scholarly journals A mutational analysis of the 5′ HoxD genes: dissection of genetic interactions during limb development in the mouse

Development ◽  
1996 ◽  
Vol 122 (4) ◽  
pp. 1175-1185 ◽  
Author(s):  
A.P. Davis ◽  
M.R. Capecchi
Keyword(s):  
Limb Development ◽  
Hox Genes ◽  
Mutational Analysis ◽  
Genetic Interactions ◽  
Carpal Bone ◽  
Evolutionary Adaptation ◽  
Limb Defects ◽  
Vertebrate Limb ◽  
Mutant Strains ◽  
The Individual

Using gene targeting in mice, we have undertaken a systematic mutational analysis of the homeobox-containing 5′ HoxD genes. In particular, we have characterized the limb defects observed in mice with independent targeted disruptions of hoxd-12 and hoxd-13. Animals defective for hoxd-12 are viable, fertile, and appear outwardly normal yet have minor autopodal defects in the forelimb which include a reduction in the bone length of metacarpals and phalanges, and a malformation of the distal carpal bone d4. The limb phenotypes observed in hoxd-13 mutant mice are more extensive, including strong reductions in length, complete absences, or improper segmentations of many metacarpal and phalangeal bones. Additionally, the d4 carpal bone is not properly formed and often produces an extra rudimentary digit. To examine the genetic interactions between the 5′ HoxD genes, we bred these mutant strains with each other and with our previously characterized hoxd-11 mouse to produce a series of trans-heterozygotes. Skeletal analyses of these mice reveal that these genes interact in the formation of the vertebrate limb, since the trans-heterozygotes display phenotypes not present in the individual heterozygotes, including more severe carpal, metacarpal and phalangeal defects. Some of these phenotypes appear to be accounted for by a delay in the ossification events in the autopod, which lead to either the failure of fusion or the elimination of cartilaginous elements. Characteristically, these mutations lead to the overall truncation of digits II and V on the forelimb. Additionally, some trans-animals show the growth of an extra postaxial digit VI, which is composed of a bony element resembling a phalange. The results demonstrate that these genes interact in the formation of the limb. In addition to the previously characterized paralogous interactions, a multitude of interactions between Hox genes is used to finely sculpt the forelimb. The 5′ Hox genes could therefore act as a major permissive genetic milieu that has been exploited by evolutionary adaptation to form the tetrapod limbs.

scholarly journals Biosynthetic Analysis of the Petrobactin Siderophore Pathway from Bacillusanthracis

2006 ◽  
Vol 189 (5) ◽  
pp. 1698-1710 ◽  
Author(s):  
Jung Yeop Lee ◽  
Brian K. Janes ◽  
Karla D. Passalacqua ◽  
Brian F. Pfleger ◽  
Nicholas H. Bergman ◽  
...  
Keyword(s):  
Mutational Analysis ◽  
Acyl Carrier Protein ◽  
Iron Acquisition ◽  
Culture Conditions ◽  
Growth Defect ◽  
Starting Point ◽  
Mutant Strains ◽  
The Individual ◽  
Vitro Analysis

ABSTRACT The asbABCDEF gene cluster from Bacillus anthracis is responsible for biosynthesis of petrobactin, a catecholate siderophore that functions in both iron acquisition and virulence in a murine model of anthrax. We initiated studies to determine the biosynthetic details of petrobactin assembly based on mutational analysis of the asb operon, identification of accumulated intermediates, and addition of exogenous siderophores to asb mutant strains. As a starting point, in-frame deletions of each of the genes in the asb locus (asbABCDEF) were constructed. The individual mutations resulted in complete abrogation of petrobactin biosynthesis when strains were grown on iron-depleted medium. However, in vitro analysis showed that each asb mutant grew to a very limited extent as vegetative cells in iron-depleted medium. In contrast, none of the B. anthracis asb mutant strains were able to outgrow from spores under the same culture conditions. Provision of exogenous petrobactin was able to rescue the growth defect in each asb mutant strain. Taken together, these data provide compelling evidence that AsbA performs the penultimate step in the biosynthesis of petrobactin, involving condensation of 3,4-dihydroxybenzoyl spermidine with citrate to form 3,4-dihydroxybenzoyl spermidinyl citrate. As a final step, the data reveal that AsbB catalyzes condensation of a second molecule of 3,4-dihydroxybenzoyl spermidine with 3,4-dihydroxybenzoyl spermidinyl citrate to form the mature siderophore. This work sets the stage for detailed biochemical studies with this unique acyl carrier protein-dependent, nonribosomal peptide synthetase-independent biosynthetic system.

