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K Chada

Publications and source records attributed to K Chada.

At least 19 recordsLinked to original sources
PubMed2000

In vivo modulation of Hmgic reduces obesity.

The HMGI family of proteins consists of three members, HMGIC, HMGI and HMGI(Y), that function as architectural factors and are essential components of the enhancesome. HMGIC is predominantly expressed in proliferating, undifferentiated mesenchymal cells and is not detected in adult tissues. It is disrupted and misexpressed in a number of mesenchymal tumour cell types, including fat-cell tumours (lipomas). In addition Hmgic-/- mice have a deficiency in fat tissue. To study its role in adipogenesis and obesity, we examined Hmgic expression in the adipose tissue of adult, obese mice. Mice with a partial or complete deficiency of Hmgic resisted diet-induced obesity. Disruption of Hmgic caused a reduction in the obesity induced by leptin deficiency (Lepob/Lepob) in a gene-dose-dependent manner. Our studies implicate a role for HMGIC in fat-cell proliferation, indicating that it may be an adipose-specific target for the treatment of obesity.

Adipose Tissue↗
PubMed1998

Preferential expression of HMGI-C isoforms lacking the acidic carboxy terminal in human leukemia.

The high mobility group HMGI chromosomal proteins are an important component of chromatin. The HMGI-C protein consists of three amino terminal DNA binding domains ("AT hooks"), a linker region and an acidic carboxy domain. In mesenchymal tumors, chromosomal translocations of 12q13-15 result in fusion proteins containing the AT hooks and novel carboxy terminals. We have investigated the status of the HMGI-C gene in two cases of leukemia with anomalies of chromosome 12q and identified three novel isoforms (designated alpha, beta and gamma) derived from alternate splicing. One of the patients expressed all three isoforms, whereas the second patient expressed only the gamma isoform; preferential expression of the HMGI-C gamma isoform was also detected in the leukemic cell lines ML3 and BV173. The results are consistent with a crucial role for truncation of the acidic carboxy domain of HMGI-C in abnormal growth.

Alternative Splicing↗
PubMed1998

HMGI family proteins: architectural transcription factors in mammalian development and cancer.

The HMGI proteins, a subfamily of the high mobility group (HMG) proteins, play an important role in the regulation of gene expression. They bind to AT-rich DNA sequences and alter DNA conformation to modulate the binding affinity of transcription factors to their cognate sites. They are expressed almost exclusively during embryogenesis and Hmgi-c null mice have the mouse pygmy phenotype. Studies have revealed the disruption of HMGI family genes in a variety of mesenchymal-derived benign tumors. Therefore, the HMGI genes function in the coordination of cell proliferation and differentiation during mammalian development.

Amino Acid Sequence↗
PubMed1997

Tissue, temporal and inducible expression pattern of haptoglobin in mice.

Haptoglobin (Hp) is a member of the acute phase plasma proteins previously thought to be synthesized solely by the adult liver. The present study analyzes the tissue and temporal expression pattern of endogenous haptoglobin in the mouse and acute phase inducibility in various tissues. The liver is found to be the major site of haptoglobin expression but significant expression levels were also observed in the lung and skin. Acute phase induction by bacterial lipopolysaccharide (LPS) demonstrated that haptoglobin was induced not only in the liver but also in other tissues, including lung, skin, spleen, and kidney. Temporal analyses demonstrated that haptoglobin is expressed during embryogenesis in the liver and is inducible in various tissues surveyed throughout development. Transgenic mice that harbored a 1.05-kilobase (kb) region of the human haptoglobin promoter linked to two different reporter genes gave rise to lung-specific expression in the majority of transgenic lines with minimal liver expression. However, when induced with lipopolysaccharide, the 1.05-kb fragment contained the necessary elements for a response comparable to endogenous expression levels. In conclusion, these studies demonstrate that haptoglobin is not an adult liver specific gene, and its role as an acute phase reactant may well be more diverse than previously suspected.

Acute-Phase Reaction↗
PubMed1996

Genomic structure and expression of the murine Hmgi-c gene.

