M. Wherlock

BACKGROUND AND OBJECTIVES: Up to 95% of children presenting with steroid-resistant nephrotic syndrome in early life will have a pathogenic single-gene mutation in 1 of 24 genes currently associated with this disease. Others may be affected by polymorphic variants. There is currently no accepted diagnostic algorithm for clinical genetic testing. The hypothesis was that the increasing reliability of next generation sequencing allows comprehensive one-step genetic investigation of this group and similar patient groups. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: This study used next generation sequencing to screen 446 genes, including the 24 genes known to be associated with hereditary steroid-resistant nephrotic syndrome. The first 36 pediatric patients collected through a national United Kingdom Renal Registry were chosen with comprehensive phenotypic detail. Significant variants detected by next generation sequencing were confirmed by conventional Sanger sequencing. RESULTS: Analysis revealed known and novel disease-associated variations in expected genes such as NPHS1, NPHS2, and PLCe1 in 19% of patients. Phenotypically unexpected mutations were also detected in COQ2 and COL4A4 in two patients with isolated nephropathy and associated sensorineural deafness, respectively. The presence of an additional heterozygous polymorphism in WT1 in a patient with NPHS1 mutation was associated with earlier-onset disease, supporting modification of phenotype through genetic epistasis. CONCLUSIONS: This study shows that next generation sequencing analysis of pediatric steroid-resistant nephrotic syndrome patients is accurate and revealing. This analysis should be considered part of the routine genetic workup of diseases such as childhood steroid-resistant nephrotic syndrome, where the chance of genetic mutation is high but requires sequencing of multiple genes.

The activation of protein kinase B (or Akt) plays a central role in the stimulation of glucose uptake by insulin. Currently, however, numerous questions remain unanswered regarding the role of this kinase in bringing about this effect. For example, we do not know precisely where in the GLUT4 trafficking pathway this kinase acts. Nor do we know which protein substrates are responsible for mediating the effects of protein kinase B, although two recently identified proteins (AS160 and PIKfyve) may play a role. This paper addresses these important questions by reviewing recent progress in the field.

Background Bohring-Opitz syndrome (BOS) is a rare genetic disorder characterised by a recognisable craniofacial appearance and a typical ‘BOS’ posture. BOS is caused by sporadic mutations of ASXL1 . However, several typical patients with BOS have no molecular diagnosis, suggesting clinical and genetic heterogeneity. Objectives To expand the phenotypical spectrum of autosomal recessive variants of KLHL7 , reported as causing Crisponi syndrome/cold-induced sweating syndrome type 1 (CS/CISS1)-like syndrome. Methods We performed whole-exome sequencing in two families with a suspected recessive mode of inheritance. We used the Matchmaker Exchange initiative to identify additional patients. Results Here, we report six patients with microcephaly, facial dysmorphism, including exophthalmos, nevus flammeus of the glabella and joint contractures with a suspected BOS posture in five out of six patients. We identified autosomal recessive truncating mutations in the KLHL7 gene. KLHL7 encodes a BTB–kelch protein implicated in the cell cycle and in protein degradation by the ubiquitin–proteasome pathway. Recently, biallelic mutations in the KLHL7 gene were reported in four families and associated with CS/CISS1, characterised by clinical features overlapping with our patients. Conclusion We have expanded the clinical spectrum of KLHL7 autosomal recessive variants by describing a syndrome with features overlapping CS/CISS1 and BOS.

Several members of the extensive family of small GTP-binding proteins are regulated by insulin, and have been implicated in insulin action on glucose uptake. These proteins are themselves negatively regulated by a series of specific GAPs (GTPase-activating proteins). Interestingly, there is increasing evidence to suggest that PKB (protein kinase B)-dependent phosphorylation of some GAPs may relieve this negative regulation and so lead to the activation of the target small GTP-binding protein. We review recent evidence that this may be the case, and place specific emphasis on the role of these pathways in insulin-stimulated glucose uptake.

Several members of the extensive family of small GTP-binding proteins are regulated by insulin, and have been implicated in insulin action on glucose uptake. These proteins are themselves negatively regulated by a series of specific GAPs (GTPase-activating proteins). Interestingly, there is increasing evidence to suggest that PKB (protein kinase B)-dependent phosphorylation of some GAPs may relieve this negative regulation and so lead to the activation of the target small GTP-binding protein. We review recent evidence that this may be the case, and place specific emphasis on the role of these pathways in insulin-stimulated glucose uptake.