Female meiotic drive preferentially segregates derived metacentric chromosomes in Drosophila

Mapping Intimacies ◽

10.1101/638684 ◽

2019 ◽

Author(s):

Nicholas B. Stewart ◽

Yasir H. Ahmed-Braimah ◽

Daniel G. Cerne ◽

Bryant F. McAllister

Keyword(s):

Chromosome Segregation ◽

Meiotic Drive ◽

Average Frequency ◽

Mendelian Segregation ◽

Closely Related Species ◽

Chromosomal Inversions ◽

Ideal System ◽

Inversion Status ◽

Paracentric Inversions

AbstractA vast diversity of karyotypes exists within and between species, yet the mechanisms that shape this diversity are poorly understood. Here we investigate the role of biased meiotic segregation—i.e., meiotic drive—in karyotype evolution. The closely related species, Drosophila americana and D. novamexicana, provide an ideal system to investigate mechanisms of karyotypic diversification. Since their recent divergence, D. americana has evolved two centromeric fusions: one between the 2nd and 3rd chromosomes, and another between the X and 4th chromosomes. The 2-3 fusion is fixed in D. americana, but the X-4 fusion is polymorphic and varies in frequency along a latitudinal cline. Here we evaluate the hypothesis that these derived metacentric chromosomes segregate preferentially to the egg nucleus during female meiosis in D. americana. Using two different methods, we show that the fused X-4 chromosome is transmitted at an average frequency of ~57%, exceeding expectations of 50:50 Mendelian segregation. Three paracentric inversions are found in the vicinity of the X-4 fusion and could potentially influence chromosome segregation. Using crosses between lines with differing inversion arrangements, we show that the transmission bias persists regardless of inversion status. Transmission rates are also biased in D. americana/D. novamexicana hybrid females, favoring both the X-4 and 2-3 fused arrangements over their unfused homologs. Our results show that meiotic drive influences chromosome segregation in D. americana favoring derived arrangements in its reorganized karyotype. Moreover, the fused centromeres are the facilitators of biased segregation rather than associated chromosomal inversions.

Spindle asymmetry drives non-Mendelian chromosome segregation

10.1101/180869 ◽

2017 ◽

Author(s):

Takashi Akera ◽

Lukáš Chmátal ◽

Emily Trimm ◽

Karren Yang ◽

Chanat Aonbangkhen ◽

...

Keyword(s):

Chromosome Segregation ◽

Molecular Mechanisms ◽

Asymmetric Cell Division ◽

Meiotic Drive ◽

Cell Cortex ◽

Female Meiosis ◽

Mendelian Segregation ◽

Diploid Parent ◽

Two Sides ◽

Cortical Polarization

Genetic elements compete for transmission through meiosis, when haploid gametes are created from a diploid parent. Selfish elements can enhance their transmission through meiotic drive, in violation of Mendel’s Law of Segregation. In female meiosis, selfish elements drive by preferentially attaching to the egg side of the spindle, which implies some asymmetry between the two sides of the spindle, but molecular mechanisms underlying spindle asymmetry are unknown. Here we show that CDC42 signaling from the cell cortex regulates microtubule tyrosination to induce spindle asymmetry, and non-Mendelian segregation depends on this asymmetry. These signals depend on cortical polarization directed by chromosomes, which are positioned near the cortex to allow the asymmetric cell division. Thus, selfish meiotic drivers exploit the asymmetry inherent in female meiosis to bias their transmission.

Meiotic CENP-C is a shepherd: bridging the space between the centromere and the kinetochore in time and space

Essays in Biochemistry ◽

10.1042/ebc20190080 ◽

2020 ◽

Vol 64 (2) ◽

pp. 251-261

Author(s):

Jessica E. Fellmeth ◽

Kim S. McKim

Keyword(s):

Chromosome Segregation ◽

New Technologies ◽

Early Prophase ◽

Unique Role ◽

Kinetochore Assembly ◽

M Phase ◽

In Vivo Analysis ◽

Meiosis I

Abstract While many of the proteins involved in the mitotic centromere and kinetochore are conserved in meiosis, they often gain a novel function due to the unique needs of homolog segregation during meiosis I (MI). CENP-C is a critical component of the centromere for kinetochore assembly in mitosis. Recent work, however, has highlighted the unique features of meiotic CENP-C. Centromere establishment and stability require CENP-C loading at the centromere for CENP-A function. Pre-meiotic loading of proteins necessary for homolog recombination as well as cohesion also rely on CENP-C, as do the main scaffolding components of the kinetochore. Much of this work relies on new technologies that enable in vivo analysis of meiosis like never before. Here, we strive to highlight the unique role of this highly conserved centromere protein that loads on to centromeres prior to M-phase onset, but continues to perform critical functions through chromosome segregation. CENP-C is not merely a structural link between the centromere and the kinetochore, but also a functional one joining the processes of early prophase homolog synapsis to late metaphase kinetochore assembly and signaling.

