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Abstract Background Deficiency of complex II (succinate dehydrogenase, SDH) represents a rare cause of mitochondrial disease and is associated with a wide range of clinical symptoms. Recently, mutations of SDHAF1, the gene encoding for the SDH assembly factor 1, were reported in SDH-defective infantile leukoencephalopathy. Our goal was to identify SDHAF1 mutations in further patients and to delineate the clinical phenotype. Methods In a retrospective data collection study we identified nine children with biochemically proven complex II deficiency among our cohorts of patients with mitochondrial disorders. The cohort comprised five patients from three families affected by SDH-defective infantile leukoencephalopathy with accumulation of succinate in disordered cerebral white matter, as detected by in vivo proton MR spectroscopy. One of these patients had neuropathological features of Leigh syndrome. Four further unrelated patients of the cohort showed diverse clinical phenotypes without leukoencephalopathy. SDHAF1 was sequenced in all nine patients. Results Homozygous mutations of SDHAF1 were detected in all five patients affected by leukoencephalopathy with accumulated succinate, but not in any of the four patients with other, diverse clinical phenotypes. Two sisters had a mutation reported previously, in three patients two novel mutations were found. Conclusion Leukoencephalopathy with accumulated succinate is a key symptom of defective complex II assembly due to SDHAF1 mutations.

Abstract Background Mutations in PEX1 are the most common primary cause of Zellweger syndrome. In addition to exonic mutations, deletions and splice site mutations two 5' polymorphisms at c.-137 and c.-53 with a potential influence on PEX1 protein levels have been described in the 5' untranslated region (UTR) of the PEX1 gene. Methods We used RACE and in silico promoter prediction analysis to study the 5' UTR of PEX1. We determined the distribution of PEX1 5' polymorphisms in a cohort of 30 Zellweger syndrome patients by standard DNA sequencing. 5' polymorphisms were analysed in relation to the two most common mutations in PEX1 and were incorporated into a novel genotype-phenotype analysis by correlation of three classes of PEX1 mutations with patient survival. Results We provide evidence that the polymorphism 137 bp upstream of the ATG codon is not part of the UTR, rendering it a promoter polymorphism. We show that the first, but not the second most common PEX1 mutation arose independently of a specific upstream polymorphic constellation. By genotype-phenotype analysis we identified patients with identical exonic mutation and identical 5' polymorphisms, but strongly differing survival. Conclusions Our study suggests that two different types of PEX1 5' polymorphisms have to be distinguished: a 5' UTR polymorphism at position c.-53 and a promoter polymorphism 137 bp upstream of the PEX1 start codon. Our results indicate that the exonic PEX1 mutation correlates with patient survival, but the two 5' polymorphisms analysed in this study do not have to be considered for diagnostic and/or prognostic purposes.

Mild clinical phenotypes of ataxia‐telangiectasia (variant A‐T) are associated with biallelic ATM variants resulting in residual function of the ATM kinase. At least one regulatory, missense, or leaky splice site mutation resulting in expression of ATM with low level kinase activity was identified in subjects with variant A‐T. Studies on the pathogenicity of the germline splicing ATM variant c.1066‐6T>G have provided conflicting results. Using whole‐exome sequencing, we identified two splice site ATM variants, c.1066‐6T>G; [p.?], and c.2250G>A, [p.Ile709_Lys750del], in a compound heterozygous state in a 27‐year‐old woman who had been diagnosed as having congenital ocular motor apraxia type Cogan in her childhood. Reappraisal of her clinical phenotype revealed consistency with variant A‐T. Functional analyses showed reduced expression of ATM protein and residual activity of the ATM kinase at a level consistent with variant A‐T. Our results provide evidence for pathogenicity of the leaky ATM splice site variant c.1066‐6T>G. [ABSTRACT FROM AUTHOR]

To determine whether particular Borrelia burgdofferi s.l, genospecies associate solely with rodent reservoir hosts, we compared the genospecies prevalence in questing nymphal lxodes ticks with that in xenodiagnostic ticks that [...]