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1.  Clustering of transcriptional profiles identifies changes to insulin signaling as an early event in a mouse model of Alzheimer’s disease 
BMC Genomics  2013;14:831.
Background
Alzheimer’s disease affects more than 35 million people worldwide but there is no known cure. Age is the strongest risk factor for Alzheimer’s disease but it is not clear how age-related changes impact the disease. Here, we used a mouse model of Alzheimer’s disease to identify age-specific changes that occur prior to and at the onset of traditional Alzheimer-related phenotypes including amyloid plaque formation. To identify these early events we used transcriptional profiling of mouse brains combined with computational approaches including singular value decomposition and hierarchical clustering.
Results
Our study identifies three key events in early stages of Alzheimer’s disease. First, the most important drivers of Alzheimer’s disease onset in these mice are age-specific changes. These include perturbations of the ribosome and oxidative phosphorylation pathways. Second, the earliest detectable disease-specific changes occur to genes commonly associated with the hypothalamic-adrenal-pituitary (HPA) axis. These include the down-regulation of genes relating to metabolism, depression and appetite. Finally, insulin signaling, in particular the down-regulation of the insulin receptor substrate 4 (Irs4) gene, may be an important event in the transition from age-related changes to Alzheimer’s disease specific-changes.
Conclusion
A combination of transcriptional profiling combined with computational analyses has uncovered novel features relevant to Alzheimer’s disease in a widely used mouse model and offers avenues for further exploration into early stages of AD.
doi:10.1186/1471-2164-14-831
PMCID: PMC3907022  PMID: 24274089
2.  Retinal Ganglion Cell Dendritic Atrophy in DBA/2J Glaucoma 
PLoS ONE  2013;8(8):e72282.
Glaucoma is a complex disease affecting an estimated 70 million people worldwide, characterised by the progressive degeneration of retinal ganglion cells and accompanying visual field loss. The common site of damage to retinal ganglion cells is thought to be at the optic nerve head, however evidence from other optic neuropathies and neurodegenerative disorders suggests that dendritic structures undergo a prolonged period of atrophy that may accompany or even precede soma loss and neuronal cell death. Using the DBA/2J mouse model of glaucoma this investigation aims to elucidate the impact of increasing intraocular pressure on retinal ganglion cell dendrites using DBA/2J mice that express YFP throughout the retinal ganglion cells driven by Thy1 (DBA/2J.Thy1(YFP)) and DiOlistically labelled retinal ganglion cells in DBA/2J mice. Here we show retinal ganglion cell dendritic degeneration in DiOlistically labelled DBA/2J retinal ganglion cells but not in the DBA/2J.Thy1(YFP) retinal ganglion cells suggesting that a potential downregulation of Thy1 allows only ‘healthy’ retinal ganglion cells to express YFP. These data may highlight alternative pathways to retinal ganglion cell loss in DBA/2J glaucoma.
doi:10.1371/journal.pone.0072282
PMCID: PMC3747092  PMID: 23977271
3.  High throughput sequencing approaches to mutation discovery in the mouse 
Phenotype driven approaches in mice are powerful strategies for the discovery of genes, gene functions and for unravelling complex biological mechanisms. Traditional methods for mutation discovery are reliable and robust, but they can also be laborious and time consuming. Recently, high throughput sequencing (HTS) technologies have revolutionised the process of forward genetics in mice by paving the way to rapid mutation discovery. However, successful application of HTS for mutation discovery is relies heavily on the sequencing approach employed and strategies for data analysis. Here, we review current HTS applications and resources for mutation discovery and provide an overview of the practical considerations for HTS implementation and data analysis.
doi:10.1007/s00335-012-9424-0
PMCID: PMC3724459  PMID: 22991087
4.  Deficiency of complement component 5 ameliorates glaucoma in DBA/2J mice 
Background
Glaucoma is an age-related neurodegenerative disorder involving the loss of retinal ganglion cells (RGCs), which results in blindness. Studies in animal models have shown that activation of inflammatory processes occurs early in the disease. In particular, the complement cascade is activated very early in DBA/2J mice, a widely used mouse model of glaucoma. A comprehensive analysis of the role of the complement cascade in DBA/2J glaucoma has not been possible because DBA/2J mice are naturally deficient in complement component 5 (C5, also known as hemolytic complement, Hc), a key mediator of the downstream processes of the complement cascade, including the formation of the membrane attack complex.
