Modulation of cell morphogenesis by tousled‐like kinase in the Drosophila follicle cell

Abstract

Background: Tousled-like kinase (Tlk) is a conserved serine/threonine kinase regulating DNA replication, chromatin assembly, and DNA repair. Previous studies have suggested that Tlk is involved in cell morphogenesis in vitro. In addition, tlk genetically interact with Rho1, which encodes a key regulator of the cytoskeleton. However, whether Tlk plays a physiological role in cell morphogenesis and cytoskeleton rearrangement remains unknown. Results: In tlk mutant follicle cells, area of the apical domain was reduced. The density of microtubules was increased in tlk mutant cells. The density of actin filaments was increased in the apical region and decreased in the basal region. Because area of the apical domain was reduced, we examined the levels of proteins located in the apical region by using immunofluorescence. The fluorescence intensities of two adherens junction proteins Armadillo (Arm) and DE-cadherin (DE-cad), atypical protein kinase C (aPKC), and Notch, were all increased in tlk mutant cells. The basolateral localized Discs large (Dlg) shifted apically in tlk mutant cells. Conclusions: Increase of protein densities in the apical region might be resulted from disruption of the cytoskeleton and shrinkage of the apical domain. Together, these data suggest a novel role of Tlk in maintaining cell morphology, possibly through modulating the cytoskeleton. Developmental Dynamics 244:852-865, 2015. V C 2015 Wiley Periodicals, Inc.

Unique genetic signatures of local adaptation over space and time for diapause, an ecologically relevant complex trait, in Drosophila melanogaster

“…However, unlike the clinal signal, the seasonal signal does not appear genome-wide (in all SNPs), suggesting a lack of predictable seasonal evolution of diapause-associated alleles. Interestingly, the gene tlk, which is involved in ovary follicle cell morphogenesis [108] and chromosome segregation [109], was also identified as a candidate gene in a genomic study of balancing selection in D. melanogaster [110]. Seasonally varying selection related to diapause or other phenotypes could contribute to this signal of balancing selection.…”

Inactive Tlk associating with Tak1 increases p38 MAPK activity to prolong the G2 phase

“…Tlk and p38b DN co-overexpression results in disordered positioning of nuclei in the eye disc, leading to some M phase cells on the same focal plane with smaller and weaker signals, indicated by yellow arrows. This phenotype is also observed in follicle cells with Tlk loss-of-function 32 . ( b ) The bar graph shows the number of M phase cell in the 4–6 rows of neuronal clusters.…”

“…A similar scenario is observed in eye disc. The apical region of a row of epithelial cells inside MF is constricted, which resembles the narrow apical region of follicle cells that lack Tlk activity 32 . This supports that the overexpressed Tlk is inactive in the 1–4 rows of neuronal clusters.…”

“…Based on the effect of mechanic stress on Tlk (Supplementary Fig. S7) and the requirement of Tlk activity to maintain the columnar shape of follicle cells 32 , mechanic stress likely activates Tlk activity. The autophosphorylation further increases the Tlk activity when its protein level is high.…”

βPS-Integrin acts downstream of Innexin 2 in modulating stretched cell morphogenesis in the Drosophila ovary

“…UAS-GFP driven by c306-GAL4 was used as a control. Immunofluorescence of DE-cad was used for labeling the apical-lateral membrane of follicle cells and border cell clusters ( Geisbrecht and Montell 2002 ; Yeh et al 2015 ). Knockdown of Inx s driven by c306-GAL4 did not affect follicle cell differentiation during early oogenesis (data not shown).…”