The role of Hox genes during vertebrate limb development

2007 ◽  
Vol 17 (4) ◽  
pp. 359-366 ◽  
Author(s):  
Jozsef Zakany ◽  
Denis Duboule
Keyword(s):  
Limb Development ◽  
Hox Genes ◽  
Vertebrate Limb ◽  
Vertebrate Limb Development

scholarly journals Reciprocal Mouse and Human Limb Phenotypes Caused by Gain- and Loss-of-Function Mutations Affecting Lmbr1

Genetics ◽  
2001 ◽  
Vol 159 (2) ◽  
pp. 715-726
Author(s):  
Richard M Clark ◽  
Paul C Marker ◽  
Erich Roessler ◽  
Amalia Dutra ◽  
John C Schimenti ◽  
...  
Keyword(s):  
Limb Development ◽  
Chromosomal Region ◽  
Loss Of Function ◽  
Digit Number ◽  
Limb Defects ◽  
Major Locus ◽  
Preaxial Polydactyly ◽  
Vertebrate Limb ◽  
In Trans ◽  
Human Limb

Abstract The major locus for dominant preaxial polydactyly in humans has been mapped to 7q36. In mice the dominant Hemimelic extra toes (Hx) and Hammertoe (Hm) mutations map to a homologous chromosomal region and cause similar limb defects. The Lmbr1 gene is entirely within the small critical intervals recently defined for both the mouse and human mutations and is misexpressed at the exact time that the mouse Hx phenotype becomes apparent during limb development. This result suggests that Lmbr1 may underlie preaxial polydactyly in both mice and humans. We have used deletion chromosomes to demonstrate that the dominant mouse and human limb defects arise from gain-of-function mutations and not from haploinsufficiency. Furthermore, we created a loss-of-function mutation in the mouse Lmbr1 gene that causes digit number reduction (oligodactyly) on its own and in trans to a deletion chromosome. The loss of digits that we observed in mice with reduced Lmbr1 activity is in contrast to the gain of digits observed in Hx mice and human polydactyly patients. Our results suggest that the Lmbr1 gene is required for limb formation and that reciprocal changes in levels of Lmbr1 activity can lead to either increases or decreases in the number of digits in the vertebrate limb.

Genetic and developmental bases of serial homology in vertebrate limb evolution

Development ◽  
2000 ◽  
Vol 127 (24) ◽  
pp. 5233-5244 ◽  
Author(s):  
I. Ruvinsky ◽  
J.J. Gibson-Brown
Keyword(s):  
Limb Development ◽  
Molecular Mechanisms ◽  
Hox Genes ◽  
Single Gene ◽  
Genetic Data ◽  
Gene Families ◽  
The Body ◽  
Morphological Description ◽  
Developmental Systems ◽  
Vertebrate Limb

Two sets of paired appendages are a characteristic feature of the body plan of jawed vertebrates. While the fossil record provides a good morphological description of limb evolution, the molecular mechanisms involved in this process are only now beginning to be understood. It is likely that the genes essential for limb development in modern vertebrates were also important players during limb evolution. In recent years, genes from a number of gene families have been described that play important roles both in limb induction and in later patterning processes. These advances facilitate inquiries into several important aspects of limb evolution such as their origin, position along the body axis, number and identity. Integrating paleontological, developmental and genetic data, we propose models to explain the evolution of paired appendages in vertebrates. Whereas previous syntheses have tended to focus on the roles of genes from a single gene family, most notably Hox genes, we emphasize the importance of considering the interactions among multiple genes from different gene families for understanding the evolution of complex developmental systems. Our models, which underscore the roles of gene duplication and regulatory ‘tinkering’, provide a conceptual framework for elucidating the evolution of serially homologous structures in general, and thus contribute to the burgeoning field seeking to uncover the genetic and developmental bases of evolution.

