1
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Gao J, Skidmore JM, Cimerman J, Ritter KE, Qiu J, Wilson LMQ, Raphael Y, Kwan KY, Martin DM. CHD7 and SOX2 act in a common gene regulatory network during mammalian semicircular canal and cochlear development. Proc Natl Acad Sci U S A 2024; 121:e2311720121. [PMID: 38408234 DOI: 10.1073/pnas.2311720121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2023] [Accepted: 01/19/2024] [Indexed: 02/28/2024] Open
Abstract
Inner ear morphogenesis requires tightly regulated epigenetic and transcriptional control of gene expression. CHD7, an ATP-dependent chromodomain helicase DNA-binding protein, and SOX2, an SRY-related HMG box pioneer transcription factor, are known to contribute to vestibular and auditory system development, but their genetic interactions in the ear have not been explored. Here, we analyzed inner ear development and the transcriptional regulatory landscapes in mice with variable dosages of Chd7 and/or Sox2. We show that combined haploinsufficiency for Chd7 and Sox2 results in reduced otic cell proliferation, severe malformations of semicircular canals, and shortened cochleae with ectopic hair cells. Examination of mice with conditional, inducible Chd7 loss by Sox2CreER reveals a critical period (~E9.5) of susceptibility in the inner ear to combined Chd7 and Sox2 loss. Data from genome-wide RNA-sequencing and CUT&Tag studies in the otocyst show that CHD7 regulates Sox2 expression and acts early in a gene regulatory network to control expression of key otic patterning genes, including Pax2 and Otx2. CHD7 and SOX2 directly bind independently and cooperatively at transcription start sites and enhancers to regulate otic progenitor cell gene expression. Together, our findings reveal essential roles for Chd7 and Sox2 in early inner ear development and may be applicable for syndromic and other forms of hearing or balance disorders.
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Affiliation(s)
- Jingxia Gao
- Department of Pediatrics, The University of Michigan, Ann Arbor, MI 48109
| | | | - Jelka Cimerman
- Department of Pediatrics, The University of Michigan, Ann Arbor, MI 48109
| | - K Elaine Ritter
- Department of Pediatrics, The University of Michigan, Ann Arbor, MI 48109
| | - Jingyun Qiu
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08854
- Keck Center for Collaborative Neuroscience, Stem Cell Research Center, Rutgers University, Piscataway, NJ 08854
| | - Lindsey M Q Wilson
- Medical Scientist Training Program, The University of Michigan, Ann Arbor, MI 48109
| | - Yehoash Raphael
- Department of Otolaryngology-Head and Neck Surgery, The University of Michigan, Ann Arbor, MI 48109
| | - Kelvin Y Kwan
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08854
- Keck Center for Collaborative Neuroscience, Stem Cell Research Center, Rutgers University, Piscataway, NJ 08854
| | - Donna M Martin
- Department of Pediatrics, The University of Michigan, Ann Arbor, MI 48109
- Department of Human Genetics, The University of Michigan, Ann Arbor, MI 48109
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2
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Krueger LA, Bills JD, Lim ZY, Skidmore JM, Martin DM, Morris AC. Chromatin remodeler Chd7 regulates photoreceptor development and outer segment length. Exp Eye Res 2023; 226:109299. [PMID: 36343670 PMCID: PMC10354686 DOI: 10.1016/j.exer.2022.109299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 09/29/2022] [Accepted: 10/21/2022] [Indexed: 11/06/2022]
Abstract
Mutations in the chromatin remodeling factor CHD7 are the predominant cause of CHARGE syndrome, a congenital disorder that frequently includes ocular coloboma. Although CHD7 is known to be required for proper ocular morphogenesis, its role in retinal development has not been thoroughly investigated. Given that individuals with CHARGE syndrome can experience visual impairment even in the absence of coloboma, a better understanding of CHD7 function in the retina is needed. In this study, we characterized the expression pattern of Chd7 in the developing zebrafish and mouse retina and documented ocular and retinal phenotypes in Chd7 loss-of-function mutants. Zebrafish Chd7 was expressed throughout the retinal neuroepithelium when retinal progenitor cells were actively proliferating, and later in subsets of newly post-mitotic retinal cells. At stages of retinal development when most retinal cell types had terminally differentiated, Chd7 expression remained strong in the ganglion cell layer and in some cells in the inner nuclear layer. Intriguingly, strong expression of Chd7 was also observed in the outer nuclear layer where it was co-expressed with markers of post-mitotic cone and rod photoreceptors. Expression of mouse CHD7 displayed a similar pattern, including expression in the ganglion cells, subsets of inner nuclear layer cells, and in the distal outer nuclear layer as late as P15. Two different mutant chd7 zebrafish lines were characterized for ocular and retinal defects. These mutants displayed microphthalmia, reduced numbers of cone photoreceptors, and truncated rod and cone photoreceptor outer segments. Reduced cone photoreceptor number and abnormal outer segments were also observed in heterozygous Chd7 mutant mice. Taken together, our results in zebrafish and mouse reveal a conserved, previously undescribed role for Chd7 in retinal development and photoreceptor outer segment morphogenesis. Moreover, our work suggests an avenue of future investigation into the pathogenesis of visual system defects in CHARGE syndrome.
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Affiliation(s)
- Laura A Krueger
- Department of Biology, University of Kentucky, Lexington, KY, 40506-0225, USA
| | - Jessica D Bills
- Department of Biology, University of Kentucky, Lexington, KY, 40506-0225, USA
| | - Zun Yi Lim
- Department of Biology, University of Kentucky, Lexington, KY, 40506-0225, USA
| | | | - Donna M Martin
- Department of Pediatrics, University of Michigan, Ann Arbor, MI, USA; Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Ann C Morris
- Department of Biology, University of Kentucky, Lexington, KY, 40506-0225, USA.
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3
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Guo J, Ma X, Skidmore JM, Cimerman J, Prieskorn DM, Beyer LA, Swiderski DL, Dolan DF, Martin DM, Raphael Y. GJB2 gene therapy and conditional deletion reveal developmental stage-dependent effects on inner ear structure and function. Mol Ther Methods Clin Dev 2021; 23:319-333. [PMID: 34729379 PMCID: PMC8531464 DOI: 10.1016/j.omtm.2021.09.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 09/24/2021] [Indexed: 11/15/2022]
Abstract
Pathogenic variants in GJB2, the gene encoding connexin 26, are the most common cause of autosomal-recessive hereditary deafness. Despite this high prevalence, pathogenic mechanisms leading to GJB2-related deafness are not well understood, and cures are absent. Humans with GJB2-related deafness retain at least some auditory hair cells and neurons, and their deafness is usually stable. In contrast, mice with conditional loss of Gjb2 in supporting cells exhibit extensive loss of hair cells and neurons and rapidly progress to profound deafness, precluding the application of therapies that require intact cochlear cells. In an attempt to design a less severe Gjb2 animal model, we generated mice with inducible Sox10iCre ERT2 -mediated loss of Gjb2. Tamoxifen injection led to reduced connexin 26 expression and impaired function, but cochlear hair cells and neurons survived for 2 months, allowing phenotypic rescue attempts within this time. AAV-mediated gene transfer of GJB2 in mature mutant ears did not demonstrate threshold improvement and in some animals exacerbated hearing loss and resulted in hair cell loss. We conclude that Sox10iCre ERT2 ;Gjb2 flox/flox mice are valuable for studying the biology of connexin 26 in the cochlea. In particular, these mice may be useful for evaluating gene therapy vectors and development of therapies for GJB2-related deafness.
