Chromosomal and cytoplasmic context determines predisposition to maternal age-related aneuploidy: brief overview and update on MCAK in mammalian oocytes

2010 ◽  
Vol 38 (6) ◽  
pp. 1681-1686 ◽  
Author(s):  
Ursula Eichenlaub-Ritter ◽  
Nora Staubach ◽  
Tom Trapphoff
Keyword(s):  
Cell Cycle ◽  
Chromosome Segregation ◽  
Maternal Age ◽  
Fluorescent Protein ◽  
Expression Patterns ◽  
Model Organisms ◽  
Aged Mouse ◽  
Protein Fusion ◽  
Mouse Oocytes ◽  
Age Related

It has been known for more than half a century that the risk of conceiving a child with trisomy increases with advanced maternal age. However, the origin of the high susceptibility to nondisjunction of whole chromosomes and precocious separation of sister chromatids, leading to aneuploidy in aged oocytes and embryos derived from them, cannot be traced back to a single disturbance and mechanism. Instead, analysis of recombination patterns of meiotic chromosomes of spread oocytes from embryonal ovary, and of origins and exchange patterns of extra chromosomes in trisomies, as well as morphological and molecular studies of oocytes and somatic cells from young and aged females, show chromosome-specific risk patterns and cellular aberrations related to the chronological age of the female. In addition, analysis of the function of meiotic- and cell-cycle-regulating genes in oogenesis, and the study of the spindle and chromosomal status of maturing oocytes, suggest that several events contribute synergistically to errors in chromosome segregation in aged oocytes in a chromosome-specific fashion. For instance, loss of cohesion may differentially predispose chromosomes with distal or pericentromeric chiasmata to nondisjunction. Studies on expression in young and aged oocytes from human or model organisms, like the mouse, indicate that the presence and functionality/activity of gene products involved in cell-cycle regulation, spindle formation and organelle integrity may be altered in aged oocytes, thus contributing to a high risk of error in chromosome segregation in meiosis I and II. Genes that are often altered in aged mouse oocytes include MCAK (mitotic-centromere-associated protein), a microtubule depolymerase, and AURKB (Aurora kinase B), a protein of the chromosomal passenger complex that has many targets and can also phosphorylate and regulate MCAK localization and activity. Therefore we explored the role of MCAK in maturing mouse oocytes by immunofluorescence, overexpression of a MCAK–EGFP (enhanced green fluorescent protein) fusion protein, knockdown of MCAK by RNAi (RNA interference) and inhibition of AURKB. The observations suggest that MCAK is involved in spindle regulation, chromosome congression and cell-cycle control, and that reductions in mRNA and protein in a context of permissive SAC (spindle assembly checkpoint) predispose to aneuploidy. Failure to recruit MCAK to centromeres and low expression patterns, as well as disturbances in regulation of enzyme localization and activity, e.g. due to alterations in activity of AURKB, may therefore contribute to maternal age-related rises in aneuploidy in mammalian oocytes.

scholarly journals Distinct classes of lagging chromosome underpin age-related oocyte aneuploidy in mouse

2021 ◽  
Author(s):  
Aleksandar I. Mihajlović ◽  
Jenna Haverfield ◽  
Greg FitzHarris
Keyword(s):  
Cell Cycle ◽  
Chromosome Segregation ◽  
Maternal Age ◽  
Class Ii ◽  
Class I ◽  
Mouse Oocytes ◽  
Age Related ◽  
Lagging Chromosome ◽  
Segregation Phenomenon ◽  
Meiosis I

SUMMARYChromosome segregation errors that cause oocyte aneuploidy increase in frequency with maternal age and are considered a major contributing factor of age-related fertility decline in females. A common age-associated chromosome segregation phenomenon in oocytes is the lagging anaphase chromosome, but whether anaphase laggards actually missegregate and cause aneuploidy is unclear. Here we show unexpectedly that lagging chromosomes in mouse oocytes comprise two mechanistically distinct classes of motion that we refer to as ‘Class-I’ and ‘Class-II’. We use imaging approaches and mechanistic interventions to dissociate the two classes, and find that whereas Class-II laggards are benign, Class-I laggards can directly cause aneuploidy. Most notably, a controlled prolongation of meiosis-I specifically lessens Class-I lagging to prevent aneuploidy. Our data thus reveal lagging chromosomes to be a cause of age-related aneuploidy in mouse oocytes and suggest that manipulating the cell cycle could increase the yield of useful oocytes in some contexts.

scholarly journals Structure and Location Studies on Key Enzymes in Saponins Biosynthesis of Panax notoginseng

