1
|
Li N, Zhu Y, Wang J, Zhu M, Gao S, Chen Q, Shen X. Müller cells derived neurotrophin-3 inhibits hypoxia-induced photoreceptor apoptosis via the TrkC/ERK pathway. Cytotechnology 2019; 72:47-56. [PMID: 31768729 DOI: 10.1007/s10616-019-00356-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2019] [Accepted: 11/12/2019] [Indexed: 12/01/2022] Open
Abstract
Neurotrophin-3 (NT-3), a neurotrophic factor that mainly binds to the tyrosine kinase C (trkC) receptor, has been shown to play a crucial role in proliferation, differentiation, and survival. However, the role of NT-3 in the hypoxia-induced retinopathy has not been investigated extensively. Here, we created a model of hypoxia (1% O2) in vitro and found that hypoxia promoted the apoptosis of mouse cone photoreceptor-derived 661W cells, increased the expression of TrkC and cleaved caspase-3. In contrast, the hypoxia-mediated 661W cell apoptosis was markedly alleviated by co-culturing with primary mouse Müller cells. Further mechanism studies revealed that hypoxia increased the synthesis and secretion of NT-3 by Müller cells, and exogenous NT-3 stimulation increased the phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 by binding to TrkC in 661W cells. Besides, both siRNA knockdown of TrkC expression and incubation with an ERK-specific inhibitor PD98059 triggered apoptosis in hypoxic 661W cells. Altogether, these data suggest that NT-3 originating from Müller cells protects photoreceptors from hypoxia-induced apoptosis through a TrkC/ERK-dependent pathway. Our findings may facilitate future studies on the therapeutic implications of NT-3 in the treatment of hypoxia-relevant retinal diseases.
Collapse
Affiliation(s)
- Na Li
- Department of Ophthalmology, Ruijin Hospital, Affiliated Shanghai Jiaotong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China
| | - Yanji Zhu
- Department of Ophthalmology, Ruijin Hospital, Affiliated Shanghai Jiaotong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China
| | - Jing Wang
- Department of Ophthalmology, Ruijin Hospital, Affiliated Shanghai Jiaotong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China
| | - Minqi Zhu
- Department of Ophthalmology, Ruijin Hospital, Affiliated Shanghai Jiaotong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China
| | - Shuang Gao
- Department of Ophthalmology, Ruijin Hospital, Affiliated Shanghai Jiaotong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China
| | - Qi Chen
- Department of Ophthalmology, Ruijin Hospital, Affiliated Shanghai Jiaotong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China
| | - Xi Shen
- Department of Ophthalmology, Ruijin Hospital, Affiliated Shanghai Jiaotong University School of Medicine, 197 Ruijin Er Road, Shanghai, 200025, China.
| |
Collapse
|
2
|
Saragovi HU, Galan A, Levin LA. Neuroprotection: Pro-survival and Anti-neurotoxic Mechanisms as Therapeutic Strategies in Neurodegeneration. Front Cell Neurosci 2019; 13:231. [PMID: 31244606 PMCID: PMC6563757 DOI: 10.3389/fncel.2019.00231] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Accepted: 05/08/2019] [Indexed: 12/14/2022] Open
Abstract
Neurotrophins (NTs) are a subset of the neurotrophic factor family. These growth factors were originally named based on the nerve growth functional assays used to identify them. NTs act as paracrine or autocrine factors for cells expressing NT receptors. The receptors and their function have been studied primarily in cells of the nervous system, but are also present in the cardiovascular, endocrine, and immune systems, as well as in many neoplastic cells. The signals activated by NTs can be varied, depending on cellular stage and context, healthy or disease states, and depending on whether the specific NTs and their receptors are expressed in the relevant cells. In the healthy central and peripheral adult nervous systems, NTs drive neuronal survival, phenotype, synaptic maintenance, and function. Deficiencies of the NT/NT receptor axis are causally associated with disease onset or disease progression. Paradoxically, NTs can also drive synaptic loss and neuronal death. In the embryonic stage this activity is essential for proper developmental pruning of the nervous system, but in the adult it can be associated with neurodegenerative disease. Given their key role in neuronal survival and death, NTs and NT receptors have long been considered therapeutic targets to achieve neuroprotection. The first neuroprotective approaches consisted of enhancing neuronal survival signals using NTs. Later strategies selectively targeted receptors to induce survival signals specifically, while avoiding activation of death signals. Recently, the concept of selectively targeting receptors to reduce neuronal death signals has emerged. Here, we review the rationale of each neuroprotective strategy with respect to the complex cell biology and pharmacology of each target receptor.
