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Timothy KW, Bauer R, Larkin KA, Walsh EP, Abrams DJ, Corcia CG, Valsamakis A, Pitt GS, Dick IE, Golden A. A Natural History Study of Timothy Syndrome. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2024:2024.05.20.24307583. [PMID: 38826393 PMCID: PMC11142284 DOI: 10.1101/2024.05.20.24307583] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2024]
Abstract
Timothy syndrome (OMIM #601005) is a rare disease caused by variants in the gene CACNA1C . Timothy syndrome patients were first identified as having a cardiac presentation of Long QT and syndactyly of the fingers and/or toes, and an identical variant in CACNA1C , Gly406Arg. However, since this original identification, more individuals harboring diverse variants in CACNA1C have been identified and have presented with various cardiac and extra-cardiac symptoms. Furthermore, it has remained underexplored whether individuals harboring canonical Gly406Arg variants in mutually exclusive exon 8A (Timothy syndrome 1) or exon 8 (Timothy syndrome 2) have additional symptoms. Here, we describe the first Natural History Study for Timothy syndrome, providing a thorough resource describing the current understanding of disease manifestation in Timothy syndrome patients. Parents of Timothy syndrome children were queried regarding a wide-ranging set of symptoms and features via a survey. Importantly, we find that in addition to cardiac concerns, Timothy syndrome patients commonly share extra-cardiac features including neurodevelopmental impairments, hypoglycemia, and respiratory problems. Our work expands the current understanding of the disorder to better inform the care of Timothy syndrome patients.
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Jiang C, Zhang Y. Current updates on arrhythmia within Timothy syndrome: genetics, mechanisms and therapeutics. Expert Rev Mol Med 2023; 25:e17. [PMID: 37132248 PMCID: PMC10407238 DOI: 10.1017/erm.2023.11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2023] [Revised: 04/13/2023] [Accepted: 04/23/2023] [Indexed: 05/04/2023]
Abstract
Timothy syndrome (TS), characterised by multiple system malfunction especially the prolonged corrected QT interval and synchronised appearance of hand/foot syndactyly, is an extremely rare disease affecting early life with devastating arrhythmia. In this work, firstly, the various mutations in causative gene CACNA1C encoding cardiac L-type voltage-gated calcium channel (LTCC), regard with the genetic pathogeny and nomenclature of TS are reviewed. Secondly, the expression profile and function of CACNA1C gene encoding Cav1.2 proteins, and its gain-of-function mutation in TS leading to multiple organ disease phenotypes especially arrhythmia are discussed. More importantly, we focus on the altered molecular mechanism underlying arrhythmia in TS, and discuss about how LTCC malfunction in TS can cause disorganised calcium handling with excessive intracellular calcium and its triggered dysregulated excitation-transcription coupling. In addition, current therapeutics for TS cardiac phenotypes including LTCC blockers, beta-adrenergic blocking agents, sodium channel blocker, multichannel inhibitors and pacemakers are summarised. Eventually, the research strategy using patient-specific induced pluripotent stem cells is recommended as one of the promising future directions for developing therapeutic approaches. This review updates our understanding on the research progress and future avenues to study the genetics and molecular mechanism underlying the pathogenesis of devastating arrhythmia within TS, and provides novel insights for developing therapeutic measures.
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Affiliation(s)
- Congshan Jiang
- National Regional Children's Medical Centre (Northwest), Key Laboratory of Precision Medicine to Pediatric Diseases of Shaanxi Province, Xi'an Key Laboratory of Children's Health and Diseases, Shaanxi Institute for Pediatric Diseases, Xi'an Children's Hospital, Affiliated Children's Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710003, China
| | - Yanmin Zhang
- National Regional Children's Medical Centre (Northwest), Key Laboratory of Precision Medicine to Pediatric Diseases of Shaanxi Province, Xi'an Key Laboratory of Children's Health and Diseases, Shaanxi Institute for Pediatric Diseases, Xi'an Children's Hospital, Affiliated Children's Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710003, China
- Department of Cardiology, Xi'an Children's Hospital, Affiliated Children's Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710003, China
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Borbás J, Vámos M, Hategan L, Hanák L, Farkas N, Szakács Z, Csupor D, Tél B, Kupó P, Csányi B, Nagy V, Komócsi A, Habon T, Hegyi P, Sepp R. Geno- and phenotypic characteristics and clinical outcomes of CACNA1C gene mutation associated Timothy syndrome, “cardiac only” Timothy syndrome and isolated long QT syndrome 8: A systematic review. Front Cardiovasc Med 2022; 9:1021009. [DOI: 10.3389/fcvm.2022.1021009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Accepted: 11/02/2022] [Indexed: 11/30/2022] Open
