Project description:A three-generation family with four patients affected by a mesomelic dysplasia was investigated for genome-wide DNA copy number variation profiles. This revealed a microduplication of a 1.0-Mb chromosomal segment at 2q31.1 spanning nine Homeo box D (HOXD) genes that co-segregated with the phenotype. Quantitative PCR analysis of a gene within this duplicated region showed consistent results. A phenotypically similar condition, mesomelic dysplasia Kantaputra type (MDKa; MIM 156232)[1], has also been mapped to this chromosomal region[2], raising the possibility that MDKa and the condition observed in this family may be allelic. three-generation family including four affected individuals and two unaffected individuals
Project description:A three-generation family with four patients affected by a mesomelic dysplasia was investigated for genome-wide DNA copy number variation profiles. This revealed a microduplication of a 1.0-Mb chromosomal segment at 2q31.1 spanning nine Homeo box D (HOXD) genes that co-segregated with the phenotype. Quantitative PCR analysis of a gene within this duplicated region showed consistent results. A phenotypically similar condition, mesomelic dysplasia Kantaputra type (MDKa; MIM 156232)[1], has also been mapped to this chromosomal region[2], raising the possibility that MDKa and the condition observed in this family may be allelic.
Project description:Some human families display severe shortening and bending of the radius and ulna, a condition referred to as mesomelic dysplasia. Many of these families contain chromosomal rearrangements at 2q31, where the human HOXD locus maps. In mice, the dominant X-ray-induced Ulnaless inversion of the HoxD gene cluster produces a similar phenotype suggesting that the same pathological mechanism is at work in humans and mice. A tentative hypothesis was proposed where the various alterations to the genomic structure of HOXD could translocate Hoxd13 near to proximal limb enhancers, leading to its deleterious gain-of-expression in the embryonic forelimb. We evaluated this hypothesis by engineering a ca. 1Mb large inversion including the HoxD gene cluster, in order to position Hoxd13 within a chromatin domain rich in proximal limb enhancers. We show that these enhancers contact and activate Hoxd13 in proximal cells, concomitant to the formation of a mesomelic dysplasia phenotype. A secondary mutation in the coding frame of the HOXD13 protein in-cis with the inversion completely rescued the limb alterations, demonstrating that ectopic HOXD13 is indeed the unique cause of this bone anomaly. Single cell expression analysis and evaluation of HOXD13 binding sites in cells from this ectopic expression domain suggests that the phenotype arises primarily by acting through genes normally controlled by HOXD13 in distal limb cells. Altogether, these results provide a conceptual and mechanistic framework to understand and unify the molecular origins of human mesomelic dysplasia associated with 2q31.
Project description:Some human families display severe shortening and bending of the radius and ulna, a condition referred to as mesomelic dysplasia. Many of these families contain chromosomal rearrangements at 2q31, where the human HOXD locus maps. In mice, the dominant X-ray-induced Ulnaless inversion of the HoxD gene cluster produces a similar phenotype suggesting that the same pathological mechanism is at work in humans and mice. A tentative hypothesis was proposed where the various alterations to the genomic structure of HOXD could translocate Hoxd13 near to proximal limb enhancers, leading to its deleterious gain-of-expression in the embryonic forelimb. We evaluated this hypothesis by engineering a ca. 1Mb large inversion including the HoxD gene cluster, in order to position Hoxd13 within a chromatin domain rich in proximal limb enhancers. We show that these enhancers contact and activate Hoxd13 in proximal cells, concomitant to the formation of a mesomelic dysplasia phenotype. A secondary mutation in the coding frame of the HOXD13 protein in-cis with the inversion completely rescued the limb alterations, demonstrating that ectopic HOXD13 is indeed the unique cause of this bone anomaly. Single cell expression analysis and evaluation of HOXD13 binding sites in cells from this ectopic expression domain suggests that the phenotype arises primarily by acting through genes normally controlled by HOXD13 in distal limb cells. Altogether, these results provide a conceptual and mechanistic framework to understand and unify the molecular origins of human mesomelic dysplasia associated with 2q31.
