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16 result(s) for "Ozel, Ayse Bilge"
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Increased soluble urokinase plasminogen activator levels modulate monocyte function to promote atherosclerosis
People with kidney disease are disproportionately affected by atherosclerosis for unclear reasons. Soluble urokinase plasminogen activator receptor (suPAR) is an immune-derived mediator of kidney disease, levels of which are strongly associated with cardiovascular outcomes. We assessed suPAR's pathogenic involvement in atherosclerosis using epidemiologic, genetic, and experimental approaches. We found serum suPAR levels to be predictive of coronary artery calcification and cardiovascular events in 5,406 participants without known coronary disease. In a genome-wide association meta-analysis including over 25,000 individuals, we identified a missense variant in the plasminogen activator, urokinase receptor (PLAUR) gene (rs4760), confirmed experimentally to lead to higher suPAR levels. Mendelian randomization analysis in the UK Biobank using rs4760 indicated a causal association between genetically predicted suPAR levels and atherosclerotic phenotypes. In an experimental model of atherosclerosis, proprotein convertase subtilisin/kexin-9 (Pcsk9) transfection in mice overexpressing suPAR (suPARTg) led to substantially increased atherosclerotic plaques with necrotic cores and macrophage infiltration compared with those in WT mice, despite similar cholesterol levels. Prior to induction of atherosclerosis, aortas of suPARTg mice excreted higher levels of CCL2 and had higher monocyte counts compared with WT aortas. Aortic and circulating suPARTg monocytes exhibited a proinflammatory profile and enhanced chemotaxis. These findings characterize suPAR as a pathogenic factor for atherosclerosis acting at least partially through modulation of monocyte function.
Variants in myelin regulatory factor (MYRF) cause autosomal dominant and syndromic nanophthalmos in humans and retinal degeneration in mice
Nanophthalmos is a rare, potentially devastating eye condition characterized by small eyes with relatively normal anatomy, a high hyperopic refractive error, and frequent association with angle closure glaucoma and vision loss. The condition constitutes the extreme of hyperopia or farsightedness, a common refractive error that is associated with strabismus and amblyopia in children. NNO1 was the first mapped nanophthalmos locus. We used combined pooled exome sequencing and strong linkage data in the large family used to map this locus to identify a canonical splice site alteration upstream of the last exon of the gene encoding myelin regulatory factor (MYRF c.3376-1G>A), a membrane bound transcription factor that undergoes autoproteolytic cleavage for nuclear localization. This variant produced a stable RNA transcript, leading to a frameshift mutation p.Gly1126Valfs*31 in the C-terminus of the protein. In addition, we identified an early truncating MYRF frameshift mutation, c.769dupC (p.S264QfsX74), in a patient with extreme axial hyperopia and syndromic features. Myrf conditional knockout mice (CKO) developed depigmentation of the retinal pigment epithelium (RPE) and retinal degeneration supporting a role of this gene in retinal and RPE development. Furthermore, we demonstrated the reduced expression of Tmem98, another known nanophthalmos gene, in Myrf CKO mice, and the physical interaction of MYRF with TMEM98. Our study establishes MYRF as a nanophthalmos gene and uncovers a new pathway for eye growth and development.
A genome-wide screen identifies genes required for erythroid differentiation
The complete array of genes required for terminal erythroid differentiation remains unknown. To address this knowledge gap, we perform a genome-scale CRISPR knock-out screen in the human erythroid progenitor cell line HUDEP-2 and validate candidate regulators of erythroid differentiation in a custom secondary screen. Comparison of sgRNA abundance in the CRISPR library, proerythroblasts, and orthochromatic erythroblasts, resulted in the identification of genes that are essential for proerythroblast survival and genes that are required for terminal erythroid differentiation. Among the top genes identified are known regulators of erythropoiesis, underscoring the validity of this screen. Notably, using a Log2 fold change of <−1 and false discovery rate of <0.01, the screen identified 277 genes that are required for terminal erythroid differentiation, including multiple genes not previously nominated through GWAS. NHLRC2 , which was previously implicated in hemolytic anemia, was a highly ranked gene. We suggest that anemia due to NHLRC2 mutation results at least in part from a defect in erythroid differentiation. Another highly ranked gene in the screen is VAC14 , which we validated for its requirement in erythropoiesis in vitro and in vivo. Thus, data from this CRISPR screen may help classify the underlying mechanisms that contribute to erythroid disorders. Using a genome-wide CRISPR knock-out screen, the authors defined the repertoire of genes that are required for proerythroblast survival and for terminal erythroid differentiation.
