2022: A pivotal year for diagnosis and treatment of rare genetic diseases
Cold Spring Harb Mol Case Stud. 2022 Feb 25:mcs.a006204. doi: 10.1101/mcs.a006204. Online ahead of print.
The start of 2022 is an inflection point in the development of diagnostics and treatments for rare genetic diseases in prenatal, pediatric, and adult individuals; the theme of this special issue. Here I briefly review recent developments in the latter two aspects of rare genetic disease diagnostics and treatments.
February 25, 2022
Rare DiseaseRPM for NICU and PICU
Activated phosphoinositide 3-kinase δ syndrome associated with nephromegaly, growth hormone deficiency, bronchiectasis: a case report
Craig M, Geng B, Wigby K, Phillips SA, Bakhoum C, Naheedy J, Cernelc-Kohan M.
Allergy Asthma Clin Immunol. 2022 Feb 21;18(1):15. doi: 10.1186/s13223-022-00655-5.
BACKGROUND: Activated phosphoinositide 3-kinase (PI3K) δ syndrome (APDS) is a rare form of primary immunodeficiency with 243 known cases reported in the literature. Known findings associated with the condition include recurrent sinusitis and bronchitis, bronchiectasis, immune cytopenias, mild developmental delay, splenomegaly, and lymphadenopathy. We report the case of a child with APDS accompanied by unique clinical features: nephromegaly and growth hormone deficiency with associated pituitary anatomic abnormality.
CASE PRESENTATION: The patient is a nine-year-old boy with a heterozygous de novo variant in phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit δ (p.E1021K), previously reported in association with APDS. Our patient, who had no family history of immunodeficiency, exhibits classic findings of this syndrome but also has unique features that extend the phenotypic spectrum of this disorder. At 5 years of age, the patient showed marked growth deceleration and was demonstrated to have growth hormone (GH) deficiency with associated pituitary anatomic abnormality. He started GH therapy with an excellent response. He additionally has bilateral nephromegaly of unclear etiology, microscopic hematuria and proteinuria, asthma, and has developed left hip pain with arthrocentesis consistent with oligoarticular juvenile idiopathic arthritis. At age nine, the patient was referred to genetics and whole exome sequencing revealed APDS. Though there was initial concern that GH may increase risk for malignancy as GH signals through the PI3K pathway, he was allowed to continue treatment as the PI3K pathway was considered constitutively active at baseline.
CONCLUSIONS: Our patient’s unique presentation adds to the clinical information regarding APDS, demonstrates the utility of genetic testing and illustrates the importance of a multidisciplinary collaborative approach in managing this complex syndrome.
February 21, 2022
Expanding the phenotypic and molecular spectrum of NFS1-related disorders that cause functional deficiencies in mitochondrial and cytosolic iron-sulfur cluster containing enzymes
Yang JH, Friederich MW, Ellsworth KA, Frederick A, Foreman E, Malicki D, Dimmock D, Lenberg J, Prasad C, Yu AC, Anthony Rupar C, Hegele RA, Manickam K, Koboldt DC, Crist E, Choi SS, Farhan SMK, Harvey H, Sattar S, Karp N, Wong T, Haas R, Van Hove JLK, Wigby K.
Hum Mutat. 2022 Jan 13. doi: 10.1002/humu.24330. Online ahead of print.
Iron-sulfur cluster proteins are involved in critical functions for gene expression regulation and mitochondrial bioenergetics including the oxidative phosphorylation system. The c.215G>A p.(Arg72Gln) variant in NFS1 has been previously reported to cause infantile mitochondrial complex II and III deficiency. We describe three additional unrelated patients with the same missense variant. Two infants with the same homozygous variant presented with hypotonia, weakness and lactic acidosis, and one patient with compound heterozygous p.(Arg72Gln) and p.(Arg412His) variants presented as a young adult with gastrointestinal symptoms and fatigue. Skeletal muscle biopsy from patients 1 and 3 showed abnormal mitochondrial morphology, and functional analyses demonstrated decreased activity in respiratory chain complex II and variably in complexes I and III. We found decreased mitochondrial and cytosolic aconitase activities but only mildly affected lipoylation of pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase enzymes. Our studies expand the phenotypic spectrum and provide further evidence for the pathogenicity and functional sequelae of NFS1-related disorders with disturbances in both mitochondrial and cytosolic iron-sulfur cluster containing enzymes.
