We tracked the segregation of the m.3243A>G mutation (MT-TL1 gene) responsible for the MELAS syndrome in the developing embryo/fetus, using tissues and cells from eight carrier females, their 38 embryos and 12 fetuses.
To investigate this point, we compared the mutant levels in 51 first polar bodies (PBs) and their counterpart (oocytes, blastomeres, or whole embryos), at risk of having (1) the "MELAS" m.3243A>G mutation in MT-TL1 (n = 30), (2) the "MERRF" m.8344A>G mutation in MT-TK (n = 15), and (3) the m.9185T>G mutation located in MT-ATP6 (n = 6).
This report highlights the need to screen various tissues to achieve an accurate mitochondrial genetic diagnosis and suggests the likelihood of myositis arising secondary to the MELASMT-TL1 m.3243A>G mutation.
The nucleotide change A to G at position m.3243 in the mitochondrial tRNA leucine (UUR) gene (MT-TL1) is the most common point mutation reported in association with the Mitochondrial Encephalomyopathy, Lactic Acidosis and Stroke-like episodes (MELAS) syndrome.
The m.3243A>G mutation in the mitochondrial gene MT-TL1 leads to a wide clinical spectrum ranging from asymptomatic carriers to MELAS (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes) at the severe end.
Stroke-like lesions (SLL) are common radiological findings in patients with mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (SLE; MELAS) harboring the m.3243A>G MTTL1 mutation.
Maternally inherited mitochondrial cardiomyopathy associated with a C-to-T transition at nucleotide 3303 of mitochondrial DNA in the tRNA(Leu(UUR)) gene.
However, patients carrying the m.3243A>G mutation in the mitochondrial tRNA leucine 1 (MT-TL1) do not always meet all the proposed criteria for the most frequently encountered mitochondrial syndrome "MELAS," an acronym for Mitochondrial Encephalomyopathy, Lactic Acidosis, and at least one Stroke-like episode.
Genetic studies have reported that approximately 80% of MELAS cases are caused by the mutation m.3243A>G of the mitochondrial transfer RNA (Leu (UUR)) gene (MT-TL1).
Fatal mitochondrial myopathy, lactic acidosis, and complex I deficiency associated with a heteroplasmic A --> G mutation at position 3251 in the mitochondrial tRNALeu(UUR) gne.
Defective respiratory capacity and mitochondrial protein synthesis in transformant cybrids harboring the tRNA(Leu(UUR)) mutation associated with maternally inherited myopathy and cardiomyopathy.