Aneuploidy renders cancer cells vulnerable to mitotic checkpoint inhibition

Selective targeting of aneuploid cells is an attractive strategy for cancer treatment(1). Here, we mapped the aneuploidy landscapes of ~1,000 human cancer cell lines, and analyzed genetic and chemical perturbation screens(2–9) to reveal aneuploidy-associated cellular vulnerabilities. We identified and validated an increased sensitivity of aneuploid cancer cells to genetic perturbation of core components of the spindle assembly checkpoint (SAC), which ensures the proper segregation of chromosomes during mitosis(10). Surprisingly, we also found aneuploid cancer cells to be less sensitive to short-term exposures to multiple SAC inhibitors. Indeed, aneuploid cancer cells became increasingly more sensitive to SAC inhibition (SACi) over time. Aneuploid cells exhibited aberrant spindle geometry and dynamics, and kept dividing in the presence of SACi, resulting in accumulating mitotic defects, and in unstable and less fit karyotypes. Therefore, although aneuploid cancer cells could overcome SACi more readily than diploid cells, their long-term proliferation was jeopardized. We identified a specific mitotic kinesin, KIF18A, whose activity was perturbed in aneuploid cancer cells. Aneuploid cancer cells were particularly vulnerable to KIF18A depletion, and KIF18A overexpression restored their response to SACi. Our study reveals a novel, therapeutically-relevant, synthetic lethal interaction between aneuploidy and the SAC

Precise Doppler Monitoring of Barnard's Star

We present 248 precise Doppler measurements of Barnard's Star (Gl 699), the second nearest star system to Earth, obtained from Lick and Keck Observatories during 25 years between 1987 and 2012. The early precision was 20 \ms{} but was 2 \ms{} during the last 8 years, constituting the most extensive and sensitive search for Doppler signatures of planets around this stellar neighbor. We carefully analyze the 136 Keck radial velocities spanning 8 years by first applying a periodogram analysis to search for nearly circular orbits. We find no significant periodic Doppler signals with amplitudes above $\sim$2 \ms{}, setting firm upper limits on the minimum mass (\msini) of any planets with orbital periods from 0.1 to 1000 days. Using a Monte Carlo analysis for circular orbits, we determine that planetary companions to Barnard's Star with masses above 2 \mearth{} and periods below 10 days would have been detected. Planets with periods up to 2 years and masses above 10 \mearth{} (0.03 \mjup) are also ruled out. A similar analysis allowing for eccentric orbits yields comparable mass limits. The habitable zone of Barnard's Star appears to be devoid of roughly Earth-mass planets or larger, save for face-on orbits. Previous claims of planets around the star by van de Kamp are strongly refuted. The radial velocity of Barnard's Star increases with time at $4.515\pm0.002$ \msy{}, consistent with the predicted geometrical effect, secular acceleration, that exchanges transverse for radial components of velocity.Comment: 21 pages & 11 figures; accepted to ApJ for publication; revision comments: the conclusions and results remain unchanged, removed the last paragraph in section 4.2, a few minor changes to the text, replaced figure 7 with figures 7 and 8, corrected typos in the rv data tables (tables 2 and 3, data downloadable from ApJ

Metaphase kinetochore dynamics [1c. First place]

In this HeLa cell, which is expressing both a kinetochore marker (EGFP-CENP-B) and a centrosome marker (Venus-centrin), one can visualize the dynamic nature of kinetochore movements during metaphase. At this stage in mitosis, sister kinetochore pairs, seen as paired dots oriented parallel to the x-axis, are attached to opposite spindle poles, marked by the two pairs of venus centrin dots near the left and right edges of the movie (usually oriented perpendicular to the x-axis in this movie). Kinetochores in metaphase HeLa cells typically undergo oscillatory movements around the equator of the spindle with average oscillation amplitudes of 1.2 microns. The sister kinetochores display primarily coordinated movements but also move relative to each other, which can be seen as increases and decreases in the distance between the sisters. These movements are highly coordinated with the dynamics of microtubules attached to the kinetochores. Note that the centrin dots are approximately 12 microns apart at the start of the movieComponente Curricular::Educação Superior::Ciências Biológicas::Biologia Gera

Metaphase kinetochore dynamics [1c. First place]

In this HeLa cell, which is expressing both a kinetochore marker (EGFP-CENP-B) and a centrosome marker (Venus-centrin), one can visualize the dynamic nature of kinetochore movements during metaphase. At this stage in mitosis, sister kinetochore pairs, seen as paired dots oriented parallel to the x-axis, are attached to opposite spindle poles, marked by the two pairs of venus centrin dots near the left and right edges of the movie (usually oriented perpendicular to the x-axis in this movie). Kinetochores in metaphase HeLa cells typically undergo oscillatory movements around the equator of the spindle with average oscillation amplitudes of 1.2 microns. The sister kinetochores display primarily coordinated movements but also move relative to each other, which can be seen as increases and decreases in the distance between the sisters. These movements are highly coordinated with the dynamics of microtubules attached to the kinetochores. Note that the centrin dots are approximately 12 microns apart at the start of the movieComponente Curricular::Educação Superior::Ciências Biológicas::Biologia Gera

