Mitotic Maturation Compensates for Premature Centrosome Splitting and PCM Loss in Human cep135 Knockout Cells

Abstract

Centrosomes represent main microtubule organizing centers (MTOCs) in animal cells. Their duplication in S-phase enables the establishment of two MTOCs in M-phase that define the poles of the spindle and ensure equal distribution of chromosomes and centrosomes to the two daughter cells. While key functions of many centrosomal proteins have been addressed in RNAi experiments and chronic knockdown, knockout experiments with complete loss of function in all cells enable quantitative analysis of cellular phenotypes at all cell-cycle stages. Here, we show that the centriolar satellite proteins SSX2IP and WDR8 and the centriolar protein CEP135 form a complex before centrosome assembly in vertebrate oocytes and further functionally interact in somatic cells with established centrosomes. We present stable knockouts of SSX2IP, WDR8, and CEP135 in human cells. While loss of SSX2IP and WDR8 are compensated for, cep135 knockout cells display compromised PCM recruitment, reduced MTOC function, and premature centrosome splitting with imbalanced PCMs. Defective cep135 knockout centrosomes, however, manage to establish balanced spindle poles, allowing unperturbed mitosis and regular cell proliferation. Our data show essential functions of CEP135 in interphase MTOCs and demonstrate that loss of individual functions of SSX2IP, WDR8, and CEP135 are fully compensated for in mitosis.

Protamine 2 Deficiency Results In Septin 12 Abnormalities

“…This finding is in accordance with results from the yeast 2-hybrid system, which predicted interaction between Septin 12 and PCM1 (Yeh et al, 2015), a component of centriolar satellites (Dammermann and Merdes, 2002). It has been shown that PCM1 and centriolar satellites play a role in regulating the composition of centrioles (Hall et al, 2023) and conversely, PCM1 requires centrosomal localization of CEP135 for efficient localization around centrosomes (Chu and Gruss, 2022). It suggests that the interaction between Septin 12 and PCM1 may regulate the structure and function of sperm centrioles and that the undetected expression of Septin 12 in the connecting piece of Prm2 -/- sperm could indirectly result in their immotility.…”

Emerging roles of centrosome cohesion

“…In human cells, C-Nap1 is anchored to centrioles by binding to CEP135. However, CEP135 KO cells still recruit C-Nap1 but with reduced efficiency, indicating alternative docking mechanisms [ 28 ]. Nevertheless, both knockdown [ 29 ] or KO [ 28 ] of CEP135 in cultured mammalian cell lines displayed centrosome linker defects.…”

“…However, CEP135 KO cells still recruit C-Nap1 but with reduced efficiency, indicating alternative docking mechanisms [ 28 ]. Nevertheless, both knockdown [ 29 ] or KO [ 28 ] of CEP135 in cultured mammalian cell lines displayed centrosome linker defects. Intriguingly, CEP135 KO in chicken DT40 cells seemed not to result in defects in centrosome cohesion [ 30 ], implying differences in the anchoring of C-Nap1 to centrioles dependent on the organism.…”

“…In cells, CEP135 and CDK5RAP2/CEP215 depletion/mutation affect centrosome cohesion [ 15 , 28 , 29 , 81 , 82 ]. As discussed above, CEP135 functions as an anchoring point for C-Nap1 at centrioles and CEP135 KO cells displayed centrosome linker defects [ 28 , 29 ]. CDK5RAP2/CEP215 was originally described as a putative centrosome linker component.…”