Abstract
BackgroundMutations in the CACNA1C gene–encoding for the major Ca2+ channel of the heart–may exhibit a variety of clinical manifestations. These include typical or atypical Timothy syndromes (TS) which are associated with multiple organ manifestations, and cardiac involvement in form of malignant arrhythmias, QTc prolongation, or AV block. “Cardiac only” Timothy syndrome (COTS) shows no extracardiac manifestation, whereas some CACNA1C gene mutations are associated with QTc prolongation alone (isolated long QT syndrome 8, LQT8).MethodsA systematic search of the literature reporting cases of CACNA1C gene mutation associated syndromes, including TS, COTS and isolated LQT8 via major databases published from 2004 through 2019 was performed. Detailed patient-level phenotypic and genotypic characteristics, as well as long-term outcome measures were collected and compared between pre-specified patient groups, defined both on phenotype and genotype.ResultsA total of 59 TS, 6 COTS, and 20 isolated LQT8 index cases were identified. Apart of syndactyly or baldness, there were no major differences regarding clinical manifestations or outcome measures between TS subtypes, either defining TS subtypes on the genotype or based on the phenotype. Both subtypes were characterized by an extreme degree of QTc prolongation (median ≥600 ms) which were reflected in high major adverse cardiac event rate. On the other hand, there were marked differences between TS, COTS, and isolated LQT8. Timothy syndrome was characterized by a much earlier disease onset, much more pronounced QTc prolongation and much higher mortality rate than COTS or isolated LQT8. Similar differences were observed comparing CACNA1C exon 8/8A vs. non-exon 8/8A mutation carriers. TS showed a high degree of genetic homogeneity, as the p.Gly406Arg mutation either in exon 8 or exon 8A alone was responsible for 70% of the cases.ConclusionsClinical phenotypes associated with mutations in the CACNA1C gene show important clinical differences. Timothy syndrome is associated with the most severe clinical phenotype and with the highest risk of morbidity and mortality. However, distinguishing TS subtypes, in any form, are not supported by our data.Systematic review registration[https://www.crd.york.ac.uk/prospero/], identifier [CRD42020184737].
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Kessi M, Chen B, Peng J, Yan F, Yang L, Yin F. Calcium channelopathies and intellectual disability: a systematic review. Orphanet J Rare Dis 2021; 16:219. [PMID: 33985586 PMCID: PMC8120735 DOI: 10.1186/s13023-021-01850-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Accepted: 05/04/2021] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Calcium ions are involved in several human cellular processes including corticogenesis, transcription, and synaptogenesis. Nevertheless, the relationship between calcium channelopathies (CCs) and intellectual disability (ID)/global developmental delay (GDD) has been poorly investigated. We hypothesised that CCs play a major role in the development of ID/GDD and that both gain- and loss-of-function variants of calcium channel genes can induce ID/GDD. As a result, we performed a systematic review to investigate the contribution of CCs, potential mechanisms underlying their involvement in ID/GDD, advancements in cell and animal models, treatments, brain anomalies in patients with CCs, and the existing gaps in the knowledge. We performed a systematic search in PubMed, Embase, ClinVar, OMIM, ClinGen, Gene Reviews, DECIPHER and LOVD databases to search for articles/records published before March 2021. The following search strategies were employed: ID and calcium channel, mental retardation and calcium channel, GDD and calcium channel, developmental delay and calcium channel. MAIN BODY A total of 59 reports describing 159 cases were found in PubMed, Embase, ClinVar, and LOVD databases. Variations in ten calcium channel genes including CACNA1A, CACNA1C, CACNA1I, CACNA1H, CACNA1D, CACNA2D1, CACNA2D2, CACNA1E, CACNA1F, and CACNA1G were found to be associated with ID/GDD. Most variants exhibited gain-of-function effect. Severe to profound ID/GDD was observed more for the cases with gain-of-function variants as compared to those with loss-of-function. CACNA1E, CACNA1G, CACNA1F, CACNA2D2 and CACNA1A associated with more severe phenotype. Furthermore, 157 copy number variations (CNVs) spanning calcium genes were identified in DECIPHER database. The leading genes included CACNA1C, CACNA1A, and CACNA1E. Overall, the underlying mechanisms included gain- and/ or loss-of-function, alteration in kinetics (activation, inactivation) and dominant-negative effects of truncated forms of alpha1 subunits. Forty of the identified cases featured cerebellar atrophy. We identified only a few cell and animal studies that focused on the mechanisms of ID/GDD in relation to CCs. There is a scarcity of studies on treatment options for ID/GDD both in vivo and in vitro. CONCLUSION Our results suggest that CCs play a major role in ID/GDD. While both gain- and loss-of-function variants are associated with ID/GDD, the mechanisms underlying their involvement need further scrutiny.
