance (sex-ratio) by depleting male progeny. We show that Dox emerged via stepwise mobilization and acquisition of portions of multiple D. melanogaster genes, including the sperm chromatin packaging gene protamine. Moreover, we reveal novel Dox homologs in Dsim and massive, recent, amplification of Dox superfamily genes specifically on X chromosomes of its closest sister species D. mauritiana (Dmau) and D. sechellia (Dsech). The emergence of Dox superfamily genes is tightly associated with 1.688 family satellite repeats that flank de novo genomic copies. In concert, we find coordinated emergence and diversification of autosomal hairpin RNA/siRNAs loci that target subsets of Dox superfamily genes across simulans clade species. Finally, an independent set of protamine amplifications the Y chromosome of D. melanogaster indicates that protamine genes are frequent and recurrent players in sex chromosome dynamics. Overall, we reveal fierce genetic arms races between meiotic drive factors and siRNA suppressors associated with recent speciation.

scholarly journals Contingency in the convergent evolution of a regulatory network: Dosage compensation in Drosophila

2018 ◽  
Author(s):  
Doris Bachtrog ◽  
Chris Ellison
Keyword(s):  
Transposable Element ◽  
Dosage Compensation ◽  
Sex Chromosomes ◽  
Binding Sites ◽  
Evolutionary Biology ◽  
De Novo ◽  
Binding Motif ◽  
Sequence Motif ◽  
X Chromosomes ◽  
Msl Complex

The repeatability or predictability of evolution is a central question in evolutionary biology, and most often addressed in experimental evolution studies. Here, we infer how genetically heterogeneous natural systems acquire the same molecular changes, to address how genomic background affects adaptation in natural populations. In particular, we take advantage of independently formed neo-sex chromosomes in Drosophila species that have evolved dosage compensation by co-opting the dosage compensation (MSL) complex, to study the mutational paths that have led to the acquisition of 100s of novel binding sites for the MSL complex in different species. This complex recognizes a conserved 21-bp GA-rich sequence motif that is enriched on the X chromosome, and newly formed X chromosomes recruit the MSL complex by de novo acquisition of this binding motif. We identify recently formed sex chromosomes in the Drosophila repleta and robusta species groups by genome sequencing, and generate genomic occupancy maps of the MSL complex to infer the location of novel binding sites. We find that diverse mutational paths were utilized in each species to evolve 100s of de novo binding motifs along the neo-X, including expansions of microsatellites and transposable element insertions. However, the propensity to utilize a particular mutational path differs between independently formed X chromosomes, and appears to be contingent on genomic properties of that species, such as simple repeat or transposable element density. This establishes the “genomic environment” as an important determinant in predicting the outcome of evolutionary adaptations.

Sex-ratio meiotic drive in Drosophila simulans: cellular mechanism, candidate genes and evolution

2006 ◽  
Vol 34 (4) ◽  
pp. 562-565 ◽  
Author(s):  
C. Montchamp-Moreau
Keyword(s):  
Sex Ratio ◽  
X Chromosome ◽  
Natural Populations ◽  
Meiotic Drive ◽  
Female Offspring ◽  
Drosophila Simulans ◽  
X Chromosomes ◽  
Individual Fitness ◽  
Primary Sex Ratio ◽  
Intragenomic Conflict

The sex-ratio trait, reported in a dozen Drosophila species, is a type of naturally occurring meiotic drive in which the driving elements are located on the X chromosome. Typically, as the result of a shortage of Y-bearing spermatozoa, males carrying a sex-ratio X chromosome produce a large excess of female offspring. The presence of sex-ratio chromosomes in a species can have considerable evolutionary consequences, because they can affect individual fitness and trigger extended intragenomic conflict. Here, I present the main results of the study performed in Drosophila simulans. In this species, the loss of Y-bearing spermatozoa is related to the inability of the Y chromosome sister-chromatids to separate properly during meiosis II. Fine genetic mapping has shown that the primary sex-ratio locus on the X chromosome contains two distorter elements acting synergistically, both of which are required for drive expression. One element has been genetically mapped to a tandem duplication. To infer the natural history of the trait, the pattern of DNA sequence polymorphism in the surrounding chromosomal region is being analysed in natural populations of D. simulans harbouring sex-ratio X chromosomes. Initial results have revealed the recent spread of a distorter allele.

scholarly journals Natural Bactericidal Antibodies: Observations on the Bactericidal Mechanism of Normal Serum

