An ancient founder mutation located between ROBO1 and ROBO2 is responsible for increased microtia risk in Amerindigenous populations
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE202442 | GEO | 2022/05/14
REPOSITORIES: GEO
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Project description:Microtia is a congenital malformation that encompasses mild hypoplasia to complete loss of the external ear, or pinna. Although contribution of genetic variation and environmental factors to microtia remains elusive, Amerindigenous populations have the highest reported incidence. Here, using both transmission disequilibrium tests (TDT) and association studies in microtia trios (parents and affected child) and microtia cohorts enrolled in Latin America, we map a ~10 kb microtia locus (OR 4.7; p=6.78e-18) to the intergenic region between Roundabout 1 (ROBO1) and Roundabout 2 (ROBO2) (chr3: 78546526-78555137). While alleles at the microtia locus significantly increase the risk of microtia, their penetrance is low (<1%). We demonstrate that the microtia locus contains a polymorphic complex repeat element that is expanded in affected individuals. The locus is located near a chromatin loop region that regulates ROBO1 and ROBO2 expression in induced pluripotent stem cell-derived neural crest cells. Furthermore, we use single nuclear RNA sequencing (snRNAseq) to demonstrate ROBO1 and ROBO2 expression in both fibroblasts and chondrocytes of the mature human pinna. Because the microtia allele is enriched in Amerindigenous populations and shared by some East Asian subjects with craniofacial malformations, we propose both populations share a mutation that arose in a common ancestor prior to the ancient migration of Eurasian populations into the Americas, and that the high incidence of microtia among Amerindigenous populations reflects the population bottleneck that occurred during the migration out of Eurasia.
2022-05-14 | GSE202441 | GEO
Project description:Microtia is a congenital malformation that encompasses mild hypoplasia to complete loss of the external ear, or pinna. Although contribution of genetic variation and environmental factors to microtia remains elusive, Amerindigenous populations have the highest reported incidence. Here, using both transmission disequilibrium tests (TDT) and association studies in microtia trios (parents and affected child) and microtia cohorts enrolled in Latin America, we map a ~10 kb microtia locus (OR 4.7; p=6.78e-18) to the intergenic region between Roundabout 1 (ROBO1) and Roundabout 2 (ROBO2) (chr3: 78546526-78555137). While alleles at the microtia locus significantly increase the risk of microtia, their penetrance is low (<1%). We demonstrate that the microtia locus contains a polymorphic complex repeat element that is expanded in affected individuals. The locus is located near a chromatin loop region that regulates ROBO1 and ROBO2 expression in induced pluripotent stem cell-derived neural crest cells. Furthermore, we use single nuclear RNA sequencing (snRNAseq) to demonstrate ROBO1 and ROBO2 expression in both fibroblasts and chondrocytes of the mature human pinna. Because the microtia allele is enriched in Amerindigenous populations and shared by some East Asian subjects with craniofacial malformations, we propose both populations share a mutation that arose in a common ancestor prior to the ancient migration of Eurasian populations into the Americas, and that the high incidence of microtia among Amerindigenous populations reflects the population bottleneck that occurred during the migration out of Eurasia.
2022-05-14 | GSE202440 | GEO
Project description:Microtia is a congenital malformation that encompasses mild hypoplasia to complete loss of the external ear, or pinna. Although the contribution of genetic variation and environmental factors to microtia remains elusive, Amerindigenous populations have the highest reported incidence. Here, using both transmission disequilibrium tests and association studies in microtia trios (parents and affected child) and microtia cohorts enrolled in Latin America, we map an ∼10-kb microtia locus (odds ratio = 4.7; P = 6.78e-18) to the intergenic region between Roundabout 1 (ROBO1) and Roundabout 2 (ROBO2) (chr3: 78546526 to 78555137). While alleles at the microtia locus significantly increase the risk of microtia, their penetrance is low (<1%). We demonstrate that the microtia locus contains a polymorphic complex repeat element that is expanded in affected individuals. The locus is located near a chromatin loop region that regulates ROBO1 and ROBO2 expression in induced pluripotent stem cell–derived neural crest cells. Furthermore, we use single nuclear RNA sequencing to demonstrate ROBO1 and ROBO2 expression in both fibroblasts and chondrocytes of the mature human pinna. Because the microtia allele is enriched in Amerindigenous populations and is shared by some East Asian subjects with craniofacial malformations, we propose that both populations share a mutation that arose in a common ancestor prior to the ancient migration of Eurasian populations into the Americas and that the high incidence of microtia among Amerindigenous populations reflects the population bottleneck that occurred during the migration out of Eurasia.