January 13, 2022
DNA methylation episignature in Gabriele-de Vries syndrome
Cherik F, Reilly J, Kerkhof J, Levy M, McConkey H, Barat-Houari M, Butler KM, Coubes C, Lee JA, Le Guyader G, Louie RJ, Patterson WG, Tedder ML, Bak M, Hammer TB, Craigen W, Démurger F, Dubourg C, Fradin M, Franciskovich R, Frengen E, Friedman J, Palares NR, Iascone M, Misceo D, Monin P, Odent S, Philippe C, Rouxel F, Saletti V, Strømme P, Thulin PC, Sadikovic B, Genevieve D.
Genet Med. 2022 Jan 10:S1098-3600(21)05422-8. doi: 10.1016/j.gim.2021.12.003. Online ahead of print.
PURPOSE: Gabriele-de Vries syndrome (GADEVS) is a rare genetic disorder characterized by developmental delay and/or intellectual disability, hypotonia, feeding difficulties, and distinct facial features. To refine the phenotype and to better understand the molecular basis of the syndrome, we analyzed clinical data and performed genome-wide DNA methylation analysis of a series of individuals carrying a YY1 variant.
METHODS: Clinical data were collected for 13 individuals not yet reported through an international call for collaboration. DNA was collected for 11 of these individuals and 2 previously reported individuals in an attempt to delineate a specific DNA methylation signature in GADEVS.
RESULTS: Phenotype in most individuals overlapped with the previously described features. We described 1 individual with atypical phenotype, heterozygous for a missense variant in a domain usually not involved in individuals with YY1 pathogenic missense variations. We also described a specific peripheral blood DNA methylation profile associated with YY1 variants.
CONCLUSION: We reported a distinct DNA methylation episignature in GADEVS. We expanded the clinical profile of GADEVS to include thin/sparse hair and cryptorchidism. We also highlighted the utility of DNA methylation episignature analysis for classification of variants of unknown clinical significance.
January 10, 2022
AHDC1 missense mutations in Xia-Gibbs syndrome
Khayat MM, Hu J, Jiang Y, Li H, Chander V, Dawood M, Hansen AW, Li S, Friedman J, Cross L, Bijlsma EK, Ruivenkamp CAL, Sansbury FH, Innis JW, O’Shea JO, Meng Q, Rosenfeld JA, McWalter K, Wangler MF, Lupski JR, Posey JE, Murdock D, Gibbs RA.
HGG Adv. 2021 Oct 14;2(4):100049. doi: 10.1016/j.xhgg.2021.100049. Epub 2021 Aug 10.
Xia-Gibbs syndrome (XGS; MIM: 615829) is a phenotypically heterogeneous neurodevelopmental disorder (NDD) caused by newly arising mutations in the AT-Hook DNA-Binding Motif-Containing 1 (AHDC1) gene that are predicted to lead to truncated AHDC1 protein synthesis. More than 270 individuals have been diagnosed with XGS worldwide. Despite the absence of an independent assay for AHDC1 protein function to corroborate potential functional consequences of rare variant genetic findings, there are also reports of individuals with XGS-like trait manifestations who have de novo missense AHDC1 mutations and who have been provided a molecular diagnosis of the disorder. To investigate a potential contribution of missense mutations to XGS, we mapped the missense mutations from 10 such individuals to the AHDC1 conserved protein domain structure and detailed the observed phenotypes. Five newly identified individuals were ascertained from a local XGS Registry, and an additional five were taken from external reports or databases, including one publication. Where clinical data were available, individuals with missense mutations all displayed phenotypes consistent with those observed in individuals with AHDC1 truncating mutations, including delayed motor milestones, intellectual disability (ID), hypotonia, and speech delay. A subset of the 10 reported missense mutations cluster in two regions of the AHDC1 protein with known conserved domains, likely representing functional motifs. Variants outside the clustered regions score lower for computational prediction of their likely damaging effects. Overall, de novo missense variants in AHDC1 are likely diagnostic of XGS when in silico analysis of their position relative to conserved regions is considered together with disease trait manifestations.
