Research priorities for mitochondrial disorders: Current landscape and patient and professional views.

Primary mitochondrial disorders encompass a wide range of clinical presentations and a spectrum of severity. They currently lack effective disease-modifying therapies and have a high mortality and morbidity rate. It is therefore essential to know that competitively funded research designed by academics meets the core needs of people with mitochondrial disorders and their clinicians. Priority setting partnerships are an established collaborative methodology that brings patients, carers and families, charity representatives and clinicians together to try to establish the most pressing and unanswered research priorities for a particular disease. We developed a web-based questionnaire, requesting all patients affected by primary mitochondrial disease, their carers and clinicians to pose their research questions. This yielded 709 questions from 147 participants. These were grouped into overarching themes including basic biology, causation, health services, clinical management, social impacts, prognosis, prevention, symptoms, treatment and psychological impact. Following the removal of "answered questions", the process resulted in a list of 42 discrete, answerable questions. This was further refined by web-based ranking by the community to 24 questions. These were debated at a face-to-face workshop attended by a diverse range of patients, carers, charity representatives and clinicians to create a definitive "Top 10 of unanswered research questions for primary mitochondrial disorders". These Top 10 questions related to understanding biological processes, including triggers of disease onset, mechanisms underlying progression and reasons for differential symptoms between individuals with identical genetic mutations; new treatments; biomarker discovery; psychological support and optimal management of stroke-like episodes and fatigue.

Clinical application of sequencing-based methods for parallel preimplantation genetic testing for mitochondrial DNA disease and aneuploidy.

OBJECTIVE: To validate and apply a strategy permitting parallel preimplantation genetic testing (PGT) for mitochondrial DNA (mtDNA) disease and aneuploidy (PGT-A). DESIGN: Preclinical test validation and case reports. SETTING: Fertility centers. Diagnostics laboratory. PATIENTS: Four patients at risk of transmitting mtDNA disease caused by m.8993T>G (Patients A and B), m.10191T>G (Patient C), and m.3243A>G (Patient D). Patients A, B, and C had affected children. Patients A and D displayed somatic heteroplasmy for mtDNA mutations. INTERVENTIONS: Embryo biopsy, genetic testing, and uterine transfer of embryos predicted to be euploid and mutation-free. MAIN OUTCOME MEASURES: Test accuracy, treatment outcomes, and mutation segregation. RESULTS: Accuracy of mtDNA mutation quantification was confirmed. The test was compatible with PGT-A, and half of the embryos tested were shown to be aneuploid (16/33). Mutations were detected in approximately 40% of embryo biopsies from Patients A and D (10/24) but in none from Patients B and C (n = 29). Patients B and C had healthy children following PGT and natural conception, respectively. The m.8993T>G mutation displayed skewed segregation, whereas m.3243A>G mutation levels were relatively low and potentially impacted embryo development. CONCLUSIONS: Considering the high aneuploidy rate, strategies providing a combination of PGT for mtDNA disease and aneuploidy may be advantageous compared with approaches that consider only mtDNA. Heteroplasmic women had a higher incidence of affected embryos than those with undetectable somatic mutant mtDNA but were still able to produce mutation-free embryos. While not conclusive, the results are consistent with the existence of mutation-specific segregation mechanisms occurring during oogenesis and possibly embryogenesis.

Dysregulated mitophagy and mitochondrial organization in optic atrophy due to OPA1 mutations.

OBJECTIVE: To investigate mitophagy in 5 patients with severe dominantly inherited optic atrophy (DOA), caused by depletion of OPA1 (a protein that is essential for mitochondrial fusion), compared with healthy controls. METHODS: Patients with severe DOA (DOA plus) had peripheral neuropathy, cognitive regression, and epilepsy in addition to loss of vision. We quantified mitophagy in dermal fibroblasts, using 2 high throughput imaging systems, by visualizing colocalization of mitochondrial fragments with engulfing autophagosomes. RESULTS: Fibroblasts from 3 biallelic OPA1(-/-) patients with severe DOA had increased mitochondrial fragmentation and mitochondrial DNA (mtDNA)-depleted cells due to decreased levels of OPA1 protein. Similarly, in siRNA-treated control fibroblasts, profound OPA1 knockdown caused mitochondrial fragmentation, loss of mtDNA, impaired mitochondrial function, and mitochondrial mislocalization. Compared to controls, basal mitophagy (abundance of autophagosomes colocalizing with mitochondria) was increased in (1) biallelic patients, (2) monoallelic patients with DOA plus, and (3) OPA1 siRNA-treated control cultures. Mitophagic flux was also increased. Genetic knockdown of the mitophagy protein ATG7 confirmed this by eliminating differences between patient and control fibroblasts. CONCLUSIONS: We demonstrated increased mitophagy and excessive mitochondrial fragmentation in primary human cultures associated with DOA plus due to biallelic OPA1 mutations. We previously found that increased mitophagy (mitochondrial recycling) was associated with visual loss in another mitochondrial optic neuropathy, Leber hereditary optic neuropathy (LHON). Combined with our LHON findings, this implicates excessive mitochondrial fragmentation, dysregulated mitophagy, and impaired response to energetic stress in the pathogenesis of mitochondrial optic neuropathies, potentially linked with mitochondrial mislocalization and mtDNA depletion.