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Affiliation(s)
- Miriam Kessi
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China
- Hunan Intellectual and Developmental Disabilities Research Center, Changsha, Hunan, China
- Kilimanjaro Christian Medical University College, Moshi, Tanzania
- Mawenzi Regional Referral Hospital, Moshi, Tanzania
| | - Baiyu Chen
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China
- Hunan Intellectual and Developmental Disabilities Research Center, Changsha, Hunan, China
| | - Jing Peng
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China
- Hunan Intellectual and Developmental Disabilities Research Center, Changsha, Hunan, China
| | - Fangling Yan
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China
- Hunan Intellectual and Developmental Disabilities Research Center, Changsha, Hunan, China
| | - Lifen Yang
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China
- Hunan Intellectual and Developmental Disabilities Research Center, Changsha, Hunan, China
| | - Fei Yin
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, 410008, Hunan, China.
- Hunan Intellectual and Developmental Disabilities Research Center, Changsha, Hunan, China.
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Bauer R, Timothy KW, Golden A. Update on the Molecular Genetics of Timothy Syndrome. Front Pediatr 2021; 9:668546. [PMID: 34079780 PMCID: PMC8165229 DOI: 10.3389/fped.2021.668546] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Accepted: 04/19/2021] [Indexed: 12/11/2022] Open
Abstract
Timothy Syndrome (TS) (OMIM #601005) is a rare autosomal dominant syndrome caused by variants in CACNA1C, which encodes the α1C subunit of the voltage-gated calcium channel Cav1.2. TS is classically caused by only a few different genetic changes and characterized by prolonged QT interval, syndactyly, and neurodevelopmental delay; however, the number of identified TS-causing variants is growing, and the resulting symptom profiles are incredibly complex and variable. Here, we aim to review the genetic and clinical findings of all published case reports of TS to date. We discuss multiple possible mechanisms for the variability seen in clinical features across these cases, including mosaicism, genetic background, isoform complexity of CACNA1C and differential expression of transcripts, and biophysical changes in mutant CACNA1C channels. Finally, we propose future research directions such as variant validation, in vivo modeling, and natural history characterization.
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Affiliation(s)
- Rosemary Bauer
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
| | | | - Andy Golden
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
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Ozekin YH, Isner T, Bates EA. Ion Channel Contributions to Morphological Development: Insights From the Role of Kir2.1 in Bone Development. Front Mol Neurosci 2020; 13:99. [PMID: 32581710 PMCID: PMC7296152 DOI: 10.3389/fnmol.2020.00099] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2020] [Accepted: 05/08/2020] [Indexed: 12/21/2022] Open
Abstract
The role of ion channels in neurons and muscles has been well characterized. However, recent work has demonstrated both the presence and necessity of ion channels in diverse cell types for morphological development. For example, mutations that disrupt ion channels give rise to abnormal structural development in species of flies, frogs, fish, mice, and humans. Furthermore, medications and recreational drugs that target ion channels are associated with higher incidence of birth defects in humans. In this review we establish the effects of several teratogens on development including epilepsy treatment drugs (topiramate, valproate, ethosuximide, phenobarbital, phenytoin, and carbamazepine), nicotine, heat, and cannabinoids. We then propose potential links between these teratogenic agents and ion channels with mechanistic insights from model organisms. Finally, we talk about the role of a particular ion channel, Kir2.1, in the formation and development of bone as an example of how ion channels can be used to uncover important processes in morphogenesis. Because ion channels are common targets of many currently used medications, understanding how ion channels impact morphological development will be important for prevention of birth defects. It is becoming increasingly clear that ion channels have functional roles outside of tissues that have been classically considered excitable.