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Affiliation(s)
- Jingying Guo
- Kresge Hearing Research Institute, Otolaryngology, Head and Neck Surgery, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA.,Department of Otolaryngology Head and Neck Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing, China
| | - Xiaobo Ma
- Department of Otolaryngology Head and Neck Surgery, Beijing Tongren Hospital, Capital Medical University, Beijing, China
| | - Jennifer M Skidmore
- Department of Pediatrics, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Jelka Cimerman
- Department of Pediatrics, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Diane M Prieskorn
- Kresge Hearing Research Institute, Otolaryngology, Head and Neck Surgery, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Lisa A Beyer
- Kresge Hearing Research Institute, Otolaryngology, Head and Neck Surgery, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Donald L Swiderski
- Kresge Hearing Research Institute, Otolaryngology, Head and Neck Surgery, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA
| | - David F Dolan
- Kresge Hearing Research Institute, Otolaryngology, Head and Neck Surgery, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Donna M Martin
- Department of Pediatrics, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA.,Department of Human Genetics, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Yehoash Raphael
- Kresge Hearing Research Institute, Otolaryngology, Head and Neck Surgery, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA
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4
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Balendran V, Skidmore JM, Ritter KE, Gao J, Cimerman J, Beyer LA, Hurd EA, Raphael Y, Martin DM. Chromatin remodeler CHD7 is critical for cochlear morphogenesis and neurosensory patterning. Dev Biol 2021; 477:11-21. [PMID: 34004180 DOI: 10.1016/j.ydbio.2021.05.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 04/12/2021] [Accepted: 05/10/2021] [Indexed: 11/18/2022]
Abstract
Epigenetic regulation of gene transcription by chromatin remodeling proteins has recently emerged as an important contributing factor in inner ear development. Pathogenic variants in CHD7, the gene encoding Chromodomain Helicase DNA binding protein 7, cause CHARGE syndrome, which presents with malformations in the developing ear. Chd7 is broadly expressed in the developing mouse otocyst and mature auditory epithelium, yet the pathogenic effects of Chd7 loss in the cochlea are not well understood. Here we characterized cochlear epithelial phenotypes in mice with deletion of Chd7 throughout the otocyst (using Foxg1Cre/+ and Pax2Cre), in the otic mesenchyme (using TCre), in hair cells (using Atoh1Cre), in developing neuroblasts (using NgnCre), or in spiral ganglion neurons (using ShhCre/+). Pan-otic deletion of Chd7 resulted in shortened cochleae with aberrant projections and axonal looping, disorganized, supernumerary hair cells at the apical turn and a narrowed epithelium with missing hair cells in the middle region. Deletion of Chd7 in the otic mesenchyme had no effect on overall cochlear morphology. Loss of Chd7 in hair cells did not disrupt their formation or organization of the auditory epithelium. Similarly, absence of Chd7 in spiral ganglion neurons had no effect on axonal projections. In contrast, deletion of Chd7 in developing neuroblasts led to smaller spiral ganglia and disorganized cochlear neurites. Together, these observations reveal dosage-, tissue-, and time-sensitive cell autonomous roles for Chd7 in cochlear elongation and cochlear neuron organization, with minimal functions for Chd7 in hair cells. These studies provide novel information about roles for Chd7 in development of auditory neurons.
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Affiliation(s)
- Vinodh Balendran
- Departments of Pediatrics, The University of Michigan, Ann Arbor, MI, USA
| | | | - K Elaine Ritter
- Departments of Pediatrics, The University of Michigan, Ann Arbor, MI, USA
| | - Jingxia Gao
- Departments of Pediatrics, The University of Michigan, Ann Arbor, MI, USA
| | - Jelka Cimerman
- Departments of Pediatrics, The University of Michigan, Ann Arbor, MI, USA
| | - Lisa A Beyer
- Otolaryngology - Head and Neck Surgery, The University of Michigan, Ann Arbor, MI, USA
| | | | - Yehoash Raphael
- Otolaryngology - Head and Neck Surgery, The University of Michigan, Ann Arbor, MI, USA
| | - Donna M Martin
- Departments of Pediatrics, The University of Michigan, Ann Arbor, MI, USA; Otolaryngology - Head and Neck Surgery, The University of Michigan, Ann Arbor, MI, USA; Human Genetics, The University of Michigan, Ann Arbor, MI, USA.
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5
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Yao H, Hannum DF, Zhai Y, Hill SF, Albanus RD'O, Lou W, Skidmore JM, Sanchez G, Saiakhova A, Bielas SL, Scacheri P, Ljungman M, Parker SCJ, Martin DM. CHD7 promotes neural progenitor differentiation in embryonic stem cells via altered chromatin accessibility and nascent gene expression. Sci Rep 2020; 10:17445. [PMID: 33060836 PMCID: PMC7562747 DOI: 10.1038/s41598-020-74537-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Accepted: 09/30/2020] [Indexed: 01/09/2023] Open
Abstract
CHARGE syndrome, a rare multiple congenital anomaly condition, is caused by haploinsufficiency of the chromatin remodeling protein gene CHD7 (Chromodomain helicase DNA binding protein 7). Brain abnormalities and intellectual disability are commonly observed in individuals with CHARGE, and neuronal differentiation is reduced in CHARGE patient-derived iPSCs and conditional knockout mouse brains. However, the mechanisms of CHD7 function in nervous system development are not well understood. In this study, we asked whether CHD7 promotes gene transcription in neural progenitor cells via changes in chromatin accessibility. We used Chd7 null embryonic stem cells (ESCs) derived from Chd7 mutant mouse blastocysts as a tool to investigate roles of CHD7 in neuronal and glial differentiation. Loss of Chd7 significantly reduced neuronal and glial differentiation. Sholl analysis showed that loss of Chd7 impaired neuronal complexity and neurite length in differentiated neurons. Genome-wide studies demonstrated that loss of Chd7 leads to modified chromatin accessibility (ATAC-seq) and differential nascent expression (Bru-Seq) of neural-specific genes. These results suggest that CHD7 acts preferentially to alter chromatin accessibility of key genes during the transition of NPCs to neurons to promote differentiation. Our results form a basis for understanding the cell stage-specific roles for CHD7-mediated chromatin remodeling during cell lineage acquisition.
