Feng H, Thompson EM.

Front Cell Dev Biol. 2023 Dec 7;11:1323378. doi:10.3389/fcell.2023.1323378

Functional specialization of Aurora kinase homologs during oogenic meiosis in the tunicate Oikopleura dioica.

“a C-terminal GFP fusion [of OdAur1] was localized on centrosomes throughout mitosis” “a commercial phospho-Aurora antibody that can recognize the phosphorylated forms of both Aurora1 and Aurora2 in O. dioica [localised] on centrosomes and chromosomes in prophase and metaphase, and on centrosomes and the central spindle in anaphase” “This suggests that Aurora1 and Aurora2 in O. dioica represent the polar and equatorial forms of Aurora kinases”. “[Knockdown] suggests that Aurora1 is involved in promoting the progression of prometaphase I. In all the Aur2 KD oocytes, both H3-pS10 and H3-pS28 were absent, and chromosomes were decondensed, reminiscent of INCENPa knockdown phenotypes”

Ma X, Øvrebø JI, Thompson EM.

Front Cell Dev Biol. 2022 Jan 28;9:770939. doi:10.3389/fcell.2021.770939

Evolution of CDK1 Paralog Specializations in a Lineage With Fast Developing Planktonic Embryos.

The last common ancestors of all oiks probably had only one CDK1 as Fritillaria borealis also has only 1. Oiks in general have 3 paralogs (a, b, c), and O. dioica has 5 (a, b, c, plus d and e which appear to originate from c). They are found on chr1 (c, e), chr2, (a, b) and the XSR of chr3 (d). CycBa is also found on the XSR, and interacts with CDK1d for functions essential to meiosis of oocytes. In contrary to the ancestral CDK1 in other animals, the levels of CDK1d oscillate. “Interspecies clustering of CDK1 paralogs [show] conservation of their intron-exon structures” “O. dioica CDK1a and b locate on the same autosome whereas CDK1c is present on a different autosome that also contains CDK1e. CDK1d is found on the X chromosome where, at a distance of 5 MB, the CycBa locus is also located.” “The PSTAIRE helix is modified in all Oikopleura CDK1 paralogs whereas Oikopleura CDK2s retain the canonical PSTAIRE sequence. All of the 17 identified Oikopleura CDK1 sequences share the A48S substitution.”

Dev Biol. 2022 Jan;481:188-200. doi:10.1016/j.ydbio.2021.10.009

Nishida H, Matsuo M, Konishi S, Ohno N, Manni L, Onuma TA.

Germline development during embryogenesis of the larvacean, Oikopleura dioica.

Identified a CAB (centrosome-attracting body) “for the following reasons. (1) There was a clear boundary between the CAB-like region and the general cytoplasm, but the membrane structure did not surround the CAB. (2) It contained an electron-dense matrix that resembled a germplasm. (3) The region was devoid of mitochondria but contained ER. (4) It was present beneath the cell membrane, and the cell surface exhibited microvilli. (5) It was present in the germline lineage cells.” ”The longest diameter of the CAB was approximately 10 ​μm.“ It was observed between the late 8-cell stage and some 1.5-h embryos, but not after 2h. It was stained by the H3S28p rat monoclonal antibody (Abcam ab10543) but not by DAPI. The snail mRNA also colocalises with the CAB's H3S28p staining. A germ body (GB) “appeared [in PGCs] 13 ​min after the 5th cleavage [and] disappeared 1.5 ​h after fertilization at 20 ​°C. It is discussed whether the GB and the CAB are or are not the same structure.

Øvrebø JI, Campsteijn C, Kourtesis I, Hausen H, Raasholm M, Thompson EM.

Cell Cycle. 2015;14(6):880-93. doi:10.1080/15384101.2015.1006000

Functional specialization of chordate CDK1 paralogs during oogenic meiosis.

”Differential spatiotemporal dynamics of the odCDK1a, d and e paralogs and the meiotic polo-like kinase 1 (Plk1) and aurora kinase determine the subset of meiotic nuclei in prophase I arrest that will seed growing oocytes and complete meiosis. Whereas we find odCDK1e to be non-essential, knockdown of the odCDK1a paralog resulted in the spawning of non-viable oocytes of reduced size. Knockdown of odCDK1d also resulted in the spawning of non-viable oocytes. In this case, the oocytes were of normal size, but were unable to extrude polar bodies upon exposure to sperm, because they were unable to resume meiosis from prophase I arrest, a classical function of the sole CDK1 during meiosis in other organisms.“

Ganot P, Moosmann-Schulmeister A, Thompson EM.