Collapse
Affiliation(s)
- Horacio Uri Saragovi
- Lady Davis Institute, Montreal, QC, Canada.,Jewish General Hospital, Montreal, QC, Canada.,Department of Ophthalmology and Visual Sciences, McGill University, Montreal, QC, Canada
| | - Alba Galan
- Lady Davis Institute, Montreal, QC, Canada.,Jewish General Hospital, Montreal, QC, Canada
| | - Leonard A Levin
- Department of Ophthalmology and Visual Sciences, McGill University, Montreal, QC, Canada.,McGill University Health Centre, Montreal, QC, Canada.,Montreal Neurological Institute, Mcgill University, Montreal, QC, Canada
| |
Collapse
|
3
|
Dai M, Zhang Q, Zheng Z, Wang J. Retinal ganglion cell-conditioned medium and surrounding pressure alters gene expression and differentiation of rat retinal progenitor cells. Mol Med Rep 2018; 17:7177-7183. [PMID: 29568879 PMCID: PMC5928676 DOI: 10.3892/mmr.2018.8738] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 12/04/2017] [Indexed: 12/13/2022] Open
Abstract
Loss of retinal ganglion cells is implicated in glaucoma and high intraocular pressure. Factors that affect the differentiation of retinal progenitor cells into retinal ganglion cells remain unclear. The present study aimed to investigate the effects of retinal ganglion cell‑conditioned medium on gene expression and differentiation in retinal progenitor cells, and the effects of surrounding pressure on the survival and differentiation of retinal progenitor cells. Retinal progenitor cells and retinal ganglion cells were isolated from rats. Immunofluorescence staining of Nestin and Thy1 was performed to identify rat retinal progenitor cells and retinal ganglion cells, respectively. Retinal progenitor cells and ganglion cells were cultured for 48 h under surrounding pressure of 0, 20, 40, 60 and 80 mmHg. Cellular apoptosis was detected using a caspase‑3 assay kit. In addition, the culture supernatant of rat retinal ganglion cells was collected. Retinal progenitor cells were cultured in the presence or absence of retinal ganglion‑conditioned medium for 72 h under normal pressure. Gene expression of Nestin, paired box protein 6 (PAX6), Thy1 and brain‑specific homeobox/POU domain protein 3 (Brn‑3) in retinal progenitor cells was detected by reverse transcription‑quantitative polymerase chain reaction. Retinal progenitor cells were cultured in retinal ganglion‑conditioned medium for 72 h under surrounding pressure of 0 and 40 mmHg, respectively, and flow cytometry was utilized to evaluate the effects of pressure on the differentiation of retinal progenitor cells into retinal ganglion cells. The results demonstrated that isolated retinal progenitor cells were Nestin‑positive and retinal ganglion cells were Thy1‑positive, suggesting successful isolation. The activity of caspase‑3 increased in retinal progenitor cells and retinal ganglion cells in a pressure‑dependent manner. When the surrounding pressure reached 40, 60 and 80 mmHg, the activity of caspase‑3 in retinal progenitor cells and ganglion cells increased significantly compared with cells that were not under pressure. Compared with retinal progenitor cells cultured without ganglion‑conditioned medium, those cultured with ganglion‑conditioned medium had significantly decreased expression levels of Nestin and PAX6, and increased expression levels of Thy1 and Brn3. Compared with 0 mmHg pressure, retinal progenitor cells cultured in ganglion‑conditioned medium under 40 mmHg pressure had increased percentages of Thy1‑positive cells. In conclusion, the apoptosis of rat retinal progenitor cells and retinal ganglion cells was pressure‑dependent. Retinal ganglion cell‑conditioned medium increased the differentiation of retinal progenitor cells into retinal ganglion‑like cells, and the differentiation increased as surrounding pressure increased. Current study provides insights that may contribute to the efforts of developing a treatment for glaucoma.
Collapse
Affiliation(s)
- Min Dai
- Department of Ophthalmology, Second People's Hospital of Yunnan Province, Kunming, Yunan 650021, P.R. China
| | - Qing Zhang
- Department of Ophthalmology, Second People's Hospital of Yunnan Province, Kunming, Yunan 650021, P.R. China
| | - Zhikun Zheng
- Department of Ophthalmology, Second People's Hospital of Yunnan Province, Kunming, Yunan 650021, P.R. China
| | - Jianzhou Wang
- Department of Ophthalmology, Yan'an Hospital, Kunming, Yunan 650051, P.R. China
| |
Collapse
|
4
|
Abed E, Corbo G, Falsini B. Neurotrophin Family Members as Neuroprotectants in Retinal Degenerations. BioDrugs 2014; 29:1-13. [DOI: 10.1007/s40259-014-0110-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
|
5
|
Mysona BA, Shanab AY, Elshaer SL, El-Remessy AB. Nerve growth factor in diabetic retinopathy: beyond neurons. EXPERT REVIEW OF OPHTHALMOLOGY 2014; 9:99-107. [PMID: 25031607 PMCID: PMC4096131 DOI: 10.1586/17469899.2014.903157] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Diabetic retinopathy (DR), a major ocular complication of diabetes, is a leading cause of blindness in US working age adults with limited treatments. Neurotrophins (NTs), a family of proteins essential for growth, differentiation and survival of retinal neurons, have emerged as potential players in the pathogenesis of DR. NTs can signal through their corresponding tropomyosin kinase related receptor to mediate cell survival or through the p75 neurotrophin receptor with the co-receptor, sortilin, to mediate cell death. This review focuses on the role of NGF, the first discovered NT, in the development of DR. Impaired processing of proNGF has been found in ocular fluids from diabetic patients as well as experimental models. Evidence from literature and our studies support the notion that NTs appear to play multiple potential roles in DR, hence, understanding their contribution to DR may lead to promising therapeutic approaches for this devastating disease.
