Mutant dominant-negative rhodopsin∆I256 causes protein aggregates degraded via ERAD and prevents normal rhodopsin from proper membrane trafficking.

Dominant mutations in the rhodopsin gene (Rho) contribute to 25% of autosomal dominant retinitis pigmentosa (adRP), characterized by photoreceptor loss and progressive blindness. One such mutation, Rho ∆I256 , carries a 3-bp deletion, resulting in the loss of one of two isoleucines at codons 255 and 256. Our investigation, using recombinant expression in HEK293 and COS-7 cells, revealed that Rho ∆I256, akin to the known adRP mutation Rho P23H, induces the formation of rhodopsin protein (RHO) aggregates at the perinuclear region. Co-expression of Rho ∆I256 or Rho P23H with wild-type Rho WT, mimicking the heterozygous genotype of adRP patients, demonstrated the dominant-negative effect, as all isoforms were retained in perinuclear aggregates, impeding membrane trafficking. In retinal explants from WT mice, mislocalization of labeled adRP isoforms at the outer nuclear layer was observed. Further analysis revealed that RHO∆I256 aggregates are retained at the endoplasmic reticulum (ER), undergo ER-associated degradation (ERAD), and colocalize with the AAA-ATPase escort chaperone valosin-containing protein (VCP). These aggregates are polyubiquitinated and partially colocalized with the 20S proteasome subunit beta-5 (PSMB5). Pharmacological inhibition of proteasome- or VCP activity increased RHO∆I256 aggregate size. In summary, RHO∆I256 exhibits dominant pathogenicity by sequestering normal RHOWT in ER aggregates, preventing its membrane trafficking and following the ERAD degradation.

Assessment fidelity of a language screening instrument for 4-year-olds.

AIM: The aim of the study was to explore the assessment fidelity of Språkfyran, a language screening instrument for four-year-old children. Språkfyran is a mandatory part of the healthcare program within the Swedish Child Health Service (CHS) and is offered to all four-year-olds in the region Scania in Sweden. METHODS: The study was based on structured observations of twenty-four specialist CHS nurses' adherence to the Språkfyran protocol during screening. RESULTS: All the observed nurses deviated from the test protocol. There was a large variation in the number of deviations from the test protocol per nurse, with the highest number of deviations occurring for three specific testing items. Significantly more deviations were made with four-year-old bilingual children as opposed to four-year-old monolingual children. Half of the nurses did not use the test protocol. CONCLUSIONS: There is a clear need to improve the assessment fidelity of Språkfyran. Both the training that the nurses are offered, and the development of the test, are essential in securing the aim of high-quality work within the CHS. Support from experts in child speech-language development and disorders is suggested to be available at the CHS in Sweden.