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Affiliation(s)
- Yunus H Ozekin
- Department of Pediatrics, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Trevor Isner
- Department of Pediatrics, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Emily A Bates
- Department of Pediatrics, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
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An autism-causing calcium channel variant functions with selective autophagy to alter axon targeting and behavior. PLoS Genet 2019; 15:e1008488. [PMID: 31805042 PMCID: PMC6894750 DOI: 10.1371/journal.pgen.1008488] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Accepted: 10/21/2019] [Indexed: 11/22/2022] Open
Abstract
Common and rare variants of the CACNA1C voltage-gated calcium channel gene have been associated with autism and other neurodevelopmental disorders including schizophrenia, bipolar disorder and ADHD. However, little is known about how CACNA1C variants affect cellular processes to alter neurodevelopment. The Timothy syndrome mutation is a rare de novo gain-of-function variant in CACNA1C that causes autism with high penetrance, providing a powerful avenue into investigating the role of CACNA1C variants in neurodevelopmental disorders. Here, we use egl-19, the C. elegans homolog of CACNA1C, to investigate the role of voltage-gated calcium channels in autism. We show that an egl-19(gof) mutation that is equivalent to the Timothy syndrome mutation can alter axon targeting and affect behavior in C. elegans. We find that wildtype egl-19 negatively regulates axon termination. The egl-19(gof) mutation represses axon termination to cause axon targeting defects that lead to the misplacement of electrical synapses and alterations in habituation to light touch. Moreover, genetic interactions indicate that the egl-19(gof) mutation functions with genes that promote selective autophagy to cause defects in axon termination and behavior. These results reveal a novel genetic mechanism whereby a de novo mutation in CACNA1C can drive alterations in circuit formation and behavior. Autism is a disorder that affects neuronal development, leading to alterations in cognition and behavior. Imaging studies have revealed alterations in axonal connectivity as a key feature of autism. However, the underlying perturbations in cell biology that drive these alterations remain largely unknown. To address this issue, we have taken advantage of the Timothy syndrome mutation, a variant in a voltage-gated calcium channel that has the unusual property of causing autism with high penetrance. We identify a role for wild-type voltage-gated calcium channels in regulating axon targeting in C. elegans. Moreover, we find that two different versions of the Timothy syndrome mutation disrupt axon targeting. Our results suggest that the Timothy syndrome mutations disrupt axon targeting and behavior by interacting with genes that promote selective autophagy, the process through which cellular components are selected for degradation. These results reveal a mechanism through which variants in voltage-gated calcium channels can cause the disruptions in axonal connectivity that underlie autism.
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8
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Han D, Xue X, Yan Y, Li G. Dysfunctional Cav1.2 channel in Timothy syndrome, from cell to bedside. Exp Biol Med (Maywood) 2019; 244:960-971. [PMID: 31324123 DOI: 10.1177/1535370219863149] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Timothy syndrome is a rare disorder caused by CACNA1C gene mutations and characterized by multi-organ system dysfunctions, including ventricular arrhythmias, syndactyly, dysmorphic facial features, intermittent hypoglycemia, immunodeficiency, developmental delay, and autism. Because of the low morbidity and high mortality at a young age, it remains a huge challenge to establish a diagnosis and treatment system to manage Timothy syndrome patients. Here, we aim to provide a detailed review of Timothy syndrome, discuss the mechanisms underlying dysfunctional Cav1.2 due to CACNA1C mutations, and provide some new emerging evidences in treating Timothy syndrome from cell to bedside, promoting the management of this rare disease. Impact statement The knowledge of Timothy syndrome (TS) caused by dysfunctional Cav1.2 channel due to CACNA1C mutations is rapidly evolving as novel technologies of electrophysiology are introduced and our understanding of the mechanisms of TS develops. In this review, we focus on the TS-related dysfunctional Cav1.2 and the underlying mechanisms. We update TS-related CACNA1C mutations in a precise way over the past 20 years and summarize all reported TS patients based on their clinical presentations and molecular mechanisms, respectively. We hope this review will provide a new comprehensive way to better understand the electrophysiological mechanisms underlying TS from cell to bedside, promoting the management of TS in practice.
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Affiliation(s)
- Dan Han
- 1 Department of Cardiology, the First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, P. R. China.,2 Department of Cardiovascular Surgery, First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, P.R. China*These authors contributed equally to this work and should be considered to share first authorship
| | - Xiaolin Xue
- 1 Department of Cardiology, the First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, P. R. China
| | - Yang Yan
- 2 Department of Cardiovascular Surgery, First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, P.R. China*These authors contributed equally to this work and should be considered to share first authorship
| | - Guoliang Li
- 1 Department of Cardiology, the First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, P. R. China
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Colson C, Mittre H, Busson A, Leenhardt A, Denjoy I, Fressard V, Troadec Y. Unusual clinical description of adult with Timothy syndrome, carrier of a new heterozygote mutation of CACNA1C. Eur J Med Genet 2019; 62:103648. [PMID: 30998997 DOI: 10.1016/j.ejmg.2019.04.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 02/11/2019] [Accepted: 04/02/2019] [Indexed: 11/19/2022]
Abstract
CANAC1C encodes for the main cardiac L-type calcium channel and mutations on it lead to a prolonged QT interval in Timothy Syndrome (TS). We provide a new de novo constitutional heterozygote missense variation in CACNA1C in a living adult woman, also carrier of the known c.2146-1G>C heterozygous variation of PKP2 inherited from her father. To our knowledge, this patient is the first to have the two variations in these genes. Theses clinical and molecular findings expand the clinical and molecular spectrum of TS and show the interest of next generation sequencing or whole exome sequencing in rare disorders, atypical or novel phenotype.