December 28, 2021
Characterization of a patient-derived variant of GPX4 for precision therapy
Liu H, Forouhar F, Seibt T, Saneto R, Wigby K, Friedman J, Xia X, Shchepinov MS, Ramesh SK, Conrad M, Stockwell BR.
Nat Chem Biol. 2021 Dec 20. doi: 10.1038/s41589-021-00915-2. Online ahead of print.
Glutathione peroxidase 4 (GPX4), as the only enzyme in mammals capable of reducing esterified phospholipid hydroperoxides within a cellular context, protects cells from ferroptosis. We identified a homozygous point mutation in the GPX4 gene, resulting in an R152H coding mutation, in three patients with Sedaghatian-type spondylometaphyseal dysplasia. Using structure-based analyses and cell models, including patient fibroblasts, of this variant, we found that the missense variant destabilized a critical loop, which disrupted the active site and caused a substantial loss of enzymatic function. We also found that the R152H variant of GPX4 is less susceptible to degradation, revealing the degradation mechanism of the GPX4 protein. Proof-of-concept therapeutic treatments, which overcome the impaired R152H GPX4 activity, including selenium supplementation, selective antioxidants and a deuterated polyunsaturated fatty acid were identified. In addition to revealing a general approach to investigating rare genetic diseases, we demonstrate the biochemical foundations of therapeutic strategies targeting GPX4.
December 28, 2021
Development of therapies for rare genetic disorders of GPX4: roadmap and opportunities
Cheff DM, Muotri AR, Stockwell BR, Schmidt EE, Ran Q, Kartha RV, Johnson SC, Mittal P, Arnér ESJ, Wigby KM, Hall MD, Ramesh SK
Orphanet J Rare Dis. 2021 Oct 23;16(1):446. doi: 10.1186/s13023-021-02048-0.
BACKGROUND: Extremely rare progressive diseases like Sedaghatian-type Spondylometaphyseal Dysplasia (SSMD) can be neonatally lethal and therefore go undiagnosed or are difficult to treat. Recent sequencing efforts have linked this disease to mutations in GPX4, with consequences in the resulting enzyme, glutathione peroxidase 4. This offers potential diagnostic and therapeutic avenues for those suffering from this disease, though the steps toward these treatments is often convoluted, expensive, and time-consuming.
MAIN BODY: The CureGPX4 organization was developed to promote awareness of GPX4-related diseases like SSMD, as well as support research that could lead to essential therapeutics for patients. We provide an overview of the 21 published SSMD cases and have compiled additional sequencing data for four previously unpublished individuals to illustrate the genetic component of SSMD, and the role of sequencing data in diagnosis. We outline in detail the steps CureGPX4 has taken to reach milestones of team creation, disease understanding, drug repurposing, and design of future studies.
CONCLUSION: The primary aim of this review is to provide a roadmap for therapy development for rare, ultra-rare, and difficult to diagnose diseases, as well as increase awareness of the genetic component of SSMD. This work will offer a better understanding of GPx4-related diseases, and help guide researchers, clinicians, and patients interested in other rare diseases find a path towards treatments.
October 26, 2021
Artificial intelligence enables comprehensive genome interpretation and nomination of candidate diagnoses for rare genetic diseases
De La Vega FM, Chowdhury S, Moore B, Frise E, McCarthy J, Hernandez EJ, Wong T, James K, Guidugli L, Agrawal PB, Genetti CA, Brownstein CA, Beggs AH, Löscher BS, Franke A, Boone B, Levy SE, Õunap K, Pajusalu S, Huentelman M, Ramsey K, Naymik M, Narayanan V, Veeraraghavan N, Billings P, Reese MG, Yandell M, Kingsmore SF.
Genome Med. 2021 Oct 14;13(1):153. doi: 10.1186/s13073-021-00965-0.
