Immunofluorescence studies for myosin, α-actinin and tropomyosin in developing hearts of normal and cardiac lethal mutant Mexican axolotls, Ambystoma mexicanum

Development ◽  
1980 ◽  
Vol 55 (1) ◽  
pp. 1-15
Author(s):  
Larry F. Lemanski ◽  
Rebecca A. Fuldner ◽  
Daniel J. Paulson
Keyword(s):  
Heart Function ◽  
Mutant Gene ◽  
Progressive Increase ◽  
Ambystoma Mexicanum ◽  
Myocardial Cells ◽  
Lethal Mutant ◽  
Normal Cells ◽  
Immunofluorescence Studies ◽  
Recessive Mutant ◽  
Mutant Cells

Recessive mutant gene c in axolotl embryos results in an absence of normal heart function. Immunofluorescence studies were done to determine the distributions of myosin, tropomyosin and α-actinin in the hearts of normal and mutant siblings. Anti-myosin specifically stains the A bands of myofibrils in normal hearts and reveals a progressive increase in myofibril organization with development. Mutant hearts display less staining for myosin than normal and localization is mainly in amorphous collections. Anti-α-actinin stains the Z lines of myofibrils in normal myocytes. Mutant cells also have significant staining for α-actinin but show no striations. Antitropomyosin intensely stains the I bands of myofibrils in normal cells; however, there is very little staining for tropomyosin in mutant hearts. Thus, mutant myocardial cells have reduced but significant amounts of actin (Lemanski, Mooseker, Peachey & lyengar, 1976) and myosin, even though non-filamentous, and substantial amounts of α-actinin. The cells appear to contain little tropomyosin.

Myofibrillogenesis and Heart Induction in Cardiac Mutant Axolotls

1981 ◽  
Vol 39 ◽  
pp. 476-479
Author(s):  
Larry F. Lemanski
Keyword(s):  
Heart Function ◽  
Mutant Gene ◽  
Heart Beat ◽  
Ambystoma Mexicanum ◽  
Lethal Mutant ◽  
Initial Development ◽  
Biological Phenomena ◽  
Recessive Mutant ◽  
Heart Induction ◽  
Mutant Genes

Mutant genes have been used in the past as research ‘tools’ for better understanding selected biological phenomena and for solving certain biological problems. It is particularly exciting when these mutations affect specific major organs of vertebrates. One such naturally-occurring recessive mutant gene, designated c for ‘cardiac lethal’ was discovered recently in the Mexican axolotl, Ambystoma mexicanum. Homozygous embryos (c/c) exhibit a lack of heart Function even though initial development of the organ seems normal. Cardiac lethal mutant (c/c) embryos are obtained by mating heterozygous adults (+/c x +/c) and can first be distinguished from their normal (+/+ or +/c) siblings at stage 35 (one week postfertilization) when the normals develop vigorously contracting hearts. Mutant embryos at this stage appear grossly normal, but their hearts fail to contract and cardiovascular circulation is not established. In spite of their nonfunctional hearts, mutant embryos survive through stage 41 (about 20 days beyond the heart-beat stage) and during this time display normal swimming movements indicating that skeletal muscle is not affected by the mutation.

Morphological Observations on Anterior Endoderm in Cardiac Mutant Mexican Salamanders (Ambystoma Mexicanum)

1975 ◽  
Vol 33 ◽  
pp. 484-485
Author(s):  
Larry F. Lemanski ◽  
Barry S. Marx
Keyword(s):  
Heart Development ◽  
Mutant Gene ◽  
Heart Beat ◽  
Ambystoma Mexicanum ◽  
Myocardial Cells ◽  
Cardiac Defect ◽  
Ultrastructural Studies ◽  
Total Absence ◽  
Reciprocal Transplants ◽  
Recessive Mutant

Humphrey reported the discovery of a recessive mutant gene, designated c for "cardiac lethal" in a dark stock of axolotls, Ambystoma mexicanum, imported from Mexico by Dr. Louis DeLanney. Homozygous recessive embryos exhibit a total absence of heart contractions even though initial heart development appears normal. Ultrastructural studies indicate that the mutant hearts fail to contract because the myocardial cells lack organized myofibrils. In further studies, Humphrey performed transplants of mutant (c/c) heart primordia into the heart regions of normal (+/+) recipients and found the cardiac defect to be corrected. When reciprocal transplants were made, no heart beat was observed. It was further shown that parabiosis of normal embryos with mutant siblings did not correct the cardiac deficiency nor were the normal parabiotic twins adversely affected by this procedure; such conjoined animals lived for up to several months and the mutant twins, except for lacking a functional heart, appeared normal.