| S-EPMC9173816 | biostudies-literature
Project description:An ancient founder mutation located between ROBO1 and ROBO2 is responsible for increased microtia risk in Amerindigenous populations
| PRJNA836119 | ENA
Project description:An ancient founder mutation located between ROBO1 and ROBO2 is responsible for increased microtia risk in Amerindigenous populations (scRNA-Seq)
| PRJNA836121 | ENA
Project description:An ancient founder mutation located between ROBO1 and ROBO2 is responsible for increased microtia risk in Amerindigenous populations (RNA-Seq)
| PRJNA836122 | ENA
Project description:Imerslund-Gräsbeck syndrome (IGS) was described just over 50 years ago by Olga Imerslund and Ralph Gräsbeck and colleagues. IGS is caused by specific malabsorption of cobalamin (Cbl) due to bi-allelic mutations in either the cubilin gene (CUBN) or the human amnionless homolog (AMN). Mutations in the two genes are commonly seen in founder populations or in societies with a high degree of consanguineous marriages. One particular mutation in AMN, c.208-2A>G, causing an out-of-frame loss of exon 4 in the mRNA, is responsible for some 15% of IGS cases globally. We present evidence that this founder mutation causes a substantial percentage of cases among diverse ethnicities and that the mutation is as old as human civilization.Partial genotyping indicated a founder event but its presence in diverse peoples of Arabic, Turkish, Jewish, and Hispanic ancestry suggested that the mutation might be recurrent. We therefore studied the flanking sequence spanning 3.5 Mb to elucidate the origin of the haplotype and estimate the age of the mutation using a Bayesian inference method based on observed linkage disequilibrium.The mutation's distribution, the size of the shared haplotype, and estimates of growth rate and carrier frequency indicated that the mutation was a single prehistoric event. Dating back to the ancient Middle East around 11,600 BC, the mutation predates the advent of writing, farming, and the monotheistic religions of the region.This mutation causes over 50% of the IGS cases among Arabic, Turkish, and Sephardic Jewish families, making it a primary target for genetic screening among diverse IGS cases originating from the Middle East. Thus, rare founder mutations may cause a substantial number of cases, even among diverse ethnicities not usually thought to be related.
| S-EPMC3226546 | biostudies-literature
Project description:Ocular neovascular diseases are a leading cause of blindness. Vascular endothelial growth factor (VEGF) blockade improves vision, but not all individuals respond to anti-VEGF treatment, making additional means to prevent neovascularization necessary. Slit-family proteins (Slits) are ligands of Roundabout (Robo) receptors that repel developing axons in the nervous system. Robo1 expression is altered in ocular neovascular diseases, and previous in vitro studies have reported both pro- and anti-angiogenic effects of Slits. However, genetic evidence supporting a role for Slits in ocular neovascularization is lacking. Here we generated conditional knockout mice deficient in various Slit and Robo proteins and found that Slit2 potently and selectively promoted angiogenesis via Robo1 and Robo2 in mouse postnatal retina and in a model of ocular neovascular disease. Mechanistically, Slit2 acting through Robo1 and Robo2 promoted the migration of endothelial cells. These receptors are required for both Slit2- and VEGF-induced Rac1 activation and lamellipodia formation. Thus, Slit2 blockade could potentially be used therapeutically to inhibit angiogenesis in individuals with ocular neovascular disease.
| S-EPMC4819398 | biostudies-literature
Project description:Pioneer longitudinal axons grow long distances parallel to the floor plate and precisely maintain their positions using guidance molecules released from the floor plate. Two receptors, Robo1 and Robo2, are critical for longitudinal axon guidance by the Slit family of chemorepellents. Previous studies showed that Robo1(-/-);2(-/-) double mutant mouse embryos have disruptions in both ventral and dorsal longitudinal tracts. However, the role of each Robo isoform remained unclear, because Robo1 or 2 single mutants have mild or no errors. Here we utilized a more sensitive genetic strategy to reduce Robo levels for determining any separate functions of the Robo1 and 2 isoforms. We found that Robo1 is the predominant receptor for guiding axons in ventral tracts and prevents midline crossing. In contrast, Robo2 is the main receptor for directing axons within dorsal tracts. Robo2 also has a distinct function in repelling neuron cell bodies from the floor plate. Therefore, while Robo1 and 2 have some genetic overlap to cooperate in guiding longitudinal axons, each isoform has distinct functions in specific longitudinal axon populations.
| S-EPMC3171630 | biostudies-literature
Project description:During nervous system development, commissural axons cross the midline despite the presence of repellant ligands. In Drosophila, commissural axons avoid premature responsiveness to the midline repellant Slit by expressing the endosomal sorting receptor Commissureless, which reduces surface expression of the Slit receptor Roundabout1 (Robo1). In this study, we describe a distinct mechanism to inhibit Robo1 repulsion and promote midline crossing, in which Roundabout2 (Robo2) binds to and prevents Robo1 signaling. Unexpectedly, we find that Robo2 is expressed in midline cells during the early stages of commissural axon guidance, and that over-expression of Robo2 can rescue robo2-dependent midline crossing defects non-cell autonomously. We show that the extracellular domains required for binding to Robo1 are also required for Robo2's ability to promote midline crossing, in both gain-of-function and rescue assays. These findings indicate that at least two independent mechanisms to overcome Slit-Robo1 repulsion in pre-crossing commissural axons have evolved in Drosophila.
| S-EPMC4505356 | biostudies-literature