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Yuan X, Chen R, Luo G, Sun P, Song X, Ma J, Sun R, Yu T, Jiang Z. Role and mechanism of miR-871-3p/Megf8 in regulating formaldehyde-induced cardiomyocyte inflammation and congenital heart disease. Int Immunopharmacol 2024; 126:111297. [PMID: 38039718 DOI: 10.1016/j.intimp.2023.111297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Revised: 11/02/2023] [Accepted: 11/24/2023] [Indexed: 12/03/2023]
Abstract
OBJECTIVE AND DESIGN We aimed to investigate the molecular mechanism underlying formaldehyde (FA)-induced congenital heart disease (CHD) using in vitro and in vivo models. MATERIALS AND SUBJECTS Neonatal rat heart tissues and H9C2 cells were used for in vitro studies, while FA-exposed new-born rats were used for in vivo studies. TREATMENT H9C2 cells were exposed to FA concentrations of 0, 50, 100 and 150 μM/mL for 24 h. METHODS Whole transcriptome gene sequencing identified differentially expressed miRNAs in neonatal rat heart tissues, while Real-time quantitative PCR (RT-qPCR) assessed miR-871-3p and Megf8 expression. RNA pull-down and dual-luciferase reporter assays determined miR-871-3p and Megf8 relationships. Inflammatory cytokine expression was assessed by western blotting. A FA-induced CHD model was used to validate miR-871-3p regulatory effects in vivo. RESULTS We identified 89 differentially expressed miRNAs, with 28 up-regulated and 61 down-regulated (fold change ≥ 2.0, P < 0.05). Inflammation (interleukin) and signalling pathways were found to control FA-induced cardiac dysplasia. miR-871-3p was upregulated in FA-exposed heart tissues, modulated inflammation, and directly targeted Megf8. In vivo experiments showed miR-871-3p knockdown inhibited FA-induced inflammation and CHD. CONCLUSION We demonstrated miR-871-3p's role in FA-induced CHD by targeting Megf8, providing potential targets for CHD intervention and improved diagnosis and treatment strategies.
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Affiliation(s)
- Xiaoli Yuan
- Department of Cardiac Ultrasound, The Affiliated Hospital of Qingdao University, Road No. 59 Haier, Qingdao 266100, Shandong Province, People's Republic of China
| | - Rui Chen
- Heart Center, Women and Children's Hospital, Qingdao University, Qingdao 266034, Shandong Province, People's Republic of China
| | - Gang Luo
- Heart Center, Women and Children's Hospital, Qingdao University, Qingdao 266034, Shandong Province, People's Republic of China
| | - Pin Sun
- Department of Cardiac Ultrasound, The Affiliated Hospital of Qingdao University, Road No. 59 Haier, Qingdao 266100, Shandong Province, People's Republic of China
| | - Xiaoxia Song
- Department of Cardiac Ultrasound, The Affiliated Hospital of Qingdao University, Road No. 59 Haier, Qingdao 266100, Shandong Province, People's Republic of China
| | - Jianmin Ma
- Department of Cardiac Ultrasound, The Affiliated Hospital of Qingdao University, Road No. 59 Haier, Qingdao 266100, Shandong Province, People's Republic of China
| | - Ruicong Sun
- Department of Cardiac Ultrasound, The Affiliated Hospital of Qingdao University, Road No. 59 Haier, Qingdao 266100, Shandong Province, People's Republic of China
| | - Tao Yu
- Department of Cardiac Ultrasound, The Affiliated Hospital of Qingdao University, Road No. 59 Haier, Qingdao 266100, Shandong Province, People's Republic of China; Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, No. 38 Dengzhou Road, Qingdao 266021, Shandong Province, People's Republic of China.
| | - Zhirong Jiang
- Department of Cardiac Ultrasound, The Affiliated Hospital of Qingdao University, Road No. 59 Haier, Qingdao 266100, Shandong Province, People's Republic of China.
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Gabriel GC, Lo CW. Molecular Pathways and Animal Models of Defects in Situs. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2024; 1441:719-738. [PMID: 38884745 DOI: 10.1007/978-3-031-44087-8_43] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2024]
Abstract
Left-right patterning is among the least well understood of the three axes defining the body plan, and yet it is no less important, with left-right patterning defects causing structural birth defects with high morbidity and mortality, such as complex congenital heart disease, biliary atresia, or intestinal malrotation. The cell signaling pathways governing left-right asymmetry are highly conserved and involve multiple components of the TGF-β superfamily of cell signaling molecules. Central to left-right patterning is the differential activation of Nodal on the left, and BMP signaling on the right. In addition, a plethora of other cell signaling pathways including Shh, FGF, and Notch also contribute to the regulation of left-right patterning. In vertebrate embryos such as the mouse, frog, or zebrafish, the specification of left-right identity requires the left-right organizer (LRO) containing cells with motile and primary cilia that mediate the left-sided propagation of Nodal signaling, followed by left-sided activation of Lefty and then Pitx2, a transcription factor that specifies visceral organ asymmetry. While this overall scheme is well conserved, there are striking species differences, including the finding that motile cilia do not play a role in left-right patterning in some vertebrates. Surprisingly, the direction of heart looping, one of the first signs of organ left-right asymmetry, was recently shown to be specified by intrinsic cell chirality, not Nodal signaling, possibly a reflection of the early origin of Nodal signaling in radially symmetric organisms. How this intrinsic chirality interacts with downstream molecular pathways regulating visceral organ asymmetry will need to be further investigated to elucidate how disturbance in left-right patterning may contribute to complex CHD.