Conserved and distinct roles of kreisler in regulation of the paralogous Hoxa3 and Hoxb3 genes

Development ◽  
1999 ◽  
Vol 126 (4) ◽  
pp. 759-769 ◽  
Author(s):  
M. Manzanares ◽  
S. Cordes ◽  
L. Ariza-McNaughton ◽  
V. Sadl ◽  
K. Maruthainar ◽  
...  
Keyword(s):  
Binding Sites ◽  
Hox Genes ◽  
Expression Patterns ◽  
Regulatory Elements ◽  
Enhancer Activity ◽  
Anteroposterior Patterning ◽  
Endogenous Gene ◽  
Transgenic Embryos ◽  
The Individual ◽  
Segmental Expression

During anteroposterior patterning of the developing hindbrain, the anterior expression of 3′ Hox genes maps to distinct rhombomeric boundaries and, in many cases, is upregulated in specific segments. Paralogous genes frequently have similar anterior boundaries of expression but it is not known if these are controlled by common mechanisms. The expression of the paralogous Hoxa3 and Hoxb3 genes extends from the posterior spinal cord up to the rhombomere (r) 4/5 boundary and both genes are upregulated specifically in r5. However, in this study, we have found that Hoxa3 expression is also upregulated in r6, showing that there are differences in segmental expression between paralogues. We have used transgenic analysis to investigate the mechanisms underlying the pattern of segmental expression of Hoxa3. We found that the intergenic region between Hoxa3 and Hoxa4 contains several enhancers, which summed together mediate a pattern of expression closely resembling that of the endogenous Hoxa3 gene. One enhancer specifically directs expression in r5 and r6, in a manner that reflects the upregulation of the endogenous gene in these segments. Deletion analysis localized this activity to a 600 bp fragment that was found to contain a single high-affinity binding site for the Maf bZIP protein Krml1, encoded by the kreisler gene. This site is necessary for enhancer activity and when multimerized it is sufficient to direct a kreisler-like pattern in transgenic embryos. Furthermore the r5/r6 enhancer activity is dependent upon endogenous kreisler and is activated by ectopic kreisler expression. This demonstrates that Hoxa3, along with its paralog Hoxb3, is a direct target of kreisler in the mouse hindbrain. Comparisons between the Krml1-binding sites in the Hoxa3 and Hoxb3 enhancers reveal that there are differences in both the number of binding sites and way that kreisler activity is integrated and restricted by these two control regions. Analysis of the individual sites revealed that they have different requirements for mediating r5/r6 and dorsal roof plate expression. Therefore, the restriction of Hoxb3 to r5 and Hoxa3 to r5 and r6, together with expression patterns of Hoxb3 in other vertebrate species suggests that these regulatory elements have a common origin but have later diverged during vertebrate evolution.

Genetic interactions and dosage effects of Polycomb group genes in mice

Development ◽  
1998 ◽  
Vol 125 (18) ◽  
pp. 3543-3551 ◽  
Author(s):  
S. Bel ◽  
N. Core ◽  
M. Djabali ◽  
K. Kieboom ◽  
N. Van der Lugt ◽  
...  
Keyword(s):  
Hox Genes ◽  
Expression Patterns ◽  
Axial Skeleton ◽  
Polycomb Group ◽  
Genetic Interactions ◽  
Homeotic Gene ◽  
Polycomb Group Genes ◽  
Dosage Effects ◽  
Somitic Mesoderm ◽  
Homeotic Gene Expression

In Drosophila and mouse, Polycomb group genes are involved in the maintenance of homeotic gene expression patterns throughout development. Here we report the skeletal phenotypes of compound mutants for two Polycomb group genes bmi1 and M33. We show that mice deficient for both bmi1 and M33 present stronger homeotic transformations of the axial skeleton as compared to each single Polycomb group mutant, indicating strong dosage interactions between those two genes. These skeletal transformations are accompanied with an enhanced shift of the anterior limit of expression of several Hox genes in the somitic mesoderm. Our results demonstrate that in mice the Polycomb group genes act in synergy to control the nested expression pattern of some Hox genes in somitic mesodermal tissues during development.

Sign in / Sign up

Export Citation Format

Share Document