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Affiliation(s)
- Hui Yao
- Department of Pediatrics, University of Michigan, 8220C MSRB III, 1150 W. Medical Center Dr., Ann Arbor, MI, 48109-5652, USA
| | - Douglas F Hannum
- Department of Biostatistics, University of Michigan, Ann Arbor, MI, USA
| | - Yiwen Zhai
- Department of Pediatrics, University of Michigan, 8220C MSRB III, 1150 W. Medical Center Dr., Ann Arbor, MI, 48109-5652, USA.,Center of Genetic and Prenatal Diagnosis, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Sophie F Hill
- College of Literature, Science, and the Arts, University of Michigan, Ann Arbor, MI, USA
| | | | - Wenjia Lou
- Department of Pediatrics, University of Michigan, 8220C MSRB III, 1150 W. Medical Center Dr., Ann Arbor, MI, 48109-5652, USA
| | - Jennifer M Skidmore
- Department of Pediatrics, University of Michigan, 8220C MSRB III, 1150 W. Medical Center Dr., Ann Arbor, MI, 48109-5652, USA
| | - Gilson Sanchez
- Department of Pediatrics, University of Michigan, 8220C MSRB III, 1150 W. Medical Center Dr., Ann Arbor, MI, 48109-5652, USA
| | - Alina Saiakhova
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, USA
| | - Stephanie L Bielas
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Peter Scacheri
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, USA
| | - Mats Ljungman
- Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, USA
| | - Stephen C J Parker
- Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI, USA.,Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Donna M Martin
- Department of Pediatrics, University of Michigan, 8220C MSRB III, 1150 W. Medical Center Dr., Ann Arbor, MI, 48109-5652, USA. .,Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA.
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6
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Moccia A, Srivastava A, Skidmore JM, Bernat JA, Wheeler M, Chong JX, Nickerson D, Bamshad M, Hefner MA, Martin DM, Bielas SL. Genetic analysis of CHARGE syndrome identifies overlapping molecular biology. Genet Med 2018; 20:1022-1029. [PMID: 29300383 PMCID: PMC6034995 DOI: 10.1038/gim.2017.233] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Accepted: 11/15/2017] [Indexed: 11/09/2022] Open
Abstract
PURPOSE CHARGE syndrome is an autosomal-dominant, multiple congenital anomaly condition characterized by vision and hearing loss, congenital heart disease, and malformations of craniofacial and other structures. Pathogenic variants in CHD7, encoding adenosine triphosphate-dependent chromodomain helicase DNA binding protein 7, are present in the majority of affected individuals. However, no causal variant can be found in 5-30% (depending on the cohort) of individuals with a clinical diagnosis of CHARGE syndrome. METHODS We performed whole-exome sequencing (WES) on 28 families from which at least one individual presented with features highly suggestive of CHARGE syndrome. RESULTS Pathogenic variants in CHD7 were present in 15 of 28 individuals (53.6%), whereas 4 (14.3%) individuals had pathogenic variants in other genes (RERE, KMT2D, EP300, or PUF60). A variant of uncertain clinical significance in KDM6A was identified in one (3.5%) individual. The remaining eight (28.6%) individuals were not found to have pathogenic variants by WES. CONCLUSION These results demonstrate that the phenotypic features of CHARGE syndrome overlap with multiple other rare single-gene syndromes. Additionally, they implicate a shared molecular pathology that disrupts epigenetic regulation of multiple-organ development.
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Affiliation(s)
- Amanda Moccia
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Anshika Srivastava
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Jennifer M Skidmore
- Department of Pediatrics, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - John A Bernat
- Department of Pediatrics, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA
| | - Marsha Wheeler
- University of Washington Center for Mendelian Genomics, University of Washington, Seattle, Washington, USA
| | - Jessica X Chong
- University of Washington Center for Mendelian Genomics, University of Washington, Seattle, Washington, USA
| | - Deborah Nickerson
- University of Washington Center for Mendelian Genomics, University of Washington, Seattle, Washington, USA
| | - Michael Bamshad
- University of Washington Center for Mendelian Genomics, University of Washington, Seattle, Washington, USA
| | - Margaret A Hefner
- Department of Pediatrics, Saint Louis University School of Medicine, St. Louis, Missouri, USA
| | - Donna M Martin
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, Michigan, USA.
- Department of Pediatrics, University of Michigan Medical School, Ann Arbor, Michigan, USA.
| | - Stephanie L Bielas
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, Michigan, USA.
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7
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Yao H, Hill SF, Skidmore JM, Sperry ED, Swiderski DL, Sanchez GJ, Bartels CF, Raphael Y, Scacheri PC, Iwase S, Martin DM. CHD7 represses the retinoic acid synthesis enzyme ALDH1A3 during inner ear development. JCI Insight 2018; 3:97440. [PMID: 29467333 DOI: 10.1172/jci.insight.97440] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 01/23/2018] [Indexed: 12/13/2022] Open
Abstract
CHD7, an ATP-dependent chromatin remodeler, is disrupted in CHARGE syndrome, an autosomal dominant disorder characterized by variably penetrant abnormalities in craniofacial, cardiac, and nervous system tissues. The inner ear is uniquely sensitive to CHD7 levels and is the most commonly affected organ in individuals with CHARGE. Interestingly, upregulation or downregulation of retinoic acid (RA) signaling during embryogenesis also leads to developmental defects similar to those in CHARGE syndrome, suggesting that CHD7 and RA may have common target genes or signaling pathways. Here, we tested three separate potential mechanisms for CHD7 and RA interaction: (a) direct binding of CHD7 with RA receptors, (b) regulation of CHD7 levels by RA, and (c) CHD7 binding and regulation of RA-related genes. We show that CHD7 directly regulates expression of Aldh1a3, the gene encoding the RA synthetic enzyme ALDH1A3 and that loss of Aldh1a3 partially rescues Chd7 mutant mouse inner ear defects. Together, these studies indicate that ALDH1A3 acts with CHD7 in a common genetic pathway to regulate inner ear development, providing insights into how CHD7 and RA regulate gene expression and morphogenesis in the developing embryo.
