Regulation of dynein localization and centrosome positioning by Lis-1 and asunder during Drosophila spermatogenesis

Abstract

Dynein, a microtubule motor complex, plays crucial roles in cell-cycle progression in many systems. The LIS1 accessory protein directly binds dynein, although its precise role in regulating dynein remains unclear. Mutation of human LIS1 causes lissencephaly, a developmental brain disorder. To gain insight into the in vivo functions of LIS1, we characterized a male-sterile allele of the Drosophila homolog of human LIS1. We found that centrosomes do not properly detach from the cell cortex at the onset of meiosis in most Lis-1 spermatocytes; centrosomes that do break cortical associations fail to attach to the nucleus. In Lis-1 spermatids, we observed loss of attachments between the nucleus, basal body and mitochondria. The localization pattern of LIS-1 protein throughout Drosophila spermatogenesis mirrors that of dynein. We show that dynein recruitment to the nuclear surface and spindle poles is severely reduced in Lis-1 male germ cells. We propose that Lis-1 spermatogenesis phenotypes are due to loss of dynein regulation, as we observed similar phenotypes in flies null for Tctex-1, a dynein light chain. We have previously identified asunder (asun) as another regulator of dynein localization and centrosome positioning during Drosophila spermatogenesis. We now report that Lis-1 is a strong dominant enhancer of asun and that localization of LIS-1 in male germ cells is ASUN dependent. We found that Drosophila LIS-1 and ASUN colocalize and coimmunoprecipitate from transfected cells, suggesting that they function within a common complex. We present a model in which Lis-1 and asun cooperate to regulate dynein localization and centrosome positioning during Drosophila spermatogenesis.

Centrosomin represses dendrite branching by orienting microtubule nucleation

“…1j--m; Supplementary Fig. 1) Lis1 enhances Dynein--mediated minus end--directed transport along microtubules, and previous characterization of tagged Lis1 revealed that this marker is transported towards microtubule minus ends during mitosis and meiosis 24,25 . We found that dendritic localization of tagged Lis1 24,25 also differed between class I and IV neurons, and was regulated by ab.…”

Conserved roles for cytoskeletal components in determining laterality

“…The dynein accessory factor Lis1 is required for dynein-dependent processes such as positioning of the nucleus during neuronal migration in humans (82) and spermatogenesis in Drosophila (83), and in particular has a role in asymmetric cell division demonstrated in mouse (84). …”

Adhesion in the stem cell niche: biological roles and regulation

“…In the Drosophila ovary, Lissencephaly-1 (Lis-1), which is encoded by the Drosophila homolog of the causative gene (LIS1, also known as PAFAH1B1) for the human disease lissencephaly, is required in GSCs to maintain E-cadherin accumulation at the GSC-niche junction via an unknown mechanism (Chen et al, 2010). In addition, Lis-1 is required for centrosome positioning in Drosophila ovarian and testicular GSCs as well as for spindle orientation in neuroblasts and mouse neural progenitor cells (Chen et al, 2010;Siller and Doe, 2008;Sitaram et al, 2012;Yingling et al, 2008). However, it remains unclear whether centrosome positioning and spindle orientation are connected with the adhesion role of Lis-1.…”