Understanding the expectations of patients with inherited retinal dystrophies.

BACKGROUND: UK genetic ophthalmology services for patients with retinal dystrophy (RD) are variable. Little research exists to define service requirements, or expectations, of patients and their families. This study aimed to explore the views and perceived benefits of genetic ophthalmology services among members of families with RD. METHODS: Twenty participants with known RD mutations were recruited through UK genetic ophthalmic clinics. Semistructured qualitative interviews explored interviewees' perceptions of the role of these services. Interviews were transcribed verbatim and analysed using inductive thematic analysis. RESULTS: Interviewees' expectations and requirements of genetic ophthalmology services were wide-ranging and often perceived to be unmet. Participant expectations were classified in three groups: (1) Medical expectations included obtaining a diagnosis and information about disease/prognosis, genetic risks and research (2) Psychosocial expectations related to participants' need for support in adjusting to RD (3) Practical expectations included the desire for information about welfare and support. CONCLUSIONS: Expectations of RD families for clinical services are complex, encompassing a range of healthcare specialties. Services that align to these expectations will need to reach beyond the diagnostic arena and provide practical and psychosocial support. The identification of measurable outcomes will facilitate future development and evaluation of service delivery models. Many of the expectations identified here map to an existing, previously validated, outcomes framework for clinical genetic services. However, an additional outcome domain, labelled 'Independence' was also identified; this could either be specific to vision loss or relate generally to disability caused by genetic conditions.

PAX6 mutation in association with ptosis, cataract, iris hypoplasia, corneal opacification and diabetes: a new variant of familial aniridia?

BACKGROUND: We report a family with ptosis, cataract, iris hypoplasia and gradual corneal opacification occurring in association with a PAX6 mutation. DESIGN: Case-series. PARTICIPANTS: Fourteen family members - 8 affected, 6 unaffected controls. METHODS: All participants underwent ophthalmological assessment, including best-corrected visual acuity, slit-lamp-examination, pachymetry, endothelial cell-count, tonometry and dilated fundoscopy. All subjects underwent anthropometry and assessment of glycaemic status. Genetic analysis of the PAX6 gene was performed. MAIN OUTCOME MEASURES: Presence of ptosis, corneal, iris and lenticular changes, gycaemic and PAX6 status. RESULTS: All eight affected subjects had ptosis with reduced levator function, anterior polar cataracts, and corneal changes of variable severity - two patients had undergone penetrating keratoplasties, with graft histology revealing conjunctival cells on the cornea and severe fibroinflammatory change. Five patients had iris hypoplasia. One patient had aphakic glaucoma and another had hypoplastic optic discs. Four of the six controls had no ocular features of this syndrome, and two had isolated mild ptosis. There was no difference in height or body mass index between cases and family controls (p > 0.05), but Haemoglobin A1c was greater in the cases (median [interquartile range] 5.6(0.8) vs 5.1(0.3), p = 0.028). Genetic analysis confirmed a pathogenic PAX6 mutation in exon 12 (c1439delC) in all eight patients, but none of the controls. CONCLUSION: This is the first report of this particular constellation of ocular signs occurring in association with a PAX6 mutation. There was no association with anthropometric features, but affected subjects had worse glycaemia than controls, which may be related to the known role of PAX6 in development of the pancreas.

Understanding the impact of genetic testing for inherited retinal dystrophy.

The capability of genetic technologies is expanding rapidly in the field of inherited eye disease. New genetic testing approaches will deliver a step change in the ability to diagnose and extend the possibility of targeted treatments. However, evidence is lacking about the benefits of genetic testing to support service planning. Here, we report qualitative data about retinal dystrophy families' experiences of genetic testing in United Kingdom. The data were part of a wider study examining genetic eye service provision. Twenty interviewees from families in which a causative mutation had been identified by a genetic eye clinic were recruited to the study. Fourteen interviewees had chosen to have a genetic test and five had not; one was uncertain. In-depth telephone interviews were conducted allowing a thorough exploration of interviewees' views and experiences of the benefits of genetic counselling and testing. Transcripts were analysed using thematic analysis. Both affected and unaffected interviewees expressed mainly positive views about genetic testing, highlighting benefits such as diagnostic confirmation, risk information, and better preparation for the future. Negative consequences included the burden of knowledge, moral dilemmas around reproduction, and potential impact on insurance. The offer of genetic testing was often taken up, but was felt unnecessary in some cases. Interviewees in the study reported many benefits, suggesting genetic testing should be available to this patient group. The benefits and risks identified will inform future evaluation of models of service delivery. This research was part of a wider study exploring experiences of families with retinal dystrophy.