BACKGROUND: Clinical interpretation of genetic variants in the context of the patient’s phenotype is becoming the largest component of cost and time expenditure for genome-based diagnosis of rare genetic diseases. Artificial intelligence (AI) holds promise to greatly simplify and speed genome interpretation by integrating predictive methods with the growing knowledge of genetic disease. Here we assess the diagnostic performance of Fabric GEM, a new, AI-based, clinical decision support tool for expediting genome interpretation.
METHODS: We benchmarked GEM in a retrospective cohort of 119 probands, mostly NICU infants, diagnosed with rare genetic diseases, who received whole-genome or whole-exome sequencing (WGS, WES). We replicated our analyses in a separate cohort of 60 cases collected from five academic medical centers. For comparison, we also analyzed these cases with current state-of-the-art variant prioritization tools. Included in the comparisons were trio, duo, and singleton cases. Variants underpinning diagnoses spanned diverse modes of inheritance and types, including structural variants (SVs). Patient phenotypes were extracted from clinical notes by two means: manually and using an automated clinical natural language processing (CNLP) tool. Finally, 14 previously unsolved cases were reanalyzed.
RESULTS: GEM ranked over 90% of the causal genes among the top or second candidate and prioritized for review a median of 3 candidate genes per case, using either manually curated or CNLP-derived phenotype descriptions. Ranking of trios and duos was unchanged when analyzed as singletons. In 17 of 20 cases with diagnostic SVs, GEM identified the causal SVs as the top candidate and in 19/20 within the top five, irrespective of whether SV calls were provided or inferred ab initio by GEM using its own internal SV detection algorithm. GEM showed similar performance in absence of parental genotypes. Analysis of 14 previously unsolved cases resulted in a novel finding for one case, candidates ultimately not advanced upon manual review for 3 cases, and no new findings for 10 cases.
CONCLUSIONS: GEM enabled diagnostic interpretation inclusive of all variant types through automated nomination of a very short list of candidate genes and disorders for final review and reporting. In combination with deep phenotyping by CNLP, GEM enables substantial automation of genetic disease diagnosis, potentially decreasing cost and expediting case review.
October 14, 2021
Insights into the expanding phenotypic spectrum of inherited disorders of biogenic amines
Kuseyri Hübschmann O, Horvath G, Cortès-Saladelafont E, Yıldız Y, Mastrangelo M, Pons R, Friedman J, Mercimek-Andrews S, Wong SN, Pearson TS, Zafeiriou DI, Kulhánek J, Kurian MA, López-Laso E, Oppebøen M, Kılavuz S, Wassenberg T, Goez H, Scholl-Bürgi S, Porta F, Honzík T, Santer R, Burlina A, Sivri HS, Leuzzi V, Hoffmann GF, Jeltsch K, Hübschmann D, Garbade SF; iNTD Registry Study Group, García-Cazorla A, Opladen T.
Nat Commun. 2021 Sep 20;12(1):5529. doi: 10.1038/s41467-021-25515-5.
Inherited disorders of neurotransmitter metabolism are rare neurodevelopmental diseases presenting with movement disorders and global developmental delay. This study presents the results of the first standardized deep phenotyping approach and describes the clinical and biochemical presentation at disease onset as well as diagnostic approaches of 275 patients from the registry of the International Working Group on Neurotransmitter related Disorders. The results reveal an increased rate of prematurity, a high risk for being small for gestational age and for congenital microcephaly in some disorders. Age at diagnosis and the diagnostic delay are influenced by the diagnostic methods applied and by disease-specific symptoms. The timepoint of investigation was also a significant factor: delay to diagnosis has decreased in recent years, possibly due to novel diagnostic approaches or raised awareness. Although each disorder has a specific biochemical pattern, we observed confounding exceptions to the rule. The data provide comprehensive insights into the phenotypic spectrum of neurotransmitter disorders.
September 23, 2021
Commentary: Galactosemia Diagnosis by Whole Exome Sequencing Later in Life
Friedman J, Lucas-Del-Pozo S, Moreno-Martinez D, Camprodon-Gomez M, Moreno-Martinez D, Hernandez-Vara J, Kurian MA.
September 16, 2021