2019 ◽  
Vol 20 (24) ◽  
pp. 6121
Author(s):  
Pengguo Xia ◽  
Yujie Zheng ◽  
Zongsuo Liang
Keyword(s):  
Subcellular Localization ◽  
Fluorescent Protein ◽  
Expression Patterns ◽  
Three Dimensional ◽  
Panax Notoginseng ◽  
Squalene Epoxidase ◽  
Protein Fusion ◽  
Active Components ◽  
Key Enzymes ◽  
Saponin Biosynthesis

Panax notoginseng is one of the most widely used traditional herbs for the treatment of various diseases, in which saponins were the main active components. At present, the research of P. notoginseng mainly focused on the discovery of new compounds and pharmacology. However, there were few studies on the molecular mechanism of the synthesis of secondary metabolites of P. notoginseng. In our study, four coding sequences (CDS) encoding the key enzymes involved in saponin biosynthesis were cloned, namely farnesyl diphosphate synthase (FPS), squalene synthase (SS), squalene epoxidase (SE), and dammarenediol-II synthase (DS), which contained open reading frame (ORF) of 1029 bp, 1248 bp, 1614 bp, and 2310 bp, and coded 342, 415, 537, and 769 amino acids, respectively. At the same time, their domains, secondary structures, three-dimensional structures, and phylogenetics trees were analyzed by kinds of bioinformatics tools. Their phylogenetics relationships were also analyzed. In addition, GFP (Green fluorescent protein) fusion genes were constructed by the plasmid transformation system to determine the subcellular localization. The results of subcellular localization showed that FPS, SE, and DS were mainly located in cytomembrane and its surrounding, while SS was located both in cytoplasm and cytomembrane. Our findings provided data demonstrating the expression patterns of genes involved in saponin biosynthesis and would facilitate efforts to further elucidate the biosynthesis of the bioactive components in P. notoginseng.

scholarly journals Sister kinetochore splitting and precocious disintegration of bivalents could explain the maternal age effect

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Agata P Zielinska ◽  
Zuzana Holubcova ◽  
Martyn Blayney ◽  
Kay Elder ◽  
Melina Schuh
Keyword(s):  
Chromosome Segregation ◽  
Maternal Age ◽  
Progenitor Cell ◽  
Pregnancy Loss ◽  
Functional Unit ◽  
Advanced Maternal Age ◽  
Chromosome Architecture ◽  
Age Related ◽  
Maternal Age Effect ◽  
Sister Kinetochore

Aneuploidy in human eggs is the leading cause of pregnancy loss and Down’s syndrome. Aneuploid eggs result from chromosome segregation errors when an egg develops from a progenitor cell, called an oocyte. The mechanisms that lead to an increase in aneuploidy with advanced maternal age are largely unclear. Here, we show that many sister kinetochores in human oocytes are separated and do not behave as a single functional unit during the first meiotic division. Having separated sister kinetochores allowed bivalents to rotate by 90 degrees on the spindle and increased the risk of merotelic kinetochore-microtubule attachments. Advanced maternal age led to an increase in sister kinetochore separation, rotated bivalents and merotelic attachments. Chromosome arm cohesion was weakened, and the fraction of bivalents that precociously dissociated into univalents was increased. Together, our data reveal multiple age-related changes in chromosome architecture that could explain why oocyte aneuploidy increases with advanced maternal age.

scholarly journals The Sudden Recruitment of γ-Tubulin to the Centrosome at the Onset of Mitosis and Its Dynamic Exchange Throughout the Cell Cycle, Do Not Require Microtubules

1999 ◽  
Vol 146 (3) ◽  
pp. 585-596 ◽  
Author(s):  
Alexey Khodjakov ◽  
Conly L. Rieder
Keyword(s):  
Cell Cycle ◽  
Green Fluorescent Protein ◽  
Fluorescence Recovery After Photobleaching ◽  
Fluorescent Protein ◽  
Green Fluorescent Protein Fusion ◽  
Protein Fusion ◽  
Green Fluorescent ◽  
Dynamic Exchange ◽  
Two Populations

