Takahisa Furukawa

Scratch1 and Scratch2 (Scrt1/2) of the Snail superfamily transcriptional repressors are evolutionarily well-conserved from nematodes to humans and are predominantly expressed in the developing central nervous system. However, the in vivo functions and underlying mechanisms of Scratch remain unclear because of the lack of analysis using Scratch- deficient animals. Transcriptional and histological analyses revealed that Scrt1/2 are coexpressed in retinal ganglion cells (RGCs), amacrine cells, and horizontal cells in the mouse retina from early embryonic stages to adulthood. We generated Scrt1 ^−/− and Scrt2 ^−/− mice, in which no detectable phenotypic changes were observed in appearance or retinal morphology. Nevertheless, Scrt1/2 double knock-out (DKO) mice of either sex displayed small body size and low postnatal viability, as well as decreased RGC density and thinner optic nerves in the retina. Single-cell RNA sequencing analysis of control and Scrt DKO retinas at embryonic day 17.5 revealed upregulation of the proapoptotic gene S100a11 in RGCs. Forced expression of S100a11 in adult mouse retinas induced RGC apoptosis chronically. Consistent with the reduction of RGC density and thinning of optic nerves, Scrt DKO mice showed impaired RGC axonal projections to the accessory optic system (AOS) and consequently exhibited defective optokinetic responses (OKRs). Together, the present study suggests that the repressive regulation of proapoptotic and axon guidance genes by mouse Scratch is essential for maintaining RGC survival and normal visual function.

The biological functions and mechanisms of many cell type-specific transcriptional cofactors remain unclear. We previously identified Panky ( Ankrd33 ) as a repressive transcriptional cofactor that suppresses Crx-mediated transactivation of photoreceptor genes; however, the biological function of Panky remains unclarified. Here, we investigated the functions of Panky and its paralog, Panky-like ( Ankrd33b ), in mice of either sex. Single knock-out (KO) mouse retinas of Panky or Panky-like did not show significant alterations at both histological and functional levels compared with those of control mice. We then established and examined Panky and Panky-like double knock-out ( PPL DKO) mice. PPL DKO mice exhibited decreased light-evoked activities detected by electroretinogram (ERG), impaired cone photoreceptor morphology revealed by immunohistochemistry, and structural deformity of cone outer segments and synaptic terminals indicated by transmission electron microscopy, followed by cone death at a later stage. Lipidomics analysis revealed elevated ganglioside levels in PPL DKO retinas, consistent with the increased immunoreactivity of GT1b and GD3 in the outer segment layer. RNA-seq analysis was conducted in a cone-enriched context resulting from Nrl deficiency and showed that the Cerkl gene, whose mutations in humans cause retinitis pigmentosa (RP26), was upregulated in Panky/Panky-like/Nrl triple KO mice. Transcriptional assays showed that PPL suppressed Crx-mediated transactivation of Cerkl . In addition, AAV-mediated Cerkl overexpression in the mouse retina induced significant photoreceptor cell death. Taken together, these findings suggest that the repressive Panky and Panky-like cofactors, which modulate Crx transcriptional activities and thus ganglioside levels in the mouse retina, are essential for cone photoreceptor structure and maintenance.

This study found that age-associated sleep changes are ameliorated by DR in the presence of Prdm13 signaling in the DMH, suggesting Prdm13+ DMH neurons will be of great interest to explore a potential intervention on age-associated sleep changes.

Transducin is a heterotrimeric G-protein that is a component of the phototransduction cascade in rod and cone photoreceptor cells of the retina. Gnat1, a rod-specific transducin α-subunit, regulates light/dark adaptation by changing its subcellular localization depending on light. Our previous study revealed that Gnat1 translocation in rod photoreceptor cells under light/dark conditions requires E3 ligase Klhl18-mediated ubiquitination and degradation of Unc119, a Gnat1-binding protein. A mutation in the human UNC119 gene is associated with cone–rod dystrophy (CRD); however, the underlying pathological mechanism remains unclear. In this study, we generated and analyzed Unc119 -deficient ( Unc119 ^−/− ) mice. We found that the retinas of Unc119 ^−/− mice of both sexes exhibited progressive photoreceptor degeneration, resembling CRD in humans. We also found that Unc119 interacts with Gnat2 in cone photoreceptor cells and that Unc119 is essential for the translocation of Gnat2 to the outer segment in cone photoreceptor cells. RNA-seq and subsequent bioinformatics analysis revealed the predicted activation of the JAK-STAT and NF-κB pathways in the Unc119 ^−/− retina. Treatment of Unc119 ^−/− mice with curcumin, an inhibitor of the JAK-STAT and NF-κB pathways, suppressed inflammation and cone photoreceptor cell degeneration in Unc119 ^−/− retinas. Furthermore, a human CRD-associated UNC119 mutant protein competitively inhibited the interaction between UNC119 and GNAT1 or GNAT2. Taken together, the current study suggests that UNC119 dysfunction leads to CRD by affecting the JAK-STAT and NF-κB pathways and may advance our understanding of the pathological mechanisms of CRD.

Primary cilia are evolutionarily conserved microtubule-based structures that extend from the surfaces of many different cell types and decode a wide range of extracellular chemical and physical stimuli. Ciliary defects cause human diseases, termed ciliopathies, which are characterized by a variety of symptoms, such as developmental and sensory abnormalities. The formation and function of primary cilia depend on intraflagellar transport (IFT), which is a bidirectional protein transport system coordinated by three multi-subunit protein complexes with kinesin and dynein motors along the ciliary axoneme. Accumulating evidence has demonstrated that several serine-threonine kinases play key roles in the regulation of IFT. Here, we review the current understanding of the roles of these kinases during the IFT process, as well as their regulatory mechanisms, physiological and pathophysiological significance, and potential to treat ciliopathies and age-related obesity.