Autophagy in a Mouse Model of Distal Myopathy with Rimmed Vacuoles or Hereditary Inclusion Body Myopathy

Distal myopathy with rimmed vacuoles (DMRV) or hereditary inclusion body myopathy (hIBM) is an autosomal recessive disorder clinically characterized by weakness that initially involves the distal muscles, although other muscles can be affected as well. Pathological hallmarks include the presence of rimmed vacuoles (RVs) and intracellular Congo red-positive depositions in vacuolated or non-vacuolated fibers. Mutations in the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) gene, which encodes the rate-limiting enzyme in sialic acid biosynthesis, are causative of DMRV/hIBM. Recently, we have generated a mouse model (Gne^-/-hGNEV572L-Tg ) for this disease, and have shown that these mice exhibit hyposialylation and intracellular amyloid deposition before the characteristic RVs are detected, indicating that autophagy is a downstream phenomenon to hyposialylation and amyloid deposition in DMRV/hIBM.

Addendum to:

A Gne Knockout Mouse Expressing Human V572L Mutation Develops Features Similar to Distal Myopathy with Rimmed Vacuoles or Hereditary Inclusion Body Myopathy

M.C. Malicdan, S. Noguchi, I. Nonaka, Y.K. Hayashi and I. Nishino

Hum Mol Genet 2007; 16:115-28     

Generation of precise point mutation mice by footprintless genome modification

Point mutation mice are a key tool in the study of biological functions of genomic DNA sequences and the creation of human disease models. These mice are produced by homologous recombination combined with site‐specific recombinase, which allows removal of drug selection cassettes. However, the methods currently available leave ectopic sequences in the “inactive” intron region of the targeted genome in addition to the desired mutation. Since recent research suggests that the intron region may actually have some functionality, these sequences could potentially interfere with neighboring gene expression and, as a result, affect the mouse phenotype. To completely avoid this issue, we used the PiggyBac transposon to remove selection cassettes and achieve precise genome modification without leaving behind a footprint. This PiggyBac system allowed us to successfully generate mice carrying an artificially introduced W^v point mutation in the Kit gene, and these mice were confirmed to have phenotypes identical to spontaneous W^v mutation mice. Generation of W^v‐mutation corrected mice was also possible, and phenotypes were completely restored. Our footprintless genome modification technology can generate precise point mutation mice with only the desired mutation, and they reflect an accurate phenotype that makes these mice a reliable and “worry‐free” research resource. 52:68–77, 2014. © 2013 Wiley Periodicals, Inc.     

Decrease in pool of T lymphocytes with surface phenotypes of effector and central memory cells under Influence of TCR transgenic β-chain expression

Peripheral T lymphocytes can be subdivided into naive and antigen-experienced T cells. The latter, in turn, are represented by effector and central memory cells that are identified by different profiles of activation markers expression, such as CD44 and CD62L in mice. These markers determine different traffic of T lymphocytes in the organism, but hardly reproduce real antigenic experience of a T lymphocyte. Mechanisms of homeostasis maintenance of T lymphocytes with different activation phenotypes remain largely unknown. To investigate impact of T cell receptor (TCR) transgenic chains on formation of T lymphocytes, their peripheral survival and activation surface phenotypes, we have generated the transgenic mouse strain expressing transgenic β-chain of TCR 1D1 (belonging to the Vβ6 family) on the genetic background B10.D2(R101). Intrathymic development of T cells in these transgenic mice is not impaired. The repertoire of peripheral T lymphocytes in these mice contains 70–80% of T cells expressing transgenic β-chain and 20–30% of T cells expressing endogenous β-chains. The ratio of peripheral CD4⁺CD8^? and CD4^?CD8⁺ T lymphocytes remained unchanged in the transgenic animals, but the percent of T lymphocytes with the “naive” phenotype CD44^?CD62L⁺ was significantly increased, whereas the levels of effector memory CD44⁺CD62L^? and central memory CD44⁺CD62L⁺ T lymphocytes were markedly decreased in both subpopulations. On the contrary, T lymphocytes expressing endogenous β-chains had surface phenotype of activated T cells CD44⁺. Thus, for the first time we have shown that the pool of T lymphocytes with different activation phenotypes depends on the structure of T cell receptors.     