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Affiliation(s)
- Cindy Colson
- Service Génétique, Génétique Clinique, CHU, Caen, France; Normandy University, UNICAEN, BIOTARGEN, Caen, France.
| | - Hervé Mittre
- Service Génétique, Génétique Moléculaire, CHU, Caen, France
| | - Adeline Busson
- Service de Génétique Clinique, Hôpital Erasme, Bruxelles, Belgium
| | - Antoine Leenhardt
- Service de cardiologie, Hôpital Xavier Bichat-Claude Bernard, Paris, France
| | - Isabelle Denjoy
- Service de cardiologie, Hôpital Xavier Bichat-Claude Bernard, Paris, France
| | - Véronique Fressard
- Centre de génétique moléculaire et chromosomique, UF cardiogénétique et myogénétique moléculaire et cellulaire, Hôpital Pitié-Salpétrière, Paris, France
| | - Yann Troadec
- Service Génétique, Génétique Clinique, CHU, Caen, France; Normandy University, UNICAEN, BIOTARGEN, Caen, France
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Crotti L, Ghidoni A, Dagradi F. Genetics of Adult and Fetal Forms of Long QT Syndrome. GENETIC CAUSES OF CARDIAC DISEASE 2019. [DOI: 10.1007/978-3-030-27371-2_1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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12
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Belus MT, Rogers MA, Elzubeir A, Josey M, Rose S, Andreeva V, Yelick PC, Bates EA. Kir2.1 is important for efficient BMP signaling in mammalian face development. Dev Biol 2018; 444 Suppl 1:S297-S307. [PMID: 29571612 PMCID: PMC6148416 DOI: 10.1016/j.ydbio.2018.02.012] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Revised: 02/21/2018] [Accepted: 02/21/2018] [Indexed: 12/23/2022]
Abstract
Mutations that disrupt the inwardly rectifying potassium channel Kir2.1 lead to Andersen-Tawil syndrome that includes periodic paralysis, cardiac arrhythmia, cognitive deficits, craniofacial dysmorphologies and limb defects. The molecular mechanism that underlies the developmental consequences of inhibition of these channels has remained a mystery. We show that while loss of Kir2.1 function does not affect expression of several early facial patterning genes, the domain in which Pou3f3 is expressed in the maxillary arch is reduced. Pou3f3 is important for development of the jugal and squamosal bones. The reduced expression domain of Pou3f3 is consistent with the reduction in the size of the squamosal and jugal bones in Kcnj2KO/KO animals, however it does not account for the diverse craniofacial defects observed in Kcnj2KO/KO animals. We show that Kir2.1 function is required in the cranial neural crest for morphogenesis of several craniofacial structures including palate closure. We find that while the palatal shelves of Kir2.1-null embryos elevate properly, they are reduced in size due to decreased proliferation of the palatal mesenchyme. While we find no reduction in expression of BMP ligands, receptors, and associated Smads in this setting, loss of Kir2.1 reduces the efficacy of BMP signaling as shown by the reduction of phosphorylated Smad 1/5/8 and reduced expression of BMP targets Smad6 and Satb2.
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Affiliation(s)
- Matthew T Belus
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO 80045, United States
| | - Madison A Rogers
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO 80045, United States
| | - Alaaeddin Elzubeir
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO 80045, United States
| | - Megan Josey
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO 80045, United States
| | - Steven Rose
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO 80045, United States
| | - Viktoria Andreeva
- Department of Orthodontics, Division of Craniofacial and Molecular Genetics, Tufts University, Boston, MA 02111, United States
| | - Pamela C Yelick
- Department of Orthodontics, Division of Craniofacial and Molecular Genetics, Tufts University, Boston, MA 02111, United States
| | - Emily A Bates
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO 80045, United States.
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Gardner RJM, Crozier IG, Binfield AL, Love DR, Lehnert K, Gibson K, Lintott CJ, Snell RG, Jacobsen JC, Jones PP, Waddell-Smith KE, Kennedy MA, Skinner JR. Penetrance and expressivity of the R858H CACNA1C variant in a five-generation pedigree segregating an arrhythmogenic channelopathy. Mol Genet Genomic Med 2018; 7:e00476. [PMID: 30345660 PMCID: PMC6382452 DOI: 10.1002/mgg3.476] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 08/22/2018] [Accepted: 08/23/2018] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Isolated cardiac arrhythmia due to a variant in CACNA1C is of recent knowledge. Most reports have been of singleton cases or of quite small families, and estimates of penetrance and expressivity have been difficult to obtain. We here describe a large pedigree, from which such estimates have been calculated. METHODS We studied a five-generation family, in which a CACNA1C variant c.2573G>A p.Arg858His co-segregates with syncope and cardiac arrest, documenting electrocardiographic data and cardiac symptomatology. The reported patients/families from the literature with CACNA1C gene variants were reviewed, and genotype-phenotype correlations are drawn. RESULTS The range of phenotype in the studied family is wide, from no apparent effect, through an asymptomatic QT interval prolongation on electrocardiography, to episodes of presyncope and syncope, ventricular fibrillation, and sudden death. QT prolongation showed inconsistent correlation with functional cardiology. Based upon analysis of 28 heterozygous family members, estimates of penetrance and expressivity are derived. CONCLUSIONS These estimates of penetrance and expressivity, for this specific variant, may be useful in clinical practice. Review of the literature indicates that individual CACNA1C variants have their own particular genotype-phenotype correlations. We suggest that, at least in respect of the particular variant reported here, "arrhythmogenic channelopathy" may be a more fitting nomenclature than long QT syndrome.