Methods
To assess the role of C5 in DBA/2J glaucoma, we backcrossed a functional C5 gene from strain C57BL/6J to strain DBA/2J for at least 10 generations. The prevalence and severity of glaucoma was evaluated using ocular examinations, IOP measurements, and assessments of optic nerve damage and RGC degeneration. To understand how C5 affects glaucoma, C5 expression was assessed in the retinas and optic nerves of C5-sufficient DBA/2J mice, using immunofluorescence.
Results
C5-sufficient DBA/2J mice developed a more severe glaucoma at an earlier age than standard DBA/2J mice, which are therefore protected by C5 deficiency. Components of the membrane attack complex were found to be deposited at sites of axonal injury in the optic nerve head and associated with RGC soma in the retina.
Conclusion
C5 plays an important role in glaucoma, with its deficiency lessening disease severity. These results highlight the importance of fully understanding the role of the complement cascade in neurodegenerative diseases. Inhibiting C5 may be beneficial as a therapy for human glaucoma.
doi:10.1186/1742-2094-10-76
PMCID: PMC3708765  PMID: 23806181
5.  Generating Embryonic Stem Cells from the Inbred Mouse Strain DBA/2J, a Model of Glaucoma and Other Complex Diseases 
PLoS ONE  2012;7(11):e50081.
Mouse embryonic stem (ES) cells are derived from the inner cell mass of blastocyst stage embryos and are used primarily for the creation of genetically engineered strains through gene targeting. While some inbred strains of mice are permissive to the derivation of embryonic stem cell lines and are therefore easily engineered, others are nonpermissive or recalcitrant. Genetic engineering of recalcitrant strain backgrounds requires gene targeting in a permissive background followed by extensive backcrossing of the engineered allele into the desired strain background. The inbred mouse strain DBA/2J is a recalcitrant strain that is used as a model of many human diseases, including glaucoma, deafness and schizophrenia. Here, we describe the generation of germ-line competent ES cell lines derived from DBA/2J mice. We also demonstrate the utility of DBA/2J ES cells with the creation of conditional knockout allele for Endothelin-2 (Edn2) directly on the DBA/2J strain background.
doi:10.1371/journal.pone.0050081
PMCID: PMC3507949  PMID: 23209647
6.  Radiation treatment inhibits monocyte entry into the optic nerve head and prevents neuronal damage in a mouse model of glaucoma 
The Journal of Clinical Investigation  2012;122(4):1246-1261.
Glaucoma is a common ocular disorder that is a leading cause of blindness worldwide. It is characterized by the dysfunction and loss of retinal ganglion cells (RGCs). Although many studies have implicated various molecules in glaucoma, no mechanism has been shown to be responsible for the earliest detectable damage to RGCs and their axons in the optic nerve. Here, we show that the leukocyte transendothelial migration pathway is activated in the optic nerve head at the earliest stages of disease in an inherited mouse model of glaucoma. This resulted in proinflammatory monocytes entering the optic nerve prior to detectable neuronal damage. A 1-time x-ray treatment prevented monocyte entry and subsequent glaucomatous damage. A single x-ray treatment of an individual eye in young mice provided that eye with long-term protection from glaucoma but had no effect on the contralateral eye. Localized radiation treatment prevented detectable neuronal damage and dysfunction in treated eyes, despite the continued presence of other glaucomatous stresses and signaling pathways. Injection of endothelin-2, a damaging mediator produced by the monocytes, into irradiated eyes, combined with the other glaucomatous stresses, restored neural damage with a topography characteristic of glaucoma. Together, these data support a model of glaucomatous damage involving monocyte entry into the optic nerve.
doi:10.1172/JCI61135
PMCID: PMC3314470  PMID: 22426214
7.  Mutations in the RNA Granule Component TDRD7 Cause Cataract and Glaucoma 
Science (New York, N.y.)  2011;331(6024):1571-1576.
