Molecular studies on the development of the vertebrate nervous system

Lead Research Organisation: MRC National Inst for Medical Research

Abstract

The enteric nervous system is an important part of the peripheral nervous system that controls the peristalsis and secretions of the gut and food digestion. Defects in the innervation of the gut are among the most common congenital abnormalities of the nervous system (1 in 4,000). One of the molecules critical for the normal formation and function of the enteric nervous system is a cell surface receptor called RET. If this protein is faulty, newborn individuals have a partial or total absence of the gut nervous system. Using animal models of this condition, our current work is directed towards understanding the role played by RET in the development of the enteric nervous system during embryogenesis and at correcting this deficiency by replacing the missing cells for the gut. Using similar approaches, we are also trying to understand the role intracellular proteins play in the development of specific neurons, which control cognitive and motor activity and are affected in common diseases, such as Alzheimers and Parkinsons disease and epilepsy.

Technical Summary

We are investigating the molecular and cellular mechanisms that control the development of the nervous system in mouse embryos. As it is becoming increasingly clear that these mechanisms are common between all vertebrates, studies in the mouse will improve our understanding of normal development and disease states in humans. Our work uses a variety of experimental techniques including classical embryology, targeted mutagenesis and transgenesis, light and fluorescence microscopy as well as cell and molecular biology and biochemistry. One of the main aims of our research is to understand the role of the c-Ret proto-oncogene in the development of the nervous system. c-Ret encodes a receptor tyrosine kinase that is required for normal development of the enteric nervous system and motor neurons of the spinal cord. c-Ret encodes two isoforms (RET9 and RET51) which differ at their carboxy-terminal end. To understand the role of each isoform in nervous system development, we have generated transgenic mice that express only one of the two isoforms. Analysis of these mice has shown that normal development of the nervous system requires primarily the function of the RET9 isoform. We have been using functional genetic analysis to understand in detail the role of various intracellular parts of the RET9 receptor in mouse development. For this, we have generated mice that carry mutated forms of the RET9 isoform and have examined the consequences of these mutations in the development of the enteric nervous system. So far, we have identified a single amino acid (Tyrosine 1062) that appears to play a critical role in the intracellular signalling by RET during embryogenesis. Using similar approach, we are working towards identifying additional amino acid motifs that might be critical for RET function. The defects in the enteric nervous system of RET-deficient mice reproduce a human disease called congenital megacolon or Hirschsprungs disease, which is characterised by absence of enteric ganglia from varying lengths of the gastrointestinal tract. Our goal is to exploit the animal models we have generated in order to understand the parameters important for colonisation of the human gut by enteric neurons and develop strategies for the treatment of Hirschsprungs disease by cell transplantation. Given the critical role of the RET tyrosine kinase receptor in the development of the mammalian enteric nervous system, our studies also focus on understanding the intracellular signalling cascades and the gene networks that are activated by RET during normal embryogenesis. The previous studies have led to the identification of two novel genes, Lhx6 and Lhx7, which encode members of the LIM-homeodomain family of transcription factors that are expressed in the basal forebrain and the cortex. We have generated mice deficient in Lhx7 and Lhx6 and shown that the product of this gene is important for the differentiation of forebrain cholinergic neurons and cortical GABAergic interneurons, respectively. We are currently investigating the molecular and signalling cascades control by these LIM homeodomain proteins during embryogenesis.

Publications


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Bogni S (2008) Non-cell-autonomous effects of Ret deletion in early enteric neurogenesis. in Development (Cambridge, England)
Burns AJ (2009) Development of the enteric nervous system: bringing together cells, signals and genes. in Neurogastroenterology and motility : the official journal of the European Gastrointestinal Motility Society
Butt SJ (2007) Transcriptional regulation of cortical interneuron development. in The Journal of neuroscience : the official journal of the Society for Neuroscience
Cassiman D (2006) Hepatic stellate cells do not derive from the neural crest. in Journal of hepatology
 
Description UCL-Research Grant-2009
Amount £235,503 (GBP)
Organisation University College London (UCL) 
Sector Academic/University
Country United Kingdom of Great Britain & Northern Ireland (UK)
Start 07/2009 
End 06/2012
 
Title ENS stem cells 
Description Transgenic mouse 
Type Of Material Database/Collection of Data/Biological Samples 
Provided To Others? No  
Impact Identification of enteric nervous system stem cells 
 