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Affiliation(s)
- Hui Yao
- Department of Pediatrics and Communicable Diseases
| | | | | | - Ethan D Sperry
- Department of Human Genetics.,Medical Scientist Training Program, and
| | - Donald L Swiderski
- Department of Otolaryngology, University of Michigan, Ann Arbor, Michigan, USA
| | | | - Cynthia F Bartels
- Department of Genetics, Case Western Reserve University, Cleveland, Ohio, USA
| | - Yehoash Raphael
- Department of Otolaryngology, University of Michigan, Ann Arbor, Michigan, USA
| | - Peter C Scacheri
- Department of Genetics, Case Western Reserve University, Cleveland, Ohio, USA
| | | | - Donna M Martin
- Department of Pediatrics and Communicable Diseases.,Department of Human Genetics.,Medical Scientist Training Program, and
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8
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Charoy C, Dinvaut S, Chaix Y, Morlé L, Sanyas I, Bozon M, Kindbeiter K, Durand B, Skidmore JM, De Groef L, Seki M, Moons L, Ruhrberg C, Martin JF, Martin DM, Falk J, Castellani V. Genetic specification of left-right asymmetry in the diaphragm muscles and their motor innervation. eLife 2017. [PMID: 28639940 PMCID: PMC5481184 DOI: 10.7554/elife.18481] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The diaphragm muscle is essential for breathing in mammals. Its asymmetric elevation during contraction correlates with morphological features suggestive of inherent left–right (L/R) asymmetry. Whether this asymmetry is due to L versus R differences in the muscle or in the phrenic nerve activity is unknown. Here, we have combined the analysis of genetically modified mouse models with transcriptomic analysis to show that both the diaphragm muscle and phrenic nerves have asymmetries, which can be established independently of each other during early embryogenesis in pathway instructed by Nodal, a morphogen that also conveys asymmetry in other organs. We further found that phrenic motoneurons receive an early L/R genetic imprint, with L versus R differences both in Slit/Robo signaling and MMP2 activity and in the contribution of both pathways to establish phrenic nerve asymmetry. Our study therefore demonstrates L–R imprinting of spinal motoneurons and describes how L/R modulation of axon guidance signaling helps to match neural circuit formation to organ asymmetry. DOI:http://dx.doi.org/10.7554/eLife.18481.001 The diaphragm is a dome-shaped muscle that forms the floor of the rib cage, separating the lungs from the abdomen. As we breathe in, the diaphragm contracts. This causes the chest cavity to expand, drawing air into the lungs. A pair of nerves called the phrenic nerves carry signals from the spinal cord to the diaphragm to tell it when to contract. These nerves project from the left and right sides of the spinal cord to the left and right sides of the diaphragm respectively. The left and right sides of the diaphragm are not entirely level, but it was not known why. To investigate, Charoy et al. studied how the diaphragm develops in mouse embryos. This revealed that the left and right phrenic nerves are not symmetrical. Neither are the muscles on each side of the diaphragm. Further investigation revealed that a genetic program that establishes other differences between the left and right sides of the embryo also gives rise to the differences between the left and right sides of the diaphragm. This program switches on different genes in the left and right phrenic nerves, which activate different molecular pathways in the left and right sides of the diaphragm muscle. The differences between the nerves and muscles on the left and right sides of the diaphragm could explain why some muscle disorders affect only one side of the diaphragm. Similarly, they could explain why congenital hernias caused by abdominal organs pushing through the diaphragm into the chest cavity mostly affect the left side of the diaphragm. Further studies are now needed to investigate these possibilities. The techniques used by Charoy et al. to map the molecular diversity of spinal cord neurons could also lead to new strategies for repairing damage to the spinal cord following injury or disease. DOI:http://dx.doi.org/10.7554/eLife.18481.002
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Affiliation(s)
- Camille Charoy
- University of Lyon, Claude Bernard University Lyon 1, INMG UMR CNRS 5310, INSERM U1217, Lyon, France
| | - Sarah Dinvaut
- University of Lyon, Claude Bernard University Lyon 1, INMG UMR CNRS 5310, INSERM U1217, Lyon, France
| | - Yohan Chaix
- University of Lyon, Claude Bernard University Lyon 1, INMG UMR CNRS 5310, INSERM U1217, Lyon, France
| | - Laurette Morlé
- University of Lyon, Claude Bernard University Lyon 1, INMG UMR CNRS 5310, INSERM U1217, Lyon, France
| | - Isabelle Sanyas
- University of Lyon, Claude Bernard University Lyon 1, INMG UMR CNRS 5310, INSERM U1217, Lyon, France
| | - Muriel Bozon
- University of Lyon, Claude Bernard University Lyon 1, INMG UMR CNRS 5310, INSERM U1217, Lyon, France
| | - Karine Kindbeiter
- University of Lyon, Claude Bernard University Lyon 1, INMG UMR CNRS 5310, INSERM U1217, Lyon, France
| | - Bénédicte Durand
- University of Lyon, Claude Bernard University Lyon 1, INMG UMR CNRS 5310, INSERM U1217, Lyon, France
| | - Jennifer M Skidmore
- Department of Pediatrics, University of Michigan Medical Center, Ann Arbor, United States.,Department of Communicable Diseases, University of Michigan Medical Center, Ann Arbor, United States
| | - Lies De Groef
- Animal Physiology and Neurobiology Section, Department of Biology, Laboratory of Neural Circuit Development and Regeneration, Leuven, Belgium
| | - Motoaki Seki
- Research Center for Advanced Science and Technology, University of Tokyo, Tokyo, Japan
| | - Lieve Moons
- Animal Physiology and Neurobiology Section, Department of Biology, Laboratory of Neural Circuit Development and Regeneration, Leuven, Belgium
| | - Christiana Ruhrberg
- UCL Institute of Ophthalmology, University College London, London, United Kingdom
| | | | - Donna M Martin
- Department of Pediatrics, University of Michigan Medical Center, Ann Arbor, United States.,Department of Communicable Diseases, University of Michigan Medical Center, Ann Arbor, United States.,Department of Human Genetics, University of Michigan Medical Center, Ann Arbor, United States
| | - Julien Falk
- University of Lyon, Claude Bernard University Lyon 1, INMG UMR CNRS 5310, INSERM U1217, Lyon, France
| | - Valerie Castellani
- University of Lyon, Claude Bernard University Lyon 1, INMG UMR CNRS 5310, INSERM U1217, Lyon, France
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9
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Micucci JA, Layman WS, Hurd EA, Sperry ED, Frank SF, Durham MA, Swiderski DL, Skidmore JM, Scacheri PC, Raphael Y, Martin DM. CHD7 and retinoic acid signaling cooperate to regulate neural stem cell and inner ear development in mouse models of CHARGE syndrome. Hum Mol Genet 2013; 23:434-48. [PMID: 24026680 DOI: 10.1093/hmg/ddt435] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
CHARGE syndrome is a multiple congenital anomaly disorder that leads to life-threatening birth defects, such as choanal atresia and cardiac malformations as well as multiple sensory impairments, that affect hearing, vision, olfaction and balance. CHARGE is caused by heterozygous mutations in CHD7, which encodes an ATP-dependent chromatin remodeling enzyme. Identification of the mechanisms underlying neurological and sensory defects in CHARGE is a first step toward developing treatments for CHARGE individuals. Here, we used mouse models of Chd7 deficiency to explore the function of CHD7 in the development of the subventricular zone (SVZ) neural stem cell niche and inner ear, structures that are important for olfactory bulb neurogenesis and hearing and balance, respectively. We found that loss of Chd7 results in cell-autonomous proliferative, neurogenic and self-renewal defects in the perinatal and mature mouse SVZ stem cell niche. Modulation of retinoic acid (RA) signaling prevented in vivo inner ear and in vitro neural stem cell defects caused by Chd7 deficiency. Our findings demonstrate critical, cooperative roles for RA and CHD7 in SVZ neural stem cell function and inner ear development, suggesting that altered RA signaling may be an effective method for treating Chd7 deficiency.