The Ultrastructure of Myocardial Cells in Normal and Cardiac Lethal Mutant Mexican Axolotls, (Ambystoma Mexicanum)

1970 ◽  
Vol 28 ◽  
pp. 62-63
Author(s):  
Larry F. Lemanski ◽  
Eldridge M. Bertke ◽  
J. T. Justus
Keyword(s):  
Fine Structure ◽  
Heart Development ◽  
Osmium Tetroxide ◽  
Picric Acid ◽  
Ambystoma Mexicanum ◽  
Recessive Mutation ◽  
Acid Mixture ◽  
Myocardial Cells ◽  
Lethal Mutant ◽  
Mexican Axolotl

A recessive mutation has been recently described in the Mexican Axolotl, Ambystoma mexicanum; in which the heart forms structurally, but does not contract (Humphrey, 1968. Anat. Rec. 160:475). In this study, the fine structure of myocardial cells from normal (+/+; +/c) and cardiac lethal mutant (c/c) embryos at Harrison's stage 40 was compared. The hearts were fixed in a 0.1 M phosphate buffered formaldehyde-glutaraldehyde-picric acid-styphnic acid mixture and were post fixed in 0.1 M s-collidine buffered 1% osmium tetroxide. A detailed study of heart development in normal and mutant embryos from stages 25-46 will be described elsewhere.

Accumulation and localization of troponin-T in developing hearts of Ambystoma mexicanum

Development ◽  
1984 ◽  
Vol 84 (1) ◽  
pp. 1-17
Author(s):  
Rebecca A. Fuldner ◽  
Soo-Siang Lim ◽  
Marion L. Greaser ◽  
Larry F. Lemanski
Keyword(s):  
Monoclonal Antibodies ◽  
Indirect Immunofluorescence ◽  
Gel Electrophoresis ◽  
Troponin T ◽  
Polyacrylamide Gel Electrophoresis ◽  
Protein Composition ◽  
Ambystoma Mexicanum ◽  
Striking Difference ◽  
Lethal Mutant ◽  
Mutant Cells

Troponin-T (Tn-T) expression in developing hearts of axolotls, Ambystoma mexicanum, was studied with the use of polyclonal and monoclonal antibodies and SDS-polyacrylamide gel electrophoresis. In precontractile hearts (stage 32/33), Tn-T was present in addition to myosin, actin and tropomyosin as evidenced by the presence of the protein bands in SDSgels and by indirect immunofluorescence. Tn-T was localized in amorphous collections at the peripheries of these precontractile cells. Hearts of normal and cardiac lethal mutant siblings were also analysed for Tn-T expression. No detectable differences in the quantity of protein present was observed by gel electrophoresis or by indirect immuno-fluorescence. The most striking difference concerned the localization of the protein. In normal hearts, Tn-T was primarily localized in the I-bands of organized myofibrils; however, in mutant cells the Tn-T was localized in amorphous collections at the cell peripheries suggesting a reduction of myofibrillar organization in these cells. No differences were observed in the contractile protein composition between normal and mutant em-bryonic hearts by gel electrophoresis experiments.

scholarly journals Role of tropomyosin in actin filament formation in embryonic salamander heart cells.

1979 ◽  
Vol 82 (1) ◽  
pp. 227-238 ◽  
Author(s):  
L F Lemanski
Keyword(s):  
Heart Development ◽  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Mutant Gene ◽  
Ambystoma Mexicanum ◽  
Heart Cells ◽  
Large Numbers ◽  
Recessive Mutant ◽  
Chicken Skeletal Muscle

Recessive mutant gene c in Ambystoma mexicanum embryos causes a failure of the heart to function even though initial heart development appears normal. An analysis of the constituent proteins of normal and mutant hearts by SDS-poly-acrylamide gel electrophoresis shows that actin (43,000 daltons) is present in almost normal amounts, while myosin heavy chain (200,000 daltons) is somewhat reduced in mutants. Both SDS-polyacrylamide gel electrophoresis and immunofluorescence studies reveal that tropomyosin is abundant in normal hearts, but very much reduced in mutants. Electron microscope studies of normal hearts show numerous well-organized myofibrils. Although mutant cardiomyocytes contain a few 60- and 150-A filaments, organized sacromeres are absent. Instead, amorphous proteinaceous collections are prominent. Previously reported heavy meromyosin (HMM)-binding experiments on glycerinated hearts demonstrate that most of the actin is contained within the amorphous collections in a nonfilamentous state, and the addition of HMM causes polymerization into F actin (Lemanski et al., 1976, J. Cell. Biol. 68:375-388). In the present study, glycerol-extracted hearts are incubated with tropomyosin, purified from rabbit or chicken skeletal muscle. This treatment causes the amorphous collections to disappear, and large numbers of distinct thin actin (60- to 80-A) filaments are seen in their place. Negative staining experiments corroborate this observation. These results suggest that the nonfilamentous actin located in the amorphous collections of mutant heart cells is induced to form into filaments with the addition of tropomyosin.

