Hall Brian K.

No Thumbnail Available
Last Name
Hall
First Name
Brian K.
ORCID

Filters

2016 - 2019 2
2
2
Reset filters

Settings

Search Results

Now showing 1 - 2 of 2
  • Article
    Extraocular, rod-like photoreceptors in a flatworm express xenopsin photopigment
    (eLife Sciences Publications, 2019-10-22) Rawlinson, Kate A. ; Lapraz, Francois ; Ballister, Edward R. ; Terasaki, Mark ; Rodgers, Jessica ; McDowell, Richard J. ; Girstmair, Johannes ; Criswell, Katharine E. ; Boldogkoi, Miklos ; Simpson, Fraser ; Goulding, David ; Cormie, Claire ; Hall, Brian K. ; Lucas, Robert J. ; Telford, Maximilian J.
    Animals detect light using opsin photopigments. Xenopsin, a recently classified subtype of opsin, challenges our views on opsin and photoreceptor evolution. Originally thought to belong to the Gαi-coupled ciliary opsins, xenopsins are now understood to have diverged from ciliary opsins in pre-bilaterian times, but little is known about the cells that deploy these proteins, or if they form a photopigment and drive phototransduction. We characterized xenopsin in a flatworm, Maritigrella crozieri, and found it expressed in ciliary cells of eyes in the larva, and in extraocular cells around the brain in the adult. These extraocular cells house hundreds of cilia in an intra-cellular vacuole (phaosome). Functional assays in human cells show Maritigrella xenopsin drives phototransduction primarily by coupling to Gαi. These findings highlight similarities between xenopsin and c-opsin and reveal a novel type of opsin-expressing cell that, like jawed vertebrate rods, encloses the ciliary membrane within their own plasma membrane.
  • Article
    A shared role for sonic hedgehog signalling in patterning chondrichthyan gill arch appendages and tetrapod limbs
    (Company of Biologists, 2016-04-19) Gillis, J. Andrew ; Hall, Brian K.
    Chondrichthyans (sharks, skates, rays and holocephalans) possess paired appendages that project laterally from their gill arches, known as branchial rays. This led Carl Gegenbaur to propose that paired fins (and hence tetrapod limbs) originally evolved via transformation of gill arches. Tetrapod limbs are patterned by a sonic hedgehog (Shh)-expressing signalling centre known as the zone of polarising activity, which establishes the anteroposterior axis of the limb bud and maintains proliferative expansion of limb endoskeletal progenitors. Here, we use loss-of-function, label-retention and fate-mapping approaches in the little skate to demonstrate that Shh secretion from a signalling centre in the developing gill arches establishes gill arch anteroposterior polarity and maintains the proliferative expansion of branchial ray endoskeletal progenitor cells. These findings highlight striking parallels in the axial patterning mechanisms employed by chondrichthyan branchial rays and paired fins/limbs, and provide mechanistic insight into the anatomical foundation of Gegenbaur's gill arch hypothesis.