Figure 1. Most sister kinetochores are not unified and attach to two discrete k-fibers during meiosis I in human oocytes.
(A) Maximum intensity z-projection immunofluorescence images of kinetochores and chromosomes in meiosis I oocytes from young donors (≤30 years old). Representative examples from 5 different oocytes. Scale bar represents 1 µm. (B) Categories of sister kinetochore configurations shown in (A) and their frequency in oocytes from young donors (≤30 years old). 1,051 kinetochore pairs from 23 oocytes were analyzed. (C) Examples of kinetochore configurations from 26 human oocytes across all age groups in which sister kinetochores are separated (marked with white arrows). Scale bar represents 1 µm. (D) Maximum intensity z-projection immunofluorescence images of microtubules and distinct sister kinetochore pairs in cold-treated meiotic spindles from human oocytes across all age groups. Drawings illustrate the different modes of microtubule attachments in the immunofluorescence images. Scale bar represents 5 µm in overview and 1 µm in insets. (E) Quantification of the number of individual k-fibers attaching to sister kinetochore pairs. 949 attachments from 25 cold-treated human oocytes from donors across all age groups were evaluated. (F) Frequency of the different modes of kinetochore-microtubule attachments shown in (D).
Figure 1—figure supplement 1. The majority of sister kinetochores are split during meiosis I in human oocytes.
Figure 1—figure supplement 2. Sister kinetochore separation is already evident in the initial stages of spindle assembly.
Figure 1—figure supplement 3. Sister kinetochores can interact with k-fibers that originate from different regions of the meiotic spindle.
Figure 1—figure supplement 4. Individual kinetochores can attach to multiple k-fibers during meiosis I in human oocytes.
