Heterochromatin endoreduplication prior to gametogenesis and chromatin diminution during early embryogenesis in Mesocyclops edax (Copepoda: Crustacea)

2007 ◽  
Vol 269 (4) ◽  
pp. 387-397 ◽  
Author(s):  
Ellen M. Rasch ◽  
Grace A. Wyngaard ◽  
Barbara A. Connelly
Keyword(s):  
Early Embryogenesis ◽  
Chromatin Diminution ◽  
Mesocyclops Edax

Chromatin Diminution in Cyclops kolensis Lill. (Copepoda, Crustacea) as a Radical Way to Inactivate Redundant Genome in Somatic Cells

2018 ◽  
Vol 156 (3) ◽  
pp. 165-172 ◽  
Author(s):  
Andrey K. Grishanin ◽  
Maxim V. Zagoskin
Keyword(s):  
Chromosome Number ◽  
Repetitive Sequences ◽  
Early Embryogenesis ◽  
Chromosome Size ◽  
Chromatin Diminution ◽  
Elimination Process ◽  
Dna Elimination ◽  
Molecular Studies ◽  
Cyclops Kolensis

Chromatin diminution (CD) is a phenomenon of programmed DNA elimination which takes place in early embryogenesis in some eukaryotes. The mechanism and biological role of CD remain largely unknown. During CD in the freshwater copepod Cyclops kolensis, the genome of cells of the somatic lineage is reorganized and reduced in size by more than 90% without affecting the genome of germline cells. Although the diploid chromosome number is unchanged, chromosome size is dramatically reduced by CD. The eliminated DNA consists primarily of repetitive sequences and localizes within granules during the elimination process. In this review, we provide an overview of CD in C. kolensis including both cytological and molecular studies.

Analysis of DNA Levels During Gonomery in Early Cleavage Divisions of the Freshwater Copepod Mesocyclops Edax

1997 ◽  
Vol 3 (S2) ◽  
pp. 191-192 ◽  
Author(s):  
E.M. Rasch ◽  
G.A. Wyngaard
Keyword(s):  
Acetic Acid ◽  
Early Cleavage ◽  
Chromatin Diminution ◽  
Cleavage Division ◽  
Relative Contribution ◽  
Male Genome ◽  
Egg Carrying ◽  
Mesocyclops Edax ◽  
Chromosome Regions ◽  
Absolute Etoh

Gonomery, the separate grouping of maternal and paternal chromosomes during the first few mitoses following fertilization (Fig. 1) and chromatin diminution, the fragmentation and elimination of whole chromosome regions during specific stages of early cleavage in all primordial cells of the soma, occur in several species of copepods, ascarid nematodes, ciliated protozoa, Japanese hagfish 9 and a few other invertebrates. Because of the marked loss of DNA from all presumptive somatic cells by selective chromatin diminution during the 4th cleavage division in M. edax, it was of interest to determine DNA levels in chromosomes during gonomery in anaphases preceding diminution (Fig. 1). It was also important to estimate the DNA content of sperm as an index of the relative contribution by the male genome at fertilization in this species.Mature males and egg-carrying females were fixed in 3:1 methanol/acetic acid for 3-5 mins, swollen in 45% acetic acid for 2-3 mins, squashed, frozen in liquid N2 for coverslip removal, thawed in 2 changes of absolute ETOH and air dried.

DNA levels in somatic and germ line cells of a freshwater crustacean, Mesocyclops edax

1995 ◽  
Vol 53 ◽  
pp. 924-925
Author(s):  
E. M. Rasch ◽  
G.A. Wyngaard
Keyword(s):  
Acetic Acid ◽  
Somatic Cell ◽  
Nuclear Dna ◽  
Germ Line ◽  
Internal Reference ◽  
Chromatin Diminution ◽  
Internal Reference Standard ◽  
Freshwater Crustacean ◽  
Mesocyclops Edax ◽  
Chromosome Regions

Chromatin diminution--the fragmentation and elimination of chromosome Regions--provides an unusual opportunity to study genomic reorganization during development. Some species of copepods regularly excise and discard large amounts of nuclear DNA from presumptive somatic cell lines during early cleavage stages . To study this phenomenon in M. edax we determined DNA-Feulgen levels for more than 5,600 individual nuclei from squash preparations of 30 female and 25 male adults collected from lakes in Nova Scotia, Virginia and Florida. Fixation in 3:1 methanol/acetic acid was followed by squashing individual specimens in 45% acetic acid, freezing each slide in liquid N2 and thawing in absolute ethanol before air drying. Each series of slides was stained with the feulgen reaction for DNA and measured with a Vickers M86 scanning and integrating microdensitometer at 560 nm, using chicken RBC nuclei as an internal reference standard of 2.5 pg DNA per cell. This allowed us to ask several questions: are there differences in genome size (1) among specimens from different collecting localities, (2) between females and males at any single locality, and (3) between cells of germ line and somatic cell lineages?