Allelic Variants in Established Hypopituitarism Genes Expand Our Knowledge of the Phenotypic Spectrum
We report four allelic variants (three novel) in three genes previously established as causal for hypopituitarism or related disorders. A novel homozygous variant in the growth hormone gene, GH1 c.171delT (p.Phe 57Leufs*43), was found in a male patient with severe isolated growth hormone deficiency (IGHD) born to consanguineous parents. A hemizygous SOX3 allelic variant (p.Met304Ile) was found in a male patient with IGHD and hypoplastic anterior pituitary. YASARA, a tool to evaluate protein stability, suggests that p.Met304Ile destabilizes the SOX3 protein (ΔΔG = 2.49 kcal/mol). A rare, heterozygous missense variant in the TALE homeobox protein gene, TGIF1 (c.268C>T:p.Arg90Cys) was found in a patient with combined pituitary hormone deficiency (CPHD), diabetes insipidus, and syndromic features of holoprosencephaly (HPE). This variant was previously reported in a patient with severe holoprosencephaly and shown to affect TGIF1 function. A novel heterozygous TGIF1 variant (c.82T>C:p.Ser28Pro) was identified in a patient with CPHD, pituitary aplasia and ectopic posterior lobe. Both TGIF1 variants have an autosomal dominant pattern of inheritance with incomplete penetrance. In conclusion, we have found allelic variants in three genes in hypopituitarism patients. We discuss these variants and associated patient phenotypes in relation to previously reported variants in these genes, expanding our knowledge of the phenotypic spectrum in patient populations.
A vagal–brainstem interoceptive circuit for cough-like defensive behaviors in mice
Coughing is a respiratory behavior that plays a crucial role in protecting the respiratory system. Here we show that the nucleus of the solitary tract (NTS) in mice contains heterogenous neuronal populations that differentially control breathing. Within these subtypes, activation of tachykinin 1 (Tac1)-expressing neurons triggers specific respiratory behaviors that, as revealed by our detailed characterization, are cough-like behaviors. Chemogenetic silencing or genetic ablation of Tac1 neurons inhibits cough-like behaviors induced by tussive challenges. These Tac1 neurons receive synaptic inputs from the bronchopulmonary chemosensory and mechanosensory neurons in the vagal ganglion and coordinate medullary regions to control distinct aspects of cough-like defensive behaviors. We propose that these Tac1 neurons in the NTS are a key component of the airway–vagal–brain neural circuit that controls cough-like defensive behaviors in mice and that they coordinate the downstream modular circuits to elicit the sequential motor pattern of forceful expiratory responses. Gannot et al. show that Tac1 neurons in the NTS mediate an airway–vagal–brain pathway that is crucial for coughing in mice. These neurons receive direct vagal sensory inputs and coordinate downstream circuits to control coughing.