γ-Tubulin is a centrosomal component involved in microtubule nucleation. To determine how this molecule behaves during the cell cycle, we have established several vertebrate somatic cell lines that constitutively express a γ-tubulin/green fluorescent protein fusion protein. Near simultaneous fluorescence and DIC light microscopy reveals that the amount of γ-tubulin associated with the centrosome remains relatively constant throughout interphase, suddenly increases during prophase, and then decreases to interphase levels as the cell exits mitosis. This mitosis-specific recruitment of γ-tubulin does not require microtubules. Fluorescence recovery after photobleaching (FRAP) studies reveal that the centrosome possesses two populations of γ-tubulin: one that turns over rapidly and another that is more tightly bound. The dynamic exchange of centrosome-associated γ-tubulin occurs throughout the cell cycle, including mitosis, and it does not require microtubules. These data are the first to characterize the dynamics of centrosome-associated γ-tubulin in vertebrate cells in vivo and to demonstrate the microtubule-independent nature of these dynamics. They reveal that the additional γ-tubulin required for spindle formation does not accumulate progressively at the centrosome during interphase. Rather, at the onset of mitosis, the centrosome suddenly gains the ability to bind greater than three times the amount of γ-tubulin than during interphase.

scholarly journals Polar Localization of the CckA Histidine Kinase and Cell Cycle Periodicity of the Essential Master Regulator CtrA in Caulobacter crescentus

2009 ◽  
Vol 192 (2) ◽  
pp. 539-552 ◽  
Author(s):  
Peter S. Angelastro ◽  
Oleksii Sliusarenko ◽  
Christine Jacobs-Wagner
Keyword(s):  
Cell Cycle ◽  
Histidine Kinase ◽  
Cell Cycle Progression ◽  
Fluorescent Protein ◽  
Caulobacter Crescentus ◽  
Replication Initiation ◽  
Protein Fusion ◽  
Cycle Progression ◽  
Polar Localization ◽  
And Function

ABSTRACT The phosphorylated form of the response regulator CtrA represses DNA replication initiation and regulates the transcription of about 100 cell cycle-regulated genes in Caulobacter crescentus. CtrA activity fluctuates during the cell cycle, and its periodicity is a key element of the engine that drives cell cycle progression. The histidine kinase CckA controls the phosphorylation not only of CtrA but also of CpdR, whose unphosphorylated form promotes CtrA proteolysis. Thus, CckA has a central role in establishing the cell cycle periodicity of CtrA activity by controlling both its phosphorylation and stability. Evidence suggests that the polar localization of CckA during the cell cycle plays a role in CckA function. However, the exact pattern of CckA localization remains controversial. Here, we describe a thorough, quantitative analysis of the spatiotemporal distribution of a functional and chromosomally produced CckA-monomeric green fluorescent protein fusion that affects current models of cell cycle regulation. We also identify two cis-acting regions in CckA that are important for its proper localization and function. The disruption of a PAS-like motif in the sensor domain affects the stability of CckA accumulation at the poles. This is accompanied by a partial loss in CckA function. Shortening an extended linker between β-sheets within the CckA catalysis-assisting ATP-binding domain has a more severe effect on CckA polar localization and function. This mutant strain exhibits a dramatic cell-to-cell variability in CpdR levels and CtrA cell cycle periodicity, suggesting that the cell cycle-coordinated polar localization of CckA may be important for the robustness of signal transduction and cell cycle progression.

scholarly journals Identification of Genes Periodically Expressed in the Human Cell Cycle and Their Expression in Tumors

2002 ◽  
Vol 13 (6) ◽  
pp. 1977-2000 ◽  
Author(s):  
Michael L. Whitfield ◽  
Gavin Sherlock ◽  
Alok J. Saldanha ◽  
John I. Murray ◽  
Catherine A. Ball ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Hela Cell ◽  
Chromosome Segregation ◽  
Human Cancer ◽  
Expression Patterns ◽  
Cancer Cell Line ◽  
Periodic Variation ◽  
Starting Point ◽  
Cell Line Hela

The genome-wide program of gene expression during the cell division cycle in a human cancer cell line (HeLa) was characterized using cDNA microarrays. Transcripts of >850 genes showed periodic variation during the cell cycle. Hierarchical clustering of the expression patterns revealed coexpressed groups of previously well-characterized genes involved in essential cell cycle processes such as DNA replication, chromosome segregation, and cell adhesion along with genes of uncharacterized function. Most of the genes whose expression had previously been reported to correlate with the proliferative state of tumors were found herein also to be periodically expressed during the HeLa cell cycle. However, some of the genes periodically expressed in the HeLa cell cycle do not have a consistent correlation with tumor proliferation. Cell cycle-regulated transcripts of genes involved in fundamental processes such as DNA replication and chromosome segregation seem to be more highly expressed in proliferative tumors simply because they contain more cycling cells. The data in this report provide a comprehensive catalog of cell cycle regulated genes that can serve as a starting point for functional discovery. The full dataset is available at http://genome-www.stanford.edu/Human-CellCycle/HeLa/ .