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Affiliation(s)
- George C Gabriel
- Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Cecilia W Lo
- Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
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3
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Nakadate K, Kawakami K. Immunohistochemical and Immunoelectron Microscopical Distribution of MEGF8 in the Mouse Central Nervous System. Cells 2023; 13:63. [PMID: 38201267 PMCID: PMC10778434 DOI: 10.3390/cells13010063] [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: 11/28/2023] [Revised: 12/20/2023] [Accepted: 12/25/2023] [Indexed: 01/12/2024] Open
Abstract
Mutations in multiple epidermal growth factor-like domain 8 (MEGF8), a multidomain transmembrane protein encoded by a gene conserved across species, cause Carpenter's syndrome, which is associated with learning disabilities, mental health issues, and left-right patterning abnormalities. MEGF8 interacts with MGRN1, a protein that functions as an E3 ubiquitin ligase and is involved in multiple physiological and pathological processes. However, the mechanism underlying the distribution of MEGF8 in the central nervous system (CNS) and its cellular and subcellular locations remain unknown. This study aimed to map MEGF8 in the mouse CNS using a new antibody. We discovered that MEGF8 was distributed in the majority of neuronal cell somata across most CNS regions. High levels of MEGF8 were expressed in the neuropils of the CNS gray matter. Immunoelectron microscopy showed that MEGF8 was present in the synapses and around the outer mitochondrial membrane. These findings show that MEGF8 is uniformly distributed throughout the mouse CNS, and its distribution indicates that it plays a substantial role in synaptic and mitochondrial functions. To the best of our knowledge, this is the first study to document MEGF8 distribution in the CNS.
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Affiliation(s)
- Kazuhiko Nakadate
- Department of Basic Science, Educational and Research Center for Pharmacy, Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose 204-8588, Tokyo, Japan;
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The MicroRNA Ame-Bantam-3p Controls Larval Pupal Development by Targeting the Multiple Epidermal Growth Factor-like Domains 8 Gene (megf8) in the Honeybee, Apis mellifera. Int J Mol Sci 2023; 24:ijms24065726. [PMID: 36982800 PMCID: PMC10054489 DOI: 10.3390/ijms24065726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 02/28/2023] [Accepted: 03/02/2023] [Indexed: 03/19/2023] Open
Abstract
20-Hydroxyecdysone (20E) plays an essential role in coordinating developmental transitions in insects through responsive protein-coding genes and microRNAs (miRNAs). However, the interplay between 20E and miRNAs during insect metamorphosis is unknown. In this study, using small RNA sequencing, a comparative miRNA transcriptomic analysis in different development stages, and 20E treatment, we identified ame-bantam-3p as a key candidate miRNA involved in honeybee metamorphosis. Target prediction and in vitro dual-luciferase assays confirmed that ame-bantam-3p interacts with the coding region of the megf8 gene and promotes its expression. Meanwhile, temporal expression analysis revealed that the expression of ame-bantam-3p is higher in the larval stage than in prepupal and pupal stages, and that this expression pattern is similar to that of megf8. In vivo, we found that the mRNA level of megf8 was significantly increased after the injection of ame-bantam-3p agomir. A 20E feeding assay showed that 20E downregulated the expression of both ame-bantam-3p and its target gene megf8 on larval days five, six, and seven. Meanwhile, the injection of ame-bantam-3p agomir also reduced the 20E titer, as well as the transcript levels of essential ecdysteroid synthesis genes, including Dib, Phm, Sad, and Nvd. The transcript levels of 20E cascade genes, including EcRA, ECRB1, USP, E75, E93, and Br-c, were also significantly decreased after ame-bantam-3p agomir injection. However, ame-bantam-3p antagomir injection and dsmegf8 injection showed the opposite effect to ame-bantam-3p agomir injection. Ame-bantam-3p agomir treatment ultimately led to mortality and the failure of larval pupation by inhibiting ecdysteroid synthesis and the 20E signaling pathway. However, the expression of 20E signaling-related genes was significantly increased after megf8 knockdown, and larvae injected with dsmegf8 showed early pupation. Combined, our results indicate that ame-bantam-3p is involved in the 20E signaling pathway through positively regulating its target gene megf8 and is indispensable for larval–pupal development in the honeybee. These findings may enhance our understanding of the relationship between 20E signaling and small RNAs during honeybee development.
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Nawaratne V, Kudumala S, Kakad PP, Godenschwege TA. The conserved MASRPF motif in the Attractin homolog, Distracted, is required for association with Drosophila E3-ligase Mgrn1. MICROPUBLICATION BIOLOGY 2021; 2021. [PMID: 34235405 PMCID: PMC8254101 DOI: 10.17912/micropub.biology.000416] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/27/2021] [Revised: 06/14/2021] [Accepted: 06/15/2021] [Indexed: 11/06/2022]
Abstract
In rodents, all three paralogs of the Attractin (Atrn) transmembrane protein family exhibit strong phenotypic overlap and are implicated in the regulation of the same G-protein coupled receptors (GPCR) as E3-ligase Mahogunin ring finger 1 (Mgrn1). Recently it was shown that the highly conserved intracellular MASRPF motif in mammal Multiple epidermal growth factor-like domain 8 protein is required for binding of Mgrn1 to mediate ubiquitination of GPCR Smoothened in vitro. Here, we show that the MASRPF motif of Drosophila Distracted, the ortholog of ATRN and Attractin-like 1, is required for association with Drosophila Mgrn1 (dMgrn1) in vivo.