Chromatin diminution in the copepod Mesocyclops edax: diminution of tandemly repeated DNA families from somatic cells

Genome ◽  
2006 ◽  
Vol 49 (6) ◽  
pp. 657-665 ◽  
Author(s):  
Guy Drouin
Keyword(s):  
Dna Sequences ◽  
Germ Line ◽  
Somatic Cells ◽  
Repeated Sequences ◽  
Cyclopoid Copepod ◽  
Embryonic Cells ◽  
Repeated Dna ◽  
Chromatin Diminution ◽  
Mesocyclops Edax ◽  
Tandemly Repeated Dna

Chromatin diminution, i.e., the loss of selected chromosomal regions during the differentiation of early embryonic cells into somatic cells, has been described in taxa as varied as ciliates, copepods, insects, nematodes, and hagfish. The nature of the eliminated DNA has been extensively studied in ciliate, nematode, and hagfish species. However, the small size of copepods, which makes it difficult to obtain enough DNA from early embryonic cells for cloning and sequencing, has limited such studies. Here, to identify the sequences eliminated from the somatic cells of a copepod species that undergoes chromatin diminution, we randomly amplified DNA fragments from germ line and somatic line cells of Mesocyclops edax, a freshwater cyclopoid copepod. Of 47 randomly amplified germ line clones, 45 (96%) contained short, tandemly repeated sequences composed of either 2 bp CA-repeats, 8 bp CAAATAGA-repeats, or 9 bp CAAATTAAA-repeats. In contrast, of 83 randomly amplified somatic line clones, only 47 (57%) contained such short, tandemly repeated sequences. As previously observed in some nematode species, our results therefore show that there is partial elimination of chromosomal regions containing (CAAATAGA and CAAATTAAA) repeated sequences during the chromatin diminution observed in the somatic cells of M. edax. We speculate that chromatin diminution might have evolved repeatedly by recruitment of RNAi-related mechanisms to eliminate nonfunctional tandemly repeated DNA sequences from the somatic genome of some species.Key words: chromatin diminution, Mesocyclops edax, copepod, satellite DNA, hetorochromatin.

Chromatin diminution in the copepod Mesocyclops edax: elimination of both highly repetitive and nonhighly repetitive DNA

Genome ◽  
2013 ◽  
Vol 56 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Christian McKinnon ◽  
Guy Drouin
Keyword(s):  
Repetitive Dna ◽  
Tandem Repeats ◽  
Repetitive Sequences ◽  
Embryonic Cells ◽  
Chromatin Diminution ◽  
Developmentally Regulated ◽  
Dna Elimination ◽  
Eukaryotic Species ◽  
Cyclops Kolensis ◽  
Mesocyclops Edax

Chromatin diminution, a developmentally regulated process of DNA elimination, is found in numerous eukaryotic species. In the copepod Mesocyclops edax, some 90% of its genomic DNA is eliminated during the differentiation of embryonic cells into somatic cells. Previous studies have shown that the eliminated DNA contains highly repetitive sequences. Here, we sequenced DNA fragments from pre- and postdiminution cells to determine whether nonhighly repetitive sequences are also eliminated during the process of chromatin diminution. Comparative analyses of these sequences, as well as the sequences eliminated from the genome of the copepod Cyclops kolensis, show that they all share similar abundances of tandem repeats, dispersed repeats, transposable elements, and various coding and noncoding sequences. This suggests that, in the chromatin diminution observed in M. edax, both highly repetitive and nonhighly repetitive sequences are eliminated and that there is no bias in the type of nonhighly repetitive DNA being eliminated.

BIVALENT FORMING RACE OF MESOCYCLOPS EDAX (COPEPODA, CRUSTACEA)

1980 ◽  
Vol 22 (3) ◽  
pp. 427-431 ◽  
Author(s):  
C. C. Chinnappa
Keyword(s):  
Chromosome Morphology ◽  
Chromatin Diminution ◽  
Cleavage Division ◽  
Large Rings ◽  
Bivalent Formation ◽  
Cleavage Stages ◽  
Mesocyclops Edax

Meiosis and chromosome morphology in females of a bivalent forming race of Mesocyclops edax (S. A. Forbes) are described. Meiosis is achiasmate and exhibits regular bivalent formation (2n = 14). Chromosome analyses of other populations of M. edax revealed that the females are heterozygous for several interchanges leading to the formation of large rings. Chromatin diminution during cleavage stages suggests that the elimination of H-segments occurs at the fourth cleavage division.

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