Title Lhx6/Lhx7 
Description Transgenic mice 
Type Of Material Database/Collection of Data/Biological Samples 
Provided To Others? No  
Impact Understanding the biology and palsticity of forebrain interneurons 
 
Title Lhx6ins 
Description Mouse model of epilepsy 
Type Of Material Model of mechanisms or symptoms - mammalian in vivo 
Provided To Others? No  
Impact Understanding of pathogenetic mechanisms of epilepsy 
 
Description Enteric nervous system stem cells and their role in the development of enteric neuropathies 
Organisation University College London (UCL)
Department UCL Institute of Child Health
Country United Kingdom of Great Britain & Northern Ireland (UK) 
Sector Academic/University 
PI Contribution Animal models and understannding of pathogenetic mechanisms of human diseases
Collaborator Contribution Direct comparison of our animal models of human diseases to clinical situations.
Impact Publications Grant applications Generation of a European network for Enteric Neuropathies
 
Description Lineage analysis of cortical interneurons 
Organisation University College London (UCL)
Department UCL Biosciences
Country United Kingdom of Great Britain & Northern Ireland (UK) 
Sector Academic/University 
PI Contribution Mouse reporter strains
Collaborator Contribution Mouse reporter strains
Impact Publications
 
Description Role of Geminin in neural crest development 
Organisation University of Patras
Country Greece, Hellenic Republic 
Sector Academic/University 
PI Contribution Provided mouse mutant strains
Collaborator Contribution Intellectrual input for analysis of mouse mutants
Impact Publications
 
Description Role of Lhx7 transcription factor in the development of forebrain cholinergic neurons 
Organisation University of Athens
Department School of Nursing Athens
Country Greece, Hellenic Republic 
Sector Academic/University 
PI Contribution Provided animal models forf behavioural analysis
Collaborator Contribution Behavioural analysis of mouse mutants for Lhx7
Impact Publications
 
Description Specification of cortical interneurons 
Organisation New York University
Department Smilow Center for Neuroscience
Country United States of America 
Sector Academic/University 
PI Contribution Provided experimental expertise and mutant mouse strains
Collaborator Contribution Exchange of expertise
Impact Publications
Start Year 2007
 
Description The role of Lhx6 and Lhx7 in mammalian dentition 
Organisation King's College London (KCL)
Department Dental Institute
Country United Kingdom of Great Britain & Northern Ireland (UK) 
Sector Academic/University 
PI Contribution Provided experimental expertise and mouse mutant strains
Collaborator Contribution Expertise in the analysis of mouse mutants
Impact Publications The LIM homeodomain transcription factors Lhx6 and Lhx7 are key regulators of mammalian dentition. Denaxa M, Sharpe PT, Pachnis V. Dev Biol. 2009 Sep 15;333(2):324-36.
Start Year 2007
 
Description The role of Ret signalling receptor in the development of the lymphoid system of the gut. 
Organisation Medical Research Council (MRC)
Department MRC National Institute for Medical Research (NIMR)
Country United Kingdom of Great Britain & Northern Ireland (UK) 
Sector Public 
PI Contribution Provided animal models and technical expertise
Collaborator Contribution Intellectual contributions and technical expertise
Impact Publications
 
Description The role of Rho GTPases on the development of cortical interneurons 
Organisation Foundation for Research and Technology Hellas (FORTH)
Department Institute of Molecular Biology and Biotechnology (IMBB)
Country Greece, Hellenic Republic 
Sector Academic/University 
PI Contribution Provided mouse strains, technical expertise and contributed to Publications
Collaborator Contribution Intellectual exchange and experimental expertise and contributions to Publications
Impact Publications
 
Description The role of enteric glia in enteric nervous system regeneration 
Organisation Catholic University of Louvain
Department Department of Gastroenterology Louvain
Country Belgium, Kingdom of 
Sector Academic/University 
PI Contribution Provided animal models and cells lines for analysis.
Collaborator Contribution Technical expertise on the physiology of enteric neurons
Impact Publications and exchange of visiting workers
Start Year 2010
 
Description Lecture 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Primary Audience Public/other audiences
Results and Impact Lecture

knowledge transfer
Year(s) Of Engagement Activity 2008