C-terminal oligomerization of podocin mediates interallelic interactions.

Interallelic interactions of membrane proteins are not taken into account while evaluating the pathogenicity of sequence variants in autosomal recessive disorders. Podocin, a membrane-anchored component of the slit diaphragm, is encoded by NPHS2, the major gene mutated in hereditary podocytopathies. We formerly showed that its R229Q variant is only pathogenic when trans-associated to specific 3' mutations and suggested the causal role of an abnormal C-terminal dimerization. Here we show by FRET analysis and size exclusion chromatography that podocin oligomerization occurs exclusively through the C-terminal tail (residues 283-382): principally through the first C-terminal helical region (H1, 283-313), which forms a coiled coil as shown by circular dichroism spectroscopy, and through the 332-348 region. We show the principal role of the oligomerization sites in mediating interallelic interactions: while the monomer-forming R286Tfs*17 podocin remains membranous irrespective of the coexpressed podocin variant identity, podocin variants with an intact H1 significantly influence each other's localization (r2 = 0.68, P = 9.2 × 10-32). The dominant negative effect resulting in intracellular retention of the pathogenic F344Lfs*4-R229Q heterooligomer occurs in parallel with a reduction in the FRET efficiency, suggesting the causal role of a conformational rearrangement. On the other hand, oligomerization can also promote the membrane localization: it can prevent the endocytosis of F344Lfs*4 or F344* podocin mutants induced by C-terminal truncation. In conclusion, C-terminal oligomerization of podocin can mediate both a dominant negative effect and interallelic complementation. Interallelic interactions of NPHS2 are not restricted to the R229Q variant and have to be considered in compound heterozygous individuals.

[Hungarian adaptation of the Caregiver Priorities and Child Health Index of Life with Disabilities questionnaire]. / Cerebralis paresisben szenvedo gyermekek egészségindexe.

INTRODUCTION: Caregiver Priorities and Child Health Index of Life with Disabilities (CPCHILD) questionnaire is a measurement tool for assessing health status and wellbeing of disabled children, which evaluates children's quality of life from the caregiver point of view. OBJECTIVE: The aim of our work was the Hungarian translation and cultural adaptation of the questionnaire and also validation of the CPCHILD on Hungarian cerebral palsy patients. Further aim was to test the eligibility of the questionnaire for superficial assessment of caregiver's psychological attitudes. METHOD: Translation of the questionnaire was carried out according to the Beaton's guidelines. Test-retest, interrater reliability (ICC) and also internal consistency (Cronbach-alpha) were calculated for reliability. The importance of the questions was assessed for face validity and known group validity test was done to measure construct validity. For examining parental attitudes, the patients were divided into ambulatory and non-ambulatory groups and the 36 quality of life questions of the 7th domain were used to find relations. RESULTS: During test-retest reliability measurements, the ICC was 0.96 (95% CI: 0.88-0.98), and Cronbach-alpha exceeded the minimal expected value of 0.7 (0.74-0.97) except in the 5th domain (0.67), while measuring interrater reliability the ICC was 0.87 (95% CI 0.70-0.94). Face validity was above the 2.0 threshold in every question (2.6-4.5; mean: 3.4 ± 1.34) and the known group validity calculations showed significant differences between the CPCHILD scores of ambulatory and non-ambulatory groups. Examining parental attitudes, a significant difference was also shown among the parents of ambulatory and non-ambulatory children in assessing the importance of sitting in the quality of life of their children (2.89 ± 1.28 vs. 3.51 ± 0.82; p<0.01). CONCLUSION: The final outcome of our study is that CPCHILD questionnaire has become widely accessible in Hungarian language. Our result, that the answers referring to the sitting abilities and the activities should be carried out in sitting position, was significantly different among the caregivers of the ambulatory and non-ambulatory children, showing that the parents of the GMFCS IV and V category children evaluate the importance of sitting ability higher compared to those parents who care for GMFCS I, II and III category children. Furthermore, the results draw attention to the wellbeing and health of the children measurable with CPCHILD as well as that parental caregiver attitudes can be recognized which may give further help in finding the balance between expectations and possibilities during the rehabilitation of cerebral palsy children. Orv Hetil. 2023; 164(16): 610-617.