scholarly journals Nuclear speckle specific hnRNP D-like prevents age- and AD-related cognitive decline by modulating RNA splicing

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Qingyang Zhang ◽  
Juan Zhang ◽  
Jin Ye ◽  
Xiaohui Li ◽  
Hongda Liu ◽  
...  
Keyword(s):  
Alternative Splicing ◽  
Rna Splicing ◽  
Expression Patterns ◽  
Critical Role ◽  
Aged Mouse ◽  
Nuclear Speckles ◽  
Direct Role ◽  
Age Related ◽  
Hnrnp D ◽  
Behavioural Tests

Abstract Background Aberrant alternative splicing plays critical role in aging and age-related diseases. Heterogeneous nuclear ribonucleoproteins (hnRNPs) reportedly regulate RNA splicing process. Whether and how hnRNPs contribute to age-related neurodegenerative diseases, especially Alzheimer’s disease (AD), remain elusive. Methods Immunoblotting and immunostaining were performed to determine expression patterns and cellular/subcellular localization of the long isoform of hnRNP D-like (L-DL), which is a hnRNP family member, in mouse hippocampus. Downregulation of L-DL in WT mice was achieved by AAV-mediated shRNA delivery, followed by memory-related behavioural tests. L-DL interactome was analysed by affinity-precipitation and mass spectrometry. Alternative RNA splicing was measured by RNA-seq and analyzed by bioinformatics-based approaches. Downregulation and upregulation of L-DL in APP/PS1 mice were performed using AAV-mediated transduction. Results We show that L-DL is specifically localized to nuclear speckles. L-DL levels are decreased in the hippocampus of aged mouse brains and downregulation of L-DL impairs cognition in mice. L-DL serves as a structural component to recruit other speckle proteins, and regulates cytoskeleton- and synapse-related gene expression by altering RNA splicing. Mechanistically, these splicing changes are modulated via L-DL-mediated interaction of SF3B3, a core component of U2 snRNP, and U2AF65, a U2 spliceosome protein that guides U2 snRNP’s binding to RNA. In addition, L-DL levels are decreased in APP/PS1 mouse brains. While downregulation of L-DL deteriorates memory deficits and overexpression of L-DL improves cognitive function in AD mice, by regulating the alternative splicing and expression of synaptic gene CAMKV. Conclusions Our findings define a molecular mechanism by which hnRNP L-DL regulates alternative RNA splicing, and establish a direct role for L-DL in AD-related synaptic dysfunction and memory decline.

scholarly journals Role of an FtsK-Like Protein in Genetic Stability in Streptomyces coelicolor A3(2)

2007 ◽  
Vol 189 (6) ◽  
pp. 2310-2318 ◽  
Author(s):  
Lei Wang ◽  
Yanfei Yu ◽  
Xinyi He ◽  
Xiufen Zhou ◽  
Zixin Deng ◽  
...  
Keyword(s):  
Cell Division ◽  
Chromosome Segregation ◽  
Fluorescent Protein ◽  
Streptomyces Coelicolor ◽  
Complex Life Cycle ◽  
Specific Gene ◽  
Chromosomal Dna ◽  
Protein Fusion ◽  
Fluorescent Reporter ◽  
Green Fluorescent

ABSTRACT Streptomyces coelicolor A3(2) does not have a canonical cell division cycle during most of its complex life cycle, yet it contains a gene (ftsKSC ) encoding a protein similar to FtsK, which couples the completion of cell division and chromosome segregation in unicellular bacteria such as Escherichia coli. Here, we show that various constructed ftsKSC mutants all grew apparently normally and sporulated but upon restreaking gave rise to many aberrant colonies and to high frequencies of chloramphenicol-sensitive mutants, a phenotype previously associated with large terminal deletions from the linear chromosome. Indeed, most of the aberrant colonies had lost large fragments near one or both chromosomal termini, as if chromosome ends had failed to reach their prespore destination before the closure of sporulation septa. A constructed FtsKSC-enhanced green fluorescent protein fusion protein was particularly abundant in aerial hyphae, forming distinctive complexes before localizing to each sporulation septum, suggesting a role for FtsKSC in chromosome segregation during sporulation. Use of a fluorescent reporter showed that when ftsKSC was deleted, several spore compartments in most spore chains failed to express the late-sporulation-specific sigma factor gene sigF, even though they contained chromosomal DNA. This suggested that sigF expression is autonomously activated in each spore compartment in response to completion of chromosome transfer, which would be a previously unknown checkpoint for late-sporulation-specific gene expression. These results provide new insight into the genetic instability prevalent among streptomycetes, including those used in the industrial production of antibiotics.

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