XB-ART-53678J Cell Biol. June 5, 2017; 216 (6): 1849-1864.
Usher syndrome type 1-associated cadherins shape the photoreceptor outer segment.
Usher syndrome type 1 (USH1) causes combined hearing and sight defects, but how mutations in USH1 genes lead to retinal dystrophy in patients remains elusive. The USH1 protein complex is associated with calyceal processes, which are microvilli of unknown function surrounding the base of the photoreceptor outer segment. We show that in Xenopus tropicalis, these processes are connected to the outer-segment membrane by links composed of protocadherin-15 (USH1F protein). Protocadherin-15 deficiency, obtained by a knockdown approach, leads to impaired photoreceptor function and abnormally shaped photoreceptor outer segments. Rod basal outer disks displayed excessive outgrowth, and cone outer segments were curved, with lamellae of heterogeneous sizes, defects also observed upon knockdown of Cdh23, encoding cadherin-23 (USH1D protein). The calyceal processes were virtually absent in cones and displayed markedly reduced F-actin content in rods, suggesting that protocadherin-15-containing links are essential for their development and/or maintenance. We propose that calyceal processes, together with their associated links, control the sizing of rod disks and cone lamellae throughout their daily renewal.
PubMed ID: 28495838
PMC ID: PMC5461027
Article link: J Cell Biol.
Genes referenced: cdh23 myo7a pcdh15 ush1c ush1g
Morpholinos referenced: cdh23 MO1 cdh23 MO2 cdh23 MO3 myo7a MO1 pcdh15 MO1 pcdh15 MO2 pcdh15 MO3 pcdh15 MO4 ush1c MO1 ush1g MO1