The diagram is divided into two main phases: Phase 1 and Phase 2. Phase 1, labeled as mitotic-like and CAL1 dependent, occurs during prophase I and prometaphase. It shows the assembly of CID, which interacts with CENP-C and CAL1. Phase 2, labeled as non-canonical and CAL1 independent, occurs post-meiotically. It shows CID assembly independent of CAL1 but still requiring CENP-C. The diagram includes stages from GSC to mature sperm, with specific stages labeled as S1 to S6, M1a/b, and T1 to T5. Arrows indicate interdependencies of CID loading, and a blue curved arrow indicates a switch in CENP-C function. The diagram also highlights the use of bam-GAL4 and Rbp4-GAL4 drivers for RNAi knockdowns at specific stages.
Meiotic CENP-C supports two mechanistically distinct phases of centromere assembly. The first phase occurs during prophase I and resembles the mitotic pathway, in which CENP-C acts together with CAL1: an early pool of CENP-C sustains CID assembly, then a later pool recruits the kinetochore as CAL1 is lost from centromeres. A second, noncanonical phase occurs after meiosis II in early spermatids, in which CID is assembled independently of CAL1 but still requires the late pool of CENP-C. These two phases were functionally dissected using two temporally distinct GAL4 RNAi drivers (bam and Rbp4, yellow bars). Black arrows indicate interdependencies of CID loading, while dotted line indicates partial dependence. Blue curved arrow indicates a switch in CENP-C function, supported by a pool independent of CAL1.