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Affiliation(s)
- R J McKinlay Gardner
- Cardiac Inherited Disease Group, Auckland, New Zealand.,Genetic Health Service New Zealand (South Island Hub), Christchurch Hospital, Christchurch, New Zealand.,Clinical Genetics Group, Department of Women's and Children's Health, University of Otago, Dunedin, New Zealand
| | - Ian G Crozier
- Cardiac Inherited Disease Group, Auckland, New Zealand.,Department of Cardiology, Christchurch Hospital, Christchurch, New Zealand
| | - Alex L Binfield
- Cardiac Inherited Disease Group, Auckland, New Zealand.,Department of Paediatrics, Christchurch Hospital, Christchurch, New Zealand.,Department of Paediatrics, University of Otago, Christchurch, New Zealand
| | - Donald R Love
- Cardiac Inherited Disease Group, Auckland, New Zealand.,LabPlus, Auckland City Hospital, Auckland, New Zealand
| | - Klaus Lehnert
- Cardiac Inherited Disease Group, Auckland, New Zealand.,School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Kate Gibson
- Cardiac Inherited Disease Group, Auckland, New Zealand.,Genetic Health Service New Zealand (South Island Hub), Christchurch Hospital, Christchurch, New Zealand
| | - Caroline J Lintott
- Cardiac Inherited Disease Group, Auckland, New Zealand.,Genetic Health Service New Zealand (South Island Hub), Christchurch Hospital, Christchurch, New Zealand
| | - Russell G Snell
- Cardiac Inherited Disease Group, Auckland, New Zealand.,School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Jessie C Jacobsen
- Cardiac Inherited Disease Group, Auckland, New Zealand.,School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Peter P Jones
- Cardiac Inherited Disease Group, Auckland, New Zealand.,Department of Physiology and HeartOtago, University of Otago, Dunedin, New Zealand
| | - Kathryn E Waddell-Smith
- Cardiac Inherited Disease Group, Auckland, New Zealand.,Department of Cardiology, Auckland City Hospital, Auckland, New Zealand
| | - Martin A Kennedy
- Department of Pathology and Biomedical Science, University of Otago, Christchurch, New Zealand
| | - Jonathan R Skinner
- Cardiac Inherited Disease Group, Auckland, New Zealand.,Department of Cardiology, Auckland City Hospital, Auckland, New Zealand
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Giudicessi JR, Ackerman MJ. Calcium Revisited: New Insights Into the Molecular Basis of Long-QT Syndrome. Circ Arrhythm Electrophysiol 2018; 9:CIRCEP.116.002480. [PMID: 27390209 DOI: 10.1161/circep.116.002480] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Accepted: 05/27/2016] [Indexed: 12/12/2022]
Affiliation(s)
- John R Giudicessi
- From the Internal Medicine Residency and Clinician-Investigator Programs, Department of Medicine (J.R.G.) and Departments of Cardiovascular Diseases, Pediatrics (Division of Pediatric Cardiology), and Molecular Pharmacology & Experimental Therapeutics (M.J.A.), Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, MN
| | - Michael J Ackerman
- From the Internal Medicine Residency and Clinician-Investigator Programs, Department of Medicine (J.R.G.) and Departments of Cardiovascular Diseases, Pediatrics (Division of Pediatric Cardiology), and Molecular Pharmacology & Experimental Therapeutics (M.J.A.), Windland Smith Rice Sudden Death Genomics Laboratory, Mayo Clinic, Rochester, MN.
