Near complete loss of retinal ganglion cells in the math5/brn3b double knockout elicits severe reductions of other cell types during retinal development

Department of Biochemistry and Molecular Biology, The University of Texas-Houston, Houston, TX 77030, USA.
Developmental Biology (Impact Factor: 3.64). 05/2008; 316(2):214-27. DOI: 10.1016/j.ydbio.2008.01.015
Source: PubMed

ABSTRACT Retinal ganglion cells (RGCs) are the first cell type to differentiate during retinal histogenesis. It has been postulated that specified RGCs subsequently influence the number and fate of the remaining progenitors to produce the rest of the retinal cell types. However, several genetic knockout models have argued against this developmental role for RGCs. Although it is known that RGCs secrete cellular factors implicated in cell proliferation, survival, and differentiation, until now, limited publications have shown that reductions in the RGC number cause significant changes in these processes. In this study, we observed that Math5 and Brn3b double null mice exhibited over a 99% reduction in the number of RGCs during development. This severe reduction of RGCs is accompanied by a drastic loss in the number of all other retinal cell types that was never seen before. Unlike Brn3b null or Math5 null animals, mice null for both alleles lack an optic nerve and have severe retinal dysfunction. Results of this study support the hypothesis that RGCs play a pivotal role in the late phase of mammalian retina development.

  • [Show abstract] [Hide abstract]
    ABSTRACT: With the establishment of the 'neuron theory' at the turn of the twentieth century, this remarkably powerful term was introduced to name a breathtaking diversity of cells unified by a characteristic structural compartmentalization and unique information processing and propagating features. At the beginning of the twenty-first century, developmental, stem cell and reprogramming studies converged to suggest a common mechanism involved in the generation of possibly all vertebrate, and at least a significant number of invertebrate, neurons. Sox and, in particular, SoxB and SoxC proteins as well as basic helix-loop-helix proteins play major roles, even though their precise contributions to progenitor programming, proliferation and differentiation are not fully resolved. In addition to neuronal development, these transcription factors also regulate sensory receptor and endocrine cell development, thus specifying a range of cells with regulatory and communicative functions. To what extent microRNAs contribute to the diversification of these cell types is an upcoming question. Understanding the transcriptional and post-transcriptional regulation of genes coding for cell type-specific cytoskeletal and motor proteins as well as synaptic and ion channel proteins, which mark differences but also similarities between the three communicator cell types, will provide a key to the comprehension of their diversification and the signature of 'generic neuronal' differentiation. Apart from the general scientific significance of a putative universal core instruction for neuronal development, the impact of this line of research for cell replacement therapy and brain tumor treatment will be of considerable interest.
    Cell and Tissue Research 11/2014; 359(1). DOI:10.1007/s00441-014-2049-8 · 3.33 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The troglomorphic phenotype shared by diverse cave-dwelling animals is regarded as a classical example of convergent evolution. One unresolved question is whether the characteristic eye loss in diverse cave species is based on interference with the same genetic program. Phreatichthys andruzzii, a Somalian cavefish, has evolved under constant conditions in complete darkness and shows severe troglomorphic characteristics, such as complete loss of eyes, pigments and scales. During early embryonic development, a complete eye is formed but is subsequently lost. In Astyanax mexicanus, another blind cavefish, eye loss has been attributed to interference during eye field patterning. To address whether similar pathways have been targeted by evolution independently, we investigated the retinal development of P. andruzzii, studying the expression of marker genes involved in eye patterning, morphogenesis, differentiation and maintenance. In contrast to Astyanax, patterning of the eye field and evagination of the optic vesicles proceeds without obvious deviation. However, the subsequent differentiation of retinal cell types is arrested during generation of the first-born cell type, retinal ganglion cells, which also fail to project correctly to the optic tectum. Eye degeneration in both species is driven by progressive apoptosis. However, it is retinal apoptosis in Phreatichthys that progresses in a wave-like manner and eliminates progenitor cells that fail to differentiate, in contrast to Astyanax, where lens apoptosis appears to serve as a driving force. Thus, evolution has targeted late retinal differentiation events, indicating that there are several ways to discontinue the development and maintenance of an eye. © 2015. Published by The Company of Biologists Ltd.
    Development 01/2015; 142(4). DOI:10.1242/dev.114629 · 6.27 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Purpose: Despite the different etiology of primary open angle glaucoma (POAG), primary angle closure glaucoma (PACG), and pseudoexfoliative glaucoma (PEXG), several studies have suggested that these forms of glaucoma have overlapping genetic risk factors. Therefore, the aim of this study was to evaluate the role of genetic variants recently associated with POAG in different types of glaucoma in Pakistani POAG, PACG, and PEXG patient cohorts. Methods: Six variants in CDKN2B-AS1 (rs4977756), CDKN2B (rs1063192), ATOH7 (rs1900004), CAV1 (rs4236601), TMCO1 (rs4656461), and SIX1 (rs10483727) were genotyped using TaqMan assays. A total of 513 unrelated patients with glaucoma (268 with POAG, 125 with PACG, and 120 with PEXG) and 233 healthy controls were included in the study. Genotypic and allelic associations were analyzed with a chi-square test. Results: The frequency of the G allele of TMCO1 rs4656461 was significantly lower in the patients with POAG (p=0.003; OR [odds ratio]=0.57), PACG (p=0.009; OR=0.52), and PEXG (p=0.01; OR=0.54) compared to the control individuals. The T allele of ATOH7 rs1900004 was observed less frequently in the patients with PACG (p=0.03; OR=0.69) compared to the control individuals. The A allele of CAV1 rs4236601 was found more frequently in the patients with POAG (p=0.008; OR=1.49) compared to the control individuals. This study demonstrates that the TMCO1 rs4656461 variant is associated with POAG, PACG and PEXG in the Pakistani population. Our study was unable to confirm previous associations reported for variants in CDKN2B-AS1, CDKN2B, and SIX1 with any type of glaucoma.
    Molecular vision 11/2014; 20:1471-1479. · 2.25 Impact Factor

Full-text (2 Sources)

Available from
May 22, 2014