Collapse
Affiliation(s)
- Barbara A Mysona
- Program in Clinical and Experimental Therapeutics, College of Pharmacy, University of Georgia, Augusta, GA, USA and Culver Vision Discovery Institute, Georgia Regents University, Augusta, GA, USA and Charlie Norwood Veterans Affairs Medical Center, Augusta, GA, USA
| | - Ahmed Y Shanab
- Program in Clinical and Experimental Therapeutics, College of Pharmacy, University of Georgia, Augusta, GA, USA and Culver Vision Discovery Institute, Georgia Regents University, Augusta, GA, USA and Charlie Norwood Veterans Affairs Medical Center, Augusta, GA, USA
| | - Sally L Elshaer
- Program in Clinical and Experimental Therapeutics, College of Pharmacy, University of Georgia, Augusta, GA, USA and Culver Vision Discovery Institute, Georgia Regents University, Augusta, GA, USA and Charlie Norwood Veterans Affairs Medical Center, Augusta, GA, USA
| | - Azza B El-Remessy
- Program in Clinical and Experimental Therapeutics, College of Pharmacy, University of Georgia, Augusta, GA, USA and Culver Vision Discovery Institute, Georgia Regents University, Augusta, GA, USA and Charlie Norwood Veterans Affairs Medical Center, Augusta, GA, USA
| |
Collapse
|
6
|
Neurotrophic molecules in the treatment of neurodegenerative disease with focus on the retina: status and perspectives. Cell Tissue Res 2013; 353:205-18. [PMID: 23463189 DOI: 10.1007/s00441-013-1585-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Accepted: 02/07/2013] [Indexed: 01/19/2023]
Abstract
Neurotrophic factors are operationally defined as molecules that promote the survival and differentiation of neurons. Chemically, they belong to divergent classes of molecules but most of the classic neurotrophic factors are proteins. Together with stem cells, viral vectors and genetically engineered cells, they constitute important tools in neuroprotective and regenerative neurobiology. Protein neurotrophic molecules signal through receptors located on the cell membrane. Their downstream signaling exploits pathways that are often common to chemically different factors and frequently target a relatively restricted set of transcription factors, RNA interference and diverse molecular machinery involved in the life vs. death decisions of neurons. Application of neurotrophic factors with the aim of curing or, at least, improving the outcome of neurodegenerative diseases requires (1) profound knowledge of the complex molecular pathology of the disease, (2) the development of animal models as closely as possible resembling the human disease, (3) the identification of target cells to be addressed, (4) intense efforts in chemical engineering to ensure the stability of molecules or to design carriers and small analogs with the ability to cross the blood-brain barrier and (5) scrutinity with regard to possible side effects. Last, but not least, engineering efforts to optimize administration, e.g., by designing the right canulae and infusion devices, are important for the successful translation of preclinical advances into clinical benefit. This article presents selected examples of neurotrophic factors that are currently being tested in animal models or developed for transfer to the clinic, with a major focus on factors with the potential of becoming applicable in various forms of retinal degeneration.
Collapse
|
7
|
Ishii Y, Weinberg K, Oda-Ishii I, Coughlin L, Mikawa T. Morphogenesis and cytodifferentiation of the avian retinal pigmented epithelium require downregulation of Group B1 Sox genes. Development 2009; 136:2579-89. [PMID: 19570849 DOI: 10.1242/dev.031344] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The optic vesicle is a multipotential primordium of the retina, which becomes subdivided into the neural retina and retinal pigmented epithelium domains. Although the roles of several paracrine factors in patterning the optic vesicle have been studied extensively, little is known about cell-autonomous mechanisms that regulate coordinated cell morphogenesis and cytodifferentiation of the retinal pigmented epithelium. Here we demonstrate that members of the SoxB1 gene family, Sox1, Sox2 and Sox3, are all downregulated in the presumptive retinal pigmented epithelium. Constitutive maintenance of SoxB1 expression in the presumptive retinal pigmented epithelium both in vivo and in vitro resulted in the absence of cuboidal morphology and pigmentation, and in concomitant induction of neural differentiation markers. We also demonstrate that exogenous Fgf4 inhibits downregulation all SoxB1 family members in the presumptive retinal pigment epithelium. These results suggest that retinal pigment epithelium morphogenesis and cytodifferentiation requires SoxB1 downregulation, which depends on the absence of exposure to an FGF-like signal.
Collapse
Affiliation(s)
- Yasuo Ishii
- University of California San Francisco, Cardiovascular Research Institute, Rock Hall Room 384D, San Francisco, CA 94158, USA
| | | | | | | | | |
Collapse
|
8
|
Stephan H, Zakrzewski JL, Bölöni R, Grasemann C, Lohmann DR, Eggert A. Neurotrophin receptor expression in human primary retinoblastomas and retinoblastoma cell lines. Pediatr Blood Cancer 2008; 50:218-22. [PMID: 17973327 DOI: 10.1002/pbc.21369] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
BACKGROUND Neurotrophin receptor signaling regulates proliferation, differentiation and death of neuronal cells. Expression of Trk receptors has been implicated in the pathogenesis and prognosis of embryonal tumors, including neuroblastoma, nephroblastoma, and medulloblastoma. PROCEDURE We analyzed TrkA, TrkB, TrkC, and p75 expression using semi-quantitative RT-PCR in 23 retinoblastomas and 8 retinoblastoma cell lines. Comparison of mRNA expression with clinical variables as well as the proliferation (PI) and apoptotic index (AI) of the tumor, was performed by Pearson correlation analysis and two-sample t-test. RESULTS Almost all tumor samples and cell lines demonstrated high expression of all Trk receptors. Expression of TrkB and its ligand, BDNF, was most pronounced, suggesting TrkB to be the major Trk receptor involved in retinoblastoma biology. In contrast, p75 expression was substantially reduced in a subset of tumors and cell lines, in particular compared to its expression in normal retina. Tumors with infiltrative growth demonstrated significantly lower relative levels of TrkC expression than localized tumors (P = 0.004). High expression of TrkA was associated with a higher AI (P = 0.04), and high expression of TrkC was associated with a younger age of the patients (P = 0.03). Inhibition of Trk signaling by K252a resulted in marked growth inhibition of retinoblastoma cells in vitro. CONCLUSIONS Our findings suggest a role for neurotrophin signaling in the biology of retinoblastoma. General Trk inhibitors are effective in decreasing growth rates of retinoblastoma cells in vitro, and should be evaluated in in vivo studies.
