William Brynildsen Reinar

• Araya, Robin Aasegg; Reinar, William Brynildsen; Tørresen, Ole K; Goubert, Clément; Daughton, Tara Jane & Hoff, Siv Nam Khang [Show all 12 contributors for this article] (2025). Chromosomal Inversions Mediated by Tandem Insertions of Transposable Elements. Genome Biology and Evolution (GBE). 17(8). doi: 10.1093/gbe/evaf131. Full text in Research Archive Show summary

  Chromosomal inversions play a crucial role in evolution by influencing phenotypes through the linkage of coadapted alleles. While inversions have been found across a large number of taxa, mapping and characterizing inversion breakpoint regions remain challenging, often due to the presence of complex tandem repeats and transposable elements. Here, we identify and quantify transposable elements in the breakpoints of the four large-scale inversions previously reported in Atlantic cod, leveraging on three high-quality long-read-based reference genome assemblies for the Norwegian Coastal cod, the Northeast Arctic cod, and Celtic cod ecotypes. We detected a significant enrichment of transposable element orders and superfamilies with terminal inverted repeats within the inversion breakpoint regions of chromosomes 1, 7 and 12. Notably, we discovered a tandem accumulation of miniature inverted-repeat transposable elements belonging to a family of hAT transposons, exclusively residing in the breakpoints of the inverted haplotype on chromosomes 1 and 7 found in the Northeast Arctic cod. The accumulation of tandemly arranged transposable elements with high sequence similarity in breakpoint regions suggests that they have driven the appearance of inversions through ectopic recombination, further supporting the potential of transposable elements in facilitating chromosomal reorganizations with large evolutionary implications.

• Reinar, William Brynildsen; Krabberød, Anders Kristian; Lalun, Vilde Olsson; Butenko, Melinka Alonso & Jakobsen, Kjetill Sigurd (2024). Short tandem repeats delineate gene bodies across eukaryotes. Nature Communications. 15(1), p. 1–13. doi: 10.1038/s41467-024-55276-w. Full text in Research Archive Show summary

  Short tandem repeats (STRs) have emerged as important and hypermutable sites where genetic variation correlates with gene expression in plant and animal systems. Recently, it has been shown that a broad range of transcription factors (TFs) are affected by STRs near or in the DNA target binding site. Despite this, the distribution of STR motif repetitiveness in eukaryote genomes is still largely unknown. Here, we identify monomer and dimer STR motif repetitiveness in 5.1 billion 10-bp windows upstream of translation starts and downstream of translation stops in 25 million genes spanning 1270 species across the eukaryotic Tree of Life. We report that all surveyed genomes have gene-proximal shifts in motif repetitiveness. Within genomes, variation in gene-proximal repetitiveness landscapes correlated to the function of genes; genes with housekeeping functions were depleted in upstream and downstream repetitiveness. Furthermore, the repetitiveness landscapes correlated with TF binding sites, indicating that gene function has evolved in conjunction with cis-regulatory STRs and TFs that recognize repetitive sites. These results suggest that the hypermutability inherent to STRs is canalized along the genome sequence and contributes to regulatory and eco-evolutionary dynamics in all eukaryotes.

• Reinar, William Brynildsen; Tørresen, Ole K.; Nederbragt, Lex; Matschiner, Michael; Jentoft, Sissel & Jakobsen, Kjetill Sigurd (2023). Teleost genomic repeat landscapes in light of diversification rates and ecology. Mobile DNA. 14(1), p. 1–12. doi: 10.1186/s13100-023-00302-9. Full text in Research Archive Show summary

  Repetitive DNA make up a considerable fraction of most eukaryotic genomes. In fish, transposable element (TE) activity has coincided with rapid species diversification. Here, we annotated the repetitive content in 100 genome assemblies, covering the major branches of the diverse lineage of teleost fish. We investigated if TE content correlates with family level net diversification rates and found support for a weak negative correlation. Further, we demonstrated that TE proportion correlates with genome size, but not to the proportion of short tandem repeats (STRs), which implies independent evolutionary paths. Marine and freshwater fish had large differences in STR content, with the most extreme propagation detected in the genomes of codfish species and Atlantic herring. Such a high density of STRs is likely to increase the mutational load, which we propose could be counterbalanced by high fecundity as seen in codfishes and herring.