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Affiliation(s)
- Vindhya Nawaratne
- Biological Science Department, Florida Atlantic University, Jupiter, FL 33458
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Kong JH, Young CB, Pusapati GV, Patel CB, Ho S, Krishnan A, Lin JHI, Devine W, Moreau de Bellaing A, Athni TS, Aravind L, Gunn TM, Lo CW, Rohatgi R. A Membrane-Tethered Ubiquitination Pathway Regulates Hedgehog Signaling and Heart Development. Dev Cell 2020; 55:432-449.e12. [PMID: 32966817 PMCID: PMC7686252 DOI: 10.1016/j.devcel.2020.08.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 07/23/2020] [Accepted: 08/27/2020] [Indexed: 12/30/2022]
Abstract
The etiology of congenital heart defects (CHDs), which are among the most common human birth defects, is poorly understood because of its complex genetic architecture. Here, we show that two genes implicated in CHDs, Megf8 and Mgrn1, interact genetically and biochemically to regulate the strength of Hedgehog signaling in target cells. MEGF8, a transmembrane protein, and MGRN1, a RING superfamily E3 ligase, assemble to form a receptor-like ubiquitin ligase complex that catalyzes the ubiquitination and degradation of the Hedgehog pathway transducer Smoothened. Homozygous Megf8 and Mgrn1 mutations increased Smoothened abundance and elevated sensitivity to Hedgehog ligands. While mice heterozygous for loss-of-function Megf8 or Mgrn1 mutations were normal, double heterozygous embryos exhibited an incompletely penetrant syndrome of CHDs with heterotaxy. Thus, genetic interactions can arise from biochemical mechanisms that calibrate morphogen signaling strength, a conclusion broadly relevant for the many human diseases in which oligogenic inheritance is emerging as a mechanism for heritability.
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Affiliation(s)
- Jennifer H Kong
- Departments of Biochemistry and Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Cullen B Young
- Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15201, USA
| | - Ganesh V Pusapati
- Departments of Biochemistry and Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Chandni B Patel
- Departments of Biochemistry and Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Sebastian Ho
- Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15201, USA
| | - Arunkumar Krishnan
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - Jiuann-Huey Ivy Lin
- Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15201, USA
| | - William Devine
- Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15201, USA
| | - Anne Moreau de Bellaing
- Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15201, USA; Department of Pediatric Cardiology, Necker-Sick Children Hospital and The University of Paris Descartes, Paris 75015, France
| | - Tejas S Athni
- Departments of Biochemistry and Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - L Aravind
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - Teresa M Gunn
- McLaughlin Research Institute, Great Falls, MT 59405, USA.
| | - Cecilia W Lo
- Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15201, USA.
| | - Rajat Rohatgi
- Departments of Biochemistry and Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA.
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Gabriel GC, Young CB, Lo CW. Role of cilia in the pathogenesis of congenital heart disease. Semin Cell Dev Biol 2020; 110:2-10. [PMID: 32418658 DOI: 10.1016/j.semcdb.2020.04.017] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 04/22/2020] [Accepted: 04/25/2020] [Indexed: 12/13/2022]
Abstract
An essential role for cilia in the pathogenesis of congenital heart disease (CHD) has emerged from findings of a large-scale mouse forward genetic screen. High throughput screening with fetal ultrasound imaging followed by whole exome sequencing analysis recovered a preponderance of cilia related genes and cilia transduced cell signaling genes among mutations identified to cause CHD. The perturbation of left-right patterning in CHD pathogenesis is suggested by the association of CHD with heterotaxy, but also by the finding of the co-occurrence of laterality defects with CHD in birth defect registries. Many of the cilia and cilia cell signaling genes recovered were found to be related to Hedgehog signaling. Studies in mice showed cilia transduced hedgehog signaling coordinates left-right patterning with heart looping and differentiation of the heart tube. Cilia transduced Shh signaling also regulates later events in heart development, including outflow tract septation and formation of the atrioventricular septum. More recent work has shown mutations in cilia related genes may also contribute to valve disease that largely manifest in adult life. Overall, these and other findings show cilia play an important role in CHD and also in more common valve diseases.
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Affiliation(s)
- George C Gabriel
- Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15201, United States
| | - Cullen B Young
- Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15201, United States
| | - Cecilia W Lo
- Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15201, United States.
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8
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Wang W, Zheng X, Song H, Yang J, Liu X, Wang Y, Zhang M, Zhang Z. Spatial and temporal deletion reveals a latent effect of Megf8 on the left-right patterning and heart development. Differentiation 2020; 113:19-25. [PMID: 32203821 DOI: 10.1016/j.diff.2020.03.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 03/10/2020] [Accepted: 03/10/2020] [Indexed: 01/23/2023]
Abstract
Laterality disease is frequently associated with congenital heart disease (CHD). However, it is unclear what is behind this association, a pleiotropic effect of common genetic causes of laterality diseases or the impact of abnormal left-right patterning on the downstream cardiovascular development. MEGF8 is a disease gene of Carpenter syndrome characterized by defective lateralization and CHD. Here we performed spatial and temporal deletion to dissect the tissue and time requirements of Megf8 on cardiovascular development. None of conditional deletions in cardiomyocytes, endothelium/endocardium, epicardium, cardiac mesoderm or neural crest cells led to cardiovascular defects. More surprisingly, temporal deletion with a ubiquitous Cre driver at embryonic day 7.5 (E7.5), a time point before symmetry break and cardiogenesis, causes preaxial polydactyly (PPD) and exencephaly, but not laterality and cardiovascular defects. These data suggested that Megf8 was dispensable for cardiac organogenesis. Only with E6.5 deletion, we observed aortic arch artery defects including right aortic arch, an indicator of reversed left-right patterning. The concurrence of laterality and cardiovascular defects in pre-streak stage deletion rather than cardiac organogenesis stage deletion indicates that the laterality defect may directly impact heart development. Interestingly, the latent effect of Megf8 on the left-right patterning suggests that the regulation of laterality may be much earlier than we previously thought.