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10
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Waite MR, Skidmore JM, Micucci JA, Shiratori H, Hamada H, Martin JF, Martin DM. Pleiotropic and isoform-specific functions for Pitx2 in superior colliculus and hypothalamic neuronal development. Mol Cell Neurosci 2013; 52:128-39. [PMID: 23147109 PMCID: PMC3540135 DOI: 10.1016/j.mcn.2012.11.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Revised: 10/01/2012] [Accepted: 11/02/2012] [Indexed: 02/01/2023] Open
Abstract
Transcriptional regulation of gene expression during development is critical for proper neuronal differentiation and migration. Alternative splicing and differential isoform expression have been demonstrated for most mammalian genes, but their specific contributions to gene function are not well understood. In mice, the transcription factor gene Pitx2 is expressed as three different isoforms (PITX2A, PITX2B, and PITX2C) which have unique amino termini and common DNA binding homeodomains and carboxyl termini. The specific roles of these isoforms in neuronal development are not known. Here we report the onset of Pitx2ab and Pitx2c isoform-specific expression by E9.5 in the developing mouse brain. Using isoform-specific Pitx2 deletion mouse strains, we show that collicular neuron migration requires PITX2AB and that collicular GABAergic differentiation and targeting of hypothalamic projections require unique Pitx2 isoform dosage. These results provide insights into Pitx2 dosage and isoform-specific requirements underlying midbrain and hypothalamic development.
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Affiliation(s)
- Mindy R Waite
- Cellular and Molecular Biology Graduate Program, 2966 Taubman Medical Library, University of Michigan, Ann Arbor, MI 48109-0619, USA.
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11
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Bedoyan JK, Schaibley VM, Peng W, Bai Y, Mondal K, Shetty AC, Durham M, Micucci JA, Dhiraaj A, Skidmore JM, Kaplan JB, Skinner C, Schwartz CE, Antonellis A, Zwick ME, Cavalcoli JD, Li JZ, Martin DM. Disruption of RAB40AL function leads to Martin--Probst syndrome, a rare X-linked multisystem neurodevelopmental human disorder. J Med Genet 2012; 49:332-40. [PMID: 22581972 PMCID: PMC3350147 DOI: 10.1136/jmedgenet-2011-100575] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
BACKGROUND AND AIM Martin--Probst syndrome (MPS) is a rare X-linked disorder characterised by deafness, cognitive impairment, short stature and distinct craniofacial dysmorphisms, among other features. The authors sought to identify the causative mutation for MPS. METHODS AND RESULTS Massively parallel sequencing in two affected, related male subjects with MPS identified a RAB40AL (also called RLGP) missense mutation (chrX:102,079,078-102,079,079AC→GA p.D59G; hg18). RAB40AL encodes a small Ras-like GTPase protein with one suppressor of cytokine signalling box. The p.D59G variant is located in a highly conserved region of the GTPase domain between β-2 and β-3 strands. Using RT-PCR, the authors show that RAB40AL is expressed in human fetal and adult brain and kidney, and adult lung, heart, liver and skeletal muscle. RAB40AL appears to be a primate innovation, with no orthologues found in mouse, Xenopus or zebrafish. Western analysis and fluorescence microscopy of GFP-tagged RAB40AL constructs from transiently transfected COS7 cells show that the D59G missense change renders RAB40AL unstable and disrupts its cytoplasmic localisation. CONCLUSIONS This is the first study to show that mutation of RAB40AL is associated with a human disorder. Identification of RAB40AL as the gene mutated in MPS allows for further investigations into the molecular mechanism(s) of RAB40AL and its roles in diverse processes such as cognition, hearing and skeletal development.
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12
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Skidmore JM, Waite MR, Alvarez-Bolado G, Puelles L, Martin DM. A novel TaulacZ allele reveals a requirement for Pitx2 in formation of the mammillothalamic tract. Genesis 2012; 50:67-73. [DOI: 10.1002/dvg.20793] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Revised: 08/04/2011] [Accepted: 08/19/2011] [Indexed: 12/25/2022]
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13
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Waite MR, Skaggs K, Kaviany P, Skidmore JM, Causeret F, Martin JF, Martin DM. Distinct populations of GABAergic neurons in mouse rhombomere 1 express but do not require the homeodomain transcription factor PITX2. Mol Cell Neurosci 2012; 49:32-43. [PMID: 21925604 PMCID: PMC3244529 DOI: 10.1016/j.mcn.2011.08.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2011] [Revised: 08/04/2011] [Accepted: 08/30/2011] [Indexed: 11/20/2022] Open
Abstract
Hindbrain rhombomere 1 (r1) is located caudal to the isthmus, a critical organizer region, and rostral to rhombomere 2 in the developing mouse brain. Dorsal r1 gives rise to the cerebellum, locus coeruleus, and several brainstem nuclei, whereas cells from ventral r1 contribute to the trochlear and trigeminal nuclei as well as serotonergic and GABAergic neurons of the dorsal raphe. Recent studies have identified several molecular events controlling dorsal r1 development. In contrast, very little is known about ventral r1 gene expression and the genetic mechanisms regulating its formation. Neurons with distinct neurotransmitter phenotypes have been identified in ventral r1 including GABAergic, serotonergic, and cholinergic neurons. Here we show that PITX2 marks a distinct population of GABAergic neurons in mouse embryonic ventral r1. This population appears to retain its GABAergic identity even in the absence of PITX2. We provide a comprehensive map of markers that places these PITX2-positive GABAergic neurons in a region of r1 that intersects and is potentially in communication with the dorsal raphe.