Dev Biol. 2008 Dec 15;324(2):266-76. doi:10.1016/j.ydbio.2008.09.016

Oocyte selection is concurrent with meiosis resumption in the coenocystic oogenesis of Oikopleura.

H3S28p signal grows becomes highest only in the subset of H2S10p-labeled oocytes that become selected for maturation. MAPK inhibition has a similar effect to microtubule destabilisation.

Mol Biol Evol. 2012 Feb;29(2):487-502. doi:10.1093/molbev/msr136

Campsteijn C, Ovrebø JI, Karlsen BO, Thompson EM.

Expansion of cyclin D and CDK1 paralogs in Oikopleura dioica, a chordate employing diverse cell cycle variants.

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Cell Cycle. 2019 Jul 15:1-20. doi:10.1080/15384101.2019.1634954

Feng H, Raasholm M, Moosmann A, Campsteijn C, Thompson EM.

Switching of INCENP paralogs controls transitions in mitotic chromosomal passenger complex functions.

Components of the constitutive centromere-associated network (CCAN) at the inner kinetochore seem to be missing in the genome. H3T3p and H3S28p mark inner centromeric regions (single spots) and H3T11p mark outer centromeric regions (pairs of spots). Fluorescent microscopy pictures supporting a 2 × 3 karyotype.

PLoS One. 2014 Apr 2;9(4):e93787. doi:10.1371/journal.pone.0093787

Subramaniam G, Campsteijn C, Thompson EM.

Lifespan extension in a semelparous chordate occurs via developmental growth arrest just prior to meiotic entry.

Growth arrest (GA) discovered by culturing animals in crowded conditions, but can also be striggered by reduction of food intake before D4. After that, starvation reduces the number of gametes produced instead of inducing GA. In GA, cell cycle stops in both the somatic and germ lines. GA can also be induced by the TOR inhibitor CCI-779. Animals in GA can survice up to ~18 days at 15°C.

Spada F, Chioda M, Thompson EM.

J Cell Biochem. 2005 Aug 1;95(5):885-901. doi:10.1002/jcb.20416

Histone H4 post-translational modifications in chordate mitotic and endoreduplicative cell cycles.

Knobs are also seem to be in H4K20me2. In endocycling cells, H4K20me2 tends to be stronger in BrdU-negative (short pulse) cells. CldU/IdU staining confirms that H4K20me2 decreases during the S phase of endocycling cells. In mitotically cycling cells, BrdU-low cells tended to be H4K20me2-weak. Strong H3S28p and H3S10p staining (M phase markers) correlated with strong H4K20me2 staining. In NIH3T3 cells, H4K20me2 peaks at M phase and then decreases from G1 to G2. H4K16Ac stainings were not reproducible across antibodies.

Chromosome Res. 2007;15(2):189-201. doi:10.1007/s10577-006-1112-z

Schulmeister A, Schmid M, Thompson EM.

Phosphorylation of the histone H3.3 variant in mitosis and meiosis of the urochordate Oikopleura dioica.

Telomeric FISH stainings with a (TTAGGG)n probe. H3.3S31 is phosphorylated during mitosis and meiosis, and not in endocycling cells. “On prometaphase chromosomes [...] H3S28P was restricted to distal chromosomal regions adjacent to telomeres whereas H3.3S31P spread throughout entire chromosomes.” “[The histone 3.3 genes] contain introns, are found outside histone clusters and their transcripts are polyadenylated.”

Cell Cycle. 2018 Jul 4. doi:10.1080/15384101.2018.1486167

Feng H & Thompson EM

Specialization of CDK1 and Cyclin B paralog functions in a coenocystic mode of oogenic meiosis.

O. dioica has multiple CDK1 and Cyclin B paralogs.

Olsen LC, Kourtesis I, Busengdal H, Jensen MF, Hausen H, Chourrout D.

BMC Dev Biol. 2018 Feb 27;18(1):4. doi:10.1186/s12861-018-0165-5

Evidence for a centrosome-attracting body like structure in germ-soma segregation during early development, in the urochordate Oikopleura dioica.

Localised pumilio (pum1) and vasa (vas4) RNAs. Prior hatching, pum1 is found outside the embryo!