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Affiliation(s)
- Wenfeng Wang
- Shanghai Pediatric Congenital Heart Disease Institute and Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai, 200127, China
| | - Xiaoling Zheng
- Shanghai Pediatric Congenital Heart Disease Institute and Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai, 200127, China
| | - Hejie Song
- Shanghai Pediatric Congenital Heart Disease Institute and Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai, 200127, China
| | - Junjie Yang
- Shanghai Pediatric Congenital Heart Disease Institute and Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai, 200127, China
| | - Xiangyang Liu
- Shanghai Pediatric Congenital Heart Disease Institute and Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai, 200127, China
| | - Ye Wang
- Shanghai Pediatric Congenital Heart Disease Institute and Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai, 200127, China
| | - Min Zhang
- Shanghai Pediatric Congenital Heart Disease Institute and Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai, 200127, China
| | - Zhen Zhang
- Shanghai Pediatric Congenital Heart Disease Institute and Pediatric Translational Medicine Institute, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai, 200127, China.
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Spontaneous Left Cardiac Isomerism in Chick Embryos: Case Report, Review of the Literature, and Possible Significance for the Understanding of Ventricular Non-Compaction Cardiomyopathy in the Setting of Human Heterotaxy Syndromes. J Cardiovasc Dev Dis 2019; 6:jcdd6040040. [PMID: 31717331 PMCID: PMC6955803 DOI: 10.3390/jcdd6040040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 10/29/2019] [Accepted: 11/05/2019] [Indexed: 11/20/2022] Open
Abstract
The outer shape of most vertebrates is normally characterized by bilateral symmetry. The inner organs, on the other hand, are normally arranged in bilaterally asymmetric patterns. Congenital deviations from the normal organ asymmetry can occur in the form of mirror imagery of the normal arrangement (situs inversus), or in the form of arrangements that have the tendency for the development of bilateral symmetry, either in a pattern of bilateral left-sidedness (left isomerism) or bilateral right-sidedness (right isomerism). The latter two forms of visceral situs anomalies are called “heterotaxy syndromes”. During the past 30 years, remarkable progress has been made in uncovering the genetic etiology of heterotaxy syndromes. However, the pathogenetic mechanisms causing the spectrum of cardiovascular defects found in these syndromes remain poorly understood. In the present report, a spontaneous case of left cardiac isomerism found in an HH-stage 23 chick embryo is described. The observations made in this case confirmed the existence of molecular isomerism in the ventricular chambers previously noted in mouse models. They, furthermore, suggest that hearts with left cardiac isomerism may have the tendency for the development of non-compaction cardiomyopathy caused by defective development of the proepicardium.
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Al-Zahrani RS, Alharbi SH, Tuwaijri RMA, Alzomaili BT, Althubaiti A, Yelbuz TM. Transposition of the great arteries: A laterality defect in the group of heterotaxy syndromes or an outflow tract malformation? Ann Pediatr Cardiol 2018; 11:237-249. [PMID: 30271012 PMCID: PMC6146851 DOI: 10.4103/apc.apc_24_18] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND/AIM Transposition of the great arteries (TGA) is traditionally classified as a "conotruncal heart defect", implying that TGA evolves from abnormal development of the outflow tract (OFT) of the embryonic heart. However, recently published genetic data suggest that TGA may be linked to laterality gene defects rather than OFT gene defects. The aim of our study was to clarify whether there is any statistically significant link between TGA and clinically diagnosed laterality defects (heterotaxy). METHODS Retrospective cross-sectional analysis of 533 patients diagnosed with TGA at our cardiac center over a period of 13 years (2002-2015). Hospital informatics and digital data recording systems were used for collecting patients' data and all patients were reviewed to check the echocardiograms for verification of the diagnosis, type (TGA, congenitally corrected TGA (ccTGA), and levo-position of the great arteries (LGA)), complexity of TGA, and all other variables (e.g., abdominal organ arrangement, cardiac position, presence or absence of other cardiac defects). RESULTS Of 533 TGA patients, 495 (92.9%) had the usual arrangement of the internal organs, 21 (3.9%) had mirror-imagery, 7 (1.3%) had left and 10 (1.8%) had right isomerism. 444 (83.3%) patients had TGA. The number of patients who had usual visceral arrangement in each TGA type was: 418 (94.1%) in TGA, 49 (92.4%) in ccTGA, and 28 (77.7%) in LGA. 6 (1.4%) TGA patients, 4 (11.1%) patients with LGA were found to have right isomerism, while no ccTGA patient presented with this asymmetry. 4 (0.9%) TGA patients, 1 (1.9%) ccTGA patient and 2 (5.6%) patients with LGA had left isomerism. Heterotaxy (mirror-imagery, left and right isomerism) was more associated with LGA than TGA or ccTGA with a statistically significant difference (P value of 0.001). CONCLUSION In contrast to recently published genetic data, our morphological data do not disclose a significant link between TGA and heterotaxy.
