Mutant

About: Mutant is a research topic. Over the lifetime, 74520 publications have been published within this topic receiving 3477079 citations.

Evidence for a critical contribution of haploinsufficiency in the complex pathogenesis of Marfan syndrome

Abstract: Marfan syndrome is a connective tissue disorder caused by mutations in the gene encoding fibrillin-1 (FBN1) A dominant-negative mechanism has been inferred based upon dominant inheritance, mulitimerization of monomers to form microfibrils, and the dramatic paucity of matrix-incorporated fibrillin-1 seen in heterozygous patient samples Yeast artificial chromosome–based transgenesis was used to overexpress a disease-associated mutant form of human fibrillin-1 (C1663R) on a normal mouse background Remarkably, these mice failed to show any abnormalities of cellular or clinical phenotype despite regulated overexpression of mutant protein in relevant tissues and developmental stages and direct evidence that mouse and human fibrillin-1 interact with high efficiency Immunostaining with a human-specific mAb provides what we believe to be the first demonstration that mutant fibrillin-1 can participate in productive microfibrillar assembly Informatively, use of homologous recombination to generate mice heterozygous for a comparable missense mutation (C1039G) revealed impaired microfibrillar deposition, skeletal deformity, and progressive deterioration of aortic wall architecture, comparable to characteristics of the human condition These data are consistent with a model that invokes haploinsufficiency for WT fibrillin-1, rather than production of mutant protein, as the primary determinant of failed microfibrillar assembly In keeping with this model, introduction of a WT FBN1 transgene on a heterozygous C1039G background rescues aortic phenotype

Zinc metalloproteinase, ZMPSTE24, is mutated in mandibuloacral dysplasia.

Abstract: Mandibuloacral dysplasia (MAD; OMIM 248370) is a rare, genetically and phenotypically heterogeneous, autosomal recessive disorder characterized by skeletal abnormalities including hypoplasia of the mandible and clavicles, acro-osteolysis, cutaneous atrophy and lipodystrophy. A homozygous missense mutation, Arg527His, in the LMNA gene which encodes nuclear lamina proteins lamins A and C has been reported in patients with MAD and partial lipodystrophy. We studied four patients with MAD who had no mutations in the LMNA gene. We now show compound heterozygous mutations, Phe361fsX379 and Trp340Arg, in the zinc metalloproteinase (ZMPSTE24) gene in one of the four patients who had severe MAD associated with progeroid appearance and generalized lipodystrophy. ZMPSTE24 is involved in post-translational proteolytic cleavage of carboxy terminal residues of farnesylated prelamin A in two steps to form mature lamin A. Deficiency of Zmpste24 in mice causes accumulation of prelamin A and phenotypic features similar to MAD. The yeast homolog, Ste24, has a parallel role in processing of prenylated mating pheromone a-factor. Since human ZMPSTE24 can also process a-factor when expressed in yeast, we assessed the functional significance of the two ZMPSTE24 mutations in the yeast to complement the mating defect of the haploid MATa yeast lacking STE24 and Ras-converting enzyme 1 (RCE1; another prenylprotein-specific endoprotease) genes. The ZMPSTE24 mutant construct, Phe361fsX379, was inactive in complementing the yeast a-factor but the mutant, Trp340Arg, was partially active compared to the wild type ZMPSTE24 construct. We conclude that mutations in ZMPSTE24 may cause MAD by affecting prelamin A processing.

Mutations in the AXR3 gene of Arabidopsis result in altered auxin response including ectopic expression from the SAUR‐AC1 promoter

Abstract: A new auxin response gene in Arabidopsis called AXR3 has been identified. This gene is defined by two semi-dominant mutations which affect many auxin-regulated developmental processes. Auxin has been shown to maintain apical dominance, inhibit root elongation, stimulate adventitious rooting, mediate root gravitropism, and stimulate transcription from the SAUR-AC1 promoter. Mutant axr3 plants show enhanced apical dominance, reduced root elongation, increased adventitious rooting, no root gravitropism, and ectopic expression from the SAUR-AC1 promoter. These phenotypes suggest an increased auxin response in the mutants. In support of this hypothesis, many of the phenotypes are partially restored to wild-type by exogenous cytokinin, a treatment that could restore a more wild-type auxin to cytokinin ratio.

A directional strategy for monitoring Cre-mediated recombination at the cellular level in the mouse

Abstract: Functional redundancies, compensatory mechanisms, and lethal phenotypes often prevent the full analysis of gene functions through generation of germline null mutations in the mouse The use of site-specific recombinases, such as Cre, which catalyzes recombination between loxP sites, has allowed the engineering of mice harboring targeted somatic mutations, which are both temporally controlled and cell-type restricted Many Cre-expressing mouse lines exist, but only a few transgenic lines are available that harbor a reporter gene whose expression is dependent on a Cre-mediated event Moreover, their use to monitor gene ablation at the level of individual cells is often limited, as in some tissues the reporter gene may be silenced, be affected by position-effect variegation, or reside in a chromatin configuration inaccessible for recombination Thus, one cannot validly extrapolate from the expression of a reporter transgene to an identical ablation pattern for the conditional allele of a given gene By combining the ability of Cre recombinase to invert or excise a DNA fragment, depending on the orientation of the flanking loxP sites, and the availability of both wild-type (WT) and mutant loxP sites, we designed a Cre-dependent genetic switch (FLEx switch) through which the expression of a given gene is turned off, while the expression of another one is concomitantly turned on We demonstrate the efficiency and reliability of this switch to readily detect, in the mouse, at the single cell level, Cre-mediated gene ablation We discuss how this strategy can be used to generate genetic modifications in a conditional manner