The precise transcriptional regulation of gene expression is essential for vertebrate development, but the role of posttranscriptional regulatory mechanisms is less clear. Cytoplasmic RNA granules (RGs) function in the posttranscriptional control of gene expression, but the extent of RG involvement in organogenesis is unknown. We describe two human cases of pediatric cataract with loss-of-function mutations in TDRD7 and demonstrate that Tdrd7 nullizygosity in mouse causes cataracts, as well as glaucoma and an arrest in spermatogenesis. TDRD7 is a Tudor domain RNA binding protein that is expressed in lens fiber cells in distinct TDRD7-RGs that interact with STAU1-ribonucleoproteins (RNPs). TDRD7 coimmunoprecipitates with specific lens messenger RNAs (mRNAs) and is required for the posttranscriptional control of mRNAs that are critical to normal lens development and to RG function. These findings demonstrate a role for RGs in vertebrate organogenesis.
doi:10.1126/science.1195970
PMCID: PMC3279122  PMID: 21436445
8.  Datgan, a reusable software system for facile interrogation and visualization of complex transcription profiling data 
BMC Genomics  2011;12:429.
Background
We introduce Glaucoma Discovery Platform (GDP), an online environment for facile visualization and interrogation of complex transcription profiling datasets for glaucoma. We also report the availability of Datgan, the suite of scripts that was developed to construct GDP. This reusable software system complements existing repositories such as NCBI GEO or EBI ArrayExpress as it allows the construction of searchable databases to maximize understanding of user-selected transcription profiling datasets.
Description
Datgan scripts were used to construct both the underlying data tables and the web interface that form GDP. GDP is populated using data from a mouse model of glaucoma. The data was generated using the DBA/2J strain, a widely used mouse model of glaucoma. The DBA/2J-Gpnmb+ strain provided a genetically matched control strain that does not develop glaucoma. We separately assessed both the retina and the optic nerve head, important tissues in glaucoma. We used hierarchical clustering to identify early molecular stages of glaucoma that could not be identified using morphological assessment of disease. GDP has two components. First, an interactive search and retrieve component provides the ability to assess gene(s) of interest in all identified stages of disease in both the retina and optic nerve head. The output is returned in graphical and tabular format with statistically significant differences highlighted for easy visual analysis. Second, a bulk download component allows lists of differentially expressed genes to be retrieved as a series of files compatible with Excel. To facilitate access to additional information available for genes of interest, GDP is linked to selected external resources including Mouse Genome Informatics and Online Medelian Inheritance in Man (OMIM).
Conclusion
Datgan-constructed databases allow user-friendly access to datasets that involve temporally ordered stages of disease or developmental stages. Datgan and GDP are available from http://glaucomadb.jax.org/glaucoma.
doi:10.1186/1471-2164-12-429
PMCID: PMC3171729  PMID: 21864367
9.  Molecular clustering identifies complement and endothelin induction as early events in a mouse model of glaucoma 
The Journal of Clinical Investigation  2011;121(4):1429-1444.
Glaucoma is one of the most common neurodegenerative diseases. Despite this, the earliest stages of this complex disease are still unclear. This study was specifically designed to identify early stages of glaucoma in DBA/2J mice. To do this, we used genome-wide expression profiling of optic nerve head and retina and a series of computational methods. Eyes with no detectable glaucoma by conventional assays were grouped into molecularly defined stages of disease using unbiased hierarchical clustering. These stages represent a temporally ordered sequence of glaucoma states. We then determined networks and biological processes that were altered at these early stages. Early-stage expression changes included upregulation of both the complement cascade and the endothelin system, and so we tested the therapeutic value of separately inhibiting them. Mice with a mutation in complement component 1a (C1qa) were protected from glaucoma. Similarly, inhibition of the endothelin system with bosentan, an endothelin receptor antagonist, was strongly protective against glaucomatous damage. Since endothelin 2 is potently vasoconstrictive and was produced by microglia/macrophages, our data provide what we believe to be a novel link between these cell types and vascular dysfunction in glaucoma. Targeting early molecular events, such as complement and endothelin induction, may provide effective new treatments for human glaucoma.
