Science - USA (2022-02-11)

analysis revealed that wild-type and aMTOC-
free mouse oocytes had a comparable fraction
of mobile mClover3-KIFC1, but the turnover
of mClover3-KIFC1 at the spindle poles was
two times slower in the absence of aMTOCs

(Fig. 8, D to F). By contrast, the absence of

aMTOCs did not affect either the turnover of

mClover3-KIFC1 in the central region of the

spindle or the turnover of the microtubule

reporter mScarlet-MAP4-MTBD (fig. S14, E

to G). Thus, the dynamics of KIFC1 at the

spindle poles is specifically altered in the

absence of aMTOCs, and KIFC1 accumula-

tion at the poles may stabilize aMTOC-free

spindles.

Soet al.,Science 375 , eabj3944 (2022) 11 February 2022 9 of 19

B

Merge

A

Control IgG

bTRIM21

Merge

Merge

anti-KIFC1-C

Microtubules

Microtubules

8:42 15:02 17:45 19:12 19:56 21:23

4:35 6:58 12:04 13:56 14:37 15:08

Microtubules

4 h:18 min 7:23 10:18 12:01 13:44 14:56

Chromosomes

Control

IgG

( 34 )

anti-

KIFC1

( 32 )

0

20

40

60

80

100

Percentage of spindles

With spindle instability

Without spindle instability

D

KIFC1-

depleted

bovine oocytes

( 26 )

Human oocytes

with multipolar

spindle

intermediates ( 47 )

0

20

40

60

80

100

Percentage of spindles

Bipolarity not restored at

anaphase onset

Bipolarity restored at

anaphase onset

Control

IgG

( 33 )

anti-

KIFC1

( 26 )

0

20

40

60

80

100

Percentage of oocytes

Misaligned chromosomes

at anaphase onset

Aligned chromosomes

at anaphase onset

E

Control

IgG

( 32 )

anti-

KIFC1

( 27 )

0

20

40

60

80

100

Percentage of oocytes

With severely lagging

chromosomes

With mildly lagging

chromosomes

No lagging chromosomes

F

Control

IgG

( 41 )

anti-

KIFC1

( 31 )

0

20

40

60

80

100

Percentage of oocytes

≥2 chromosomes gained/lost

1 chromosome gained/lost

No chromosome gained/lost

G

C

Percentage of oocytes

Cont

ro

l^ bovine

oocy

tes (

33

)

KIFC1-de

plete

d

bo

vine oocytes

(^28

)

Hum

an oocyt

es

(^83

)

Human oocytes

(fr

om

re

f.^

3 )

(^35

)

0

20

40

60

80

100 Tri-directional division

Bi-directional division

Fig. 6. Depletion of KIFC1 results in spindle instability and promotes
aneuploidy in bovine oocytes.(A) Still images from time-lapse movies of control
and KIFC1-depleted bovine oocytes. Green, microtubules (mClover3-MAP4-
MTBD); magenta, chromosomes (H2B-mScarlet). Time is given as hours:minutes
after NEBD. (B) Manual scoring of spindle instability in control and KIFC1-depleted
bovine oocytes (FisherÕs exact test,P< 0.0001). (C) Quantification of the
directionality of anaphase I in control and KIFC1-depleted bovine oocytes, and in
human oocytes from ( 2 , 3 ). (D) Quantification of spindle bipolarity restoration at

anaphase onset in KIFC1-depleted bovine oocytes and in human oocytes with

multipolar spindle intermediates from ( 2 ). (E) Quantification of chromosome

misalignment at anaphase onset in control and KIFC1-depleted bovine oocytes.

(F) Quantification of chromosome missegregation during anaphase in control and

KIFC1-depleted bovine oocytes. (G) Quantification of chromosome counts at

metaphase II in control and KIFC1-depleted bovine oocytes. Yellow dashed lines

highlight spindle poles. Yellow arrowheads highlight directions of anaphase I. The

number of oocytes analyzed is specified in italics. Scale bars are 5mm.

RESEARCH | RESEARCH ARTICLE