Structure and dynamics of photoreceptor sensory cilia

Protein Kinase A in Human Retina: Differential Localization of Cβ, Cα, RIIα, and RIIβ in Photoreceptors Highlights Non-redundancy of Protein Kinase A Subunits

“…The enrichment of Cα in this region is especially interesting because it provides a novel opportunity to study the disease mechanisms of Usher syndrome, a complicated disease previously linked to the cAMP pathway that is defined by several mutations of cilia-associated proteins ( Kremer et al, 2006 ; Mathur and Yang, 2015 ), as well as other blinding diseases that arise from improper regulation of the outer segment sensory cilium ( Wensel et al, 2016 ). Additionally, Cα localized to this area could potentially play a role in photoreceptor intracellular communication as the base of the connecting cilia, also considered the cilia transition zone, essentially acts as a funnel where vesicle trafficking between the inner and outer segments is highly regulated ( Gilliam et al, 2012 ; Wensel et al, 2021 ).…”

Where vision begins

“…Unfortunately, despite decades of study, the details of the fine structure and distribution of molecular components of these structures are still incompletely understood. Recent advances in cellular imaging techniques and animal models of inherited ciliary defects are however yielding important new insights on both of the mechanisms of trafficking and assembly and of the pathophysiological mechanisms of human blindness as discussed in the review by Wensel et al [ 22 ].…”

PCD Genes—From Patients to Model Organisms and Back to Humans

“…These a few micrometers long protrusions are formed by the vast majority of non-dividing cells [1,2]. In photoreceptor cells (rods and cones), the sensory cilium is uniquely modified to accommodate a large amount of lightabsorbing molecules [3,4]. In the inner ear, an immotile kinocilium assembled by cochlear hair cells is accompanied by numerous highly organized actin-containing mechanosensory protrusions called stereocilia or stereovilli and plays a role in their proper arrangement [5,6].…”

“…Photoreceptors can be morphologically and functionally divided into three compartments: (i) the most distal, light-sensitive outer segment, (ii) the organelle-containing (including cilium basal body) inner segment, and (iii) the connecting cilium, enabling transport between the inner and outer segments. In the connecting cilium, microtubules have a 9 × 2 + 0 organization, while in the outer segment, doublets are gradually reduced to singlets, and microtubules dislocate and lose the nine-fold symmetry [4,5]. Similarly, olfactory cilia have the 9 × 2 + 2 configuration in the proximal cilium, but peripheral doublets are reduced to singlets in the distal part (worthy of note is that these cilia are immotile as they lack dynein arms) [5,9].…”