doi:10.1172/JCI44646
PMCID: PMC3069778  PMID: 21383504
10.  The DNA sequence of the human X chromosome 
Ross, Mark T. | Grafham, Darren V. | Coffey, Alison J. | Scherer, Steven | McLay, Kirsten | Muzny, Donna | Platzer, Matthias | Howell, Gareth R. | Burrows, Christine | Bird, Christine P. | Frankish, Adam | Lovell, Frances L. | Howe, Kevin L. | Ashurst, Jennifer L. | Fulton, Robert S. | Sudbrak, Ralf | Wen, Gaiping | Jones, Matthew C. | Hurles, Matthew E. | Andrews, T. Daniel | Scott, Carol E. | Searle, Stephen | Ramser, Juliane | Whittaker, Adam | Deadman, Rebecca | Carter, Nigel P. | Hunt, Sarah E. | Chen, Rui | Cree, Andrew | Gunaratne, Preethi | Havlak, Paul | Hodgson, Anne | Metzker, Michael L. | Richards, Stephen | Scott, Graham | Steffen, David | Sodergren, Erica | Wheeler, David A. | Worley, Kim C. | Ainscough, Rachael | Ambrose, Kerrie D. | Ansari-Lari, M. Ali | Aradhya, Swaroop | Ashwell, Robert I. S. | Babbage, Anne K. | Bagguley, Claire L. | Ballabio, Andrea | Banerjee, Ruby | Barker, Gary E. | Barlow, Karen F. | Barrett, Ian P. | Bates, Karen N. | Beare, David M. | Beasley, Helen | Beasley, Oliver | Beck, Alfred | Bethel, Graeme | Blechschmidt, Karin | Brady, Nicola | Bray-Allen, Sarah | Bridgeman, Anne M. | Brown, Andrew J. | Brown, Mary J. | Bonnin, David | Bruford, Elspeth A. | Buhay, Christian | Burch, Paula | Burford, Deborah | Burgess, Joanne | Burrill, Wayne | Burton, John | Bye, Jackie M. | Carder, Carol | Carrel, Laura | Chako, Joseph | Chapman, Joanne C. | Chavez, Dean | Chen, Ellson | Chen, Guan | Chen, Yuan | Chen, Zhijian | Chinault, Craig | Ciccodicola, Alfredo | Clark, Sue Y. | Clarke, Graham | Clee, Chris M. | Clegg, Sheila | Clerc-Blankenburg, Kerstin | Clifford, Karen | Cobley, Vicky | Cole, Charlotte G. | Conquer, Jen S. | Corby, Nicole | Connor, Richard E. | David, Robert | Davies, Joy | Davis, Clay | Davis, John | Delgado, Oliver | DeShazo, Denise | Dhami, Pawandeep | Ding, Yan | Dinh, Huyen | Dodsworth, Steve | Draper, Heather | Dugan-Rocha, Shannon | Dunham, Andrew | Dunn, Matthew | Durbin, K. James | Dutta, Ireena | Eades, Tamsin | Ellwood, Matthew | Emery-Cohen, Alexandra | Errington, Helen | Evans, Kathryn L. | Faulkner, Louisa | Francis, Fiona | Frankland, John | Fraser, Audrey E. | Galgoczy, Petra | Gilbert, James | Gill, Rachel | Glöckner, Gernot | Gregory, Simon G. | Gribble, Susan | Griffiths, Coline | Grocock, Russell | Gu, Yanghong | Gwilliam, Rhian | Hamilton, Cerissa | Hart, Elizabeth A. | Hawes, Alicia | Heath, Paul D. | Heitmann, Katja | Hennig, Steffen | Hernandez, Judith | Hinzmann, Bernd | Ho, Sarah | Hoffs, Michael | Howden, Phillip J. | Huckle, Elizabeth