Nuclear chromosome locations dictate segregation error frequencies

Chromosome segregation errors during cell divisions generate aneuploidies and micronuclei, which can undergo extensive chromosomal rearrangements such as chromothripsis [1, 2, 3, 4, 5]. Selective pressures then shape distinct aneuploidy and rearrangement patterns—for example, in cancer [6, 7] —but it is unknown whether initial biases in segregation errors and micronucleation exist for particular chromosomes. Using single-cell DNA sequencing [8] after an error-prone mitosis in untransformed, diploid cell lines and organoids, we show that chromosomes have different segregation error frequencies that result in non-random aneuploidy landscapes. Isolation and sequencing of single micronuclei from these cells showed that mis-segregating chromosomes frequently also preferentially become entrapped in micronuclei. A similar bias was found in naturally occurring micronuclei of two cancer cell lines. We find that segregation error frequencies of individual chromosomes correlate with their location in the interphase nucleus, and show that this is highest for peripheral chromosomes behind spindle poles. Randomization of chromosome positions, Cas9-mediated live tracking and forced repositioning of individual chromosomes showed that a greater distance from the nuclear centre directly increases the propensity to mis-segregate. Accordingly, chromothripsis in cancer genomes [9] and aneuploidies in early development [10] occur more frequently for larger chromosomes, which are preferentially located near the nuclear periphery. Our findings reveal a direct link between nuclear chromosome positions, segregation error frequencies and micronucleus content, with implications for our understanding of tumour genome evolution and the origins of specific aneuploidies during development. 1. van Jaarsveld, R. H. & Kops, G. J. P. L. Difference makers: chromosomal instability versus aneuploidy in cancer. Trends Cancer 2, 561–571 (2016). 2. Compton, D. A. Mechanisms of aneuploidy. Curr. Opin. Cell Biol. 23, 109–113 (2011). 3. Zhang, C. Z. et al. Chromothripsis from DNA damage in micronuclei. Nature 522, 179–184 (2015). 4. Ly, P. et al. Chromosome segregation errors generate a diverse spectrum of simple and complex genomic rearrangements. Nat. Genet. 51, 705–715 (2019). 5. Shoshani, O. et al. Chromothripsis drives the evolution of gene amplification in cancer. Nature 591, 137–141 (2021). 6. Davoli, T. et al. Cumulative haploinsufficiency and triplosensitivity drive aneuploidy patterns and shape the cancer genome. Cell 155, 948–962 (2013). 7. Knouse, K. A., Davoli, T., Elledge, S. J. & Amon, A. Aneuploidy in cancer: seq-ing answers to old questions. Annu. Rev. Cancer Biol. 1, 335–354 (2017). 8. Bolhaqueiro, A. C. F. et al. Ongoing chromosomal instability and karyotype evolution in human colorectal cancer organoids. Nat. Genet. 51, 824–834 (2019). 9. Cortés-Ciriano, I. et al. Comprehensive analysis of chromothripsis in 2, 658 human cancers using whole-genome sequencing. Nat. Genet. 52, 331–341 (2020). 10. McCoy, R. C. et al. Evidence of selection against complex mitotic-origin aneuploidy during preimplantation development. PLoS Genet. 348, 235–238 (2015)

Determination of Biogenic Amines and Endotoxin in Squid, Musky Octopus, Norway Lobster, and Mussel Stored at Room Temperature

Little research has been published on the indicators of spoilage in Mediterranean molluscan shellfi sh and crustaceans. Thus is why we studied changes in the concentrations of endotoxin and four biogenic amines (histamine, putrescine, tyramine and cadaverine) in European common squid (Loligo subulata, Lamarck, 1798), musky octopus (Eledone moschata, Lamarck, 1798), Norway lobster (Nephrops norvegicus, Linnaeus, 1758), and mussel (Mytilus galloprovincialis, Lamarck, 1819) from the Adriatic Sea stored at room temperature for 24 h. Endotoxin load in fresh squid, Norway lobster, and mussel (<1 EU mg-1) indicated good microbiological quality of raw samples. Biogenic amine index (as the sum of histamine, putrescine, tyramine, and cadaverine) correlated well with endotoxin load in squid (r=0.978, p<0.001) and musky octopus (r=0.874, p<0.01). A good correlation was also found between endotoxin and putrescine in Norway lobster (r=0.777, p<0.05). The highest endotoxin load was found in decomposed mussels and was associated with histamine alone. In conclusion, increase in biogenic amine levels is species-specific. Endotoxin analysis could be used for rapid assessment of microbiological quality of cephalopods and shellfish.Istraživanja o pokazateljima kontaminacije mekušaca i člankonožaca iz mediteranskih zemalja su rijetka. Cilj ovoga rada bio je ispitivanje koncentracije endotoksina i četiriju biogenih amina (histamin, putrescin, tiramin i kadaverin) u lignji (Loligo subulata, Lamarck, 1798), muzgavcu (Eledone moschata, Lamarck, 1798), škampima (Nephrops norvegicus, Linnaeus, 1758) i dagnji (Mytilus galloprovincialis, Lamarck, 1819) iz Jadranskog mora koji su bili pohranjeni na sobnoj temperaturi tijekom 24 h. Količina endotoksina u svježoj lignji, škampima i dagnji (<1 EU mg-1) upućuje na njihovu dobru mikrobiološku kvalitetu. Visoka korelacija ustanovljena je između indeksa biogenih amina (suma histamina, putrescina, tiramina i kadaverina) i endotoksina u lignji (r=0,978, p<0,001) i muzgavcu (r=0,874, p<0,01). Također je ustanovljena visoka korelacija između endotoksina i putrescina u škampima (r = 0,777, p<0,05). Najveća razina endotoksina (povezana s porastom histamina) ustanovljena je kod dagnje. U zaključku, porast biogenih amina je species-specifi čan. Analiza endotoksina mogla bi se primijeniti kao brza metoda za određivanje mikrobiološke ispravnosti mekušaca i člankonožaca