Premating barriers in young sympatric snail species

Scientific Reports ◽

10.1038/s41598-021-84407-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Arina L. Maltseva ◽

Marina A. Varfolomeeva ◽

Arseniy A. Lobov ◽

Polina O. Tikanova ◽

Egor A. Repkin ◽

...

Keyword(s):

Gene Flow ◽

Snail Species ◽

Sympatric Populations ◽

Gastropod Species ◽

Shell Size ◽

Closely Related Species ◽

Partial Canonical Correspondence Analysis ◽

In The Wild ◽

Isolation Index

AbstractSympatric coexistence of recently diverged species raises the question of barriers restricting the gene flow between them. Reproductive isolation may be implemented at several levels, and the weakening of some, e.g. premating, barriers may require the strengthening of the others, e.g. postcopulatory ones. We analysed mating patterns and shell size of mates in recently diverged closely related species of the subgenus Littorina Neritrema (Littorinidae, Caenogastropoda) in order to assess the role of premating reproductive barriers between them. We compared mating frequencies observed in the wild with those expected based on relative densities using partial canonical correspondence analysis. We introduced the fidelity index (FI) to estimate the relative accuracy of mating with conspecific females and precopulatory isolation index (IPC) to characterize the strength of premating barriers. The species under study, with the exception of L. arcana, clearly demonstrated preferential mating with conspecifics. According to FI and IPC, L. fabalis and L. compressa appeared reliably isolated from their closest relatives within Neritrema. Individuals of these two species tend to be smaller than those of the others, highlighting the importance of shell size changes in gastropod species divergence. L. arcana males were often found in pairs with L. saxatilis females, and no interspecific size differences were revealed in this sibling species pair. We discuss the lack of discriminative mate choice in the sympatric populations of L. arcana and L. saxatilis, and possible additional mechanisms restricting gene flow between them.

Male Sterility and Meiotic Drive Associated With Sex Chromosome Rearrangements in Drosophila: Role of X-Y Pairing

Genetics ◽

10.1093/genetics/149.1.143 ◽

1998 ◽

Vol 149 (1) ◽

pp. 143-155 ◽

Cited By ~ 3

Author(s):

Bruce D McKee ◽

Kathy Wilhelm ◽

Cynthia Merrill ◽

Xiao-jia Ren

Keyword(s):

Male Sterility ◽

Sex Chromosome ◽

Meiotic Drive ◽

Repeated Sequence ◽

Meiotic Pairing ◽

Intergenic Spacers ◽

Male Specific ◽

The Relationship ◽

Novel Model

Abstract In Drosophila melanogaster, deletions of the pericentromeric X heterochromatin cause X-Y nondisjunction, reduced male fertility and distorted sperm recovery ratios (meiotic drive) in combination with a normal Y chromosome and interact with Y-autosome translocations (T(Y;A)) to cause complete male sterility. The pericentromeric heterochromatin has been shown to contain the male-specific X-Y meiotic pairing sites, which consist mostly of a 240-bp repeated sequence in the intergenic spacers (IGS) of the rDNA repeats. The experiments in this paper address the relationship between X-Y pairing failure and the meiotic drive and sterility effects of Xh deletions. X-linked insertions either of complete rDNA repeats or of rDNA fragments that contain the IGS were found to suppress X-Y nondisjunction and meiotic drive in Xh−/Y males, and to restore fertility to Xh−/T(Y;A) males for eight of nine tested Y-autosome translocations. rDNA fragments devoid of IGS repeats proved incapable of suppressing either meiotic drive or chromosomal sterility. These results indicate that the various spermatogenic disruptions associated with X heterochromatic deletions are all consequences of X-Y pairing failure. We interpret these findings in terms of a novel model in which misalignment of chromosomes triggers a checkpoint that acts by disabling the spermatids that derive from affected spermatocytes.

