Expression of lamina proteins Lamin Dm0 and Kugelkern suppresses stem cell proliferation

The nuclear lamina is involved in numerous cellular functions, such as gene expression, nuclear organization, nuclear stability, and cell proliferation. The mechanism underlying the involvement of lamina is often not clear, especially in physiological contexts. Here we investigate how the farnesylated lamina proteins Lamin Dm0 and Kugelkern are linked to proliferation control of intestinal stem cells (ISCs) in adult Drosophila flies by loss-of-function and gain-of-function experiments. We found that ISCs mutant for Lamin Dm0 or Kugelkern proliferate, whereas overexpression of Lamin Dm0 or Kugelkern strongly suppressed proliferation. The anti-proliferative activity is, at least in part, due to suppression of Jak/Stat but not Delta/Notch signalling. Lamin Dm0 expression suppresses Jak/Stat signalling by normalization of about 50% of the Stat target genes in ISCs. Author summary The nuclear lamina is a protein meshwork that lies beneath the inner side of the nuclear membrane and interacts with nuclear pores, chromatin and the cytoskeleton. Changes in proteins of the nuclear lamina cause a wide range of diseases which are often not well understood. It is hypothesized that impairment of stem cell function, as a result of lamina changes, might play a key role in some of those diseases. Here we use the well characterized Drosophila midgut as a system to investigate the role of lamina proteins Lamin Dm0 and Kugelkern on stem cell proliferation.