Collapse
Affiliation(s)
- Harald Stephan
- Department of Pediatric Hematology, Oncology and Endocrinology, University Hospital of Essen, Essen, Germany
| | | | | | | | | | | |
Collapse
|
9
|
Peng ZY, Lee SC, Chen XH. The expression and distribution of neural salient serine/arginine-rich protein 1 in rat retina. Neuroreport 2008; 18:1641-4. [PMID: 17921860 DOI: 10.1097/wnr.0b013e3282f0b542] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Neural salient serine/arginine-rich protein 1 (NSSR1) expression has been found in mouse cerebral neurons, cerebellar Purkinje cells, pyramidal neurons and granule cells of dentate gyrus and regulates the pre-mRNA splicing of genes important for neural functions. In this study, we demonstrated that NSSR1 is expressed in rat retina and extensively distributed in the outer and inner plexiform layers. Double staining experiments showed that NSSR1 distributed mainly in ON-type bipolar cells and localized in the dendrites, somata and axon terminals. The result suggests that NSSR1 may play important roles in retinal function, possibly via regulating the neural-specific alternative splicing of genes.
Collapse
Affiliation(s)
- Zheng-Yu Peng
- State Key Laboratory of Medical Neurobiology and Laboratory of Genomic Physiology, Fudan University, Shanghai, China
| | | | | |
Collapse
|
10
|
Martins RAP, Pearson RA. Control of cell proliferation by neurotransmitters in the developing vertebrate retina. Brain Res 2007; 1192:37-60. [PMID: 17597590 DOI: 10.1016/j.brainres.2007.04.076] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2007] [Revised: 04/04/2007] [Accepted: 04/20/2007] [Indexed: 01/24/2023]
Abstract
In the developing vertebrate retina, precise coordination of retinal progenitor cell proliferation and cell-cycle exit is essential for the formation of a functionally mature retina. Unregulated or disrupted cell proliferation may lead to dysplasia, retinal degeneration or retinoblastoma. Both cell-intrinsic and -extrinsic factors regulate the proliferation of progenitor cells during CNS development. There is now growing evidence that in the developing vertebrate retina, both slow and fast neurotransmitter systems modulate the proliferation of retinal progenitor cells. Classic neurotransmitters, such as GABA (gamma-amino butyric acid), glycine, glutamate, ACh (acetylcholine) and ATP (adenosine triphosphate) are released, via vesicular or non-vesicular mechanisms, into the immature retinal environment. Furthermore, these neurotransmitters signal through functional receptors even before synapses are formed. Recent evidence indicates that the activation of purinergic and muscarinic receptors may regulate the cell-cycle machinery and consequently the expansion of the retinal progenitor pool. Interestingly, GABA and glutamate appear to have opposing roles, inducing retinal progenitor cell-cycle exit. In this review, we present recent findings that begin to elucidate the roles of neurotransmitters as regulators of progenitor cell proliferation at early stages of retinal development. These studies also raise several new questions, including how these neurotransmitters regulate specific cell-cycle pathways and the mechanisms by which retinal progenitor cells integrate the signals from neurotransmitters and other exogenous factors during vertebrate retina development.
Collapse
Affiliation(s)
- Rodrigo A P Martins
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, MS323, Memphis, TN 38105, USA.
| | | |
Collapse
|
11
|
Turner BA, Sparrow J, Cai B, Monroe J, Mikawa T, Hempstead BL. TrkB/BDNF signaling regulates photoreceptor progenitor cell fate decisions. Dev Biol 2006; 299:455-65. [PMID: 17005175 PMCID: PMC2623246 DOI: 10.1016/j.ydbio.2006.08.025] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2005] [Revised: 08/07/2006] [Accepted: 08/09/2006] [Indexed: 10/24/2022]
Abstract
Neurotrophins, via activation of Trk receptor tyrosine kinases, serve as mitogens, survival factors and regulators of arborization during retinal development. Brain-derived neurotrophic factor (BDNF) and TrkB regulate neuronal arborization and survival in late retinal development. However, TrkB is expressed during early retinal development where its functions are unclear. To assess TrkB/BDNF actions in the early chick retina, replication-incompetent retroviruses were utilized to over-express a dominant negative truncated form of TrkB (trunc TrkB), or BDNF and effects were assessed at E15. Clones expressing trunc TrkB were smaller than controls, and proliferation and apoptosis assays suggest that decreased clone size correlated with increased cell death when BDNF/TrkB signaling was impaired. Analysis of clonal composition revealed that trunc TrkB over-expression decreased photoreceptor numbers (41%) and increased cell numbers in the middle third of the inner nuclear layer (INL) (23%). Conversely, BDNF over-expression increased photoreceptor numbers (25%) and decreased INL numbers (17%). Photoreceptors over-expressing trunc TrkB demonstrated no increase in apoptosis nor abnormalities in lamination suggesting that TrkB activation is not required for photoreceptor cell survival or migration. These studies suggest that TrkB signaling regulates commitment to and/or differentiation of photoreceptor cells from retinal progenitor cells, identifying a novel role for TrkB/BDNF in regulating cell fate decisions.
Collapse
Affiliation(s)
- Brian A. Turner
- Department of Medicine, Weill Medical College of Cornell University, New York, New York, 10021
| | - Janet Sparrow
- Department of Ophthalmology, Columbia University, New York, New York, 10032
| | - Bolin Cai
- Department of Ophthalmology, Columbia University, New York, New York, 10032
| | - Julie Monroe
- Department of Medicine, Weill Medical College of Cornell University, New York, New York, 10021
| | - Takashi Mikawa
- Department of Cell Biology, Weill Medical College of Cornell University, New York, New York, 10021
| | - Barbara L. Hempstead
- Department of Medicine, Weill Medical College of Cornell University, New York, New York, 10021
- *Author to whom to address correspondence: Barbara L. Hempstead, Department of Medicine, Weill Medical College of Cornell University, 1300 York Avenue, Room C606, New York, New York, 10021, phone: 212-746-6215, fax: 212-746-8647,
| |
Collapse
|
12
|
Abstract
The chick embryo is a versatile model system, in which classical embryology can be combined with modern molecular approaches. In the last two decades, several efficient methods have been developed to introduce exogenous genes into the chick embryo. These techniques allow alteration of gene expression levels in a spatially and temporally restricted manner, thereby circumventing embryonic lethality and/or eliminating secondary effects in other tissues. Here, we present the current status of avian somatic transgenic techniques, focusing on electroporation and retrovirus-mediated gene transfer. Electroporation allows quick and efficient gain-of-function studies based on transient misexpression of genes. Retroviral vectors, which are capable of integrating exogenous genes into the host chromosome, permit analysis of long-term effects of gene misexpression. The variety of methods available for somatic transgenesis, along with the recent completion of the chicken genome, are transforming the chick embryo into one of the most attractive model systems to examine function of genes that are important for embryonic development.
