scholarly journals Telomerase and Alternative Lengthening of Telomeres coexist in the regenerating zebrafish caudal fins

2021 ◽  
Author(s):  
Maria L. Cayuela ◽  
Elena Martínez-Balsalobre ◽  
Monique Anchelin-Flageul ◽  
Francisca Alcaraz-Perez ◽  
Jesús García-Castillo ◽  
...  
Keyword(s):  
Telomere Length ◽  
Molecular Mechanisms ◽  
Regeneration Process ◽  
Wild Type ◽  
Alternative Lengthening Of Telomeres ◽  
Zebrafish Model ◽  
Alternative Lengthening ◽  
Vertebrate Model ◽  
New Treatments ◽  
Dependent Processes

Telomeres are essential for chromosome protection and genomic stability, and telomerase function is critical to organ homeostasis. Zebrafish has become a useful vertebrate model for understanding the cellular and molecular mechanisms of regeneration. The regeneration capacity of the caudal fin of wild-type zebrafish is not affected by repetitive amputation, but the behavior of telomeres during this process has not yet been studied. In this study, the regeneration process was characterized in a telomerase deficient zebrafish model. Moreover, the regenerative capacity after repetitive amputations and at different ages was studied. Regenerative efficiency decreases with aging in all genotypes and surprisingly, telomere length is maintained even in telomerase deficient genotypes. Our results suggest that telomere length can be maintained by the regenerating cells through the recombination-mediated Alternative Lengthening of Telomeres (ALT) pathway, which is likely to support high rates of cell proliferation during the tailfin regeneration process. As far as we know, this is the first animal model to study ALT mechanism in regeneration, which opens a wealth of possibilities to study new treatments of ALT dependent processes.

scholarly journals Alternative Lengthening of Telomeres and Chromatin Status

Genes ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 45 ◽  
Author(s):  
Ion Udroiu ◽  
Antonella Sgura
Keyword(s):  
Homologous Recombination ◽  
Reverse Transcriptase ◽  
Spatial Heterogeneity ◽  
Telomere Length ◽  
Epigenetic Modifications ◽  
Alternative Lengthening Of Telomeres ◽  
Telomere Elongation ◽  
Alternative Lengthening ◽  
Alt Activity

Telomere length is maintained by either telomerase, a reverse transcriptase, or alternative lengthening of telomeres (ALT), a mechanism that utilizes homologous recombination (HR) proteins. Since access to DNA for HR enzymes is regulated by the chromatin status, it is expected that telomere elongation is linked to epigenetic modifications. The aim of this review is to elucidate the epigenetic features of ALT-positive cells. In order to do this, it is first necessary to understand the telomeric chromatin peculiarities. So far, the epigenetic nature of telomeres is still controversial: some authors describe them as heterochromatic, while for others, they are euchromatic. Similarly, ALT activity should be characterized by the loss (according to most researchers) or formation (as claimed by a minority) of heterochromatin in telomeres. Besides reviewing the main works in this field and the most recent findings, some hypotheses involving the role of telomere non-canonical sequences and the possible spatial heterogeneity of telomeres are given.

scholarly journals Morphological, behavioral and molecular studies on CRISPR/Cas9-mediated knockout of the NOMO1 gene in zebrafish

2021 ◽  
Author(s):  
Fei Li ◽  
Tingting Li ◽  
Jia Lin ◽  
Jing Jian ◽  
Qi Zhang ◽  
...  
Keyword(s):  
Candidate Gene ◽  
Molecular Mechanisms ◽  
Expression Patterns ◽  
Neuropsychiatric Disorders ◽  
Repetitive Behaviors ◽  
Loss Of Function ◽  
Zebrafish Model ◽  
Functional Studies ◽  
Vertebrate Model ◽  
Morphological Differences