Project description:Some human families display severe shortening and bending of the radius and ulna, a condition referred to as mesomelic dysplasia. Many of these families contain chromosomal rearrangements at 2q31, where the human HOXD locus maps. In mice, the dominant X-ray-induced Ulnaless inversion of the HoxD gene cluster produces a similar phenotype suggesting that the same pathological mechanism is at work in humans and mice. A tentative hypothesis was proposed where the various alterations to the genomic structure of HOXD could translocate Hoxd13 near to proximal limb enhancers, leading to its deleterious gain-of-expression in the embryonic forelimb. We evaluated this hypothesis by engineering a ca. 1Mb large inversion including the HoxD gene cluster, in order to position Hoxd13 within a chromatin domain rich in proximal limb enhancers. We show that these enhancers contact and activate Hoxd13 in proximal cells, concomitant to the formation of a mesomelic dysplasia phenotype. A secondary mutation in the coding frame of the HOXD13 protein in-cis with the inversion completely rescued the limb alterations, demonstrating that ectopic HOXD13 is indeed the unique cause of this bone anomaly. Single cell expression analysis and evaluation of HOXD13 binding sites in cells from this ectopic expression domain suggests that the phenotype arises primarily by acting through genes normally controlled by HOXD13 in distal limb cells. Altogether, these results provide a conceptual and mechanistic framework to understand and unify the molecular origins of human mesomelic dysplasia associated with 2q31.
Project description:Some human families display severe shortening and bending of the radius and ulna, a condition referred to as mesomelic dysplasia. Many of these families contain chromosomal rearrangements at 2q31, where the human HOXD locus maps. In mice, the dominant X-ray-induced Ulnaless inversion of the HoxD gene cluster produces a similar phenotype suggesting that the same pathological mechanism is at work in humans and mice. A tentative hypothesis was proposed where the various alterations to the genomic structure of HOXD could translocate Hoxd13 near to proximal limb enhancers, leading to its deleterious gain-of-expression in the embryonic forelimb. We evaluated this hypothesis by engineering a ca. 1Mb large inversion including the HoxD gene cluster, in order to position Hoxd13 within a chromatin domain rich in proximal limb enhancers. We show that these enhancers contact and activate Hoxd13 in proximal cells, concomitant to the formation of a mesomelic dysplasia phenotype. A secondary mutation in the coding frame of the HOXD13 protein in-cis with the inversion completely rescued the limb alterations, demonstrating that ectopic HOXD13 is indeed the unique cause of this bone anomaly. Single cell expression analysis and evaluation of HOXD13 binding sites in cells from this ectopic expression domain suggests that the phenotype arises primarily by acting through genes normally controlled by HOXD13 in distal limb cells. Altogether, these results provide a conceptual and mechanistic framework to understand and unify the molecular origins of human mesomelic dysplasia associated with 2q31.
Project description:Some human families display severe shortening and bending of the radius and ulna, a condition referred to as mesomelic dysplasia. Many of these families contain chromosomal rearrangements at 2q31, where the human HOXD locus maps. In mice, the dominant X-ray-induced Ulnaless inversion of the HoxD gene cluster produces a similar phenotype suggesting that the same pathological mechanism is at work in humans and mice. A tentative hypothesis was proposed where the various alterations to the genomic structure of HOXD could translocate Hoxd13 near to proximal limb enhancers, leading to its deleterious gain-of-expression in the embryonic forelimb. We evaluated this hypothesis by engineering a ca. 1Mb large inversion including the HoxD gene cluster, in order to position Hoxd13 within a chromatin domain rich in proximal limb enhancers. We show that these enhancers contact and activate Hoxd13 in proximal cells, concomitant to the formation of a mesomelic dysplasia phenotype. A secondary mutation in the coding frame of the HOXD13 protein in-cis with the inversion completely rescued the limb alterations, demonstrating that ectopic HOXD13 is indeed the unique cause of this bone anomaly. Single cell expression analysis and evaluation of HOXD13 binding sites in cells from this ectopic expression domain suggests that the phenotype arises primarily by acting through genes normally controlled by HOXD13 in distal limb cells. Altogether, these results provide a conceptual and mechanistic framework to understand and unify the molecular origins of human mesomelic dysplasia associated with 2q31.