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Affiliation(s)
- Mindy R Waite
- Program in Cell and Molecular Biology, 2966 Taubman Medical Library, University of Michigan, Ann Arbor, MI 48109-0619, USA.
| | - Kaia Skaggs
- Department of Neurology, 3520A MSRB I, University of Michigan, Ann Arbor, MI, 48019-5652, USA.
| | - Parisa Kaviany
- Department of Pediatrics, 3520A MSRB I, University of Michigan, Ann Arbor, MI, 48019-5652, USA.
| | - Jennifer M Skidmore
- Department of Pediatrics, 3520A MSRB I, University of Michigan, Ann Arbor, MI, 48019-5652, USA.
| | - Frédéric Causeret
- Institut Jacques Monod, Université Paris Diderot, CNRS UMR 7592, Sorbonne Paris Cité, Paris, France.
| | - James F Martin
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Cardiomyocyte Renewal Lab Texas Heart Institute, Houston Texas, 77030, USA.
| | - Donna M Martin
- Program in Cell and Molecular Biology, 2966 Taubman Medical Library, University of Michigan, Ann Arbor, MI 48109-0619, USA; Department of Pediatrics, 3520A MSRB I, University of Michigan, Ann Arbor, MI, 48019-5652, USA; Department of Human Genetics, 3520A MSRB I, University of Michigan, Ann Arbor, MI, 48019-5652, USA.
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14
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Waite MR, Skidmore JM, Billi AC, Martin JF, Martin DM. GABAergic and glutamatergic identities of developing midbrain Pitx2 neurons. Dev Dyn 2011; 240:333-46. [PMID: 21246650 PMCID: PMC3079949 DOI: 10.1002/dvdy.22532] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/30/2010] [Indexed: 12/18/2022] Open
Abstract
Pitx2, a paired-like homeodomain transcription factor, is expressed in post-mitotic neurons within highly restricted domains of the embryonic mouse brain. Previous reports identified critical roles for PITX2 in histogenesis of the hypothalamus and midbrain, but the cellular identities of PITX2-positive neurons in these regions were not fully explored. This study characterizes Pitx2 expression with respect to midbrain transcription factor and neurotransmitter phenotypes in mid-to-late mouse gestation. In the dorsal midbrain, we identified Pitx2-positive neurons in the stratum griseum intermedium (SGI) as GABAergic and observed a requirement for PITX2 in GABAergic differentiation. We also identified two Pitx2-positive neuronal populations in the ventral midbrain, the red nucleus, and a ventromedial population, both of which contain glutamatergic precursors. Our data suggest that PITX2 is present in regionally restricted subpopulations of midbrain neurons and may have unique functions that promote GABAergic and glutamatergic differentiation.
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Affiliation(s)
- MR Waite
- Cellular & Molecular Biology Program, The University of Michigan, Ann Arbor, MI 48109
| | - JM Skidmore
- Department of Pediatrics, The University of Michigan, Ann Arbor, MI 48109
| | - AC Billi
- Department of Human Genetics, The University of Michigan, Ann Arbor, MI 48109
| | - JF Martin
- Institute of Biosciences and Technology, Texas A&M System Health Science Center, Houston, TX 77030
| | - DM Martin
- Department of Pediatrics, The University of Michigan, Ann Arbor, MI 48109
- Department of Human Genetics, The University of Michigan, Ann Arbor, MI 48109
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15
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Skidmore JM, Cramer JD, Martin JF, Martin DM. Cre fate mapping reveals lineage specific defects in neuronal migration with loss of Pitx2 function in the developing mouse hypothalamus and subthalamic nucleus. Mol Cell Neurosci 2008; 37:696-707. [PMID: 18206388 PMCID: PMC2386145 DOI: 10.1016/j.mcn.2007.12.015] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2007] [Revised: 11/18/2007] [Accepted: 12/07/2007] [Indexed: 10/22/2022] Open
Abstract
Establishment of neuronal diversity is a central topic in developmental neurobiology. Prior studies implicated Pitx2, a paired-like homeodomain transcription factor, in mouse subthalamic nucleus neuronal development, but precise stages of neuronal differentiation affected (migration, axon outgrowth, fate specification) and underlying mechanisms were unknown. Here we report lineage tracing experiments using Pitx2(cre/+), Pitx2(cre/null), and conditional nuclear lacZ reporter mice to track embryonic Pitx2 expressing neurons. Migration of subthalamic nucleus and hypothalamic neurons was severely arrested in Pitx2(cre/null) embryos, and subclasses of subthalamic nucleus neurons identified by Lmx1b, Foxp1, and Foxp2-gene expression revealed differing sensitivities to Pitx2 dosage. Interestingly, embryonic subthalamic nucleus development was unaffected in Lmx1b null mice, suggesting that Pitx2 and Lmx1b act via independent genetic pathways. These data provide the first direct evidence for Pitx2-dependent neuronal migration in the developing hypothalamus, and demonstrate that complex transcriptional networks regulate regional specialization of distinct hypothalamic and subthalamic nucleus neurons.
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Affiliation(s)
- Jennifer M. Skidmore
- Department of Pediatrics, The University of Michigan Medical Center, Ann Arbor, Michigan, 48109
| | - John D. Cramer
- Department of Pediatrics, The University of Michigan Medical Center, Ann Arbor, Michigan, 48109
| | - James F. Martin
- Institute of Biosciences and Technology, Texas A&M System Health Science Center, Houston, TX 77030
| | - Donna M. Martin
- Department of Pediatrics, The University of Michigan Medical Center, Ann Arbor, Michigan, 48109
- Department of Human Genetics, The University of Michigan Medical Center, Ann Arbor, Michigan, 48109
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16
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Vue TY, Aaker J, Taniguchi A, Kazemzadeh C, Skidmore JM, Martin DM, Martin JF, Treier M, Nakagawa Y. Characterization of progenitor domains in the developing mouse thalamus. J Comp Neurol 2008; 505:73-91. [PMID: 17729296 DOI: 10.1002/cne.21467] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
To understand the molecular basis of the specification of thalamic nuclei, we analyzed the expression patterns of various transcription factors and defined progenitor cell populations in the embryonic mouse thalamus. We show that the basic helix-loop-helix (bHLH) transcription factor Olig3 is expressed in the entire thalamic ventricular zone and the zona limitans intrathalamica (ZLI). Next, we define two distinct progenitor domains within the thalamus, which we name pTH-R and pTH-C, located caudal to the ZLI. pTH-R is immediately caudal to the ZLI and expresses Nkx2.2, Mash1, and Olig3. pTH-C is caudal to pTH-R and expresses Ngn1, Ngn2, and Olig3. Short-term lineage analysis of Olig3-, Mash1-, Ngn1-, and Ngn2-expressing progenitor cells as well as tracing the Pitx2 cell lineage suggests that pTH-C is the only major source of thalamic nuclei containing neurons that project to the cerebral cortex, whereas pTH-R and ZLI are likely to produce distinct postmitotic populations outside of the cortex-projecting part of the thalamus. To determine if pTH-C is composed of subdomains, we characterized expression of the homeodomain protein Dbx1 and the bHLH protein Olig2. We show that Dbx1 is expressed in caudodorsal-high to rostroventral-low gradient within pTH-C. Analysis of heterozygous Dbx1(nlslacZ) knockin mice demonstrated that Dbx1-expressing progenitors preferentially give rise to caudodorsal thalamic nuclei. Olig2 is expressed in an opposite gradient within pTH-C to that of Dbx1. These results establish the molecular heterogeneity within the progenitor cells of the thalamus, and suggest that such heterogeneity contributes to the specification of thalamic nuclei.