Collapse
Affiliation(s)
- Yasuo Ishii
- Department of Cell and Developmental Biology, Cornell University Medical College, New York, New York 10021, USA
| | | |
Collapse
|
13
|
Abstract
Whereas the heart itself is of mesodermal origin, components of the cardiac outflow tract are formed by the neural crest, an ectodermal derivative that gives rise to the peripheral nervous system, endocrine cells, melanocytes of the skin and internal organs, and connective tissue, bone, and cartilage of the face and ventral neck, among other tissues. Cardiac neural crest cells participate in the septation of the cardiac outflow tract into aorta and pulmonary artery. The migratory cardiac neural crest consists of stem cells, fate-restricted cells, and cells that are committed to the smooth muscle cell lineage. During their migration within the posterior branchial arches, the developmental potentials of pluripotent neural crest cells become restricted. Conversely, neural crest stem cells persist at many locations, including in the cardiac outflow tract. Many aspects of neural crest cell differentiation are driven by growth factor action. Neurotrophin-3 (NT-3) and its preferred receptor, TrkC, play important roles not only in nervous system development and function, but also in cardiac development as deletion of these genes causes outflow tract malformations. In vitro clonal analysis has shown a premature commitment of cardiac neural crest stem cells in TrkC null mice and a perturbed morphology of the endothelial tube. Norepinephrine transporter (NET) function promotes the differentiation of neural crest stem cells into noradrenergic neurons. Surprisingly, many diverse nonneuronal embryonic tissues, in particular in the cardiovascular system, express NET also. It will be of interest to determine whether norepinephrine transport plays a role also in cardiovascular development.
Collapse
Affiliation(s)
- Maya Sieber-Blum
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
| |
Collapse
|
14
|
Youn YH, Feng J, Tessarollo L, Ito K, Sieber-Blum M. Neural crest stem cell and cardiac endothelium defects in the TrkC null mouse. Mol Cell Neurosci 2004; 24:160-70. [PMID: 14550777 DOI: 10.1016/s1044-7431(03)00125-8] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
TrkC null mice have multiple cardiac malformations. Since neural crest cells participate in cardiac outflow tract septation, the aim of this study was to determine at the cellular level the putative neural crest defect. We have identified three types of progenitor cells: stem cells that undergo self-renewal and can generate many cell types, cells that are restricted in their developmental potentials, and cells that are committed to the smooth muscle cell lineage. In TrkC null mice, there is a greater than 50% decrease in stem cell numbers and an equivalent increase in fate-restricted cells. The outflow tract wall is thickened and the endothelial tube is disorganized. We conclude that deletion of the TrkC gene causes precocious fate restrictions of the neural crest stem cell and a defect of the outflow tract endothelium, both of which may contribute to the outflow tract malformations that occur in TrkC null mice.
Collapse
MESH Headings
- Animals
- Biomarkers
- Body Patterning/genetics
- Cell Differentiation/genetics
- Cell Lineage/genetics
- Cell Movement/genetics
- Endothelium, Vascular/abnormalities
- Endothelium, Vascular/cytology
- Endothelium, Vascular/metabolism
- Female
- Genes, Reporter/genetics
- Heart Defects, Congenital/genetics
- Heart Defects, Congenital/metabolism
- Heart Defects, Congenital/physiopathology
- Male
- Mice
- Mice, Knockout
- Myocytes, Smooth Muscle/cytology
- Myocytes, Smooth Muscle/metabolism
- Neural Crest/abnormalities
- Neural Crest/cytology
- Neural Crest/metabolism
- Neurotrophin 3/metabolism
- Phenotype
- Receptor, trkC/deficiency
- Receptor, trkC/genetics
- Stem Cells/cytology
- Stem Cells/metabolism
- beta-Galactosidase
Collapse
Affiliation(s)
- Y H Youn
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA
| | | | | | | | | |
Collapse
|
15
|
Ishii Y, Reese DE, Mikawa T. Somatic transgenesis using retroviral vectors in the chicken embryo. Dev Dyn 2004; 229:630-42. [PMID: 14991718 DOI: 10.1002/dvdy.10484] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The avian embryo is an excellent model system for experimental studies because of its accessibility and ease of microsurgical manipulations. While the complete chicken genome sequence will soon be determined, a comprehensive germ cell transmission-based genetic approach is not available for this animal model. Several techniques of somatic cell transgenesis have been developed in the past decade. Of these, the retroviral shuttle vector system provides both (1) stable integration of exogenous genes into the host cell genome, and (2) constant expression levels in a target cell population over the course of development. This review summarizes retroviral vectors available for the avian model and outlines the uses of retroviral-mediated gene transfer for cell lineage analysis as well as functional studies of genes and proteins in the chick embryo.
