Rational diagnostic strategy for Zellweger syndrome spectrum patients

Zellweger syndrome spectrum (ZSS) comprises a clinically and genetically heterogeneous disease entity, which is caused by mutations in any of the 12 different human PEX genes leading to impaired biogenesis of the peroxisome. Patients potentially suffering from ZSS are diagnosed biochemically by measuring elevated levels of very long chain fatty acids, pristanic acid and phytanic acid in plasma and serum and reduced levels of ether phospholipids in erythrocytes. Published reports on diagnostic procedures for ZSS patients are restricted either to biochemical markers or to defined mutations in a subset of PEX genes. Clarification of the primary genetic defect in an affected patient is crucial for genetic counselling, carrier testing or prenatal diagnosis. In this study, we present a rational diagnostic strategy for patients suspected of ZSS. By combining cell biology and molecular genetic methods in an appropriate sequence, we were able to detect the underlying mutation in various PEX genes within adequate time and cost. We applied this method on 90 patients who presented at our institute, Department of Pediatrics and Pediatric Neurology at Georg August University, and detected 174 mutant alleles within six different PEX genes, including two novel deletions and three new missense mutations in PEX6. Furthermore, this strategy will extend our knowledge on genotype–phenotype correlation in various PEX genes. It will contribute to a better understanding of ZSS pathogenesis, allowing the investigation of the effects of diverse mutations on the interaction between PEX proteins and peroxisomal function in vivo

Temperature-sensitive mutation of PEX6 in peroxisome biogenesis disorders in complementation group C (CG-C): comparative study of PEX6 and PEX1

Peroxisome biogenesis disorders (PBD), including Zellweger syndrome, neonatal adrenoleukodystrophy, and infantile Refsum disease, are a group of genetically heterogeneous autosomal-recessive diseases caused by mutations in PEX genes that encode peroxins, proteins required for peroxisome biogenesis. Zellweger syndrome patients present the most severe phenotype, whereas neonatal adrenoleukodystrophy patients are intermediate and infantile Refsum disease patients have the mildest features. PEX6 is a causative gene for PBD of complementation group C (CG-C) and encodes the peroxin Pex6p, one of the ATPases associated with diverse cellular activities and a member of the same family of proteins as Pex1p, a causative protein for PBD of CG-E (CG1). Here, we identified the temperature sensitivity of peroxisomes in the fibroblasts of a patient with neonatal adrenoleukodystrophy in CG-C. Peroxisomes were morphologically and biochemically formed at 30 degrees C but not at 37 degrees C. This patient was homozygous for a missense mutation, T-->C at nucleotide 170 resulting in a change from leucine to proline at amino acid 57 (L57P) in Pex6p. CG-C cell mutants (ZP92) in the Chinese hamster ovary transfected with L57P in HsPEX6 revealed the same temperature-sensitive phenotype. However, PEX1-deficient Chinese hamster ovary cell mutants (ZP101) transfected with L111P in PEX1, the counterpart to L57P in PEX6, showed no temperature sensitivity. In addition, ZP92 transfected with G708D in PEX6, the counterpart to the temperature-sensitive mutation G843D in PEX1, revealed no temperature-sensitive phenotype. These results indicate that L57P in Pex6p is a temperature-sensitive mutation causing the milder phenotype in a patient with PBD in CG-C. They also indicate that the amino acid residues responsible for temperature sensitivity do not seem to be conserved between Pex6p and Pex1

A new horizon of moyamoya disease and associated health risks explored through RNF213

The cerebrovascular disorder moyamoya disease (MMD) was first described in 1957 in Japan, and is typically considered to be an Asian-specific disease. However, it is globally recognized as one of the major causes of childhood stroke. Although several monogenic diseases are known to be complicated by Moyamoya angiopathy, the ring finger protein 213 gene (RNF213) was identified as a susceptibility gene for MMD. RNF213 is unusual, because (1) it induces MMD with no other recognizable phenotypes, (2) the RNF213 p.R4810K variant is an Asian founder mutation common to Japanese, Korean and Chinese with carrier rates of 0.5–2 % of the general population but a low penetrance, and (3) it encodes a relatively largest proteins with a dual AAA+ ATPase and E3 Ligase activities. In this review, we focus on the genetics and genetic epidemiology of RNF213, the pathology of RNF213 R4810K, and the molecular functions of RNF213, and also address the public health contributions to current unresolved issues of MMD. We also emphasize the importance of a more updated definition for MMD, of qualified cohort studies based on genetic epidemiology and an awareness of the ethical issues associated with genetic testing of carriers