Abstract
Centrosomes are multi-protein organelles that function as microtubule (MT) organizing centers (MTOCs), ensuring spindle formation and chromosome segregation during cell division.[1][,][2][,][3] Centrosome structure includes core centrioles that recruit pericentriolar material (PCM) that anchors γ-tubulin to nucleate MTs.[1][,][2] In Drosophila melanogaster, PCM organization depends on proper regulation of proteins like Spd-2, which dynamically localizes to centrosomes and is required for PCM, γ-tubulin, and MTOC activity in brain neuroblast (NB) mitosis and male spermatocyte (SC) meiosis.[4][,][5][,][6][,][7][,][8] Some cells have distinct requirements for MTOC activity due to differences in characteristics like cell size[9][,][10] or whether they are mitotic or meiotic.[11][,][12] How centrosome proteins achieve cell-type-specific functional differences is poorly understood. Previous work identified alternative splicing[13] and binding partners[14] as contributors to cell-type-specific differences in centrosome function. Gene duplication, which can generate paralogs with specialized functions,[15][,][16] is also implicated in centrosome gene evolution,[17] including cell-type-specific centrosome genes.[18][,][19] To gain insight into cell-type-specific differences in centrosome protein function and regulation, we investigated a duplication of Spd-2 in Drosophila willistoni, which has Spd-2A (ancestral) and Spd-2B (derived). We find that Spd-2A functions in NB mitosis, whereas Spd-2B functions in SC meiosis. Ectopically expressed Spd-2B accumulates and functions in mitotic NBs, but ectopically expressed Spd-2A failed to accumulate in meiotic SCs, suggesting cell-type-specific differences in translation or protein stability. We mapped this failure to accumulate and function in meiosis to the C-terminal tail domain of Spd-2A, revealing a novel regulatory mechanism that can potentially achieve differences in PCM function across cell types.