Collapse
Affiliation(s)
- Yasuo Ishii
- Department of Cell and Developmental Biology, Cornell University Medical College, New York, New York 10021, USA
| | | | | |
Collapse
|
16
|
Green ES, Stubbs JL, Levine EM. Genetic rescue of cell number in a mouse model of microphthalmia: interactions between Chx10 and G1-phase cell cycle regulators. Development 2003; 130:539-52. [PMID: 12490560 DOI: 10.1242/dev.00275] [Citation(s) in RCA: 122] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Insufficient cell number is a primary cause of failed retinal development in the Chx10 mutant mouse. To determine if Chx10 regulates cell number by antagonizing p27(Kip1) activity, we generated Chx10, p27(Kip1) double null mice. The severe hypocellular defect in Chx10 single null mice is alleviated in the double null, and while Chx10-null retinas lack lamination, double null retinas have near normal lamination. Bipolar cells are absent in the double null retina, a defect that is attributable to a requirement for Chx10 that is independent of p27(Kip1). We find that p27(Kip1) is abnormally present in progenitors of Chx10-null retinas, and that its ectopic localization is responsible for a significant amount of the proliferation defect in this microphthalmia model system. mRNA and protein expression patterns in these mice and in cyclin D1-null mice suggest that Chx10 influences p27(Kip1) at a post-transcriptional level, through a mechanism that is largely dependent on cyclin D1. This is the first report of rescue of retinal proliferation in a microphthalmia model by deletion of a cell cycle regulatory gene.
Collapse
Affiliation(s)
- Eric S Green
- Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, UT 84132, USA
| | | | | |
Collapse
|
17
|
Ganchrow D, Ganchrow JR, Verdin-Alcazar M, Whitehead MC. Brain-derived neurotrophic factor-, neurotrophin-3-, and tyrosine kinase receptor-like immunoreactivity in lingual taste bud fields of mature hamster. J Comp Neurol 2003; 455:11-24. [PMID: 12454993 DOI: 10.1002/cne.2162] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The neurotrophins brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3), as well as their respective tyrosine kinase (Trk) receptors, TrkB and TrkC, influence peripheral target cell innervation, survival, and proliferation. In the mature taste system the role of neurotrophins and their receptors is not known. The mature hamster is an intriguing model because anterior lingual fungiform, unlike posterior lingual foliate and circumvallate, taste buds survive denervation. In light of this difference, we examined whether the degree of neurotrophin- or neurotrophin receptor-like immunoreactivity (IR) normally differs among lingual gemmal fields. In single- and double-labeled immunofluorescent experiments, 3,209 taste bud sections (profiles) from 13 hamsters were examined for immunopositive gemmal cells or nerve fibers using antibodies to BDNF and NT-3, their respective receptors TrkB and TrkC, and the neural marker ubiquitin c-terminal hydrolase L-1 [protein gene product (PGP) 9.5]. In each gemmal field, more than 75% of taste bud profiles showed immunopositivity to BDNF, NT-3, and TrkB. Across bud fields, BDNF-, TrkB-, and BDNF/TrkB-like IR, as well as PGP 9.5 and PGP 9.5/BDNF-like IR in centrally located, fungiform bud cells was greater (P < 0.0001 to P < 0.002) than in circumvallate or foliate buds. Within bud fields, the number of BDNF-like, labeled bud cells/bud profile was greater than that for NT-3-like IR in fungiform (P < 0.0002) and foliate (P < 0.0001) buds. TrkC was immunonegative in gemmal cells. The average density of TrkB- and TrkC-like fiber IR was more pronounced in fungiform than posterior gemmal-bearing papillae. Thus, fungiform papillae, whose taste buds are least affected by denervation, exhibit specific neurotrophin and receptor enrichment.
Collapse
Affiliation(s)
- Donald Ganchrow
- Department of Anatomy and Anthropology, Sackler Faculty of Medicine, Tel-Aviv University, Ramat Aviv 69978, Tel-Aviv, Israel
| | | | | | | |
Collapse
|
18
|
Ganchrow D, Ganchrow JR, Verdin-Alcazar M, Whitehead MC. Brain-derived neurotrophic factor-, neurotrophin-3-, and tyrosine kinase receptor-like immunoreactivity in lingual taste bud fields of mature hamster after sensory denervation. J Comp Neurol 2003; 455:25-39. [PMID: 12454994 DOI: 10.1002/cne.2164] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Unlike lingual taste buds in most mammals, fungiform buds on the anterior tongue of mature hamster survive sensory denervation. The role of the neurotrophin ligands, brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3), and their respective tyrosine kinase (Trk) receptors, TrkB and TrkC, in denervated taste buds is not known. The present report investigates changes in the degree of gemmal cell immunoreactivity (IR) (i.e., number of immunoreactive cells/bud profile) and density of nerve fiber-IR of these markers in unilaterally denervated mature hamsters. The fungiform bud field after chorda tympani/lingual nerve resection is compared with the nerve-dependent, posterior tongue foliate and circumvallate bud fields after glossopharyngeal nerve resection. Four weeks post lesion, the number of denervated fungiform buds matched that on the unoperated side, whereas denervated foliate and circumvallate bud counts decreased by 72% and 38%, respectively. In taste buds that survived on the posterior tongue, the degree of foliate bud cell BDNF-, NT-3-, and TrkB-like IR, and circumvallate bud cell BDNF- and NT-3-like IR, significantly decreased compared with the unoperated side. In contrast, for anterior tongue fungiform bud cells, the degree of neurotrophin- and receptor-like IR was relatively less affected: NT-3- and TrkB-like IR were unchanged; BDNF-like IR, although significantly decreased, was also maintained. Moreover, TrkB-like fiber IR was essentially eliminated within and surrounding fungiform buds. Hence, NT-3-, BDNF-, and TrkB-like IR in fungiform gemmal cells may reflect an autocrine capacity promoting survival. Because TrkC-like IR in bud cells is absent (i.e., immunonegative), and sparse in fibers intragemmally and perigemmally, NT-3 may also bind to bud cell TrkB so as to sustain fungiform gemmal cell viability post denervation.
