bims-curels 2023-03-12 papers

Issue of 2023–03–12
four papers selected by
Cure Mito Foundation

EMBO Rep. 2023 Mar 06. e55678

Modeling mitochondrial DNA diseases: from base editing to pluripotent stem-cell-derived organoids.

Isabella Tolle, Valeria Tiranti, Alessandro Prigione.

Mitochondrial DNA (mtDNA) diseases are multi-systemic disorders caused by mutations affecting a fraction or the entirety of mtDNA copies. Currently, there are no approved therapies for the majority of mtDNA diseases. Challenges associated with engineering mtDNA have in fact hindered the study of mtDNA defects. Despite these difficulties, it has been possible to develop valuable cellular and animal models of mtDNA diseases. Here, we describe recent advances in base editing of mtDNA and the generation of three-dimensional organoids from patient-derived human-induced pluripotent stem cells (iPSCs). Together with already available modeling tools, the combination of these novel technologies could allow determining the impact of specific mtDNA mutations in distinct human cell types and might help uncover how mtDNA mutation load segregates during tissue organization. iPSC-derived organoids could also represent a platform for the identification of treatment strategies and for probing the in vitro effectiveness of mtDNA gene therapies. These studies have the potential to increase our mechanistic understanding of mtDNA diseases and may open the way to highly needed and personalized therapeutic interventions.

Keywords: iPSCs; mitochondria; mitochondrial diseases; mitochondrial genome editing; organoids

DOI: https://doi.org/10.15252/embr.202255678

Am J Med Genet A. 2023 Mar 08.

MT-ATP6 mitochondrial disease identified by newborn screening reveals a distinct biochemical phenotype.

Christina G Tise, Courtney P Verscaj, Bryce A Mendelsohn, Jeremy Woods, Chung U Lee, Gregory M Enns, Zinandré Stander, Patricia L Hall, Tina M Cowan, Kristina P Cusmano-Ozog.

Although decreased citrulline is used as a newborn screening (NBS) marker to identify proximal urea cycle disorders (UCDs), it is also a feature of some mitochondrial diseases, including MT-ATP6 mitochondrial disease. Here we describe biochemical and clinical features of 11 children born to eight mothers from seven separate families who were identified with low citrulline by NBS (range 3-5 μM; screening cutoff >5) and ultimately diagnosed with MT-ATP6 mitochondrial disease. Follow-up testing revealed a pattern of hypocitrullinemia together with elevated propionyl-(C3) and 3-hydroxyisovaleryl-(C5-OH) acylcarnitines, and a homoplasmic pathogenic variant in MT-ATP6 in all cases. Single and multivariate analysis of NBS data from the 11 cases using Collaborative Laboratory Integrated Reports (CLIR; https://clir.mayo.edu) demonstrated citrulline <1st percentile, C3 > 50th percentile, and C5-OH >90th percentile when compared with reference data, as well as unequivocal separation from proximal UCD cases and false-positive low citrulline cases using dual scatter plots. Five of the eight mothers were symptomatic at the time of their child(ren)'s diagnosis, and all mothers and maternal grandmothers evaluated molecularly and biochemically had a homoplasmic pathogenic variant in MT-ATP6, low citrulline, elevated C3, and/or elevated C5-OH. All molecularly confirmed individuals (n = 17) with either no symptoms (n = 12), migraines (n = 1), or a neurogenic muscle weakness, ataxia, and retinitis pigmentosa (NARP) phenotype (n = 3) were found to have an A or U mitochondrial haplogroup, while one child with infantile-lethal Leigh syndrome had a B haplogroup.

Keywords: MT-ATP6 mitochondrial disease; elevated C3; elevated C5-OH; low citrulline; newborn screening; proximal urea cycle disorders

DOI: https://doi.org/10.1002/ajmg.a.63159

JIMD Rep. 2023 Mar;64(2): 150-155

Autonomic instability, arrhythmia and visual impairment in a new presentation of MTFMT-related mitochondrial disease.

Caoimhe Howard, Arundhati Dev-Borman, John Stokes, Declan O'Rourke, Ciara Gillespie, Eilish Twomey, Ina Knerr, Ritma Boruah.

Mitochondrial methionyl-tRNA formyltransferase (MTFMT) is required for the initiation of translation in mitochondria. Pathogenic variants in MTFMT have been described in association with clinical presentations with Leigh syndrome, as well with as multisystem involvement (particularly cardiac and ocular involvement). There is a spectrum of severity, but many reported presentations have been milder with a better prognosis than other pathogenic variants associated with Leigh syndrome. We describe the case of a 9-year-old boy homozygous for a pathogenic MTFMT variant (c.626C > T/p.Ser209Leu) who presented with hypertensive crisis on a background of hyperphagia and visual impairment. His clinical course was complicated by supraventricular tachycardia and severe autonomic instability, requiring intensive care unit admission. He also developed seizures, neurogenic bladder and bowel and had a markedly abnormal eye examination with bilateral optic atrophy. Magnetic resonance image brain showed abnormal high T2/fluid-attenuated inversion recovery signal within the dorsal brainstem and in the right globus pallidus with some reduced diffusivity. Despite recovery from the acute neurological and cardiac manifestations, he has ongoing deficits in his gross motor skills and continues to have hyperphagia with rapid weight gain (approx. 20 kg in 2 years). Ophthalmic findings are persistent. This case expands the phenotype associated with MTFMT disease.

Keywords: Leigh syndrome; MTFMT; autonomic instability; optic atrophy

DOI: https://doi.org/10.1002/jmd2.12355

Orphanet J Rare Dis. 2023 Mar 06. 18(1): 45

Diagnosing rare diseases and mental well-being: a family's story.

Zheqing Zhang.

When we experience symptoms, most of us walk into the clinic or hospital expecting immediate answers. For individuals with a rare condition, the path to diagnosis can be tortuous, involving months to years of waiting and a seemingly interminable search for answers. All this while, physical and psychological stress can negatively impact mental health. Each diagnostic journey is unique, but they epitomise common themes and inadequacies of the medical system. This article presents the stories of two sisters whose diagnostic journeys diverged then converged, reflecting on the impact of these experiences on mental well-being and what we can learn going forward. Hopefully, with more research and knowledge, we can catch these conditions earlier and provide better recommendations for treatment, management and prevention.

Keywords: Diagnosis; Mental well-being; Patient perspective; Rare disease; Vascular Ehlers-Danlos syndrome

DOI: https://doi.org/10.1186/s13023-023-02648-y