BTB domain mutations perturbing KCTD15 oligomerisation cause a distinctive frontonasal dysplasia syndrome.

INTRODUCTION: KCTD15 encodes an oligomeric BTB domain protein reported to inhibit neural crest formation through repression of Wnt/beta-catenin signalling, as well as transactivation by TFAP2. Heterozygous missense variants in the closely related paralogue KCTD1 cause scalp-ear-nipple syndrome. METHODS: Exome sequencing was performed on a two-generation family affected by a distinctive phenotype comprising a lipomatous frontonasal malformation, anosmia, cutis aplasia of the scalp and/or sparse hair, and congenital heart disease. Identification of a de novo missense substitution within KCTD15 led to targeted sequencing of DNA from a similarly affected sporadic patient, revealing a different missense mutation. Structural and biophysical analyses were performed to assess the effects of both amino acid substitutions on the KCTD15 protein. RESULTS: A heterozygous c.310G>C variant encoding p.(Asp104His) within the BTB domain of KCTD15 was identified in an affected father and daughter and segregated with the phenotype. In the sporadically affected patient, a de novo heterozygous c.263G>A variant encoding p.(Gly88Asp) was present in KCTD15. Both substitutions were found to perturb the pentameric assembly of the BTB domain. A crystal structure of the BTB domain variant p.(Gly88Asp) revealed a closed hexameric assembly, whereas biophysical analyses showed that the p.(Asp104His) substitution resulted in a monomeric BTB domain likely to be partially unfolded at physiological temperatures. CONCLUSION: BTB domain substitutions in KCTD1 and KCTD15 cause clinically overlapping phenotypes involving craniofacial abnormalities and cutis aplasia. The structural analyses demonstrate that missense substitutions act through a dominant negative mechanism by disrupting the higher order structure of the KCTD15 protein complex.

A BTB extension and ion-binding domain contribute to the pentameric structure and TFAP2A binding of KCTD1.

KCTD family proteins typically assemble into cullin-RING E3 ligases. KCTD1 is an atypical member that functions instead as a transcriptional repressor. Mutations in KCTD1 cause developmental abnormalities and kidney fibrosis in scalp-ear-nipple syndrome. Here, we present unexpected mechanistic insights from the structure of human KCTD1. Disease-causing mutation P20S maps to an unrecognized extension of the BTB domain that contributes to both its pentameric structure and TFAP2A binding. The C-terminal domain (CTD) shares its fold and pentameric assembly with the GTP cyclohydrolase I feedback regulatory protein (GFRP) despite lacking discernible sequence similarity. Most surprisingly, the KCTD1 CTD establishes a central channel occupied by alternating sodium and iodide ions that restrict TFAP2A dissociation. The elucidation of the structure redefines the KCTD1 BTB domain fold and identifies an unexpected ion-binding site for future study of KCTD1's function in the ectoderm, neural crest, and kidney.

Nutritional status and food insecurity in hemodialysis patients.

OBJECTIVE: The purpose of this study was to determine whether a relationship exists between nutrition status and food security of patients on hemodialysis (HD). DESIGN: A descriptive correlation study. SETTING: This study consisted of HD patients undergoing treatment at three northeast Louisiana dialysis centers. PATIENTS: Ninety-eight HD patients participated in the study. The mean age of subjects was 59.1 +/- 14.2 years. The sample was 44% white and 56% black; 49% male and 51% female. RESULTS: Multiple linear regression and chi2 analysis were used to assess relationships between demographics and food insecurity scores and Subjective Global Assessment scores. Race significantly predicted food insecurity (beta = 0.248; P = .019), with black patients being more food insecure than white subjects. A significant positive relationship was found between the level of education and Subjective Global Assessment scores (beta = 0.222; P = .037). In this sample, 16.3% of the subjects were found to be food insecure, and 64.3% of the patients were mildly to moderately malnourished, whereas another 13.3% were severely malnourished. CONCLUSIONS: Future research in this area should include food security questions related to the ability to obtain foods for health. Renal health care professionals should assess patients for possible food insecurity so that appropriate interventions can be implemented.

Are patients with diabetes receiving the same message from dietitians and nurses?

PURPOSE: The purpose of this study was to determine if registered dietitian (RD) and registered nurse (RN) certified diabetes educators (CDEs) provide similar recommendations regarding carbohydrates and dietary supplements to individuals with diabetes. METHODS: A survey was mailed to CDEs in the southern United States. Participants were asked to indicate their recommendations for use of carbohydrates, fiber, artificial sweeteners, and 12 selected dietary and herbal supplements when counseling individuals with diabetes. RESULTS: The survey sample consisted of 366 CDEs: 207 were RNs and 159 were RDs. No statistically significant differences were found between RNs and RDs in typical carbohydrate recommendations for treatment of diabetes. However, RDs were more likely than RNs to make recommendations for fiber intake or use of the glycemic index. A significant difference also was found in the treatment of hypoglycemia: RNs were more likely than RDs to recommend consuming a carbohydrate source with protein to treat hypoglycemia. CONCLUSIONS: Although some differences existed, RD and RN CDEs are making similar overall recommendations in the treatment of individuals with diabetes.

The effect of diet education on the laboratory values and knowledge of hemodialysis patients with hyperphosphatemia.

OBJECTIVE: The purpose of this study was to evaluate the effectiveness of 20 to 30 minutes per month of additional diet education on monthly laboratory values (phosphorus, calcium, parathyroid hormone, and calcium/phosphorus product) and knowledge of dietary phosphorus management in hemodialysis patients with hyperphosphatemia. DESIGN: A quasi-experimental design. SETTING: Three outpatient dialysis centers owned by the same corporation in 1 southern state. PATIENTS: Based on a 3-month average serum phosphorus >6.0 mg/dL, 70 patients were selected for participation; 63 dialysis patients completed the study, 32 in the experimental group and 31 in the control group. INTERVENTION: All patients completed a before-and-after knowledge test and had monthly blood samples drawn. Each month, the same registered dietitian provided the routine laboratory results review with control group. The experimental group received the routine laboratory review plus 20 to 30 minutes of additional diet education specifically targeting phosphorus. Main outcome measures Before-and-after knowledge test results and baseline and final serum calcium, phosphorus, parathyroid hormone, and calcium/phosphorus product levels. RESULTS: At baseline, there were no significant differences in any of the laboratory values, but the knowledge level of the experimental group was greater (P <.05) After 6 months, gains in knowledge were significantly higher in the intervention group, and the serum phosphorus and calcium/phosphorus product levels were significantly lower (P <.01) than in the control group. CONCLUSION: Based on this research, those patients who received extra education monthly showed positive changes, which may be beneficial in reducing hyperphosphatemia.