All-or-none craniorachischisis in Loop-tail mutant mouse chimeras

Development ◽  
1990 ◽  
Vol 110 (1) ◽  
pp. 229-237 ◽  
Author(s):  
T.S. Musci ◽  
R.J. Mullen
Keyword(s):  
Neural Tube ◽  
Mutant Gene ◽  
Mutant Phenotype ◽  
Progeny Testing ◽  
Wild Type ◽  
Glucose Phosphate ◽  
Threshold Mechanism ◽  
Mutant Cells ◽  
Intermediate Expression ◽  
Gross Examination

Mouse embryos homozygous for the mutant gene Loop-tail (Lp) are characterized by craniorachischisis, an open neural tube extending from the midbrain to the tail. In the present study, experimental chimeric mice containing mixtures of genetically mutant (from Lp/+ × Lp/+ matings) and genetically normal cells were produced. Our aim was to determine whether a ‘rescue,’ phenotypic gradient, or intermediate expression (i.e. alternating areas of open and closed neural tube) would be observed in these chimeras. We report our analyses of Loop-tail mutant chimeras (n = 82) by gross examination, progeny testing and quantitative analysis of glucose phosphate isomerase (GPI) isozyme levels. An all-or-none craniorachischisis in Loop-tail mutant chimeras was observed. Two multicolored adult chimeras, without any gross evidence of a neural tube defect, were shown to be homozygous Loop-tail chimeras (Lp/Lp in equilibrium +/+) by progeny testing. These results indicate that the normal phenotype can be expressed in the presence of mutant cells. Conversely, six neonates with craniorachischisis were shown to be chimeras by GPI analyses. These results show that the full mutant phenotype can be expressed even when one-third to one-half of the cells are genotypically wild-type. This study did not determine which tissue is primarily responsible for the defective neurulation in this mutant, but suggests that a ‘threshold’ mechanism underlies the Loop-tail mutant phenotype. In some chimeras that threshold is not reached and the neural tube remains open, whereas in other chimeras the threshold is reached and the neural tube closes completely.

Towards understanding paternal extragenic contributions to early amphibian pattern specification: the axolotl ts—1 gene as a model system

Development ◽  
1985 ◽  
Vol 89 (Supplement) ◽  
pp. 53-68
Author(s):  
George M. Malacinski ◽  
Dorothy Barone
Keyword(s):  
Genetic Data ◽  
Mutant Gene ◽  
Model System ◽  
Early Embryogenesis ◽  
Ambystoma Mexicanum ◽  
Parental Effects ◽  
Phenotypic Data ◽  
Modes Of Action ◽  
Pattern Specification ◽  
Made In

As a model system for understanding the role sperm extragenic components might play in early embryogenesis the genetics and phenotype of the ts—1 axolotl (Ambystoma mexicanum) mutant gene are reviewed. That mutant gene displays parental effects. It exhibits both maternal (egg-mediated) as well as paternal (sperm-mediated) phenotypic effects. A variety of possible modes of action of the ts—1 gene are reviewed. Comparisons of various precedents to the ts—1 genetic data are made. In addition, novel models which account for the ts—1 phenotypic data are presented.

Experimental studies on a mutant gene (p) causing premature death of Ambystoma mexicanum embryos

Development ◽  
1977 ◽  
Vol 39 (1) ◽  
pp. 139-149
Author(s):  
Thomas M. Trottier ◽  
John B. Armstrong
Keyword(s):  
Muscle Development ◽  
Experimental Studies ◽  
Circulatory System ◽  
Premature Death ◽  
Mutant Gene ◽  
Ambystoma Mexicanum ◽  
Recessive Lethal ◽  
Homozygous Condition ◽  
General Defect ◽  
Superficial Tissue

The premature death (p) mutation is a recessive lethal, which, in the homozygous condition, gives rise to a complex of abnormalities. The mutant embryos develop only to stage 37, at which time disintegration of superficial tissue begins. Many of the abnormalities observed in sections of the stage-37 mutant embryo are related to its failure to establish a functioning circulatory system, or to the resulting edema and/or ascites that distend the abdomen and flanks. There are, however, abnormalities of heart, liver, gill and muscle development which cannot be attributed to lack of circulation and edema. All of these abnormalities can be indirectly related to the endoderm, particularly the anterior and dorsal endoderm. The findings, therefore, suggest that the mutation leads to a fairly general defect of the endoderm.

The presence of synaptic and chromosome disjunction mutants in Cenchrus ciliaris (Poaceae: Paniceae)

Bothalia ◽  
1999 ◽  
Vol 29 (2) ◽  
pp. 327-334 ◽  
Author(s):  
N. C. Visser ◽  
J. J. Spies ◽  
H. J. T. Venter
Keyword(s):  
Environmental Factors ◽  
Geographical Distribution ◽  
High Temperatures ◽  
Chromosome Abnormality ◽  
Mutant Gene ◽  
Cenchrus Ciliaris ◽  
High Incidence ◽  
Low Humidity ◽  
Recessive Mutant ◽  
Chromosome Disjunction

Synaptic mutants are present in  Cenchrus ciliaris L This species, due to the presence of linear bivalents and occasion­al trivalents and quadrivalents, is an intermediate desynaptic species. In addition, geographical distribution and environmental factors, such as high temperatures and low humidity, could also have had an influence on the desynapsis observed.The disjunction of chromosomes during anaphase I was mostly abnormal in this desynaptic species. Precocious disjunction of chromosomes into chromatids occurred during anaphase I Due to the high incidence of this chromosome abnormality, a mutant gene,  'pc'  responsible for the disjunction of chromosomes, must be present. The absence of cytokinesis in one specimen indicates a recessive mutant gene,  'va' to be active in this species.

Sign in / Sign up

Export Citation Format

Share Document