Border cell polarity and collective migration require the spliceosome component Cactin

Collective cell migration is a well-studied phenomenon in developmental contexts such as border cell movement. Prior research has shown that border cells serve as a model system for understanding how cell clusters maintain organization and polarity during migration. However, the mechanisms that specifically regulate cluster polarity and migration remain unclear. It was already known that apical polarity proteins like aPKC and Crumbs (Crb) are important for cell organization. Yet, the role of RNA splicing in maintaining these processes had not been fully explored. No prior work had resolved how splicing factors might influence cell polarity in a migratory context. This gap motivated researchers to investigate whether splicing components could regulate border cell behavior. The uncertainty around splicing's role in polarity and migration drove this study. The need to connect splicing with cell migration and polarity led to the current investigation.

This study aimed to determine whether the spliceosome component Cactin is required for border cell polarity and migration. The specific problem addressed is how RNA splicing contributes to collective cell migration. The motivation stems from the observation that border cells are sensitive to disruptions in splicing and polarity. The researchers sought to clarify whether Cactin's function in splicing is essential for maintaining cluster organization. The study's goal was to test if Cactin depletion affects border cell delamination and migration. The research also aimed to identify downstream genes affected by Cactin. The authors proposed that Cactin's conserved splicing activity is necessary for border cell function. The study's focus was on understanding how splicing influences cell polarity and migration.

The study used RNA interference to deplete Cactin in border cells and observe the effects on cluster organization and migration. Researchers analyzed apical protein localization using immunostaining techniques. Whole transcriptome sequencing was performed to identify changes in isoform expression. Mutations in Sec23 and Sec24CD were introduced to test their role in rescuing Cactin depletion effects. Overexpression of Rab5 and Rab11 was used to assess their impact on polarity and migration. The experiments included tracking border cell movement and measuring cluster polarity. The researchers examined the localization of aPKC and Crb in Cactin-depleted cells. The study combined genetic manipulation with functional assays to test splicing's role in cell migration.

Cactin depletion caused abnormal concentration of aPKC and Crb at the apical cell surface. Cluster polarity was lost, and delamination defects were observed in Cactin-depleted cells. Excess aPKC tethered to the apical membrane was sufficient to cause delamination issues. Relocating aPKC partially rescued delamination in Cactin-depleted cells. Transcriptome analysis revealed altered isoform expression in Cactin-depleted cells. Mutations in Sec23 and Sec24CD partially rescued cluster organization and migration defects. Overexpression of Rab5 or Rab11 also rescued border cell migration and organization. These findings suggest that Cactin's splicing activity is required for proper cell polarity and migration.

The authors propose that Cactin's conserved spliceosome function is specifically required for border cell polarity and migration. The study suggests that splicing disruptions can lead to polarity and migration defects in border cells. The findings indicate that Cactin regulates isoform expression of genes involved in cell polarity. The research supports the idea that border cells are particularly sensitive to splicing and polarity changes. The results suggest that Sec23 and Sec24CD mutations can partially rescue Cactin depletion effects. Rab5 and Rab11 overexpression also partially rescues polarity and migration defects. The study highlights the importance of splicing in coordinating cluster polarity and migration. The authors suggest that splicing factors like Cactin play a specific role in maintaining cell organization during migration.