No waiting for anaphase [1d. First place]

This HeLa cell, which is expressing both a kinetochore marker (EGFP-CENP-B) and a centrosome marker (Venus-centrin), has been depleted of the spindle assembly checkpoint protein Mad2. In the absence of Mad2, the cell rapidly progresses from early prometaphase through anaphase and cytokinesis. The spindle assembly checkpoint functions to generate a WAIT signal until all sister kinetochore pairs become properly attached to the mitotic spindle. Loss of checkpoint function leads to anaphase initiation before kinetochores are completely aligned at the spindle equator. Despite the rapid nature of these divisions, the majority of the kinetochores appear to separate properly in Mad2-depleted cells. However, at least a few lagging chromosomes are frequently observed in these cells, demonstrating the importance of checkpoint function. Note that the frame width is approximately 30 micronsComponente Curricular::Educação Superior::Ciências Biológicas::Biologia Gera

Kinetochores fail to align [1b. First place]

This HeLa cell is expressing both a kinetochore marker (EGFP-CENP-B) and a centrosome marker (Venus-centrin) and was depleted of the mitotic kinesin, Kif18A. In control cells at this stage in mitosis, sister kinetochore pairs, seen as paired dots oriented parallel to the x-axis, are attached to opposite spindle poles, marked by the venus centrin dots near the left and right edges of the movie (usually seen as single dots in this movie), and typically undergo oscillatory movements around the equator of the spindleComponente Curricular::Educação Superior::Ciências Biológicas::Biologia Gera

No waiting for anaphase [1d. First place]

This HeLa cell, which is expressing both a kinetochore marker (EGFP-CENP-B) and a centrosome marker (Venus-centrin), has been depleted of the spindle assembly checkpoint protein Mad2. In the absence of Mad2, the cell rapidly progresses from early prometaphase through anaphase and cytokinesis. The spindle assembly checkpoint functions to generate a WAIT signal until all sister kinetochore pairs become properly attached to the mitotic spindle. Loss of checkpoint function leads to anaphase initiation before kinetochores are completely aligned at the spindle equator. Despite the rapid nature of these divisions, the majority of the kinetochores appear to separate properly in Mad2-depleted cells. However, at least a few lagging chromosomes are frequently observed in these cells, demonstrating the importance of checkpoint function. Note that the frame width is approximately 30 micronsComponente Curricular::Educação Superior::Ciências Biológicas::Biologia Gera

Kinetochores fail to align [1b. First place]

This HeLa cell is expressing both a kinetochore marker (EGFP-CENP-B) and a centrosome marker (Venus-centrin) and was depleted of the mitotic kinesin, Kif18A. In control cells at this stage in mitosis, sister kinetochore pairs, seen as paired dots oriented parallel to the x-axis, are attached to opposite spindle poles, marked by the venus centrin dots near the left and right edges of the movie (usually seen as single dots in this movie), and typically undergo oscillatory movements around the equator of the spindleComponente Curricular::Educação Superior::Ciências Biológicas::Biologia Gera

Anaphase kinetochore movements [1a. First place]

In this HeLa cell, which is expressing both a kinetochore marker (EGFP-CENP-B) and a centrosome marker (Venus-centrin), one can visualize the dynamic nature of kinetochore movements during metaphase and anaphase. During metaphase sister kinetochore pairs, seen as paired dots oriented parallel to the x-axis, are attached to opposite spindle poles, marked by the two pairs of venus centrin dots near the left and right edges of the movie (seen as single dots in this movie). Kinetochores in metaphase HeLa cells typically undergo oscillatory movements around the equator of the spindle. At the onset of anaphase, the sisters separate and move poleward. As seen in this movie, however, kinetochores can continue to switch between poleward and away from pole movements even after sister separation. Note that the centrin dots are approximately 12 microns apart at the start of the movieComponente Curricular::Educação Superior::Ciências Biológicas::Biologia Gera

Anaphase kinetochore movements [1a. First place]

In this HeLa cell, which is expressing both a kinetochore marker (EGFP-CENP-B) and a centrosome marker (Venus-centrin), one can visualize the dynamic nature of kinetochore movements during metaphase and anaphase. During metaphase sister kinetochore pairs, seen as paired dots oriented parallel to the x-axis, are attached to opposite spindle poles, marked by the two pairs of venus centrin dots near the left and right edges of the movie (seen as single dots in this movie). Kinetochores in metaphase HeLa cells typically undergo oscillatory movements around the equator of the spindle. At the onset of anaphase, the sisters separate and move poleward. As seen in this movie, however, kinetochores can continue to switch between poleward and away from pole movements even after sister separation. Note that the centrin dots are approximately 12 microns apart at the start of the movieComponente Curricular::Educação Superior::Ciências Biológicas::Biologia Gera