Analyses of LMNA-negative juvenile progeroid cases confirms biallelic POLR3A mutations in Wiedemann–Rautenstrauch-like syndrome and expands the phenotypic spectrum of PYCR1 mutations
Juvenile segmental progeroid syndromes are rare, heterogeneous disorders characterized by signs of premature aging affecting more than one tissue or organ starting in childhood. Hutchinson–Gilford progeria syndrome (HGPS), caused by a recurrent de novo synonymous LMNA mutation resulting in aberrant splicing and generation of a mutant product called progerin, is a prototypical example of such disorders. Here, we performed a joint collaborative study using massively parallel sequencing and targeted Sanger sequencing, aimed at delineating the underlying genetic cause of 14 previously undiagnosed, clinically heterogeneous, non-LMNA-associated juvenile progeroid patients. The molecular diagnosis was achieved in 11 of 14 cases (~ 79%). Furthermore, we firmly establish biallelic mutations in POLR3A as the genetic cause of a recognizable, neonatal, Wiedemann–Rautenstrauch-like progeroid syndrome. Thus, we suggest that POLR3A mutations are causal for a portion of under-diagnosed early-onset segmental progeroid syndromes. We additionally expand the clinical spectrum associated with PYCR1 mutations by showing that they can somewhat resemble HGPS in the first year of life. Moreover, our results lead to clinical reclassification in one single case. Our data emphasize the complex genetic and clinical heterogeneity underlying progeroid disorders.
Extended regions of suspected mis-assembly in the rat reference genome
We performed whole-genome sequencing for eight inbred rat strains commonly used in genetic mapping studies. They are the founders of the NIH heterogeneous stock (HS) outbred colony. We provide their sequences and variant calls to the rat genomics community. When analyzing the variant calls we identified regions with unusually high levels of heterozygosity. These regions are consistent across the eight inbred strains, including Brown Norway, which is the basis of the rat reference genome. These regions show higher read depths than other regions in the genome and contain higher rates of apparent tri-allelic variant sites. The evidence suggests that these regions may correspond to duplicated segments that were incorrectly overlaid as a single segment in the reference genome. We provide masks for these regions of suspected mis-assembly as a resource for the community to flag potentially false interpretations of mapping or functional results.
SIX3 V ariant Causes Pituitary Stalk Interruption Syndrome and Combined Pituitary Hormone Deficiency
The genetic basis for congenital hypopituitarism and related disorders is beginning to emerge, and over 30 causal genes have been identified. Mutations in some of these genes can also cause holoprosencephaly (HPE) or septo-optic dysplasia. SIX3 is a homeodomain protein expressed in the developing brain, pituitary gland, and eye. Heterozygous mutations in SIX3 cause variable HPE in humans and mice. We identified two children with neonatal GH and TSH deficiency and stalk interruption who were doubly heterozygous for rare, likely deleterious variants in SIX3 and POU1F1. Functional studies demonstrated that both variants are disruptive. We used Six3 and Pou1f1 loss of function mice to assess the genetic interaction between Six3 and Pou1f1. Six3 heterozygotes have variable pituitary gland dysmorphology, while Pou1f1 heterozygotes are normal. A significant portion of the Six3+/-; Pou1f1+/dw doubly heterozygous mice have a more pronounced pituitary phenotype than Six3+/-, supporting the possibility of digenic pituitary disease. To understand the role of SIX3 in pituitary and hypothalamic development, we used Prop1-cre and Nkx2.1-cre to delete Six3. Disruption of Six3 expression in Rathke’s pouch caused poor activation of Lhx3 expression and arrested anterior pituitary development. The Nkx2.1-cre, Six3flox/flox embryos had no evidence of infundibulum evagination and failed to induce FGF and BMP signaling, which normally drive expansion of Rathke’s pouch. By E11.5 cells in Rathke’s pouch underwent apoptosis. The Nkx2.1-cre, Six3flox/flox embryos failed to activate expression of Lhx2 and Tbx3 in the neural ectoderm. These embryos had elevated CCND1, MYCN, and Axin2 expression in the area of the presumptive infundibulum. This indicates that SIX3 is necessary to repress cell proliferation and Wnt/beta-catenin signals to promote formation of the pituitary stalk. Thus, Six3 has essential roles in both the neural and oral ectoderm for hypothalamic and pituitary development, respectively. Heterozygous loss of function variants in SIX3 could be a contributor to multiple pituitary hormone deficiencies in children, especially if there are associated craniofacial abnormalities or PSIS.