The murine Hmgi-c gene, a member of the Hmgi gene family, contains five exons encompassing >110 kb of genomic DNA at the pygmy locus on mouse chromosome 10. Northern analysis identified a 4.1 kb transcript which contains a 324 bp open reading frame encoding a 12 kDa HMGI-C protein. Further analysis defined both the 5' and 3' untranslated regions of the Hmgi-c mRNA species as 658 and 2967 bp respectively. The HMGI-C protein has three consecutive AT hook DNA binding domains and an acidic domain, each of which are encoded by individual exons; such an organization is conserved among the HMGI gene family members from insects to mammals. Similar to the HMGI/Y proteins, the HMGI-C protein does not function as a typical transcriptional activator. Developmental studies revealed that the Hmgi-c gene is expressed predominantly during mouse embryogenesis. Since the human homolog is disrupted in a number of tumors, HMGI-C could play an important role in cell proliferation and differentiation during mammalian development.

Amino Acid Sequence↗
PubMed1996

Genomic characterization of human HMGIC, a member of the accessory transcription factor family found at translocation breakpoints in lipomas.

HMGIC, a member of the HMGI family of high mobility group proteins, is disrupted in 3/3 lipomas characterized by 12q14-q15 rearrangements. To define the genomic structure of the HMGIC gene, YACs from the HMGIC locus were identified and subcloned in lambda FIXII, and genomic lambda clones containing the HMGIC exons were isolated. The HMGIC gene consists of five exons that span at least 60 kb and encodes a 4.1-kb transcript. The coding region is 330 bp, the 5'UTR is 854 bp, and the 3'UTR is 2966 bp. Intron 3, which separates the DNA-binding domains from the acidic domain, is unusually large ( > 25 kb) and is the site of disruption in lipomas with 12q14-q15 translocations. The genomic organization of HMGIC should further our understanding of the 12q14-q15 region, where other neoplasms of mesenchymal origin are also mapped.

Animals↗
PubMed1996

Translocation breakpoints upstream of the HMGIC gene in uterine leiomyomata suggest dysregulation of this gene by a mechanism different from that in lipomas.

Uterine leiomyomata are the most common pelvic tumors in women and are the indication for more than 200,000 hysterectomies annually in the United States. Rearrangement of chromosome 12 in bands q14-q15 is characteristic of uterine leiomyomata and other benign mesenchymal tumors, and we identified a yeast artificial chromosome (YAC) spanning chromosome 12 translocation breakpoints in a uterine leiomyoma, a pulmonary chondroid hamartoma, and a lipoma. Recently, we demonstrated that HMGIC, which is an architectural factor mapping within the YAC, is disrupted in lipomas, resulting in novel fusion transcripts. Here, we report on the localization of translocation breakpoints in seven uterine leiomyomata from 10 to > 100 kb upstream of HMGIC by use of fluorescence in situ hybridization. Our findings suggest a different pathobiologic mechanism in uterine leiomyomata from that in lipomas. HMGIC is the first gene identified in chromosomal rearrangements in uterine leiomyomata and has important implications for an understanding of benign mesenchymal proliferation and differentiation.

Chromosomes, Human, Pair 12↗
PubMed1995

Mutation responsible for the mouse pygmy phenotype in the developmentally regulated factor HMGI-C.

Growth is one of the fundamental aspects in the development of an organism. Classical genetic studies have isolated four viable, spontaneous mouse mutants disrupted in growth, leading to dwarfism. Pygmy is unique among these mutants because its phenotype cannot be explained by aberrations in the growth hormone-insulin-like growth factor endocrine pathway. Here we show that the pygmy phenotype arises from the inactivation of Hmgi-c (ref. 6), a member of the Hmgi family which function as architectural factors in the nuclear scaffold and are critical in the assembly of stereospecific transcriptional complexes. Hmgi-c and another Hmgi family member, Hmgi(gamma) (ref. 10), were found to be expressed predominantly during embryogenesis. The HMGI proteins are known to be regulated by cell cycle-dependent phosphorylation which alters their DNA binding affinity. These results demonstrate the important role of HMGI proteins in mammalian growth and development.

Alleles↗
PubMed1995

Disruption of the architectural factor HMGI-C: DNA-binding AT hook motifs fused in lipomas to distinct transcriptional regulatory domains.

