High Temperature Requirement Factor A1 (HTRA1) Gene Regulates Angiogenesis through Transforming Growth Factor- Family Member Growth Differentiation Factor 6

Molecular Medicine Research Center and Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu 610041, China.
Journal of Biological Chemistry (Impact Factor: 4.57). 11/2011; 287(2):1520-6. DOI: 10.1074/jbc.M111.275990
Source: PubMed


Genome-wide association study (GWAS) has identified genetic variants in the promoter region of the high temperature requirement
factor A1 (HTRA1) gene associated with age-related macular degeneration (AMD). As a secreted serine protease, HTRA1 has been reported to interact
with members of the transforming growth factor-β (TGF-β) family and regulate their signaling pathways. Growth differentiation
factor 6 (GDF6), a member of the TGF-β family, is involved in ectoderm patterning and eye development. Mutations in GDF6 have
been associated with abnormal eye development that may result in microphthalmia and anophthalmia. In this report, we identified
a single nucleotide polymorphism (SNP) rs6982567 A/G near the GDF6 gene that is significantly associated with AMD (p value = 3.54 × 10−8). We demonstrated that the GDF6 AMD risk allele (rs6982567 A) is associated with decreased expression of the GDF6 and increased expression of HTRA1. Similarly, the HTRA1 AMD risk allele (rs10490924 T) is associated with decreased GDF6 and increased HTRA1 expression. We observed decreased vascular development in the retina and significant up-regulation of GDF6 gene in the RPE layer, retinal and brain tissues in HTRA1 knock-out (htra1−/−) mice as compared with the wild-type counterparts. Furthermore, we showed enhanced SMAD signaling in htra1−/− mice. Our data suggests a critical role of HTRA1 in the regulation of angiogenesis via TGF-β signaling and identified GDF6 as a novel disease gene for AMD.

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    • "Mutations in GDF6 were recently found to be associated with age-related macular degeneration and Leber's congenital amaurosis, both representing photoreceptor degenerative disease [43], [44]. Further, we demonstrated that the retinas of zebrafish gdf6as327/s327 mutants exhibit photoreceptor deficits [43], together indicating that disruption of GDF6 leads to photoreceptor degeneration, which marks gdf6a as a potential regulatory factor in the differentiation and/or maintenance of cone photoreceptors. "
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    ABSTRACT: Functional vision restoration is within reach via stem cell therapy, but one of the largest obstacles is the derivation of colour-sensitive cone photoreceptors that are required for high-acuity daytime vision. To enhance progress made using nocturnal murine models, we instead utilize cone-rich zebrafish and herein investigate relationships between gdf6a and tbx2b in cone photoreceptor development. Growth/differentiation factor 6a (gdf6a), a bone morphogenetic protein family ligand, is an emerging factor in photoreceptor degenerative diseases. The T-box transcription factor tbx2b is required to specify UV cone photoreceptor fate instead of rod photoreceptor fate. Interactions between these factors in cone development would be unanticipated, considering the discrete phenotypes in their respective mutants. However, gdf6a positively modulates the abundance of tbx2b transcript during early eye morphogenesis, and we extended this conclusion to later stages of retinal development comprising the times when photoreceptors differentiate. Despite this, gdf6a-/- larvae possess a normal relative number of UV cones and instead present with a low abundance of blue cone photoreceptors, approximately half that of siblings (p<0.001), supporting a differential role for gdf6a amongst the spectral subtypes of cone photoreceptors. Further, gdf6a-/- larvae from breeding of compound heterozygous gdf6a+/-;tbx2b+/- mutants exhibit the recessive lots-of-rods phenotype (which also shows a paucity of UV cones) at significantly elevated rates (44% or 48% for each of two tbx2b alleles, χ2 p≤0.007 for each compared to expected Mendelian 25%). Thus the gdf6a-/- background sensitizes fish such that the recessive lots-of-rods phenotype can appear in heterozygous tbx2b+/- fish. Overall, this work establishes a novel link between tbx2b and gdf6a in determining photoreceptor fates, defining the nexus of an intricate pathway influencing the abundance of cone spectral subtypes and specifying rod vs. cone photoreceptors. Understanding this interaction is a necessary step in the refinement of stem cell-based restoration of daytime vision in humans.
    Full-text · Article · Mar 2014 · PLoS ONE
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    • "Further, gdf6a loss of function accelerated disease progression in a zebrafish model of ALS. The synthesis of this data combines with recent reports of a role for GDF6 in congenital and late-onset photoreceptor degenerations [34], [53] to compel a role for GDF6 as a modifier gene in the etiology of disparate neuropathies. "
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    ABSTRACT: Mutation of Glass bottom boat, the Drosophila homologue of the bone morphogenetic protein or growth/differentiation factor (BMP/GDF) family of genes in vertebrates, has been shown to disrupt development of neuromuscular junctions (NMJ). Here we tested whether this same conclusion can be broadened to vertebrate BMP/GDF genes. This analysis was also extended to consider whether such genes are required for NMJ maintenance in post-larval stages, as this would argue that BMP genes are viable candidates for analysis in progressive neuromuscular disease. Zebrafish mutants harboring homozygous null mutations in the BMP-family gene gdf6a were raised to adulthood and assessed for neuromuscular deficits. Fish lacking gdf6a exhibited decreased endurance (∼50%, p = 0.005) compared to wild type, and this deficit progressively worsened with age. These fish also presented with significantly disrupted NMJ morphology (p = 0.009), and a lower abundance of spinal motor neurons (∼50%, p<0.001) compared to wild type. Noting the similarity of these symptoms to those of Amyotrophic Lateral Sclerosis (ALS) model mice and fish, we asked if mutations in gdf6a would enhance the phenotypes observed in the latter, i.e. in zebrafish over-expressing mutant Superoxide Dismutase 1 (SOD1). Amongst younger adult fish only bigenic fish harboring both the SOD1 transgene and gdf6a mutations, but not siblings with other combinations of these gene modifications, displayed significantly reduced endurance (75%, p<0.05) and strength/power (75%, p<0.05), as well as disrupted NMJ morphology (p<0.001) compared to wild type siblings. Bigenic fish also had lower survival rates compared to other genotypes. Thus conclusions regarding a role for BMP ligands in effecting NMJ can be extended to vertebrates, supporting conservation of mechanisms relevant to neuromuscular degenerative diseases. These conclusions synergize with past findings to argue for further analysis of GDF6 and other BMP genes as modifier loci, potentially affecting susceptibility to ALS and perhaps a broader suite of neurodegenerative diseases.
    Full-text · Article · Feb 2014 · PLoS ONE
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    • "Total RNA extraction from mouse tissues or human lymphoblastoid cells, cDNA synthesis, and qRT-PCR experiments were performed as previously described (14). Assays were performed in triplicate. "
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    Full-text · Article · Feb 2013 · Diabetes
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