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Affiliation(s)
- Tou Yia Vue
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota 55455, USA
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17
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Abstract
Nestin-Cre mice are widely used to generate gene deletions in the developing brain. Surprisingly, fewNestin-Cre lines have been characterized for their temporal and brain region-specific recombination. In addition, some Nestin-Cre lines express Cre outside the central nervous system, making it difficult to choose appropriate lines for targeting genes with brain region-restricted expression. Here we describe the properties of a Nestin-Cre transgenic line and its use for conditional deletions of Pitx2, a paired-like homeodomain transcription factor. We report that Nestin-Cre conditional Pitx2 mutant mice have ocular and craniofacial defects consistent with the role of human PITX2 in Rieger syndrome. Conditional mutants exhibit defects in midbrain neuronal development similar to those in Pitx2 homozygous null embryos, but lack the abnormalities in subthalamic nucleus neurons that occur with complete loss of Pitx2 function. These data indicate that normal differentiation of midbrain neurons depends upon adequate Pitx2 function during the period of active neurogenesis.
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Affiliation(s)
- Anthony M Sclafani
- Molecular, Cellular and Developmental Biology Graduate Program, Yale College of Medicine, New Haven, Connecticut, USA
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18
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Datta K, Skidmore JM, Pu K, Maddock JR. The Caulobacter crescentus GTPase CgtAC is required for progression through the cell cycle and for maintaining 50S ribosomal subunit levels. Mol Microbiol 2005; 54:1379-92. [PMID: 15554976 DOI: 10.1111/j.1365-2958.2004.04354.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The Obg subfamily of bacterial GTP-binding proteins are biochemically distinct from Ras-like proteins raising the possibility that they are not controlled by conventional guanine nucleotide exchange factors (GEFs) and/or guanine nucleotide activating proteins (GAPs). To test this hypothesis, we generated mutations in the Caulobacter crescentus obg gene (cgtAC) which, in Ras-like proteins, would result in either activating or dominant negative phenotypes. In C. crescentus, a P168V mutant is not activating in vivo, although in vitro, the P168V protein showed a modest reduction in the affinity for GDP. Neither the S173N nor N280Y mutations resulted in a dominant negative phenotype. Furthermore, the S173N was significantly impaired for GTP binding, consistent with a critical role of this residue in GTP binding. In general, conserved amino acids in the GTP-binding pocket were, however, important for function. To examine the in vivo consequences of depleting CgtAC, we generated a temperature-sensitive mutant, G80E. At the permissive temperature, G80E cells grow slowly and have reduced levels of 50S ribosomal subunits, indicating that CgtAC is important for 50S assembly and/or stability. Surprisingly, at the non-permissive temperature, G80E cells rapidly lose viability and yet do not display an additional ribosome defect. Thus, the essential nature of the cgtAC gene does not appear to result from its ribosome function. G80E cells arrest as predivisional cells and stalkless cells. Flow cytometry on synchronized cells reveals a G1-S arrest. Therefore, CgtAC is necessary for DNA replication and progression through the cell cycle.
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Affiliation(s)
- Kaustuv Datta
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
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19
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Martin DM, Skidmore JM, Philips ST, Vieira C, Gage PJ, Condie BG, Raphael Y, Martinez S, Camper SA. PITX2 is required for normal development of neurons in the mouse subthalamic nucleus and midbrain. Dev Biol 2004; 267:93-108. [PMID: 14975719 DOI: 10.1016/j.ydbio.2003.10.035] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2003] [Revised: 09/23/2003] [Accepted: 10/27/2003] [Indexed: 11/25/2022]
Abstract
Pitx2, a homeodomain transcription factor, is essential for normal development of the pituitary gland, craniofacial region, eyes, heart, abdominal viscera, and limbs. Complete loss of Pitx2 in mice (Pitx2(-/-)) results in embryonic lethality by approximately e15 due to cardiac defects, whereas embryos with partial loss of function (Pitx2(neo/-) or Pitx2(neo/neo)) survive until later in development (e17-e19). Pitx2 is expressed in discrete populations of postmitotic neurons in the mouse brain, but its role in mammalian central nervous system (CNS) development is not known. We undertook an analysis of Pitx2-deficient embryos to determine whether loss of Pitx2 affects CNS development. The CNS is normal in hypomorphic e16.5 Pitx2(neo/-) and e18.5 Pitx2(neo/neo) embryos, with no evidence of midline or other defects. Midgestation (e10.5) Pitx2(-/-) embryos have normally formed neural tube structures and cerebral vesicles, whereas older (e14.5) Pitx2(-/-) embryos exhibit loss of gene expression and axonal projections in the subthalamic nucleus (a group of cells in the ventrolateral thalamus) and in the developing superior colliculus of dorsal midbrain. Our results suggest a role for Pitx2 in regulating regionally specific terminal neuronal differentiation in the developing ventrolateral thalamus and midbrain.
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Affiliation(s)
- Donna M Martin
- Department of Pediatrics and Communicable Diseases, The University of Michigan, Ann Arbor, MI 48109, USA.
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20
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Treutelaar MK, Skidmore JM, Dias-Leme CL, Hara M, Zhang L, Simeone D, Martin DM, Burant CF. Nestin-lineage cells contribute to the microvasculature but not endocrine cells of the islet. Diabetes 2003; 52:2503-12. [PMID: 14514633 DOI: 10.2337/diabetes.52.10.2503] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
To clarify the lineage relationship between cells that express the neural stem cell marker nestin and endocrine cells of the pancreas, we analyzed offspring of a cross between mice carrying a nestin promoter/enhancer-driven cre-recombinase (Nestin-cre) and C57BL/6J-Gtrosa26(tm1Sor) mice that carry a loxP-disrupted beta-galactosidase gene (Rosa26). In nestin-cre(+/tg);R26R(loxP/+) embryos, cre-recombinase was detected in association with nestin-positive cells in the pancreatic mesenchyme with some of the nestin-positive cells lining vascular channels. In postnatal mice, pancreatic beta-galactosidase expression was restricted to vascular endothelial cells of the islet and a subset of cells in the muscularis of arteries in a distribution identical to endogenous nestin expression. Ex vivo explants of mouse pancreatic ducts grew dense cultures that costained for nestin and beta-galactosidase, demonstrating recombination in vitro. The cultures could be differentiated into complex stereotypic structures that contain nestin- and insulin-expressing cells. Nestin-cre(+/tg);R26R(loxP/+)-derived duct cultures showed that insulin-positive cells were negative for beta-galactosidase. These results indicate that both in vivo and in vitro pancreatic endocrine cells arise independently of nestin-positive precursors. The apparent vascular nature of the nestin-positive cell population and the close association with endocrine cells suggest that nestin-positive cells play an important role in the growth and maintenance of the islet.