Abstract Background: Multiple clinical genome-wide analysis identified that chromosome 16p13.11 is a hotspot associated with neuropsychiatric disorders such as autism, schizophrenia and epilepsy. Nodal modulator 1 (NOMO1), located on human chromosome 16p13.11, was considered as a candidate gene with neuropsychiatric disorders. However, it is unknown whether the nomo1 deficiency causes neurological abnormalities, and the molecular mechanisms and pathogenesis of the NOMO1 gene remain unclear. To study the effects of nomo1 deficiency on brain development and neuropsychiatric system, a nomo1 knockout zebrafish model was established.Methods: We developed a viable vertebrate model of nomo1 loss-of-function using CRISPR/Cas9 technology and characterized nomo1 mutant zebrafish. Phenotypic and functional studies of developing nomo1 mutant zebrafish, including morphological measurements, behavioral assays, and functional mechanistic analyses, were performed.Results: Morphological differences in the phenotype of nomo1-/- zebrafish gradually became less noticeable during development, however, the enlarged interstitial spaces in midbrain and hindbrain were detected in nomo1 mutant zebrafish. Meanwhile, the nomo1 deficiency caused the change of expression levels in neurotransmitters of γ-aminobutyrate, glutamate and serotonin. Interestingly, the nomo1 loss-of-function zebrafish model exhibited social defects and repetitive behaviors in juvenile, which represented autism-like behaviors. The transcriptome analysis showed different gene expression patterns in mutant zebrafish at the genetic level. Further results revealed that the neuroactive drug PTZ recovered the decreased locomotor phenotype in larval mutant zebrafish.Conclusions: In this study, we established a nomo1 vertebrate animal model using CRISPR/Cas9 gene editing approach. The loss-of-function of nomo1 displayed autism-like behaviors and altered levels of the γ-aminobutyrate, glutamate and serotonin in zebrafish, which provide evidence that nomo1 as a candidate gene for autism. The versatility of zebrafish model is contributed to studying NOMO1-related disorders and conducting drug screening in future.Limitations: Further studies are needed to determine whether an intervention with a neuroactive drug in nomo1-/- zebrafish to alter the behavioral phenotype is applicable to the behavior of human patients.

scholarly journals TCGA Pan-Cancer genomic analysis of Alternative Lengthening of Telomeres (ALT) related genes

2020 ◽  
Author(s):  
Isaac Armendáriz-Castillo ◽  
Andrés López-Cortés ◽  
Jennyfer García-Cárdenas ◽  
Patricia Guevara-Ramírez ◽  
Paola E. Leone ◽  
...  
Keyword(s):  
Homologous Recombination ◽  
Molecular Mechanisms ◽  
Ex Vivo ◽  
Genomic Analysis ◽  
Interaction Network ◽  
Telomere Maintenance ◽  
The Cancer Genome Atlas ◽  
Alternative Lengthening Of Telomeres ◽  
Alternative Lengthening ◽  
Pan Cancer

AbstractTelomere maintenance mechanisms (TMM) are used by cancer cells to avoid apoptosis, 85-90% reactivate telomerase, while 10-15% use the alternative lengthening of telomeres (ALT). Due to anti-telomerase-based treatments, some tumors have the ability to switch from a telomerase-dependent mechanism to ALT, in fact, the co-existence between telomerase and the ALT pathway have been observed in a variety of cancer types. Despite different elements in the ALT pathway have been uncovered, the molecular mechanism and other factors are still poorly understood, which difficult the detection and treatment of ALT-positive cells, which are known to present poor prognosis. Therefore, with the aim to identify potential molecular markers to be used in the study of ALT, we combined simplistic in silico approaches in 411 telomere maintenance (TM) genes which have been previously validated or predicted to be involved in the ALT pathway. In consequence, we conducted a genomic analysis of these genes in 31 Pan-Cancer Atlas studies (n=9,282) from The Cancer Genome Atlas in the cBioPortal and found 325,936 genomic alterations, being mRNA high and low the top alterations with 65,.8% and 10.7% respectively. Moreover, we analyzed the highest frequency means of genomics alterations, identified and proposed 20 genes, which are highly mutated and up and down regulated in the cancer studies and could be used for future analysis in the study of ALT. Finally, we made a protein-protein interaction network and enrichment analysis to obtain an insight into the main pathways these genes are involved. We could observe their role in main processes related to the ALT mechanism like homologous recombination, homology directed repair (HDR), HDR through homologous recombination and telomere maintenance and organization.. Overall, due to the lack of understanding of the molecular mechanisms and detection of ALT-positive cancers, we identified and proposed more molecular targets that can be used for expression analysis and additional ex vivo assays to validate them as new potential therapeutic markers in the study of the ALT mechanism.

scholarly journals Alternative lengthening of telomeres in molecular subgroups of paediatric high-grade glioma