Characterization of Mutations at the Mouse Phenylalanine Hydroxylase Locus

Two genetic mouse models for human phenylketonuria have been characterized by DNA sequence analysis. For each, a distinct mutation was identified within the protein coding sequence of the phenylalanine hydroxylase gene. This establishes that the mutated locus is the same as that causing human phenylketonuria and allows a comparison between these mouse phenylketonuria models and the human disease. A genotype/phenotype relationship that is strikingly similar to the human disease emerges, underscoring the similarity of phenylketonuria in mouse and man. InPAH^ENU1,the phenotype is mild. ThePah^enu1mutation predicts a conservative valine to alanine amino acid substitution and is located in exon 3, a gene region where serious mutations are rare in humans. InPAH^ENU2,the phenotype is severe. ThePah^enu2mutation predicts a radical phenylalanine to serine substitution and is located in exon 7, a gene region where serious mutations are common in humans. InPAH^ENU2,the sequence information was used to devise a direct genotyping system based on the creation of a newAlw26I restriction endonuclease site.     

EMS-induced mutant frequency and spectrum in bone marrow of D6-2 transgenic mice

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YAC rescue of downless locus mutations in mice

Mice with mutations at the downless (dl) locus have defects in hair follicle, tooth, sweat gland, preputial gland, Meibomian gland, and tail development. The dl phenotype is analogous to the human genetic disorder termed autosomal hypohidrotic (or anhidrotic) ectodermal dysplasia (HED). On the basis of the identification of two related transgenic insertional mutations in the downless gene, yeast artificial chromosomes (YACs) were identified that map to the critical region of mouse Chromosome (Chr) 10. To determine which of the YACs contain the dl gene, we generated YAC transgenic mice by mouse embryo microinjections. The 200-kb YAC B25.D9 was found to rescue all of the downless defects. In addition, the transgenic YAC rescued the dominant Sleek (Dl ^slk ) allele. Since the sequences within the YAC are entirely deleted in one of the transgenic mutants, our results establish that Sleek encodes a dominant-negative protein whose effects can be reversed by expression of extra copies of the wild-type locus. Received: 26 June 1998 / Accepted: 17 July 1998     

Disappearance of polycystic kidney disease in revertant c-myc transgenic mice

Nineteen SBM transgenic mouse lines specifically expressing the c-myc protooncogene in renal epithelium have developed polycystic kidney disease (PKD). Transgene expression is completely penetrant, leading to death from renal failure. In the course of continuous breeding of eight transgenic lines, all lines underwent spontaneous transgene mutations characterized by partial deletion and probable rearrangement of the transgene insert. Revertant mice and their progeny have no evidence of renal disease. This constitutes the first report of spontaneous mutations occurring within transgene inserts. The high spontaneous mutation frequency of 10^-2 to 10^-3 greatly exceeds that of naturally occurring mutations and is probably favored by the transgene's multiple tandem insertion. These spontaneous mutations demonstrate that the intact transgene is necessary and sufficient to produce the SBM phenotype. Further, these results implicate deregulation of factor(s) governing epithelial cell proliferation in the pathogenesis of PKD in SBM mice.     

Physical Characterization of the Chromosomal Rearrangements That Accompany the Transgene Insertion in thechakragatiMouse Mutant

The circling phenotype of thechakragatimouse is a result of a transgenic insertional mutation. The absence of the phenotype in mice heterozygous for the transgene insertion suggests that this is due to a loss of function of an endogenous gene. Efforts to identify this gene have led to a previous report that sequences flanking the transgene,D16Ros1andD16Ros2,map 10 cM apart in wildtype mice. We present here physical mapping data indicating that the proximity ofD16Ros1andD16Ros2in theckrmouse is explained by a duplication ofD16Ros2and its insertion along with the transgene atD16Ros1.We further demonstrate thatD16Ros1sequences are also duplicated and that this duplication is also part of the insertion at the endogenousD16Ros1locus.     

Role of Autophagy in Breast Cancer

Autophagy is an evolutionarily conserved process of cytoplasm and cellular organelle degradation in lysosomes. Autophagy is a survival pathway required for cellular viability during starvation; however, if it proceeds to completion, autophagy can lead to cell death. In neurons, constitutive autophagy limits accumulation of polyubiquitinated proteins and prevents neuronal degeneration. Therefore, autophagy has emerged as a homeostatic mechanism regulating the turnover of long-lived or damaged proteins and organelles, and buffering metabolic stress under conditions of nutrient deprivation by recycling intracellular constituents. Autophagy also plays a role in tumorigenesis, as the essential autophagy regulator beclin1 is monoallelically deleted in many human ovarian, breast, and prostate cancers, and beclin1^+/- mice are tumor-prone. We found that allelic loss of beclin1 renders immortalized mouse mammary epithelial cells susceptible to metabolic stress and accelerates lumen formation in mammary acini. Autophagy defects also activate the DNA damage response in vitro and in mammary tumors in vivo, promote gene amplification, and synergize with defective apoptosis to accelerate mammary tumorigenesis. Thus, loss of the prosurvival role of autophagy likely contributes to breast cancer progression by promoting genome damage and instability. Exploring the yet unknown relationship between defective autophagy and other breast cancer-promoting functions may provide valuable insight into the pathogenesis of breast cancer and may have significant prognostic and therapeutic implications for breast cancer patients.