• Reinar, William Brynildsen; Greulich, Anne; Stø, Ida Myhrer; Knutsen, Jonfinn Mordekai Blix; Reitan, Trond & Tørresen, Ole K. [Show all 9 contributors for this article] (2023). Adaptive protein evolution through length variation of short tandem repeats in Arabidopsis. Science Advances. 9(12), p. 1–10. doi: 10.1126/sciadv.add6960. Full text in Research Archive Show summary

  Intrinsically disordered protein regions are of high importance for biotic and abiotic stress responses in plants. Tracts of identical amino acids accumulate in these regions and can vary in length over generations because of expansions and retractions of short tandem repeats at the genomic level. However, little attention has been paid to what extent length variation is shaped by natural selection. By environmental association analysis on 2514 length variable tracts in 770 whole-genome sequenced Arabidopsis thaliana, we show that length variation in glutamine and asparagine amino acid homopolymers, as well as in interaction hotspots, correlate with local bioclimatic habitat. We determined experimentally that the promoter activity of a light-stress gene depended on polyglutamine length variants in a disordered transcription factor. Our results show that length variations affect protein function and are likely adaptive. Length variants modulating protein function at a global genomic scale has implications for understanding protein evolution and eco-evolutionary biology.

• Reinar, William Brynildsen; Olsson, Vilde; Reitan, Trond; Jakobsen, Kjetill Sigurd & Butenko, Melinka Alonso (2021). Length variation in short tandem repeats affects gene expression in natural populations of Arabidopsis thaliana. The Plant Cell. ISSN 1040-4651. 33(7), p. 2221–2234. doi: 10.1093/plcell/koab107. Full text in Research Archive Show summary

  Abstract The genetic basis for the fine-tuned regulation of gene expression is complex and ultimately influences the phenotype and thus the local adaptation of natural populations. Short tandem repeats (STRs) consisting of repetitive DNA motifs have been shown to regulate gene expression. STRs are variable in length within a population and serve as a heritable, but semi-reversible, reservoir of standing genetic variation. For sessile organisms, such as plants, STRs could be of major importance in fine-tuning gene expression as a response to a shifting local environment. Here, we used a transcriptome dataset from natural accessions of Arabidopsis thaliana to investigate population-wide gene expression patterns in light of genome-wide STR variation. We empirically modeled gene expression as a response to the STR length within and around the gene and demonstrated that an association between gene expression and STR length variation is unequivocally present in the sampled population. To support our model, we explored the promoter activity in a transcriptional regulator involved in root hair formation and provided experimentally determined causality between coding sequence length variation and promoter activity. Our results support a general link between gene expression variation and STR length variation in A. thaliana.

• Wang, Nelson; Anonsen, Jan Haug; Hadjineophytou, Chris; Reinar, William Brynildsen; Børud, Bente & Vik, Åshild [Show all 7 contributors for this article] (2020). Allelic polymorphisms in a glycosyltransferase gene shape glycan repertoire in the O-linked protein glycosylation system of Neisseria. Glycobiology. ISSN 0959-6658. doi: 10.1093/glycob/cwaa073. Full text in Research Archive Show summary