Molecular Signatures of Reticulate Evolution within the Complex of European Pine Taxa

Forests ◽

10.3390/f12040489 ◽

2021 ◽

Vol 12 (4) ◽

pp. 489

Author(s):

Bartosz Łabiszak ◽

Witold Wachowiak

Keyword(s):

Gene Flow ◽

Reticulate Evolution ◽

Modeling Framework ◽

Closely Related Species ◽

Interspecific Gene Flow ◽

Nucleotide Sequence Variation ◽

History Of ◽

Best Fitting ◽

Species Integrity

Speciation mechanisms, including the role of interspecific gene flow and introgression in the emergence of new species, are the major focus of evolutionary studies. Inference of taxonomic relationship between closely related species may be challenged by past hybridization events, but at the same time, it may provide new knowledge about mechanisms responsible for the maintenance of species integrity despite interspecific gene flow. Here, using nucleotide sequence variation and utilizing a coalescent modeling framework, we tested the role of hybridization and introgression in the evolutionary history of closely related pine taxa from the Pinus mugo complex and P. sylvestris. We compared the patterns of polymorphism and divergence between taxa and found a great overlap of neutral variation within the P. mugo complex. Our phylogeny reconstruction indicated multiple instances of reticulation events in the past, suggesting an important role of interspecific gene flow in the species divergence. The best-fitting model revealed P. mugo and P. uncinata as sister species with basal P. uliginosa and asymmetric migration between all investigated species after their divergence. The magnitude of interspecies gene flow differed greatly, and it was consistently stronger from representatives of P. mugo complex to P. sylvestris than in the opposite direction. The results indicate the prominent role of reticulation evolution in those forest trees and provide a genetic framework to study species integrity maintained by selection and local adaptation.

The Role of Cdh1p in Maintaining Genomic Stability in Budding Yeast

Genetics ◽

10.1093/genetics/165.2.489 ◽

2003 ◽

Vol 165 (2) ◽

pp. 489-503 ◽

Cited By ~ 1

Author(s):

Karen E Ross ◽

Orna Cohen-Fix

Keyword(s):

Cell Cycle ◽

Chromosome Segregation ◽

Spindle Assembly Checkpoint ◽

Chromosome Loss ◽

Cyclin Dependent Kinase ◽

Anaphase Promoting Complex ◽

Growth Defects ◽

Genes Encoding ◽

Specificity Factor

Abstract Cdh1p, a substrate specificity factor for the cell cycle-regulated ubiquitin ligase, the anaphase-promoting complex/cyclosome (APC/C), promotes exit from mitosis by directing the degradation of a number of proteins, including the mitotic cyclins. Here we present evidence that Cdh1p activity at the M/G1 transition is important not only for mitotic exit but also for high-fidelity chromosome segregation in the subsequent cell cycle. CDH1 showed genetic interactions with MAD2 and PDS1, genes encoding components of the mitotic spindle assembly checkpoint that acts at metaphase to prevent premature chromosome segregation. Unlike cdh1Δ and mad2Δ single mutants, the mad2Δ cdh1Δ double mutant grew slowly and exhibited high rates of chromosome and plasmid loss. Simultaneous deletion of PDS1 and CDH1 caused extensive chromosome missegregation and cell death. Our data suggest that at least part of the chromosome loss can be attributed to kinetochore/spindle problems. Our data further suggest that Cdh1p and Sic1p, a Cdc28p/Clb inhibitor, have overlapping as well as nonoverlapping roles in ensuring proper chromosome segregation. The severe growth defects of both mad2Δ cdh1Δ and pds1Δ cdh1Δ strains were rescued by overexpressing Swe1p, a G2/M inhibitor of the cyclin-dependent kinase, Cdc28p/Clb. We propose that the failure to degrade cyclins at the end of mitosis leaves cdh1Δ mutant strains with abnormal Cdc28p/Clb activity that interferes with proper chromosome segregation.

Bub1 mediates cell death in response to chromosome missegregation and acts to suppress spontaneous tumorigenesis

The Journal of Cell Biology ◽

10.1083/jcb.200706015 ◽

2007 ◽

Vol 179 (2) ◽

pp. 255-267 ◽

Cited By ~ 147

Author(s):

Karthik Jeganathan ◽

Liviu Malureanu ◽

Darren J. Baker ◽

Susan C. Abraham ◽

Jan M. van Deursen

Keyword(s):

Cell Death ◽

Chromosome Segregation ◽

Physiological Role ◽

Mitotic Checkpoint ◽

Critical Threshold ◽

Wild Type ◽

Checkpoint Protein ◽

Chromosome Missegregation ◽

Mitotic Checkpoint Protein

The physiological role of the mitotic checkpoint protein Bub1 is unknown. To study this role, we generated a series of mutant mice with a gradient of reduced Bub1 expression using wild-type, hypomorphic, and knockout alleles. Bub1 hypomorphic mice are viable, fertile, and overtly normal despite weakened mitotic checkpoint activity and high percentages of aneuploid cells. Bub1 haploinsufficient mice, which have a milder reduction in Bub1 protein than Bub1 hypomorphic mice, also exhibit reduced checkpoint activity and increased aneuploidy, but to a lesser extent. Although cells from Bub1 hypomorphic and haploinsufficient mice have similar rates of chromosome missegregation, cell death after an aberrant separation decreases dramatically with declining Bub1 levels. Importantly, Bub1 hypomorphic mice are highly susceptible to spontaneous tumors, whereas Bub1 haploinsufficient mice are not. These findings demonstrate that loss of Bub1 below a critical threshold drives spontaneous tumorigenesis and suggest that in addition to ensuring proper chromosome segregation, Bub1 is important for mediating cell death when chromosomes missegregate.