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15
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Kosaki R, Ono H, Terashima H, Kosaki K. Timothy syndrome-like condition with syndactyly but without prolongation of the QT interval. Am J Med Genet A 2018; 176:1657-1661. [PMID: 29736926 DOI: 10.1002/ajmg.a.38833] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2017] [Revised: 03/18/2018] [Accepted: 04/17/2018] [Indexed: 01/03/2023]
Abstract
Timothy syndrome is characterized by a unique combination of a prolongation of the corrected QT interval of the electrocardiogram and bilateral cutaneous syndactyly of the fingers and the toes and is caused by heterozygous mutations in CACNA1C, a gene encoding a calcium channel. After the discovery of the CACNA1C gene as the causative gene for Timothy syndrome, patients with CACNA1C mutations with QT prolongation but without syndactyly were described. Here, we report a 5-year-old female patient with cutaneous syndactyly, developmental delay, and pulmonary hypertension. Exome analysis showed a previously undescribed de novo heterozygous mutation in the CACNA1C gene, p.Arg1024Gly. To our knowledge, this patient is the first to exhibit syndactyly and to carry a CACNA1C mutation but to not have QT prolongation, which has long been considered an obligatory feature of Timothy syndrome.
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Affiliation(s)
- Rika Kosaki
- Division of Medical Genetics, National Center for Child Health and Development, Tokyo, Japan
| | - Hiroshi Ono
- Division of Cardiology, National Center for Child Health and Development, Tokyo, Japan
| | - Hiroshi Terashima
- Division of Neulorogy, National Center for Child Health and Development, Tokyo, Japan
| | - Kenjiro Kosaki
- Center for Medical Genetics, Keio University School of Medicine, Tokyo, Japan
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16
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Clinical Outcomes and Modes of Death in Timothy Syndrome. JACC Clin Electrophysiol 2018; 4:459-466. [DOI: 10.1016/j.jacep.2017.08.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 08/21/2017] [Accepted: 08/22/2017] [Indexed: 11/19/2022]
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17
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Sepp R, Hategan L, Bácsi A, Cseklye J, Környei L, Borbás J, Széll M, Forster T, Nagy I, Hegedűs Z. Timothy syndrome 1 genotype without syndactyly and major extracardiac manifestations. Am J Med Genet A 2017; 173:784-789. [PMID: 28211989 DOI: 10.1002/ajmg.a.38084] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Accepted: 11/21/2016] [Indexed: 11/09/2022]
Abstract
Timothy syndrome 1 (TS1) is a rare genetic disorder characterized by multisystem abnormalities including QT prolongation, congenital heart defects, facial dysmorphism, episodic hypoglycemia, and neurological symptoms. A morphological hallmark of TS1 is syndactyly, present in all cases. TS1 is caused by the canonical p.Gly406Arg mutation in the alternatively spliced exon 8A in the CACNA1C gene, encoding for the main cardiac L-type calcium channel. A variant case of TS1 is reported. The proband had intermittent fetal bradycardia with heart rate of 72 bpm. On the first day of life bradycardia due to 2:1 atrioventricular (AV) block and marked QTc prolongation of 600 ms was noted. On medical therapy with propranolol and mexiletine 1:1 AV conduction returned with QTc prolongation of 470-580 ms. The patient lacked other extracardiac manifestations, most importantly syndactyly, neurological complications or autism. On genetic analysis, the canonical TS1 causing mutation, p.Gly406Arg in exon 8A of the CACNA1C gene was detected. The CACNA1C p.Gly406Arg variant was not present in the parents, but was detected in different DNA samples of the index patient. Our case highlight further phenotypic variability in TS. Most importantly, it underlines that the lack of syndactyly does not exclude the presence of a TS1 genotype. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Róbert Sepp
- Second Department of Internal Medicine and Cardiology Center, University of Szeged, Szeged, Hungary
| | - Lidia Hategan
- Second Department of Internal Medicine and Cardiology Center, University of Szeged, Szeged, Hungary
| | - Attila Bácsi
- Fejér County "Szent György" University Teaching Hospital, Székesfehérvár, Hungary
| | | | - László Környei
- "Gottsegen György" National Institute of Cardiology, Budapest, Hungary
| | - János Borbás
- Second Department of Internal Medicine and Cardiology Center, University of Szeged, Szeged, Hungary
| | - Márta Széll
- Department of Medical Genetics, University of Szeged, Szeged, Hungary
| | - Tamás Forster
- Second Department of Internal Medicine and Cardiology Center, University of Szeged, Szeged, Hungary
| | - István Nagy
- Seqomics Biotechnology Ltd., Mórahalom, Hungary.,Institute of Biochemistry, Biological Research Centre, Szeged, Hungary
| | - Zoltán Hegedűs
- Institute of Biophysics, Biological Research Centre, Szeged, Hungary.,Department of Biochemistry and Medical Chemistry, University of Pécs, Pécs, Hungary
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18