Collapse
Affiliation(s)
- Donald Ganchrow
- Department of Anatomy and Anthropology, Sackler Faculty of Medicine, Tel-Aviv University, Ramat Aviv 69978, Tel-Aviv, Israel
| | | | | | | |
Collapse
|
19
|
Cronk KM, Wilkinson GA, Grimes R, Wheeler EF, Jhaveri S, Fundin BT, Silos-Santiago I, Tessarollo L, Reichardt LF, Rice FL. Diverse dependencies of developing Merkel innervation on the trkA and both full-length and truncated isoforms of trkC. Development 2002; 129:3739-50. [PMID: 12117822 PMCID: PMC2710109 DOI: 10.1242/dev.129.15.3739] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
This study demonstrates that innervation dependent on two different neurotrophin tyrosine kinase (trk) receptors can form the same types of sensory endings (Merkel endings) in the same target (Merkel cells of vibrissa follicles). Some endings transiently express trkA during their initial development, whereas others express trkC throughout their development. Consequently, elimination of kinase domains of either trkA or trkC each result in a partial loss of Merkel endings, whereas absence of kinase domains of both receptors results in a total loss. At the onset of Merkel ending development, at least one kinase-lacking trkC isoform is transiently expressed on all the follicle cells, while neurotrophin 3 is transiently expressed only in the cells at the middle third of the follicle where the Merkel endings and cells develop. This transient non-neuronal expression of truncated trkC is essential for development of any Merkel endings, whereas some Merkel endings and cells still begin to develop in the absence of neurotrophin 3. Therefore, truncated trkC plays a more important role in the development of this innervation than kinase forms of trkA or trkC or of NT3, the only known ligand for trkC receptors.
Collapse
MESH Headings
- Animals
- Embryo, Mammalian/anatomy & histology
- Embryo, Mammalian/physiology
- Female
- Genes, Reporter
- In Situ Hybridization
- Male
- Merkel Cells/cytology
- Merkel Cells/physiology
- Mice
- Mitogen-Activated Protein Kinases/genetics
- Mitogen-Activated Protein Kinases/metabolism
- Models, Biological
- Plant Proteins/genetics
- Plant Proteins/metabolism
- Pregnancy
- Protein Isoforms
- Rats
- Rats, Sprague-Dawley
- Receptor, Nerve Growth Factor
- Receptor, trkA/genetics
- Receptor, trkA/metabolism
- Receptor, trkC/genetics
- Receptor, trkC/metabolism
- Receptors, Nerve Growth Factor/metabolism
- Recombinant Fusion Proteins
- Vibrissae/cytology
- Vibrissae/growth & development
Collapse
Affiliation(s)
- Katharine M. Cronk
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, NY 12208, USA
| | - George A. Wilkinson
- Neuroscience Unit, Howard Hughes Medical Center, University of California, San Francisco, CA 94143-0724, USA
| | - Rachel Grimes
- Division of Life Sciences, University of Texas, San Antonio, TX 78249, USA
| | - Esther F. Wheeler
- Division of Life Sciences, University of Texas, San Antonio, TX 78249, USA
| | - Sonal Jhaveri
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Bengt T. Fundin
- Astra Zeneca R&D Södertälje, Department of Molecular Sciences, SE-141 57 Huddinge, Sweden
| | | | - Lino Tessarollo
- Neural Development Group, NCI-FCRDC, Frederick, MD 21702, USA
| | | | - Frank L. Rice
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, NY 12208, USA
- Author for correspondence (e-mail: )
| |
Collapse
|
20
|
Pimentel B, Rodríguez-Borlado L, Hernández C, Carrera AC. A Role for phosphoinositide 3-kinase in the control of cell division and survival during retinal development. Dev Biol 2002; 247:295-306. [PMID: 12086468 DOI: 10.1006/dbio.2002.0703] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Neurogenesis in the retina requires the concerted action of three different cellular processes: proliferation, differentiation, and apoptosis. Class IA phosphoinositide 3-kinase (PI3K) is a heterodimer composed of a p85 regulatory and a p110 catalytic subunit. p110alpha has been shown to regulate cell division and survival. Little is known of its function in development, however, as p110alpha knockout mice exhibit CNS defects, but death at early embryonic stages impairs further study. Here, we examine the role of PI3K in mouse retina development by expressing an activating form of PI3K regulatory subunit, p65(PI3K), as a transgene in the retina. Mice expressing p65(PI3K) showed severely disrupted retina morphogenesis, with ectopic cell masses in the neuroepithelium that evolved into infoldings of adult retinal cell layers. These changes correlated with an altered cell proliferation/cell death balance at early developmental stages. Nonetheless, the most affected cell layer in adult retina was that of photoreceptors, which correlated with selectively increased survival of these cells at developmental stages at which cell division has ceased. These results demonstrate the relevance of accurate PI3K regulation for normal retinal development, supporting class IA PI3K involvement in induction of cell division at early stages of neurogenesis. These data also show that, even after cell division decline, PI3K activation mediates survival of differentiated neurons in vivo.