Addendum to:

Autophagy Mitigates Metabolic Stress and Genome Damage in Mammary Tumorigenesis

V. Karantza-Wadsworth, S. Patel, O. Kravchuk, G. Chen, R. Mathew, S. Jin and E. White

Genes Dev 2007; 21:1621-35     

Vimentin: the conundrum of the intermediate filament gene family

Intermediate filaments are a major component of the “cytoskeleton” of “higher” eukaryotes. These filaments are composed of a number of different, although structurally related, proteins. Different intermediate filament protein genes are expressed in different tissues. Spontaneous and experimentally produced mutations in the intermediate filament genes indicate that these filaments function to enhance the mechanical stability of epidermal and muscle cells. As a result, the use of transgenic mice with “knockout” or dominant negative mutations in IF genes has become an important approach for investigating the significance of IFs in other cell types. However, a knockout mutation of vimentin (^-/-), the intermediate filament protein characteristically expressed in cells of mesenchymal origin, results in very subtle phenotypes that are not obviously related to cell fragility. Although experiments with cultured cells have described a variety of discrete changes in cell properties that are associated with vimentin expression or organization, there is no evidence yet that any of these properties are affected in the vimentin^-/- mouse. BioEssays 20:79–86, 1998. © 1998 John Wiley & Sons, Inc.     

A new mouse model for infantile neuroaxonal dystrophy,inad mouse, maps to mouse Chromosome 1

Infantile neuroaxonal dystrophy (INAD) is a rare autosomal recessive hereditary neurodegenerative disease of humans. So far, no responsible gene has been cloned or mapped to any chromosome. For chromosome mapping and positional cloning of the responsible gene, establishment of an animal model would be useful. Here we describe a new mouse model for INAD, named inad mouse. In this mouse, the phenotype is inherited in an autosomal recessive manner, symptoms occur in the infantile period, and the mouse dies before sexual maturity. Axonal dystrophic change appearing as spheroid bodies in central and peripheral nervous system was observed. These features more closely resembled human INAD than did those of the gad mouse, the traditional mouse model for INAD. Linkage analysis linked the inad gene to mouse Chromosome 1, with the highest LOD score (=128.6) at the D1Mit45 marker, and haplotype study localized the inad gene to a 7.5-Mb region between D1Mit84 and D1Mit25. In this linkage area some 60 genes exist: Mutation of one of these 60 genes is likely responsible for the inad mouse phenotype. Our preliminary mutation analysis in 15 genes examining the nucleotide sequence of exons of these genes did not find any sequence difference between inad mouse and C57BL/6 mouse.     

Characterization of Two Human Skeletal Calsequestrin Mutants Implicated in Malignant Hyperthermia and Vacuolar Aggregate Myopathy

Calsequestrin 1 is the principal Ca²⁺ storage protein of the sarcoplasmic reticulum of skeletal muscle. Its inheritable D244G mutation causes a myopathy with vacuolar aggregates, whereas its M87T “variant” is weakly associated with malignant hyperthermia. We characterized the consequences of these mutations with studies of the human proteins in vitro. Equilibrium dialysis and turbidity measurements showed that D244G and, to a lesser extent, M87T partially lose Ca²⁺ binding exhibited by wild type calsequestrin 1 at high Ca²⁺ concentrations. D244G aggregates abruptly and abnormally, a property that fully explains the protein inclusions that characterize its phenotype. D244G crystallized in low Ca²⁺ concentrations lacks two Ca²⁺ ions normally present in wild type that weakens the hydrophobic core of Domain II. D244G crystallized in high Ca²⁺ concentrations regains its missing ions and Domain II order but shows a novel dimeric interaction. The M87T mutation causes a major shift of the α-helix bearing the mutated residue, significantly weakening the back-to-back interface essential for tetramerization. D244G exhibited the more severe structural and biophysical property changes, which matches the different pathophysiological impacts of these mutations.     