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Imbrici P, Liantonio A, Camerino GM, De Bellis M, Camerino C, Mele A, Giustino A, Pierno S, De Luca A, Tricarico D, Desaphy JF, Conte D. Therapeutic Approaches to Genetic Ion Channelopathies and Perspectives in Drug Discovery. Front Pharmacol 2016; 7:121. [PMID: 27242528 PMCID: PMC4861771 DOI: 10.3389/fphar.2016.00121] [Citation(s) in RCA: 98] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2016] [Accepted: 04/25/2016] [Indexed: 12/21/2022] Open
Abstract
In the human genome more than 400 genes encode ion channels, which are transmembrane proteins mediating ion fluxes across membranes. Being expressed in all cell types, they are involved in almost all physiological processes, including sense perception, neurotransmission, muscle contraction, secretion, immune response, cell proliferation, and differentiation. Due to the widespread tissue distribution of ion channels and their physiological functions, mutations in genes encoding ion channel subunits, or their interacting proteins, are responsible for inherited ion channelopathies. These diseases can range from common to very rare disorders and their severity can be mild, disabling, or life-threatening. In spite of this, ion channels are the primary target of only about 5% of the marketed drugs suggesting their potential in drug discovery. The current review summarizes the therapeutic management of the principal ion channelopathies of central and peripheral nervous system, heart, kidney, bone, skeletal muscle and pancreas, resulting from mutations in calcium, sodium, potassium, and chloride ion channels. For most channelopathies the therapy is mainly empirical and symptomatic, often limited by lack of efficacy and tolerability for a significant number of patients. Other channelopathies can exploit ion channel targeted drugs, such as marketed sodium channel blockers. Developing new and more specific therapeutic approaches is therefore required. To this aim, a major advancement in the pharmacotherapy of channelopathies has been the discovery that ion channel mutations lead to change in biophysics that can in turn specifically modify the sensitivity to drugs: this opens the way to a pharmacogenetics strategy, allowing the development of a personalized therapy with increased efficacy and reduced side effects. In addition, the identification of disease modifiers in ion channelopathies appears an alternative strategy to discover novel druggable targets.
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Affiliation(s)
- Paola Imbrici
- Department of Pharmacy - Drug Sciences, University of Bari "Aldo Moro" Bari, Italy
| | - Antonella Liantonio
- Department of Pharmacy - Drug Sciences, University of Bari "Aldo Moro" Bari, Italy
| | - Giulia M Camerino
- Department of Pharmacy - Drug Sciences, University of Bari "Aldo Moro" Bari, Italy
| | - Michela De Bellis
- Department of Pharmacy - Drug Sciences, University of Bari "Aldo Moro" Bari, Italy
| | - Claudia Camerino
- Department of Basic Medical Sciences, Neurosciences and Sense Organs, University of Bari "Aldo Moro" Bari, Italy
| | - Antonietta Mele
- Department of Pharmacy - Drug Sciences, University of Bari "Aldo Moro" Bari, Italy
| | - Arcangela Giustino
- Department of Biomedical Sciences and Human Oncology, University of Bari "Aldo Moro" Bari, Italy
| | - Sabata Pierno
- Department of Pharmacy - Drug Sciences, University of Bari "Aldo Moro" Bari, Italy
| | - Annamaria De Luca
- Department of Pharmacy - Drug Sciences, University of Bari "Aldo Moro" Bari, Italy
| | - Domenico Tricarico
- Department of Pharmacy - Drug Sciences, University of Bari "Aldo Moro" Bari, Italy
| | - Jean-Francois Desaphy
- Department of Biomedical Sciences and Human Oncology, University of Bari "Aldo Moro" Bari, Italy
| | - Diana Conte
- Department of Pharmacy - Drug Sciences, University of Bari "Aldo Moro" Bari, Italy
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Philipp LR, Rodriguez FH. Cardiac arrest refractory to standard intervention in atypical Timothy syndrome (LQT8 type 2). Proc AMIA Symp 2016; 29:160-2. [PMID: 27034553 DOI: 10.1080/08998280.2016.11929398] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
Timothy syndrome (TS) is a rare, multisystem disorder most commonly associated with profound QTc prolongation and cutaneous dysmorphia arising from mutations of the L-type calcium channel. We present a case of a 12-day-old newborn who presented with respiratory distress and cyanosis. Diagnostic workup was notable for multiple cardiac abnormalities, and genetic analysis was consistent with an exon 8 mutation of the CACNA1C gene, which is diagnostic for TS type 2 (atypical TS). This patient presented with a novel constellation of symptoms, without dysmorphic features, and with a more moderate QTc interval. The heterogeneity of phenotypes suggests that this disorder may be characterized by variable expressivity or a spectrum of disease rather than a clearly defined syndrome.
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Affiliation(s)
- Lucas R Philipp
- Emory University School of Medicine (Philipp, Rodriguez) and Sibley Heart Center Cardiology (Rodriguez), Atlanta, Georgia
| | - Fred H Rodriguez
- Emory University School of Medicine (Philipp, Rodriguez) and Sibley Heart Center Cardiology (Rodriguez), Atlanta, Georgia
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