Collapse
Affiliation(s)
- Belén Pimentel
- Department of Immunology and Oncology, Centro Nacional de Biotecnología, CSIC, E-28049 Madrid, Spain
| | | | | | | |
Collapse
|
21
|
Kanzawa N, Poma CP, Takebayashi-Suzuki K, Diaz KG, Layliev J, Mikawa T. Competency of embryonic cardiomyocytes to undergo Purkinje fiber differentiation is regulated by endothelin receptor expression. Development 2002; 129:3185-94. [PMID: 12070093 DOI: 10.1242/dev.129.13.3185] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Purkinje fibers of the cardiac conduction system differentiate from heart muscle cells during embryogenesis. In the avian heart, Purkinje fiber differentiation takes place along the endocardium and coronary arteries. To date, only the vascular cytokine endothelin (ET) has been demonstrated to induce embryonic cardiomyocytes to differentiate into Purkinje fibers. This ET-induced Purkinje fiber differentiation is mediated by binding of ET to its transmembrane receptors that are expressed by myocytes. Expression of ET converting enzyme 1, which produces a biologically active ET ligand, begins in cardiac endothelia, both arterial and endocardial, at initiation of conduction cell differentiation and continues throughout heart development. Yet, the ability of cardiomyocytes to convert their phenotype in response to ET declines as embryos mature. Therefore, the loss of responsiveness to the inductive signal appears not to be associated with the level of ET ligand in the heart. This study examines the role of ET receptors in this age-dependent loss of inductive responsiveness and the expression profiles of three different types of ET receptors, ETA, ETB and ETB2, in the embryonic chick heart. Whole-mount in situ hybridization analyses revealed that ETA was ubiquitously expressed in both ventricular and atrial myocardium during heart development, while ETB was predominantly expressed in the atrium and the left ventricle. ETB2 expression was detected in valve leaflets but not in the myocardium. RNase protection assays showed that ventricular expression of ETA and ETB increased until Purkinje fiber differentiation began. Importantly, the levels of both receptor isotypes decreased after this time. Retrovirus-mediated overexpression of ETA in ventricular myocytes in which endogenous ET receptors had been downregulated, enhanced their responsiveness to ET, allowing them to differentiate into conduction cells. These results suggest that the developmentally regulated expression of ET receptors plays a crucial role in determining the competency of ventricular myocytes to respond to inductive ET signaling in the chick embryo.
Collapse
Affiliation(s)
- Nobuyuki Kanzawa
- Department of Cell Biology, Cornell University Medical College, 1300 York Avenue, New York, NY 10021, USA
| | | | | | | | | | | |
Collapse
|
22
|
Link BA, Kainz PM, Ryou T, Dowling JE. The perplexed and confused mutations affect distinct stages during the transition from proliferating to post-mitotic cells within the zebrafish retina. Dev Biol 2001; 236:436-53. [PMID: 11476583 DOI: 10.1006/dbio.2001.0340] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
To identify and study genes essential for vertebrate retinal development, we are screening zebrafish embryos for mutations that disrupt retinal histogenesis. Key steps in retinogenesis include withdrawal from mitosis by multipotent neuroepithelial cells, specification to particular cell types, migration to the appropriate laminar positions, and molecular and morphological differentiation. In this study, we have identified two recessive mutations that affect the transition of proliferating neuroepithelial cells to postmitotic retinal cells. Both the perplexed and confused mutant phenotypes were initially detectable when the first retinal neuroepithelial cells began to leave the cell cycle. At this time, each mutant retina showed increased cell death and a lack of morphological differentiation. Cell death was found to be apoptotic in both perplexed and confused retinas based on TUNEL analysis and activation of caspase-3. TUNEL-phosphoRb-BrdU colocalization studies indicated that the perplexed mutation caused death in cells transitioning from a proliferative to postmitotic state. For the confused mutation, TUNEL-phosphoRb-BrdU analysis revealed that only a subset of postmitotic cells were induced to activate apoptosis. Mosaic analysis demonstrated that within the retina the perplexed mutation functions noncell-autonomously. Furthermore, whole lens or eye cup transplantations indicated that the retinal defect was intrinsic to the retina. Mosaic analysis with confused embryos showed this mutation acts cell-autonomously. From these studies, we conclude that the perplexed and confused genes are essential at distinct stages during the transition from proliferating to postmitotic cells within the zebrafish retina.
Collapse
Affiliation(s)
- B A Link
- Department of Molecular and Cell Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
| | | | | | | |
Collapse
|
23
|
Lin MI, Das I, Schwartz GM, Tsoulfas P, Mikawa T, Hempstead BL. Trk C receptor signaling regulates cardiac myocyte proliferation during early heart development in vivo. Dev Biol 2000; 226:180-91. [PMID: 11023679 DOI: 10.1006/dbio.2000.9850] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Neurotrophin-3 (NT-3) is a member of the neurotrophin family of growth factors, best characterized by its survival- and differentiation-inducing effects on developing neurons bearing the trk C receptor tyrosine kinase. Through analysis of NT-3 and trk C gene-targeted mice we have identified NT-3 as critically regulating cardiac septation, valvulogenesis, and conotruncal formation. Although these defects could reflect cardiac neural crest dysfunction, the expression of NT-3 and trk C by cardiac myocytes prior to neural crest migration prompted analysis of cell-autonomous actions of NT-3 on cardiac myocytes. Retroviral-mediated overexpression of truncated trk C receptor lacking kinase activity was used to inhibit activation of trk C by endogenous NT-3, during early heart development in ovo. During the first week of chicken development, expression of truncated trk C reduced myocyte clone size by more than 60% of control clones. Direct mitogenic actions of NT-3 on embryonic cardiac myocytes were demonstrated by analysis of BrdU incorporation or PCNA immunoreactivity in control and truncated trk C-expressing clones. Inhibition of trk C signaling reduced cardiac myocyte proliferation during the first week of development, but had no effect at later times. These studies demonstrate that endogenous NT-3:trk C signaling regulates cardiac myocyte proliferation during cardiac looping and the establishment of ventricular trabeculation but that myocyte proliferation becomes NT-3 independent during the second week of embryogenesis.
Collapse
Affiliation(s)
- M I Lin
- Department of Medicine, Weill Medical College of Cornell University, New York, New York 10021, USA
| | | | | | | | | | | |
Collapse
|