SIX3 Variant Causes Pituitary Stalk Interruption Syndrome and Combined Pituitary Hormone Deficiency
The genetic basis for congenital hypopituitarism and related disorders is beginning to emerge, and over 30 causal genes have been identified. Mutations in some of these genes can also cause holoprosencephaly (HPE) or septo-optic dysplasia. SIX3 is a homeodomain protein expressed in the developing brain, pituitary gland, and eye. Heterozygous mutations in SIX3 cause variable HPE in humans and mice. We identified two children with neonatal GH and TSH deficiency and stalk interruption who were doubly heterozygous for rare, likely deleterious variants in SIX3 and POU1F1. Functional studies demonstrated that both variants are disruptive. We used Six3 and Pou1f1 loss of function mice to assess the genetic interaction between Six3 and Pou1f1. Six3 heterozygotes have variable pituitary gland dysmorphology, while Pou1f1 heterozygotes are normal. A significant portion of the Six3+/-; Pou1f1+/dw doubly heterozygous mice have a more pronounced pituitary phenotype than Six3+/-, supporting the possibility of digenic pituitary disease. To understand the role of SIX3 in pituitary and hypothalamic development, we used Prop1-cre and Nkx2.1-cre to delete Six3. Disruption of Six3 expression in Rathke’s pouch caused poor activation of Lhx3 expression and arrested anterior pituitary development. The Nkx2.1-cre, Six3flox/flox embryos had no evidence of infundibulum evagination and failed to induce FGF and BMP signaling, which normally drive expansion of Rathke’s pouch. By E11.5 cells in Rathke’s pouch underwent apoptosis. The Nkx2.1-cre, Six3flox/flox embryos failed to activate expression of Lhx2 and Tbx3 in the neural ectoderm. These embryos had elevated CCND1, MYCN, and Axin2 expression in the area of the presumptive infundibulum. This indicates that SIX3 is necessary to repress cell proliferation and Wnt/beta-catenin signals to promote formation of the pituitary stalk. Thus, Six3 has essential roles in both the neural and oral ectoderm for hypothalamic and pituitary development, respectively. Heterozygous loss of function variants in SIX3 could be a contributor to multiple pituitary hormone deficiencies in children, especially if there are associated craniofacial abnormalities or PSIS.
Variants in myelin regulatory factor
Nanophthalmos is a rare, potentially devastating eye condition characterized by small eyes with relatively normal anatomy, a high hyperopic refractive error, and frequent association with angle closure glaucoma and vision loss. The condition constitutes the extreme of hyperopia or farsightedness, a common refractive error that is associated with strabismus and amblyopia in children. NNO1 was the first mapped nanophthalmos locus. We used combined pooled exome sequencing and strong linkage data in the large family used to map this locus to identify a canonical splice site alteration upstream of the last exon of the gene encoding myelin regulatory factor (MYRF c.3376-1G>A), a membrane bound transcription factor that undergoes autoproteolytic cleavage for nuclear localization. This variant produced a stable RNA transcript, leading to a frameshift mutation p.Gly1126Valfs*31 in the C-terminus of the protein. In addition, we identified an early truncating MYRF frameshift mutation, c.769dupC (p.S264QfsX74), in a patient with extreme axial hyperopia and syndromic features. Myrf conditional knockout mice (CKO) developed depigmentation of the retinal pigment epithelium (RPE) and retinal degeneration supporting a role of this gene in retinal and RPE development. Furthermore, we demonstrated the reduced expression of Tmem98, another known nanophthalmos gene, in Myrf CKO mice, and the physical interaction of MYRF with TMEM98. Our study establishes MYRF as a nanophthalmos gene and uncovers a new pathway for eye growth and development.