  Glycosylation of multiple proteins via O-linkage is well documented in bacterial species of Neisseria of import to human disease. Recent studies of protein glycosylation (pgl) gene distribution established that related protein glycosylation systems occur throughout the genus including nonpathogenic species. However, there are inconsistencies between pgl gene status and observed glycan structures. One of these relates to the widespread distribution of pglG, encoding a glycosyltransferase that in Neisseria elongata subsp. glycolytica is responsible for the addition of di-N-acetyl glucuronic acid at the third position of a tetrasaccharide. Despite pglG residing in strains of N. gonorrhoeae, N. meningitidis and N. lactamica, no glycan structures have been correlated with its presence in these backgrounds. Moreover, PglG function in N. elongata subsp. glycolytica minimally requires UDP-glucuronic acid (GlcNAcA), and yet N. gonorrhoeae, N. meningitidis and N. lactamica lack pglJ, the gene whose product is essential for UDP-GlcNAcA synthesis. We examined the functionality of pglG alleles from species spanning the Neisseria genus by genetic complementation in N. elongata subsp. glycolytica. The results indicate that select pglG alleles from N. meningitidis and N. lactamica are associated with incorporation of an N-acetyl-hexosamine at the third position and reveal the potential for an expanded glycan repertoire in those species. Similar experiments using pglG from N. gonorrhoeae failed to find any evidence of function suggesting that those alleles are missense pseudogenes. Taken together, the results are emblematic of how allelic polymorphisms can shape bacterial glycosyltransferase function and demonstrate that such alterations may be constrained to distinct phylogenetic lineages.

• Tørresen, Ole Kristian; Star, Bastiaan; Jentoft, Sissel; Reinar, William Brynildsen; Grove, Harald & Miller, Jason R. [Show all 16 contributors for this article] (2017). An improved genome assembly uncovers prolific tandem repeats in Atlantic cod. BMC Genomics. 18(1), p. 1–23. doi: 10.1186/s12864-016-3448-x. Full text in Research Archive Show summary

  Background The first Atlantic cod (Gadus morhua) genome assembly published in 2011 was one of the early genome assemblies exclusively based on high-throughput 454 pyrosequencing. Since then, rapid advances in sequencing technologies have led to a multitude of assemblies generated for complex genomes, although many of these are of a fragmented nature with a significant fraction of bases in gaps. The development of long-read sequencing and improved software now enable the generation of more contiguous genome assemblies. Results By combining data from Illumina, 454 and the longer PacBio sequencing technologies, as well as integrating the results of multiple assembly programs, we have created a substantially improved version of the Atlantic cod genome assembly. The sequence contiguity of this assembly is increased fifty-fold and the proportion of gap-bases has been reduced fifteen-fold. Compared to other vertebrates, the assembly contains an unusual high density of tandem repeats (TRs). Indeed, retrospective analyses reveal that gaps in the first genome assembly were largely associated with these TRs. We show that 21% of the TRs across the assembly, 19% in the promoter regions and 12% in the coding sequences are heterozygous in the sequenced individual. Conclusions The inclusion of PacBio reads combined with the use of multiple assembly programs drastically improved the Atlantic cod genome assembly by successfully resolving long TRs. The high frequency of heterozygous TRs within or in the vicinity of genes in the genome indicate a considerable standing genomic variation in Atlantic cod populations, which is likely of evolutionary importance.

View all works in NVA

• Reinar, William Brynildsen; Krabberød, Anders Kristian; Lalun, Vilde Olsson; Butenko, Melinka Alonso & Jakobsen, Kjetill Sigurd (2025). Author Correction: Short tandem repeats delineate gene bodies across eukaryotes. Nature Communications. 16(1), p. 1350–1350. doi: 10.1038/s41467-025-56684-2. Full text in Research Archive
• Reinar, William Brynildsen; Tørresen, Ole K.; Matschiner, Michael; Jentoft, Sissel; Nederbragt, Alexander Johan & Jakobsen, Kjetill Sigurd (2018). The impact of repetitive DNA on speciation rates in teleost fish. Full text in Research Archive
• Reinar, William Brynildsen (2017). Trinucleotide repeat variation in the global Arabidopsis thaliana population: Associations with the environment. Full text in Research Archive
• Reinar, William Brynildsen (2017). Short tandem repeat length variation in Arabidopsis thaliana genomes. Full text in Research Archive
• Brynildsen, William (2015). Transposable elements in Gadus Morhua. Full text in Research Archive
• Brynildsen, William; Tørresen, Ole Kristian; Jakobsen, Kjetill Sigurd & Nederbragt, Alexander Johan (2014). Genomic sequence repeats in fish genomes. Full text in Research Archive

View all works in NVA