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Affiliation(s)
- Rana S Al-Zahrani
- College of Medicine, King Saud Bin Abdulaziz University for Health Sciences, Riyadh, Kingdom of Saudi Arabia
| | - Samaher H Alharbi
- College of Medicine, King Saud Bin Abdulaziz University for Health Sciences, Riyadh, Kingdom of Saudi Arabia
| | - Rawan M A Tuwaijri
- College of Medicine, King Saud Bin Abdulaziz University for Health Sciences, Riyadh, Kingdom of Saudi Arabia
| | - Bayan T Alzomaili
- College of Medicine, King Saud Bin Abdulaziz University for Health Sciences, Riyadh, Kingdom of Saudi Arabia
| | - Alaa Althubaiti
- College of Medicine, King Saud Bin Abdulaziz University for Health Sciences, Riyadh, Kingdom of Saudi Arabia
| | - Talat Mesud Yelbuz
- Department of Cardiac Sciences, King Abdulaziz Cardiac Center, Section of Pediatric Cardiology, King Abdulaziz Medical City, Ministry of National Guard Health Affairs, Riyadh, Kingdom of Saudi Arabia
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Abstract
Craniosynostosis is a common craniofacial birth defect. This review focusses on the advances that have been achieved through studying the pathogenesis of craniosynostosis using mouse models. Classic methods of gene targeting which generate individual gene knockout models have successfully identified numerous genes required for normal development of the skull bones and sutures. However, the study of syndromic craniosynostosis has largely benefited from the production of knockin models that precisely mimic human mutations. These have allowed the detailed investigation of downstream events at the cellular and molecular level following otherwise unpredictable gain-of-function effects. This has greatly enhanced our understanding of the pathogenesis of this disease and has the potential to translate into improvement of the clinical management of this condition in the future.
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Affiliation(s)
- Kevin K L Lee
- UCL Great Ormond Street Institute of Child Health, London, UK
| | - Philip Stanier
- UCL Great Ormond Street Institute of Child Health, London, UK
| | - Erwin Pauws
- UCL Great Ormond Street Institute of Child Health, London, UK
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The Drosophila homologue of MEGF8 is essential for early development. Sci Rep 2018; 8:8790. [PMID: 29884872 PMCID: PMC5993795 DOI: 10.1038/s41598-018-27076-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 05/23/2018] [Indexed: 12/15/2022] Open
Abstract
Mutations of the gene MEGF8 cause Carpenter syndrome in humans, and the mouse orthologue has been functionally associated with Nodal and Bmp4 signalling. Here, we have investigated the phenotype associated with loss-of-function of CG7466, a gene that encodes the Drosophila homologue of MEGF8. We generated three different frame-shift null mutations in CG7466 using CRISPR/Cas9 gene editing. Heterozygous flies appeared normal, but homozygous animals had disorganised denticle belts and died as 2nd or 3rd instar larvae. Larvae were delayed in transition to 3rd instars and showed arrested growth, which was associated with abnormal feeding behaviour and prolonged survival when yeast food was supplemented with sucrose. RNAi-mediated knockdown using the Gal4-UAS system resulted in lethality with ubiquitous and tissue-specific Gal4 drivers, and growth defects including abnormal bristle number and orientation in a subset of escapers. We conclude that CG7466 is essential for larval development and that diminished function perturbs denticle and bristle formation.
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Zahid M, Bais A, Tian X, Devine W, Lee DM, Yau C, Sonnenberg D, Beerman L, Khalifa O, Lo CW. Airway ciliary dysfunction and respiratory symptoms in patients with transposition of the great arteries. PLoS One 2018; 13:e0191605. [PMID: 29444099 PMCID: PMC5812576 DOI: 10.1371/journal.pone.0191605] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Accepted: 01/08/2018] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Our prior work on congenital heart disease (CHD) with heterotaxy, a birth defect involving randomized left-right patterning, has shown an association of a high prevalence of airway ciliary dysfunction (CD; 18/43 or 42%) with increased respiratory symptoms. Furthermore, heterotaxy patients with ciliary dysfunction were shown to have more postsurgical pulmonary morbidities. These findings are likely a reflection of the common role of motile cilia in both airway clearance and left-right patterning. As CHD comprising transposition of the great arteries (TGA) is commonly thought to involve disturbance of left-right patterning, especially L-TGA with left-right ventricular inversion, we hypothesize CHD patients with transposition of great arteries (TGA) may have high prevalence of airway CD with increased respiratory symptoms. METHODS AND RESULTS We recruited 75 CHD patients with isolated TGA, 28% L and 72% D-TGA. Patients were assessed using two tests typically used for evaluating airway ciliary dysfunction in patients with primary ciliary dyskinesia (PCD), a recessive sinopulmonary disease caused by respiratory ciliary dysfunction. This entailed the measurement of nasal nitric oxide (nNO), which is typically low with PCD. We also obtained nasal scrapes and conducted videomicroscopy to assess respiratory ciliary motion (CM). We observed low nNO in 29% of the patients, and abnormal CM in 57%, with 22% showing both low nNO and abnormal CM. No difference was observed for the prevalence of either low nNO or abnormal ciliary motion between patients with D vs. L-TGA. Respiratory symptoms were increased with abnormal CM, but not low nNO. Sequencing analysis showed no compound heterozygous or homozygous mutations in 39 genes known to cause PCD, nor in CFTR, gene causing cystic fibrosis. As both are recessive disorders, these results indicate TGA patients with ciliary dysfunction do not have PCD or cystic fibrosis (which can cause low nNO or abnormal ciliary motion). CONCLUSIONS TGA patients have high prevalence of abnormal CM and low nNO, but ciliary dysfunction was not correlated with TGA type. Differing from PCD, respiratory symptoms were increased with abnormal CM, but not low nNO. Together with the negative findings from exome sequencing analysis, this would suggest TGA patients with ciliary dysfunction do not have PCD but nevertheless may suffer from milder airway clearance deficiency. Further studies are needed to investigate whether such ciliary dysfunction is associated with increased postsurgical complications as previously observed in CHD patients with heterotaxy.
