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Advances in Therapy Dec 2019Leber's hereditary optic neuropathy (LHON) is a relatively common, rapidly progressing inherited optic neuropathy wherein LHON-affected eyes undergo optic nerve atrophy...
Leber's hereditary optic neuropathy (LHON) is a relatively common, rapidly progressing inherited optic neuropathy wherein LHON-affected eyes undergo optic nerve atrophy due to retinal ganglion cell (RGC) loss. It is a maternally inherited (or sporadic) mitochondrial disorder caused primarily by mutations in genes that encode components of respiratory complex (RC)1 in mitochondria. Mitochondrial deficiency of RC1 compromises ATP production and oxidative stress management in RGCs. The most common LHON-causing mutations are 11778G>A, 3460G>A, and 14484T>C point mutations in MT-ND4, MT-ND1, and MT-ND6. The unusually high mitochondrial load of RGCs makes them particularly sensitive to these mutations. Patients with LHON may be prescribed ubiquinone (a component of RC3) or idebenone, a ubiquinone analogue with enhanced bioavailability to act downstream of RC1. The challenge of accessing the inner mitochondrial membrane with gene therapy for LHON, and other mitochondrial diseases, may be overcome by incorporation of a specific mitochondrion-targeting sequence (MTS) that enables allotropic expression of a nucleus-transcribed ND4 transgene. Because LHON penetrance is incomplete among carriers of the aforementioned mutations, identification of environmental factors, such as heavy smoking, that interact with genetics in the phenotypic expression of LHON may be helpful toward preventing or delaying disease development. LHON has become a model for mitochondrial and neurogenerative diseases owing to it having a clearly identified genetic cause and its early onset and rapid progression characteristics. Hence, LHON studies and genetic treatment advances may inform research of other diseases.
Topics: DNA, Mitochondrial; Electron Transport Complex I; Genetic Therapy; Humans; Mutation; Optic Atrophy, Hereditary, Leber; Phenotype; Point Mutation
PubMed: 31605306
DOI: 10.1007/s12325-019-01113-2 -
Orphanet Journal of Rare Diseases Aug 2019Chromosome 22q11.2 microdeletion syndrome, a disorder caused by heterozygous loss of genetic material in chromosome region 22q11.2, has a broad range of clinical... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Chromosome 22q11.2 microdeletion syndrome, a disorder caused by heterozygous loss of genetic material in chromosome region 22q11.2, has a broad range of clinical symptoms. The most common congenital anomalies involve the palate in 80% of patients, and the heart in 50-60% of them. The cause of the phenotypic variability is unknown. Patients usually harbor one of three common deletions sizes: 3, 2 and 1.5 Mb, between low copy repeats (LCR) designated A-D, A-C and A-B, respectively. This study aimed to analyze the association between these 3 deletion sizes and the presence of congenital cardiac and/or palatal malformations in individuals with this condition. A systematic review and meta-analysis were conducted, merging relevant published studies with data from Chilean patients to increase statistical power.
RESULTS
Eight articles out of 432 were included; the data from these studies was merged with our own, achieving a total of 1514 and 487 patients to evaluate cardiac and palate malformations, respectively. None of the compared deleted chromosomal segments were statistically associated with cardiac defects (OR: 0.654 [0.408-1.046]; OR : 1.291 [0.860-1.939]) or palate anomalies (OR: 1.731 [0.708-4.234]; OR : 0.628 [0.286-1.382]).
CONCLUSIONS
The lack of association between deletion size and CHD or PA found in this meta-analysis suggests that deletion size does not explain the incomplete penetrance of these 2 major manifestations, and that the critical region for the development of heart and palatal abnormalities is within LCR A-B, the smallest region of overlap among the three deletion sizes.
Topics: Arachnodactyly; Chromosome Deletion; Craniosynostoses; Humans; Marfan Syndrome; Phenotype
PubMed: 31399107
DOI: 10.1186/s13023-019-1170-x