Biallelic BUB1 mutations cause microcephaly, developmental delay, and variable effects on cohesion and chromosome segregation

Sara Carvalhal, Ingrid Bader, Martin A. Rooimans, Anneke B. Oostra, Jesper A. Balk, René G. Feichtinger, Christine Beichler, Michael R. Speicher, Johanna M. van Hagen, Quinten Waisfisz, Mieke van Haelst, Martijn Bruijn, Alexandra Tavares, Johannes A. Mayr, Rob M.F. Wolthuis, Raquel A. Oliveira*, Job de Lange

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

Budding uninhibited by benzimidazoles (BUB1) contributes to multiple mitotic processes. Here, we describe the first two patients with biallelic BUB1 germline mutations, who both display microcephaly, intellectual disability, and several patient-specific features. The identified mutations cause variable degrees of reduced total protein level and kinase activity, leading to distinct mitotic defects. Both patients' cells show prolonged mitosis duration, chromosome segregation errors, and an overall functional spindle assembly checkpoint. However, while BUB1 levels mostly affect BUBR1 kinetochore recruitment, impaired kinase activity prohibits centromeric recruitment of Aurora B, SGO1, and TOP2A, correlating with anaphase bridges, aneuploidy, and defective sister chromatid cohesion. We do not observe accelerated cohesion fatigue. We hypothesize that unresolved DNA catenanes increase cohesion strength, with concomitant increase in anaphase bridges. In conclusion, BUB1 mutations cause a neurodevelopmental disorder, with clinical and cellular phenotypes that partially resemble previously described syndromes, including autosomal recessive primary microcephaly, mosaic variegated aneuploidy, and cohesinopathies.

Original languageEnglish
Article numbereabk0114
Number of pages18
JournalScience advances
Volume8
Issue number3
DOIs
Publication statusPublished - Jan 2022
Externally publishedYes

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