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Affiliation(s)
- Maliha Zahid
- Dept. of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Abha Bais
- Dept. of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Xin Tian
- Office of Biostatistics Research, National Heart Lung Blood Institute, Bethesda, Maryland, United States of America
| | - William Devine
- Dept. of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Dong Ming Lee
- Dept. of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Cyrus Yau
- Division of Pediatric Cardiology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Daniel Sonnenberg
- Dept. of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Lee Beerman
- Division of Pediatric Cardiology, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Omar Khalifa
- Dept. of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Cecilia W. Lo
- Dept. of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
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14
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Loomba R, Shah PH, Anderson RH, Arora Y. Radiologic Considerations in Heterotaxy: The Need for Detailed Anatomic Evaluation. Cureus 2016; 8:e470. [PMID: 26973805 PMCID: PMC4771576 DOI: 10.7759/cureus.470] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
So-called "heterotaxy" is a laterality defect characterized by isomerism of the thoracic organs and random arrangement of the abdominal organs. These findings go beyond anatomic curiosity and have functional implications. It is, thus, of the utmost importance to be able to properly identify these findings. Radiologic studies can be invaluable in determining anomalies in the central nervous, pulmonary, cardiovascular, gastrointestinal, genitourinary, and immunologic systems in patients with isomerism. Here, we review findings associated with isomerism and their importance in the setting of isomerism with the aim of ensuring that radiologists effectively describe findings in these patients and that cardiologists understand the wide variety of congenital malformations that may be present.
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Affiliation(s)
- Rohit Loomba
- Department of Cardiology, Children's Hospital of Wisconsin
| | - Parinda H Shah
- Department of Radiology, Advocate Illinois Masonic Medical Center
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15
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Francis R, Lo C. Ex vivo method for high resolution imaging of cilia motility in rodent airway epithelia. J Vis Exp 2013. [PMID: 23963287 DOI: 10.3791/50343] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
An ex vivo technique for imaging mouse airway epithelia for quantitative analysis of motile cilia function important for insight into mucociliary clearance function has been established. Freshly harvested mouse trachea is cut longitudinally through the trachealis muscle and mounted in a shallow walled chamber on a glass-bottomed dish. The trachea sample is positioned along its long axis to take advantage of the trachealis muscle to curl longitudinally. This allows imaging of ciliary motion in the profile view along the entire tracheal length. Videos at 200 frames/sec are obtained using differential interference contrast microscopy and a high speed digital camera to allow quantitative analysis of cilia beat frequency and ciliary waveform. With the addition of fluorescent beads during imaging, cilia generated fluid flow also can be determined. The protocol time spans approximately 30 min, with 5 min for chamber preparation, 5-10 min for sample mounting, and 10-15 min for videomicroscopy.
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Affiliation(s)
- Richard Francis
- Department of Developmental Biology, University of Pittsburgh, USA
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16
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Manning DK, Sergeev M, van Heesbeen RG, Wong MD, Oh JH, Liu Y, Henkelman RM, Drummond I, Shah JV, Beier DR. Loss of the ciliary kinase Nek8 causes left-right asymmetry defects. J Am Soc Nephrol 2013; 24:100-12. [PMID: 23274954 DOI: 10.1681/asn.2012050490] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
A missense mutation in mouse Nek8, which encodes a ciliary kinase, produces the juvenile cystic kidneys (jck) model of polycystic kidney disease, but the functions of Nek8 are incompletely understood. Here, we generated a Nek8-null allele and found that homozygous mutant mice die at birth and exhibit randomization of left-right asymmetry, cardiac anomalies, and glomerular kidney cysts. The requirement for Nek8 in left-right patterning is conserved, as knockdown of the zebrafish ortholog caused randomized heart looping. Ciliogenesis was intact in Nek8-deficient embryos and cells, but we observed misexpression of left-sided marker genes early in development, suggesting that nodal ciliary signaling was perturbed. We also generated jck/Nek8 compound heterozygotes; these mutants developed less severe cystic disease than jck homozygotes and provided genetic evidence that the jck allele may encode a gain-of-function protein. Notably, NEK8 and polycystin-2 (PC2) proteins interact, and we found that Nek8(-/-) and Pkd2(-/-) embryonic phenotypes are strikingly similar. Nek8-deficient embryos and cells did express PC2 normally, which localized properly to the cilia. However, similar to cells lacking PC2, NEK8-depleted inner medullary collecting duct cells exhibited a defective response to fluid shear, suggesting that NEK8 may play a role in mediating PC2-dependent signaling.