J. | Hume, Jennifer | Hunt, Paul J. | Hunt, Adrienne R. | Isherwood, Judith | Jacob, Leni | Johnson, David | Jones, Sally | de Jong, Pieter J. | Joseph, Shirin S. | Keenan, Stephen | Kelly, Susan | Kershaw, Joanne K. | Khan, Ziad | Kioschis, Petra | Klages, Sven | Knights, Andrew J. | Kosiura, Anna | Kovar-Smith, Christie | Laird, Gavin K. | Langford, Cordelia | Lawlor, Stephanie | Leversha, Margaret | Lewis, Lora | Liu, Wen | Lloyd, Christine | Lloyd, David M. | Loulseged, Hermela | Loveland, Jane E. | Lovell, Jamieson D. | Lozado, Ryan | Lu, Jing | Lyne, Rachael | Ma, Jie | Maheshwari, Manjula | Matthews, Lucy H. | McDowall, Jennifer | McLaren, Stuart | McMurray, Amanda | Meidl, Patrick | Meitinger, Thomas | Milne, Sarah | Miner, George | Mistry, Shailesh L. | Morgan, Margaret | Morris, Sidney | Müller, Ines | Mullikin, James C. | Nguyen, Ngoc | Nordsiek, Gabriele | Nyakatura, Gerald | O’Dell, Christopher N. | Okwuonu, Geoffery | Palmer, Sophie | Pandian, Richard | Parker, David | Parrish, Julia | Pasternak, Shiran | Patel, Dina | Pearce, Alex V. | Pearson, Danita M. | Pelan, Sarah E. | Perez, Lesette | Porter, Keith M. | Ramsey, Yvonne | Reichwald, Kathrin | Rhodes, Susan | Ridler, Kerry A. | Schlessinger, David | Schueler, Mary G. | Sehra, Harminder K. | Shaw-Smith, Charles | Shen, Hua | Sheridan, Elizabeth M. | Shownkeen, Ratna | Skuce, Carl D. | Smith, Michelle L. | Sotheran, Elizabeth C. | Steingruber, Helen E. | Steward, Charles A. | Storey, Roy | Swann, R. Mark | Swarbreck, David | Tabor, Paul E. | Taudien, Stefan | Taylor, Tineace | Teague, Brian | Thomas, Karen | Thorpe, Andrea | Timms, Kirsten | Tracey, Alan | Trevanion, Steve | Tromans, Anthony C. | d’Urso, Michele | Verduzco, Daniel | Villasana, Donna | Waldron, Lenee | Wall, Melanie | Wang, Qiaoyan | Warren, James | Warry, Georgina L. | Wei, Xuehong | West, Anthony | Whitehead, Siobhan L. | Whiteley, Mathew N. | Wilkinson, Jane E. | Willey, David L. | Williams, Gabrielle | Williams, Leanne | Williamson, Angela | Williamson, Helen | Wilming, Laurens | Woodmansey, Rebecca L. | Wray, Paul W. | Yen, Jennifer | Zhang, Jingkun | Zhou, Jianling | Zoghbi, Huda | Zorilla, Sara | Buck, David | Reinhardt, Richard | Poustka, Annemarie | Rosenthal, André | Lehrach, Hans | Meindl, Alfons | Minx, Patrick J. | Hillier, LaDeana W. | Willard, Huntington F. | Wilson, Richard K. | Waterston, Robert H. | Rice, Catherine M. | Vaudin, Mark | Coulson, Alan | Nelson, David L. | Weinstock, George | Sulston, John E. | Durbin, Richard | Hubbard, Tim | Gibbs, Richard A. | Beck, Stephan | Rogers, Jane | Bentley, David R.
Nature  2005;434(7031):325-337.