1931 ◽  
Vol 31 (1) ◽  
pp. 35-55 ◽  
Author(s):  
T. J. Mackie ◽  
M. H. Finkelstein
Keyword(s):  
Analytical Study ◽  
Animal Species ◽  
De Novo ◽  
Carbonic Acid ◽  
Insoluble Fraction ◽  
Normal Serum ◽  
Natural Antibodies ◽  
Bactericidal Action ◽  
Bactericidal Antibody ◽  
High Degree

1. An analytical study has been made of the mechanism of natural bactericidal action by the serum of various animals (ox, sheep, horse, rabbit, guinea-pig, rat, man) towards certain organisms (B. typhosus, B. dysenteriae Shiga, B. proteus, V. cholerae) exhibiting the maximum reactivity to this effect.2. Serum-complement has no bactericidal action per se, and an antibodylike agent invariably acts as an intermediary agent, “sensitising” the particular organism to the action of the complement and capable of being “absorbed” by it from serum at 0° C.3. This sensitising agent is stable at 55° C. but labile at 60°–65° C. In this respect it resembles natural haemolysins and agglutinins, but contrasts with the more stable immune antibodies and the more labile natural complement-fixing antibodies (for bacterial antigens). It is resident mainly in the carbonic-acid-insoluble fraction of the serum. It is present in the serum of young animals before certain other natural antibodies have developed.4. Absorption tests demonstrate the high degree of specificity of these natural bactericidal antibodies for particular bacteria.5. A non-specific extracellular substance occurs in bacterial cultures which may neutralise or inhibit these antibodies, and interfere with their sensitising action even at 0° C.6. This substance is liberated in large amount in cultures heated at high temperatures (120° C). It can be removed by repeated washing of growths in saline solution. It may inactivate a bactericidal antibody in heated serum, though not in fresh unheated serum, and may inactivate a particular antibody in the serum of one animal species but not in another. Strains of bacteria vary in their production of this substance.7. The observations submitted in this paper, correlated with previous studies of natural antibodies by the authors and others, indicate that immune antibodies have their precursors specifically differentiated in the serum of normal animals and that, in general, immune antibodies are not substances formed de novo.

scholarly journals The Correlation between Chronic Periodontitis and Oral Cancer

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Maximilian Krüger ◽  
Torsten Hansen ◽  
Adrian Kasaj ◽  
Maximilian Moergel
Keyword(s):  
Chronic Inflammation ◽  
Chronic Periodontitis ◽  
De Novo ◽  
Clinical Signs ◽  
Clinical Findings ◽  
General Role ◽  
Papilloma Virus ◽  
Theoretical Concepts ◽  
Potential Trigger

Infections are increasingly considered as potential trigger for carcinogenesis apart from risk factors like alcohol and tobacco. The discussion about human papilloma virus (HPV) in oral squamous cell carcinoma (OSCC) points at a general role of infection for the development of oral carcinomas. Furthermore, first studies describe a correlation between chronic periodontitis and OSCC, thus, characterizing chronic inflammation as being a possible trigger for OSCC. In front of this background, we present four well-documented clinical cases. All patients showed a significant anatomical relation between OSCC and clinical signs of chronic periodontitis. The interindividual differences of the clinical findings lead to different theoretical concepts: two with coincidental appearance of OSCC and chronic periodontitis and two with possible de novo development of OSCC triggered by chronic inflammation. We conclude that the activation of different inflammatory cascades by chronic periodontitis negatively affects mucosa and bone. Furthermore, the inflammatory response has the potential to activate carcinogenesis. Apart from a mere coincidental occurrence, two out of four patients give first clinical hints for a model wherein chronic periodontitis represents a potential risk factor for the development of OSCC.

scholarly journals APRT SELECTION SYSTEM IN PLANTS

HortScience ◽  
1992 ◽  
Vol 27 (11) ◽  
pp. 1160f-1160
Author(s):  
Sunita K. Agarwal ◽  
David J. Schultz ◽  
Dennis A. Schaff
Keyword(s):  
De Novo ◽  
Selection System ◽  
Wild Type ◽  
Purine Salvage ◽  
Toxic Plants ◽  
Adenine Analogues ◽  
Salvage Pathways ◽  
Cloned Gene ◽  
High Degree ◽  
Adenine Derivatives