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Affiliation(s)
- Danielle K Manning
- Division of Genetics, Brigham and Women's Hospital, Boston, MA 02115, USA
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17
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Twigg S, Lloyd D, Jenkins D, Elçioglu N, Cooper C, Al-Sannaa N, Annagür A, Gillessen-Kaesbach G, Hüning I, Knight S, Goodship J, Keavney B, Beales P, Gileadi O, McGowan S, Wilkie A. Mutations in multidomain protein MEGF8 identify a Carpenter syndrome subtype associated with defective lateralization. Am J Hum Genet 2012; 91:897-905. [PMID: 23063620 PMCID: PMC3487118 DOI: 10.1016/j.ajhg.2012.08.027] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Revised: 08/13/2012] [Accepted: 08/27/2012] [Indexed: 10/27/2022] Open
Abstract
Carpenter syndrome is an autosomal-recessive multiple-congenital-malformation disorder characterized by multisuture craniosynostosis and polysyndactyly of the hands and feet; many other clinical features occur, and the most frequent include obesity, umbilical hernia, cryptorchidism, and congenital heart disease. Mutations of RAB23, encoding a small GTPase that regulates vesicular transport, are present in the majority of cases. Here, we describe a disorder caused by mutations in multiple epidermal-growth-factor-like-domains 8 (MEGF8), which exhibits substantial clinical overlap with Carpenter syndrome but is frequently associated with abnormal left-right patterning. We describe five affected individuals with similar dysmorphic facies, and three of them had either complete situs inversus, dextrocardia, or transposition of the great arteries; similar cardiac abnormalities were previously identified in a mouse mutant for the orthologous Megf8. The mutant alleles comprise one nonsense, three missense, and two splice-site mutations; we demonstrate in zebrafish that, in contrast to the wild-type protein, the proteins containing all three missense alterations provide only weak rescue of an early gastrulation phenotype induced by Megf8 knockdown. We conclude that mutations in MEGF8 cause a Carpenter syndrome subtype frequently associated with defective left-right patterning, probably through perturbation of signaling by hedgehog and nodal family members. We did not observe any subject with biallelic loss-of function mutations, suggesting that some residual MEGF8 function might be necessary for survival and might influence the phenotypes observed.
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Affiliation(s)
- Stephen R.F. Twigg
- Clinical Genetics Group, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, UK
| | - Deborah Lloyd
- Clinical Genetics Group, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, UK
| | - Dagan Jenkins
- Molecular Medicine Unit, University College London Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK
| | - Nursel E. Elçioglu
- Department of Pediatric Genetics, Marmara University Medical Faculty, 34660 Istanbul, Turkey
| | - Christopher D.O. Cooper
- Structural Genomics Consortium, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Nouriya Al-Sannaa
- Pediatrics Services Division, Dhahran Health Center, Saudi Aramco Medical Services Organization, Dhahran-31311, Saudi Arabia
| | - Ali Annagür
- Division of Neonatology, Selçuk University, Faculty of Medicine, 42075 Konya, Turkey
| | | | - Irina Hüning
- Institut für Humangenetik, Universität zu Lübeck, Ratzeburger Allee 160, D-23538 Lübeck, Germany
| | - Samantha J.L. Knight
- National Institute for Health Research Biomedical Research Centre, Oxford and Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - Judith A. Goodship
- Institute of Genetic Medicine, University of Newcastle, International Centre for Life, Central Parkway, Newcastle upon Tyne NE1 3BZ, UK
| | - Bernard D. Keavney
- Institute of Genetic Medicine, University of Newcastle, International Centre for Life, Central Parkway, Newcastle upon Tyne NE1 3BZ, UK
| | - Philip L. Beales
- Molecular Medicine Unit, University College London Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK
| | - Opher Gileadi
- Structural Genomics Consortium, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Simon J. McGowan
- Computational Biology Research Group, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, UK
| | - Andrew O.M. Wilkie
- Clinical Genetics Group, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, UK
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18
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Probing human cardiovascular congenital disease using transgenic mouse models. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2011; 100:83-110. [PMID: 21377625 DOI: 10.1016/b978-0-12-384878-9.00003-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Congenital heart defects (CHDs) impact in utero embryonic viability, children, and surviving adults. Since the first transfer of genes into mice, transgenic mouse models have enabled researchers to experimentally study and genetically test the roles of genes in development, physiology, and disease progression. Transgenic mice have become a bona fide human CHD pathology model and their use has dramatically increased within the past two decades. Now that the entire mouse and human genomes are known, it is possible to knock out, mutate, misexpress, and/or replace every gene. Not only have transgenic mouse models changed our understanding of normal development, CHD processes, and the complex interactions of genes and pathways required during heart development, but they are also being used to identify new avenues for medical therapy.
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19
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Tobita K, Liu X, Lo CW. Imaging modalities to assess structural birth defects in mutant mouse models. ACTA ACUST UNITED AC 2010; 90:176-84. [PMID: 20860057 DOI: 10.1002/bdrc.20187] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Assessment of structural birth defects (SBDs) in animal models usually entails conducting detailed necropsy for anatomical defects followed by histological analysis for tissue defects. Recent advances in new imaging technologies have provided the means for rapid phenotyping of SBDs, such as using ultra-high frequency ultrasound biomicroscopy, optical coherence tomography, micro-CT, and micro-MRI. These imaging modalities allow the detailed assessment of organ/tissue structure, and with ultrasound biomicroscopy, structure and function of the cardiovascular system also can be assessed noninvasively, allowing the longitudinal tracking of the fetus in utero. In this review, we briefly discuss the application of these state-of-the-art imaging technologies for phenotyping of SBDs in rodent embryos and fetuses, showing how these imaging modalities may be used for the detection of a wide variety of SBDs.