The human X chromosome has a unique biology that was shaped by its evolution as the sex chromosome shared by males and females. We have determined 99.3% of the euchromatic sequence of the X chromosome. Our analysis illustrates the autosomal origin of the mammalian sex chromosomes, the stepwise process that led to the progressive loss of recombination between X and Y, and the extent of subsequent degradation of the Y chromosome. LINE1 repeat elements cover one-third of the X chromosome, with a distribution that is consistent with their proposed role as way stations in the process of X-chromosome inactivation. We found 1,098 genes in the sequence, of which 99 encode proteins expressed in testis and in various tumour types. A disproportionately high number of mendelian diseases are documented for the X chromosome. Of this number, 168 have been explained by mutations in 113 X-linked genes, which in many cases were characterized with the aid of the DNA sequence.
doi:10.1038/nature03440
PMCID: PMC2665286  PMID: 15772651
11.  Axons of retinal ganglion cells are insulted in the optic nerve early in DBA/2J glaucoma 
The Journal of Cell Biology  2007;179(7):1523-1537.
Here, we use a mouse model (DBA/2J) to readdress the location of insult(s) to retinal ganglion cells (RGCs) in glaucoma. We localize an early sign of axon damage to an astrocyte-rich region of the optic nerve just posterior to the retina, analogous to the lamina cribrosa. In this region, a network of astrocytes associates intimately with RGC axons. Using BAX-deficient DBA/2J mice, which retain all of their RGCs, we provide experimental evidence for an insult within or very close to the lamina in the optic nerve. We show that proximal axon segments attached to their cell bodies survive to the proximity of the lamina. In contrast, axon segments in the lamina and behind the eye degenerate. Finally, the Wlds allele, which is known to protect against insults to axons, strongly protects against DBA/2J glaucoma and preserves RGC activity as measured by pattern electroretinography. These experiments provide strong evidence for a local insult to axons in the optic nerve.
doi:10.1083/jcb.200706181
PMCID: PMC2373494  PMID: 18158332
12.  Inducible nitric oxide synthase, Nos2, does not mediate optic neuropathy and retinopathy in the DBA/2J glaucoma model 
BMC Neuroscience  2007;8:108.
Background
Nitric oxide synthase 2 (NOS2) contributes to neural death in some settings, but its role in glaucoma remains controversial. NOS2 is implicated in retinal ganglion cell degeneration in a rat glaucoma model in which intraocular pressure (IOP) is experimentally elevated by blood vessel cauterization, but not in a rat glaucoma model where IOP was elevated by injection of hypertonic saline. To test the importance of NOS2 for an inherited glaucoma, in this study we both genetically and pharmacologically decreased NOS2 activity in the DBA/2J mouse glaucoma model.
Methods
The expression of Nos2 in the optic nerve head was analyzed at both the RNA and protein levels at different stages of disease pathogenesis. To test the involvement of Nos2 in glaucomatous neurodegeneration, a null allele of Nos2 was backcrossed into DBA/2J mice and the incidence and severity of glaucoma was assessed in mice of each Nos2 genotype. Additionally, DBA/2J mice were treated with the NOS2 inhibitor aminoguanidine and the disease compared to untreated mice.
Results
Optic nerve head Nos2 RNA levels varied and increased during moderate but decreased at early and severe stages of disease. Despite the presence of a few NOS2 positive cells in the optic nerve head, NOS2 protein was not substantially increased during the glaucoma. Genetic deficiency of Nos2 or aminoguanidine treatment did not alter the IOP profile of DBA/2J mice. Additionally, neither Nos2 deficiency nor aminoguanidine had any detectable affect on the glaucomatous optic nerve damage.
Conclusion
Glaucomatous neurodegeneration in DBA/2J mice does not require NOS2 activity. Further experiments involving various models are needed to assess the general importance of Nos2 in glaucoma.
doi:10.1186/1471-2202-8-108
PMCID: PMC2211487  PMID: 18093296
13.  Absence of glaucoma in DBA/2J mice homozygous for wild-type versions of Gpnmb and Tyrp1 
BMC Genetics  2007;8:45.
