Tulp1, short for tubby-like protein 1, is a photoreceptor-specific protein crucial for protein trafficking in the retina. It localizes to the inner segment (IS) and synapse of photoreceptor cells. Tulp1 likely functions as an adapter molecule, linking vesicles to molecular motors and the cytoskeletal scaffold, which is essential for the proper localization of various photoreceptor proteins [2].

In zebrafish models, knockout of tulp1a led to mislocalization of UV cone opsins and specific UV cone degeneration, while tulp1b knockout caused mislocalization of rod opsins and rod-cone degeneration. The double knockout (tulp1-dKO) zebrafish showed opsin mislocalization in all photoreceptor types, severe early-onset degeneration, reduced photoreceptor cilium length, down-regulation of tektin2 (a ciliary and flagellar microtubule component), and activation of ferroptosis [1]. In Tulp1-deficient mice, the localization of photoreceptor disc component (PRCD) to photoreceptor outer segment discs was altered [3].

In conclusion, Tulp1 is vital for opsin trafficking and cilia structure in photoreceptor cells. Gene knockout models in zebrafish and mice have revealed its role in preventing early-onset retinal degeneration, highlighting its significance in understanding the pathogenesis of retinal dystrophies [1,3].