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Affiliation(s)
- Kimimasa Tobita
- Department of Developmental Biology, University of Pittsburgh, Pennsylvania 15224, USA.
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20
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Vandenberg LN, Levin M. Far from solved: a perspective on what we know about early mechanisms of left-right asymmetry. Dev Dyn 2010; 239:3131-46. [PMID: 21031419 PMCID: PMC10468760 DOI: 10.1002/dvdy.22450] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/31/2023] Open
Abstract
Consistent laterality is a crucial aspect of embryonic development, physiology, and behavior. While strides have been made in understanding unilaterally expressed genes and the asymmetries of organogenesis, early mechanisms are still poorly understood. One popular model centers on the structure and function of motile cilia and subsequent chiral extracellular fluid flow during gastrulation. Alternative models focus on intracellular roles of the cytoskeleton in driving asymmetries of physiological signals or asymmetric chromatid segregation, at much earlier stages. All three models trace the origin of asymmetry back to the chirality of cytoskeletal organizing centers, but significant controversy exists about how this intracellular chirality is amplified onto cell fields. Analysis of specific predictions of each model and crucial recent data on new mutants suggest that ciliary function may not be a broadly conserved, initiating event in left-right patterning. Many questions about embryonic left-right asymmetry remain open, offering fascinating avenues for further research in cell, developmental, and evolutionary biology.
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Affiliation(s)
- Laura N. Vandenberg
- Biology Department, and Tufts Center for Regenerative and Developmental Biology, Tufts University, Medford, Massachusetts
| | - Michael Levin
- Biology Department, and Tufts Center for Regenerative and Developmental Biology, Tufts University, Medford, Massachusetts
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21
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22
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Francis RJB, Chatterjee B, Loges NT, Zentgraf H, Omran H, Lo CW. Initiation and maturation of cilia-generated flow in newborn and postnatal mouse airway. Am J Physiol Lung Cell Mol Physiol 2009; 296:L1067-75. [PMID: 19346437 DOI: 10.1152/ajplung.00001.2009] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Mucociliary clearance in the adult trachea is well characterized, but there are limited data in newborns. Cilia-generated flow was quantified across longitudinal sections of mouse trachea from birth through postnatal day (PND) 28 by tracking fluorescent microsphere speed and directionality. The percentage of ciliated tracheal epithelial cells, as determined by immunohistochemistry, was shown to increase linearly between PND 0 and PND 21 (R(2) = 0.94). While directionality measurements detected patches of flow starting at PND 3, uniform flow across the epithelia was not observed until PND 7 at a approximately 35% ciliated cell density. Flow became established at a maximal rate at PND 9 and beyond. A linear correlation was observed between the percentage of ciliated cells versus flow speed (R(2) = 0.495) and directionality (R(2) = 0.975) between PND 0 and PND 9. Cilia beat frequency (CBF) was higher at PND 0 than at all subsequent time points, but cilia beat waveform was not noticeably different. Tracheal epithelia from a mouse model of primary ciliary dyskinesia (PCD) harboring a Mdnah5 mutation showed that ciliated cell density was unaffected, but no cilia-generated flow was detected. Cilia in mutant airways were either immotile or with slow dyssynchronous beat and abnormal ciliary waveform. Overall, our studies showed that the initiation of cilia-generated flow is directly correlated with an increase in epithelial ciliation, with the measurement of directionality being more sensitive than speed for detecting flow. The higher CBF observed in newborn epithelia suggests unique physiology in the newborn trachea, indicating possible clinical relevance to the pathophysiology of respiratory distress seen in newborn PCD patients.
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Affiliation(s)
- Richard J B Francis
- Laboratory of Developmental Biology, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
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23
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Massively parallel sequencing identifies the gene Megf8 with ENU-induced mutation causing heterotaxy. Proc Natl Acad Sci U S A 2009; 106:3219-24. [PMID: 19218456 DOI: 10.1073/pnas.0813400106] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Forward genetic screens with ENU (N-ethyl-N-nitrosourea) mutagenesis can facilitate gene discovery, but mutation identification is often difficult. We present the first study in which an ENU-induced mutation was identified by massively parallel DNA sequencing. This mutation causes heterotaxy and complex congenital heart defects and was mapped to a 2.2-Mb interval on mouse chromosome 7. Massively parallel sequencing of the entire 2.2-Mb interval identified 2 single-base substitutions, one in an intergenic region and a second causing replacement of a highly conserved cysteine with arginine (C193R) in the gene Megf8. Megf8 is evolutionarily conserved from human to fruit fly, and is observed to be ubiquitously expressed. Morpholino knockdown of Megf8 in zebrafish embryos resulted in a high incidence of heterotaxy, indicating a conserved role in laterality specification. Megf8(C193R) mouse mutants show normal breaking of symmetry at the node, but Nodal signaling failed to be propagated to the left lateral plate mesoderm. Videomicroscopy showed nodal cilia motility, which is required for left-right patterning, is unaffected. Although this protein is predicted to have receptor function based on its amino acid sequence, surprisingly confocal imaging showed it is translocated into the nucleus, where it is colocalized with Gfi1b and Baf60C, two proteins involved in chromatin remodeling. Overall, through the recovery of an ENU-induced mutation, we uncovered Megf8 as an essential regulator of left-right patterning.
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