Most cells have an active turnover of many of their nucleic acids (particularly some types of RNA) which through degradative processes result in the release of adenine, guanine and hypoxanthine. These free purines are converted to their corresponding nucleotides through salvage pathways. Adenine is converted to its nucleotide form AMP by Adenine phosphoribosyltransferase (APRT) which is one of the enzymes associated with the purine salvage pathway. Since all organisms have a de novo pathway for the formation of AMP, APRT is classified as a `salvage enzyme'. The APRT enzyme, in general, does not show a high degree of specificity for the exact structure of adenine and can also act on cytokinins and adenine derivatives like 2,6-diaminopurine, 2-fluoroadenine and 6-methylpurine. The APRT enzyme can utilize adenine analogues as substrate and convert them into their nucleotide forms which are toxic. Plants that lack APRT activity (APRT-plants) survive in the presense of these analogues. The amount of adenine analogue used for selecting APRT-plants is such that it kills all APRT+ (wild type) plants. APRT+ plants survive when grown in the presense of azaserine and alanosine that block de novo synthesis of AMP. APRT-plants transformed with the wild type cloned gene can be selected from a mixture of transformed and non-transformed plants by selecting in the presense of adenine, azaserine and alanosine. The presense of APRT activity can be confirmed by assaying for the APRT enzyme. APRT activity has been detected in many plant species. The presense of a positive forward and backward selection system can thus allow the use of APRT as a selectable marker in plant gene transfer systems.

scholarly journals Distinct mechanisms mediate X chromosome dosage compensation in Anopheles and Drosophila

2021 ◽  
Vol 4 (9) ◽  
pp. e202000996
Author(s):  
Claudia Isabelle Keller Valsecchi ◽  
Eric Marois ◽  
M Felicia Basilicata ◽  
Plamen Georgiev ◽  
Asifa Akhtar
Keyword(s):  
X Chromosome ◽  
Dosage Compensation ◽  
Gene Dosage ◽  
Histone H4 ◽  
Ecological Constraints ◽  
Evolutionary Trajectory ◽  
X Chromosomes ◽  
Deleterious Gene ◽  
Msl Complex ◽  
High Degree

Sex chromosomes induce potentially deleterious gene expression imbalances that are frequently corrected by dosage compensation (DC). Three distinct molecular strategies to achieve DC have been previously described in nematodes, fruit flies, and mammals. Is this a consequence of distinct genomes, functional or ecological constraints, or random initial commitment to an evolutionary trajectory? Here, we study DC in the malaria mosquito Anopheles gambiae. The Anopheles and Drosophila X chromosomes evolved independently but share a high degree of homology. We find that Anopheles achieves DC by a mechanism distinct from the Drosophila MSL complex–histone H4 lysine 16 acetylation pathway. CRISPR knockout of Anopheles msl-2 leads to embryonic lethality in both sexes. Transcriptome analyses indicate that this phenotype is not a consequence of defective X chromosome DC. By immunofluorescence and ChIP, H4K16ac does not preferentially enrich on the male X. Instead, the mosquito MSL pathway regulates conserved developmental genes. We conclude that a novel mechanism confers X chromosome up-regulation in Anopheles. Our findings highlight the pluralism of gene-dosage buffering mechanisms even under similar genomic and functional constraints.

scholarly journals Complex Structure of Lasiopodomys mandarinus vinogradovi Sex Chromosomes, Sex Determination, and Intraspecific Autosomal Polymorphism

Genes ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 374 ◽  
Author(s):  
Svetlana A. Romanenko ◽  
Antonina V. Smorkatcheva ◽  
Yulia M. Kovalskaya ◽  
Dmitry Yu. Prokopov ◽  
Natalya A. Lemskaya ◽  
...  
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
De Novo ◽  
Complex Structure ◽  
X Chromosomes ◽  
Single Chromosome ◽  
Determination System ◽  
Sex Determination System ◽  
Mandarin Vole

The mandarin vole, Lasiopodomys mandarinus, is one of the most intriguing species among mammals with non-XX/XY sex chromosome system. It combines polymorphism in diploid chromosome numbers, variation in the morphology of autosomes, heteromorphism of X chromosomes, and several sex chromosome systems the origin of which remains unexplained. Here we elucidate the sex determination system in Lasiopodomys mandarinus vinogradovi using extensive karyotyping, crossbreeding experiments, molecular cytogenetic methods, and single chromosome DNA sequencing. Among 205 karyotyped voles, one male and three female combinations of sex chromosomes were revealed. The chromosome segregation pattern and karyomorph-related reproductive performances suggested an aberrant sex determination with almost half of the females carrying neo-X/neo-Y combination. The comparative chromosome painting strongly supported this proposition and revealed the mandarin vole sex chromosome systems originated due to at least two de novo autosomal translocations onto the ancestral X chromosome. The polymorphism in autosome 2 was not related to sex chromosome variability and was proved to result from pericentric inversions. Sequencing of microdissection derived of sex chromosomes allowed the determination of the coordinates for syntenic regions but did not reveal any Y-specific sequences. Several possible sex determination mechanisms as well as interpopulation karyological differences are discussed.

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