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MESH Headings
- Animals
- Animals, Newborn/metabolism
- Arteries/cytology
- Arteries/metabolism
- Blood Vessels/cytology
- Cell Line
- Endothelium, Vascular/cytology
- Endothelium, Vascular/metabolism
- In Vitro Techniques
- Insulin/metabolism
- Integrases/metabolism
- Intermediate Filament Proteins/metabolism
- Islets of Langerhans/blood supply
- Islets of Langerhans/cytology
- Islets of Langerhans/embryology
- Islets of Langerhans/metabolism
- Mesoderm/cytology
- Mesoderm/metabolism
- Mice
- Mice, Inbred C57BL
- Mice, Transgenic
- Microcirculation
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/metabolism
- Myocytes, Smooth Muscle/metabolism
- Nerve Tissue Proteins
- Nestin
- Pancreatic Ducts/cytology
- Pancreatic Ducts/metabolism
- Proteins/genetics
- RNA, Untranslated
- Viral Proteins/metabolism
- beta-Galactosidase/metabolism
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Affiliation(s)
- Mary Kay Treutelaar
- Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
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21
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Martin DM, Skidmore JM, Fox SE, Gage PJ, Camper SA. Pitx2 distinguishes subtypes of terminally differentiated neurons in the developing mouse neuroepithelium. Dev Biol 2002; 252:84-99. [PMID: 12453462 DOI: 10.1006/dbio.2002.0835] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Pitx2, a homeodomain transcription factor, is essential for normal development of pituitary, eyes, heart, and teeth. In the developing mouse brain, Pitx2 (Rieg, Ptx2, Otlx2, Brx1) mRNA is expressed in discrete regions of the diencephalon, mesencephalon, and rhombencephalon. While prior reports have provided an overview of the temporal and regional specificity of Pitx2 mRNA expression in the brain, the precise cell types that express PITX2 are not known. In this study, we analyzed Pitx2 mRNA and PITX2 protein expression in individual cells of the developing e10.5-e14.5 mouse CNS using multiple markers of cellular proliferation and differentiation. We identified Pitx2 expression in nestin-positive neural progenitors and in postmitotic, developing neurons. In the diencephalon, PITX2 is expressed in neurons of the zona limitans intrathalamica and mammillary region and in gamma-aminobutyric acid (GABA)-producing neurons of the zona incerta. In the mesencephalon, PITX2-labeled nuclei also appear in differentiated neurons, some of which are GABAergic and destined to occupy superior colliculus. Our results suggest that PITX2 expression in postmitotic neurons may contribute to development of GABAergic and other differentiated neuronal phenotypes.
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Affiliation(s)
- Donna M Martin
- Department of Pediatrics and Communicable Diseases, University of Michigan, Ann Arbor, 48109, USA.
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22
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Lin B, Skidmore JM, Bhatt A, Pfeffer SM, Pawloski L, Maddock JR. Alanine scan mutagenesis of the switch I domain of the Caulobacter crescentus CgtA protein reveals critical amino acids required for in vivo function. Mol Microbiol 2001; 39:924-34. [PMID: 11251813 DOI: 10.1046/j.1365-2958.2001.02285.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Caulobacter crescentus CgtA protein is a member of the Obg/GTP1 subfamily of monomeric GTP-binding proteins. In vitro, CgtA displays moderate affinity for both GDP and GTP and displays rapid exchange rate constants for either nucleotide, indicating that the guanine nucleotide-binding and exchange properties of CgtA are different from those of the well-characterized Ras-like GTP-binding proteins. The Obg/GTP1 proteins share sequence similarity along the putative effector-binding domain. In this study, we examined the functional consequences of altering amino acid residues within this conserved domain, and identified that T193 was critical for CgtA function. The in vitro binding, exchange and GTP hydrolysis of the T192A, T193A and T192AT193A mutant proteins was examined using fluorescent guanine nucleotide analogues (mant-GDP and mant-GTP). Substitution of either T192 and/or T193 for alanine modestly reduced binding to GDP and significantly reduced the binding affinity for GTP. Furthermore, the T193A mutant protein was more severely impaired for binding GTP than the T192A mutant. The T193A mutation appeared to account solely for the impaired GTP binding of the T192AT193A double mutation. This is the first report that demonstrates that a confirmed defect in guanine nucleotide binding and GTP hydrolysis of an Obg-like protein results in the lack of function in vivo.
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Affiliation(s)
- B Lin
- Department of Biology, University of Michigan, Ann Arbor, MI 48109-1048, USA
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Skidmore JM, Ellefson DD, McNamara BP, Couto MM, Wolfe AJ, Maddock JR. Polar clustering of the chemoreceptor complex in Escherichia coli occurs in the absence of complete CheA function. J Bacteriol 2000; 182:967-73. [PMID: 10648522 PMCID: PMC94372 DOI: 10.1128/jb.182.4.967-973.2000] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacterial chemotaxis requires a phosphorelay system initiated by the interaction of a ligand with its chemoreceptor and culminating in a change in the directional bias of flagellar rotation. Chemoreceptor-CheA-CheW ternary complexes mediate transduction of the chemotactic signal. In vivo, these complexes cluster predominantly in large groups at the cell poles. The function of chemoreceptor clustering is currently unknown. To gain insight into the relationship between signaling and chemoreceptor clustering, we examined these properties in several Escherichia coli mutant strains that produce CheA variants altered in their ability to mediate chemotaxis, autophosphorylate, or bind ATP. We show here that polar clustering of chemoreceptor complexes does not require functional CheA protein, although maximal clustering occurred only in chemotactically competent cells. Surprisingly, in cells containing a minimum of 13 gold particles at the cell pole, a significant level of clustering was observed in the absence of CheA, demonstrating that CheA is not absolutely essential for chemoreceptor clustering. Nonchemotactic cells expressing only CheA(S), a C-terminal CheA deletion, or CheA bearing a mutation in the ATP-binding site mediated slightly less than maximal chemoreceptor clustering. Cells expressing only full-length CheA (CheA(L)) from either a chromosomal or a plasmid-encoded allele displayed a methyl-accepting chemotaxis protein localization pattern indistinguishable from that of strains carrying both CheA(L) and CheA(S), demonstrating that CheA(L) alone can mediate polar clustering.
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Affiliation(s)
- J M Skidmore
- Department of Biology, University of Michigan, Ann Arbor, Michigan 48109-1048, USA
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