Gtl2 lacZ,an insertional mutation on mouse Chromosome 12 with parental origin-dependent phenotype

We have produced a transgenic mouse line, Gtl2 ^lacZ (Gene trap locus 2), that carries an insertional mutation with a dominant modified pattern of inheritance:heterozygous Gtl2 ^lacZ mice that inherited the transgene from the father show a proportionate dwarfism phenotype, whereas the penetrance and expressivity of the phenotype is strongly reduced in Gtl2 ^lacZ mice that inherited the transgene from the mother. On a mixed genetic background this pattern of inheritance was reversible upon transmission of the transgene through the germ line of the opposite sex. On a predominantly 129/Sv genetic background, however, transgene passage through the female germ line modified the transgene effect, such that the penetrance of the mutation was drastically reduced and the phenotype was no longer obvious after subsequent male germ line transmission. Expression of the transgene, however, was neither affected by genetic background nor by parental legacy. Gtl2 ^lacZ maps to mouse Chromosome 12 in a region that displays imprinting effects associated with maternal and paternal disomy. Our results suggest that the transgene insertion in Gtl2 ^lacZ mice affects an endogenous gene(s) required for fetal and postnatal growth and that this gene(s) is predominantly paternally expressed. Received: 30 May 1995 / Accepted: 7 August 1995     

Transgenic Fatal Familial Insomnia Mice Indicate Prion Infectivity-Independent Mechanisms of Pathogenesis and Phenotypic Expression of Disease

Fatal familial insomnia (FFI) and a genetic form of Creutzfeldt-Jakob disease (CJD¹⁷⁸) are clinically different prion disorders linked to the D178N prion protein (PrP) mutation. The disease phenotype is determined by the 129 M/V polymorphism on the mutant allele, which is thought to influence D178N PrP misfolding, leading to the formation of distinctive prion strains with specific neurotoxic properties. However, the mechanism by which misfolded variants of mutant PrP cause different diseases is not known. We generated transgenic (Tg) mice expressing the mouse PrP homolog of the FFI mutation. These mice synthesize a misfolded form of mutant PrP in their brains and develop a neurological illness with severe sleep disruption, highly reminiscent of FFI and different from that of analogously generated Tg(CJD) mice modeling CJD¹⁷⁸. No prion infectivity was detectable in Tg(FFI) and Tg(CJD) brains by bioassay or protein misfolding cyclic amplification, indicating that mutant PrP has disease-encoding properties that do not depend on its ability to propagate its misfolded conformation. Tg(FFI) and Tg(CJD) neurons have different patterns of intracellular PrP accumulation associated with distinct morphological abnormalities of the endoplasmic reticulum and Golgi, suggesting that mutation-specific alterations of secretory transport may contribute to the disease phenotype.     

Electrophoretic heterogeneity of mouse erythrocyte peptidases

Starch gel electrophoresis in conjunction with a specific staining method revealed the occurrence of five distinct peptidases in mouse red blood cells. These enzymes can be distinguished on the basis of substrate specificity and electrophoretic mobility. They have been designated peptidases A, B, C, D, and E to correspond with the nomenclature adopted for human peptidases with which the mouse enzymes appear to be homologous. Genetically determined variants of peptidase C are described. The phenotype Pep C1 occurs in C57BL/Gr mice and the phenotype Pep C2 in CBA/Gr and Strong A/Gr mice. These phenotypes and the presumed heterozygote, Pep C2-1, appear to be due to the occurrence of codominant autosomal alleles which have been designated Pep-C ¹ and Pep-C ². F₁ and F₂ crosses show segregation in the expected Mendelian ratios. F₂ embryos and their placentae show the same electrophoretic pattern for peptidase C. The occurrence of a separate locus controlling the structure of each distinct peptidase is postulated.     

Sharing of an HLA-B27-restricted H-Y antigen between rat and mouse

The purpose of this work was twofold: 1 to learn whether rats transgenic for HLA-B27 and the human ₂-microglobulin gene HB2M can mount B27-restricted cytolytic T lymphocyte (CTL) responses to the male H-Y antigen, and 2 to learn whether such CTLs would recognize both rat and mouse H-Y in the context of HLA-B27. Female rats of the B27/HB2M transgenic line 21-4L were primed in vivo with cells from males of the same line. CTL effectors were generated from lymph node cells of these females following culture with irradiated antigen-presenting cells from either male 21-4L rats or male mice of the B27/HB2M transgenic 56-3 line. The CTLs showed male-specific, B27-specific lysis of both rat and mouse targets. Lysis of B27 targets was inhibitable by monoclonal antibodies specific for B27 or rat CD8. Specific lysis of male B27 rat and mouse targets was inhibitable equally by either rat or mouse male B27 cold targets, but not significantly by female or nontransgenic cold targets. The B27-restricted CTLs neither recognized nor were inhibited by B27⁺ or B27^- male or female human targets. These results demonstrate that CD8⁺, B27-restricted, anti-H-Y CTLs recognize and evolutionarily conserved H-Y peptide antigen in both rats and mice. In addition, they establish the transgenic rat as a model system for examining the T-cell response to antigen presented by class I HLA molecules. Correspondence to: J. D. Taurog.