The BEAF-32 insulator protein is required for Hippo pathway activity in the terminal differentiation of neuronal subtypes

Abstract

The Hippo pathway is crucial for not only normal growth and apoptosis but also cell fate specification during development. What controls Hippo pathway activity during cell fate specification is incompletely understood. In this article, we identify the insulator protein BEAF-32 as a regulator of Hippo pathway activity in Drosophila photoreceptor differentiation. Though morphologically uniform, the fly eye is composed of two subtypes of R8 photoreceptor neurons defined by expression of light-detecting Rhodopsin proteins. In one R8 subtype, active Hippo signaling induces Rhodopsin 6 (Rh6) and represses Rhodopsin 5 (Rh5), whereas in the other subtype, inactive Hippo signaling induces Rh5 and represses Rh6. The activity state of the Hippo pathway in R8 cells is determined by the expression of warts, a core pathway kinase, which interacts with the growth regulator melted in a doublenegative feedback loop. We show that BEAF-32 is required for expression of warts and repression of melted. Furthermore, BEAF-32 plays a second role downstream of Warts to induce Rh6 and prevent Rh5 fate. BEAF-32 is dispensable for Warts feedback, indicating that BEAF-32 differentially regulates warts and Rhodopsins. Loss of BEAF-32 does not noticeably impair the functions of the Hippo pathway in eye growth regulation. Our study identifies a context-specific regulator of Hippo pathway activity in post-mitotic neuronal fate, and reveals a developmentally specific role for a broadly expressed insulator protein.

TADs pair homologous chromosomes to promote interchromosomal gene regulation

“…Dissections were performed as described in references (Hsiao et al, 2012;Johnston et al, 2011;Jukam et al, 2016;Thanawala et al, 2013). Eyes were dissected and fixed at room temperature for 15 minutes in 4% formaldehyde diluted in 1X PBX (PBS+0.3% Triton-X), then washed three times in 1X PBX.…”

The polarity protein Angiomotin p130 controls dendritic spine maturation

“…Yet how these signaling components operate in postmitotic neurons is less well understood. Studies in Drosophila melanogaster show that deregulation of the Hippo signaling cascade alters brain size and restricts neuronal differentiation ( Jukam et al, 2016 ; Poon et al, 2016 ). In mammalian neurons, Hippo kinase activity has been linked to actin remodeling ( Ultanir et al, 2012 , 2014 ) and, conversely, actin cytoskeleton changes increase Lats1/2 activity ( Piccolo et al, 2014 ).…”

Natural variation in stochastic photoreceptor specification and color preference in Drosophila

“…p R7s lacking Ss signal to p R8s to activate expression of blue-detecting Rhodopsin5 (Rh5). y R7s expressing Ss do not send this signal, resulting in expression of green-detecting Rhodopsin6 (Rh6) in y R8s ( Figure 1A ) ( Franceschini et al, 1981 ; Montell et al, 1987 ; Zuker et al, 1987 ; Chou et al, 1996 ; Huber et al, 1997 ; Chou et al, 1999a ; Mikeladze-Dvali et al, 2005 ; Mazzoni et al, 2008 ; Vasiliauskas et al, 2009 ; Jukam and Desplan, 2011 ; Hsiao et al, 2013 ; Johnston, 2013 ; Jukam et al, 2013 ; Jukam et al, 2016 ; Yan et al, 2017 ).…”