Pearring, J. N. | bioRxiv Science

bioRxiv2021

Loss of CEP162 function at the primary cilium delays ciliogenesis and causes retinal ciliopathy in humans

Defects in primary or motile cilia result in a variety of human pathologies, and retinal degeneration is frequently associated with these so-called ciliopathies. We show that homozygosity for a truncating variant in CEP162, a centrosome and microtubule-associated protein required for transition zone (TZ) assembly during ciliogenesis and neuronal differentiation in the retina, causes late-onset retinitis pigmentosa in 2 unrelated families. The mutant CEP162-E646R*5 protein is expressed and properly localized to the mitotic spindle but missing from the basal body in primary and photoreceptor cilia. This impairs recruitment of TZ components to the basal body and corresponds to complete loss of CEP162 function at the ciliary compartment, reflected by delayed formation of dysmorphic cilia. In contrast, rescue of increased cell death in the developing mouse retina after shRNA knockdown of Cep162 by expression of CEP162-E646R*5 indicates that the mutant retains its role for retinal neurogenesis. Human retinal degeneration thus results from specific loss of ciliary CEP162 function. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=134 HEIGHT=200 SRC="FIGDIR/small/469779v3_ufig1.gif" ALT="Figure 1"> View larger version (53K): org.highwire.dtl.DTLVardef@593dccorg.highwire.dtl.DTLVardef@e84d7forg.highwire.dtl.DTLVardef@137ce56org.highwire.dtl.DTLVardef@cba1f7_HPS_FORMAT_FIGEXP M_FIG C_FIG

genetics↗

bioRxiv2020

The GARP Domain of the Rod CNG Channel's β1-subunit Contains Distinct Sites for Outer Segment Targeting and Connecting to the Photoreceptor Disc Rim

Vision begins when light is captured by the outer segment organelle of photoreceptor cells in the retina. Outer segments are modified cilia filled with hundreds of flattened disc-shaped membranes. Disc membranes are separated from the surrounding plasma membrane and each membrane type has unique protein components. The mechanisms underlying this protein sorting remain entirely unknown. In this study, we investigated the outer segment delivery of the rod cyclic nucleotide-gated (CNG) channel, which is located in the outer segment plasma membrane where it mediates the electrical response to light. We now show that the targeted delivery of the CNG channel to the outer segment requires pre-assembly of its constituent 1 and {beta}1 subunits and that CNG{beta}1 contains specific targeting information encoded within the glutamic acid-rich region of its N-terminal GARP domain. We also found that the GARP domain connects the CNG channel to photoreceptor disc rims likely through an interaction with peripherin-2 and demonstrated that this function is performed by a proline-enriched region adjacent to the GARP domain. Our data reveal fine functional specializations within the structural domains of the CNG channel and suggest that channel delivery to the outer segment is independent of peripherin-2 interactions. Significance StatementThe precise delivery and organization of signaling proteins in the ciliary outer segment organelle of photoreceptor cells is critical for light detection. We report that the CNG channel, mediating the electrical response to light in rods, contains a region within the N-terminus of its CNG{beta}1 subunit that encodes the outer segment targeting information for the entire channel. This targeting region is adjacent to a region that connects CNG{beta}1 to the rims of photoreceptor discs, likely determining the subcellular compartmentalization of the CNG channel into the outer segment plasma membrane.

cell biology↗