Uniparental mitochondrial DNA inheritance is not affected in Ustilago maydis Delta atg11 mutants blocked in mitophagy
BMC MICROBIOLOGY
Authors: Wagner-Vogel, Gaby; Laemmer, Frauke; Kaemper, Joerg; Basse, Christoph W.
Abstract
Background: Maternal or uniparental inheritance (UPI) of mitochondria is generally observed in sexual eukaryotes, however, the underlying mechanisms are diverse and largely unknown. Recently, based on the use of mutants blocked in autophagy, it has been demonstrated that autophagy is required for strict maternal inheritance in the nematode Caenorhabditis elegans. Uniparental mitochondrial DNA (mtDNA) inheritance has been well documented for numerous fungal species, and in particular, has been shown to be genetically governed by the mating-type loci in the isogamous species Cryptococcus neoformans, Phycomyces blakesleeanus and Ustilago maydis. Previously, we have shown that the a2 mating-type locus gene lga2 is decisive for UPI during sexual development of Ustilago maydis. In axenic culture, conditional overexpression of lga2 triggers efficient loss of mtDNA as well as mitophagy. To assess a functional relationship, we have investigated UPI in Ustilago maydis Delta atg11 mutants, which are blocked in mitophagy. Results: This study has revealed that Delta atg11 mutants are not affected in pathogenic development and this has allowed us to analyse UPI under comparable developmental conditions between mating-compatible wild-type and mutant strain combinations. Explicitly, we have examined two independent strain combinations that gave rise to different efficiencies of UPI. We demonstrate that in both cases UPI is atg11 independent, providing evidence that mitophagy is not critical for UPI in Ustilago maydis, even under conditions of strict UPI. Conclusions: Until now, analysis of a role of mitophagy in UPI has not been reported for microbial species. Our study suggests that selective autophagy does not contribute to UPI in Ustilago maydis, but is rather a consequence of selective mtDNA elimination in response to mitochondrial damage.
Unexplained early onset epileptic encephalopathy: Exome screening and phenotype expansion
EPILEPSIA
Authors: Allen, Nicholas M.; Conroy, Judith; Shahwan, Amre; Lynch, Bryan; Correa, Raony G.; Pena, Sergio D. J.; McCreary, Dara; Magalhaes, Tiago R.; Ennis, Sean; Lynch, Sally A.; King, Mary D.
Abstract
Early onset epileptic encephalopathies (EOEEs) represent a significant diagnostic challenge. Newer genomic approaches have begun to elucidate an increasing number of responsible single genes as well as emerging diagnostic strategies. In this single-center study, we aimed to investigate a cohort of children with unexplained EOEE. We performed whole-exome sequencing (WES), targeting a list of 137 epilepsy-associated genes on 50 children with unexplained EOEE. We characterized all phenotypes in detail and classified children according to known electroclinical syndromes where possible. Infants with previous genetic diagnoses, causative brain malformations, or inborn errors of metabolism were excluded. We identified disease-causing variants in 11 children (22%) in the following genes: STXBP1 (n = 3), KCNB1 (n = 2), KCNT1, SCN1A, SCN2A, GRIN2A, DNM1, and KCNA2. We also identified two further variants (in GRIA3 and CPA6) in two children requiring further investigation. Eleven variants were de novo, and in one paternal testing was not possible. Phenotypes were broadened for some variants identified. This study demonstrates that WES is a clinically useful screening tool for previously investigated unexplained EOEE and allows for reanalysis of data as new genes are being discovered. Detailed phenotyping allows for expansion of specific gene disorders leading to epileptic encephalopathy and emerging sub-phenotypes.