Background
The glaucomas are a common but incompletely understood group of diseases. DBA/2J mice develop a pigment liberating iris disease that ultimately causes elevated intraocular pressure (IOP) and glaucoma. We have shown previously that mutations in two genes, Gpnmb and Tyrp1, initiate the iris disease. However, mechanisms involved in the subsequent IOP elevation and optic nerve degeneration remain unclear.
Results
Here we present new mouse strains with Gpnmb and/or Tyrp1 genes of normal function and with a DBA/2J genetic background. These strains do not develop elevated IOP or glaucoma with age.
Conclusion
These strains provide much needed controls for studying pathogenic mechanisms of glaucoma using DBA/2J mice. Given the involvement of Gpnmb and/or Tyrp1 in areas such as immunology and tumor development and progression, these strains are also important in other research fields.
doi:10.1186/1471-2156-8-45
PMCID: PMC1937007  PMID: 17608931
14.  A Dominant-Negative Mutation of Mouse Lmx1b Causes Glaucoma and Is Semi-lethal via LBD1-Mediated Dimerisation 
PLoS Genetics  2014;10(5):e1004359.
Mutations in the LIM-homeodomain transcription factor LMX1B cause nail-patella syndrome, an autosomal dominant pleiotrophic human disorder in which nail, patella and elbow dysplasia is associated with other skeletal abnormalities and variably nephropathy and glaucoma. It is thought to be a haploinsufficient disorder. Studies in the mouse have shown that during development Lmx1b controls limb dorsal-ventral patterning and is also required for kidney and eye development, midbrain-hindbrain boundary establishment and the specification of specific neuronal subtypes. Mice completely deficient for Lmx1b die at birth. In contrast to the situation in humans, heterozygous null mice do not have a mutant phenotype. Here we report a novel mouse mutant Icst, an N-ethyl-N-nitrosourea-induced missense substitution, V265D, in the homeodomain of LMX1B that abolishes DNA binding and thereby the ability to transactivate other genes. Although the homozygous phenotypic consequences of Icst and the null allele of Lmx1b are the same, heterozygous Icst elicits a phenotype whilst the null allele does not. Heterozygous Icst causes glaucomatous eye defects and is semi-lethal, probably due to kidney failure. We show that the null phenotype is rescued more effectively by an Lmx1b transgene than is Icst. Co-immunoprecipitation experiments show that both wild-type and Icst LMX1B are found in complexes with LIM domain binding protein 1 (LDB1), resulting in lower levels of functional LMX1B in Icst heterozygotes than null heterozygotes. We conclude that Icst is a dominant-negative allele of Lmx1b. These findings indicate a reassessment of whether nail-patella syndrome is always haploinsufficient. Furthermore, Icst is a rare example of a model of human glaucoma caused by mutation of the same gene in humans and mice.
Author Summary
Nail-patella syndrome is a human genetic disease caused by an inactivating mutation in one copy of a gene called LMX1B, with the amount of protein produced from the remaining copy of the gene not being enough for normal function. Patients with this disease have malformations of their nails, elbows and kneecaps. Some patients also develop kidney disease and glaucoma. LMX1B controls where and when other genes are expressed and it is important during development. Studies in mice have shown that complete absence of Lmx1b is lethal at birth. In contrast to humans, mice with only one copy of the gene are normal. Here we describe a new mutant mouse, Icst, which has a mutation in Lmx1b that abolishes the ability of the protein to bind near genes that it controls. Mice with one normal and one copy of Lmx1b with the Icst mutation have eye defects and some die shortly after birth probably due to kidney failure. Therefore having one functional and one mutant copy of Lmx1b is more detrimental than having a half dose of functional protein. The Icst mouse is a model of human glaucoma where mutation of the same gene causes glaucoma in humans and mice.
doi:10.1371/journal.pgen.1004359
PMCID: PMC4014447  PMID: 24809698

Results 1-14 (14)