The Pearring Lab has a new publication out in JCI! 

Collaborative science at its best. Hanno Bolz and Elfride De Baere uncover a novel human frameshift mutation in the CEP162 gene (c.1935dupA) that leads to early truncation of the CEP162 protein (Glu646Argfs*5) in two patients with late-onset retinitis pigmentosa. This rare inherited blindness affects the retina’s ability to respond to light as photoreceptors degenerate over time. CEP162 is a protein that binds to both microtubules and centrosomes and plays a role in recruiting proteins to the base of the cilium during cilia formation. Many ciliary genes are implicated in retinitis pigmentosa because the light-sensitive compartment of photoreceptors is a modified primary cilium. In our study, we find the truncated CEP162 protein is expressed and retains microtubule binding properties but loses centrosome localization and function in the primary cilium. We go on to show that the truncated CEP162 protein is able to properly participate in retinal development, which suggests that its inability to function at the cilium is likely leading to the human pathology. 

Kevin Cruz-Colón was awarded a 2023 National Science Foundation (NSF) Graduate Research Fellowship. Congratulations Kevin! The fellowship offers three years of support. He will be investigating how the ciliary outer segment of mouse rod photoreceptors remains a privileged compartment for light detection.

The Pearring lab has a new publication out in eLife. This project was spear-headed by Amanda Travis, PhD a very talented postdoc in the lab. She was initially motivated by the need to understand the growing number of human mutations in Arl3 that present with dominant and recessive retinal dystrophy. Using in vivo models, she uncovered that expression of dominant human mutations disrupted rod nuclear migration during retinal development. She then used a variety of biochemical assays to uncover the effector binding behaviors of these mutants and found the two dominant mutations have different effects: one results in a fast cycling phenotype while the other causes constitutive activity. The importance of her work lays in the definitive discovery that dominant mutations cause a rod migration defect due to excess active Arl3 rather than a loss of function, which will be critical for distinguishing patient phenotypes and developing targeted therapeutics.

To understand how excessive Arl3 activity was causing the rod migration phenotype, Amanda went on to rescue the defect by overexpressing: (1) Arl3 effectors, (2) lipidated cargos bound for the cilium, (3) a mutant that eliminates all Arl3 activity, or (4) a mutant that restores ciliary activation of wild type Arl3. Together, these experiments show that the
driving force established by a Arl3-GTP ciliary gradient, similar to Ran-GTP in nuclear import, is critical for nuclear migration of rod photoreceptors. This novel link between ciliary function and rod nuclear migration will serve as an important foundation for future studies on the developmental migration of neurons.