2020 ◽  
Author(s):  
Simone Minasi ◽  
Caterina Baldi ◽  
Francesca Gianno ◽  
Manila Antonelli ◽  
Anna Maria Buccoliero ◽  
...  
Keyword(s):  
Telomere Length ◽  
Strong Association ◽  
High Grade Glioma ◽  
Genetic Alterations ◽  
High Grade ◽  
Molecular Subgroups ◽  
Alternative Lengthening Of Telomeres ◽  
Telomere Elongation ◽  
K27m Mutation ◽  
Alternative Lengthening

Abstract Purpose The maintenance of telomere length prevents cancer cell senescence and occurs via two mutually exclusive mechanisms: (a) reactivation of telomerase expression and (b) activation of alternative lengthening of telomeres (ALT). ALT is frequently related to alterations on ATRX, a chromatin-remodelling protein. Recent data have identified different molecular subgroups of paediatric high-grade glioma (pHGG) with mutations of H3F3A, TERTp and ATRX; however, differences in telomere length among these molecular subgroups were not thoroughly examined. Methods We investigated which genetic alterations trigger the ALT mechanism in 52 IDH-wildtype, 1p/19q-wildtype pHGG. Samples were analysed for telomere length using Tel-FISH. ATRX nuclear loss of expression was assessed by IHC, H3F3A and TERTp mutations by DNA sequencing, and TERTp methylation by MS-PCR. Results Mutant H3.3 was found in 21 cases (40.3%): 19.2% with K27M mutation and 21.1% with G34R mutation. All H3.3G34R-mutated cases showed the ALT phenotype (100%); on the opposite, only 40% of the H3.3K27M-mutated showed ALT activation. ATRX nuclear loss was seen in 16 cases (30.7%), associated sometimes with the G34R mutation, and never with the K27M mutation. ATRX nuclear loss was always related to telomere elongation. TERTp C250T mutations were rare (5.4%) and were not associated with high intensity Tel-FISH signals, as TERTp hyper-methylation detected in 21% of the cases. H3.3/ATRX/TERTp-wildtype pHGG revealed all basal levels of telomere length. Conclusion Our results show a strong association between H3.3 mutations and ALT, and highlight the different telomeric profiles in histone-defined subgroups: H3.3-G34R mutants always trigger ALT to maintain telomere length, irrespective of ATRX status, whereas only some H3.3-K27M tumours activate ALT. These findings suggest that acquiring the gly34 mutation on H3.3 might suffice to trigger the ALT mechanism.

scholarly journals TCGA Pan-Cancer Genomic Analysis of Alternative Lengthening of Telomeres (ALT) Related Genes

Genes ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 834
Author(s):  
Isaac Armendáriz-Castillo ◽  
Andrés López-Cortés ◽  
Jennyfer García-Cárdenas ◽  
Patricia Guevara-Ramírez ◽  
Paola E. Leone ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Ex Vivo ◽  
Genomic Analysis ◽  
Interaction Network ◽  
Enrichment Analysis ◽  
Telomere Maintenance ◽  
The Cancer Genome Atlas ◽  
Alternative Lengthening Of Telomeres ◽  
Alternative Lengthening ◽  
Pan Cancer

Telomere maintenance mechanisms (TMM) are used by cancer cells to avoid apoptosis, 85–90% reactivate telomerase, while 10–15% use the alternative lengthening of telomeres (ALT). Due to anti-telomerase-based treatments, some tumors switch from a telomerase-dependent mechanism to ALT; in fact, the co-existence between both mechanisms has been observed in some cancers. Although different elements in the ALT pathway are uncovered, some molecular mechanisms are still poorly understood. Therefore, with the aim to identify potential molecular markers for the study of ALT, we combined in silico approaches in a 411 telomere maintenance gene set. As a consequence, we conducted a genomic analysis of these genes in 31 Pan-Cancer Atlas studies from The Cancer Genome Atlas and found 325,936 genomic alterations; from which, we identified 20 genes highly mutated in the cancer studies. Finally, we made a protein-protein interaction network and enrichment analysis to observe the main pathways of these genes and discuss their role in ALT-related processes, like homologous recombination and homology directed repair. Overall, due to the lack of understanding of the molecular mechanisms of ALT cancers, we proposed a group of genes, which after ex vivo validations, could represent new potential therapeutic markers in the study of ALT.

Sign in / Sign up

Export Citation Format

Share Document