Persisting demibivalents: a unique meiotic behaviour in Cuscuta babylonica Choisy

Genome ◽

10.1139/g87-010 ◽

1987 ◽

Vol 29 (1) ◽

pp. 63-66 ◽

Cited By ~ 14

Author(s):

Batia Pazy ◽

Uzi Plitmann

Keyword(s):

Key Words ◽

Chromosome Segregation ◽

Meiotic Behaviour ◽

Chromosome Behaviour ◽

Chromosome Movement ◽

Pollen Mother Cells ◽

Key Words Meiosis ◽

Mother Cells ◽

Telomeric Association

Idiosyncratic chromosome behaviour during meiosis was found in pollen mother cells of Cuscuta babylonica Choisy, a thread-like holoparasitic herb. Its main features are among the following: (i) telomeric association between homologues through most stages of the process, which leads to persisting chromatid bivalents (= "demibivalents"); (ii) uncommon chromosome segregation in first and second anaphase; and (iii) prolonged intensified heterochromatinization. Although "regular" in its own way, this process leads to the formation of unviable products. Its further investigation might contribute to our understanding of the role of the spindle and chromosome movement in the ordinary process of meiosis. Key words: meiosis (abnormal), persisting demibivalents, Cuscuta babylonica.

fumble Encodes a Pantothenate Kinase Homolog Required for Proper Mitosis and Meiosis in Drosophila melanogaster

Genetics ◽

10.1093/genetics/157.3.1267 ◽

2001 ◽

Vol 157 (3) ◽

pp. 1267-1276

Author(s):

Katayoun Afshar ◽

Pierre Gönczy ◽

Stephen DiNardo ◽

Steven A Wasserman

Keyword(s):

Cell Division ◽

Chromosome Segregation ◽

Cell Division Cycle ◽

Protein Isoforms ◽

Pantothenate Kinase ◽

Male Germline ◽

Dividing Cells ◽

Mutant Cells ◽

Mitosis And Meiosis

Abstract A number of fundamental processes comprise the cell division cycle, including spindle formation, chromosome segregation, and cytokinesis. Our current understanding of these processes has benefited from the isolation and analysis of mutants, with the meiotic divisions in the male germline of Drosophila being particularly well suited to the identification of the required genes. We show here that the fumble (fbl) gene is required for cell division in Drosophila. We find that dividing cells in fbl-deficient testes exhibit abnormalities in bipolar spindle organization, chromosome segregation, and contractile ring formation. Cytological analysis of larval neuroblasts from null mutants reveals a reduced mitotic index and the presence of polyploid cells. Molecular analysis demonstrates that fbl encodes three protein isoforms, all of which contain a domain with high similarity to the pantothenate kinases of A. nidulans and mouse. The largest Fumble isoform is dispersed in the cytoplasm during interphase, concentrates around the spindle at metaphase, and localizes to the spindle midbody at telophase. During early embryonic development, the protein localizes to areas of membrane deposition and/or rearrangement, such as the metaphase and cellularization furrows. Given the role of pantothenate kinase in production of Coenzyme A and in phospholipid biosynthesis, this pattern of localization is suggestive of a role for fbl in membrane synthesis. We propose that abnormalities in synthesis and redistribution of membranous structures during the cell division cycle underlie the cell division defects in fbl mutant cells.

The Muslim and the Law: A Brunei Experience

10.53105/jig.3-5 ◽

2017 ◽

Vol 3 ◽

Author(s):

Zabaidah Haji Kamaludin

Keyword(s):

Islamic Law ◽

Critical Factor ◽

Legal Issues ◽

Core Element ◽

The Core ◽

Ideal System ◽

The Law ◽

Islamic Values

An Islamic system of governance is an ideal system, which is a tantalising objective for many Muslims but often times not achieved in practice. Countries may call themselves ‘Islamic’ but the core element of Islamicity, that of values such as compassion, equity and justice may not have breached the consciousness of their leaders and citizens. Sometimes it is individuals who act as the catalyst for sparking action. For a Muslim, it is his īmān that serves to light his conscience, and guiding him the dispensation of his everyday tasks within his organisation. This individualised īmān may at times serve as a small but critical factor tilting the different organisational functions of government towards integrations under an Islamic system of governance. This paper recounts the challenges of a Muslim engaging in legal issues in a non-Islamic context, seeking to help enable his organisation to undertake the role of incorporating non-Islamic law with Islamic values.