The effect of alternative oxidase (AOX) expression on early-onset manifestations in respiratory chain complex III deficient Bcs1l mutant mice

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http://urn.fi/URN:NBN:fi:hulib-201905021797
Title: The effect of alternative oxidase (AOX) expression on early-onset manifestations in respiratory chain complex III deficient Bcs1l mutant mice
Author: Wanne, Vilma
Contributor: University of Helsinki, Faculty of Biological and Environmental Sciences
Publisher: Helsingin yliopisto
Date: 2019
URI: http://urn.fi/URN:NBN:fi:hulib-201905021797
http://hdl.handle.net/10138/301475
Thesis level: master's thesis
Abstract: GRACILE (Growth Retardation, Aminoaciduria, Cholestasis, Iron Overload, Lactic Acidosis, and Early death) syndrome (Fellman disease, MIM603358) is a mitochondrial disorder that belongs to the Finnish disease heritage and follows an autosomal recessive inheritance pattern. It is a lethal neonatal disease and the affected infants usually survive only a couple of days, but in some cases up to four months. The disease is very rare affecting about 1 in 47,000 infants in Finland. GRACILE syndrome is caused by a homozygous Finnish founder mutation (c.A232G) in the BCS1L gene, which encodes an assembly factor for the mitochondrial respiratory chain complex III. The missense mutation (c.A232G) causes an amino acid change (p.S78G) in the BCS1L protein. Alternative oxidase (AOX) is a terminal oxidase that is not naturally present in mammals. It enables the respiratory chain electron flow to bypass complexes III and IV. The AOX pathway works parallel with the respiratory chain and gets activated under stress conditions in plants and lower animals. In mitochondrial diseases with a complex III deficiency, such as GRACILE syndrome, AOX expression could alleviate the symptoms caused by the complex III dysfunction. The aim of this study was to investigate the effects of AOX expression on early-onset manifestations of the disease in the Bcs1lc.A232G mouse model of GRACILE syndrome. The mice used in this study have a genetic background with a short survival to P35-40. The respiratory chain function in freshly isolated mitochondria from the liver and kidney was studied, as well as complex III activity, mitochondrial mass and liver and kidney histology. The findings of this study suggest that AOX has a strong beneficial effect on both liver and kidney histology and it is able to restore the glycogen stores to some extent, thus alleviating the glycogen depletion seen in the mice. The Bcs1lc.A232G mice also had an improved body weight in the presence of AOX, suggesting a less severe energy deficiency due to the activity of the AOX transgene. CI- and CII-linked respiration was also robustly improved in the liver. Overall, the condition of the Bcs1lc.A232G mice was improved by the presence of the AOX transgene compared to the Bcs1lc.A232G mice not expressing AOX. These results are highly encouraging for further studies on the rescue effects that AOX seems to have on this disease model.
Subject: GRACILE
BCS1L
AOX


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