Lipomas are one of the most common mesenchymal neoplasms in humans. They are characterized by consistent cytogenetic aberrations involving chromosome 12 in bands q14-15. Interestingly, this region is also the site of rearrangement for other mesenchymally derived tumors. This study demonstrates that HMGI-C, an architectural factor that functions in transcriptional regulation, has been disrupted by rearrangement at the 12q14-15 chromosomal breakpoint in lipomas. Chimeric transcripts were isolated from two lipomas in which HMGI-C DNA-binding domains (AT hook motifs) are fused to either a LIM or an acidic transactivation domain. These results, identifying a gene rearranged in a benign neoplastic process that does not proceed to a malignancy, suggest a role for HMGI-C in adipogenesis and mesenchyme differentiation.

Amino Acid Sequence↗
PubMed1995

Identification and characterization of a novel conserved DNA repeat.

Homozygous In(10)17Rk mice contain a paracentric inversion within Chromosome (Chr) 10 and exhibit a pygmy phenotype, suggesting that the distal inversion breakpoint is within the pygmy (pg) locus. In order to obtain the pygmy gene by positional cloning procedures, In(10)17Rk DNA was subjected to RFLP analysis with single-copy probes derived from the wild-type pygmy locus. This analysis identified a DNA polymorphism in the DBA/2J mouse strain on which the In(10)17Rk mutation was originally induced. A detailed characterization of this polymorphism revealed the presence of a novel, tandemly repeated DNA element. Copy number estimation experiments indicate that there are approximately 100,000 copies of this element in the haploid DBA/2J genome. PCR typing studies revealed the presence of the repeat at the pygmy locus of 6 of the 18 Mus domesticus strains analyzed. The absence of the repeat from the pygmy locus of 12 strains of the M. domesticus species and from the M. caroli, M. spretus, M. castaneus, and M. molossinus species suggests that the repeat could serve as a strain-specific hybridization probe in genetic mapping studies. Finally, the novel tandem DNA repeat is conserved in both rat and human genomes as indicated by Southern hybridization experiments.

Alleles↗
PubMed1995

Optical mapping of lambda bacteriophage clones using restriction endonucleases.

Optical mapping is an emerging single molecule approach for the rapid generation of ordered restriction maps, using fluorescence microscopy. We have improved the size resolution of optical mapping by imaging individual DNA molecules elongated and fixed onto derivatized glass surfaces. Averaged fluorescence intensity and apparent length measurements accurately determined the mass of restriction fragments 800 basepairs long. We have used optical mapping to create ordered restriction maps for lambda clones derived from the mouse pygmy locus.

Animals↗
PubMed1995

Collagenase expression in transgenic mouse skin causes hyperkeratosis and acanthosis and increases susceptibility to tumorigenesis.

In a series of transgenic mice, the human tissue collagenase gene was expressed in the suprabasal layer of the skin epidermis. Visually, the mice had dry and scaly skin which upon histological analysis revealed acanthosis, hyperkeratosis, and epidermal hyperplasia. At the ultrastructural level, intercellular granular materials were absent in the transgenic skin epidermis but contact was maintained through the intact desmosomes. Despite a diversity of underlying etiologies, similar morphological hyperproliferative changes in the epidermis are observed in the human skin diseases of lamellar ichthyosis, atopic dermatitis, and psoriasis. Subsequent experiments demonstrate that when the transgenic mouse skin was treated once with an initiator (7,12-dimethyl-benz[a]anthracene) and then twice weekly with a promoter (12-O-tetradecanoylphorbol-13-acetate), there was a marked increase in tumor incidence among transgenic mice compared with that among control littermates. These experiments demonstrate that by overexpressing the highly specific proteolytic enzyme collagenase, a cascade of events leading to profound morphological changes which augment the sensitivity of the skin towards carcinogenesis is initiated in the epidermis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1994

Rapid isolation of tissue-specific and developmentally regulated brain cDNAs using RNA arbitrarily primed PCR (RAP-PCR).

RNA arbitrarily primed PCR (RAP-PCR) was used to isolate cDNAs that represent developmentally regulated brain-specific genes. Five clones with a restricted pattern of expression were identified and sequenced. Four cDNAs had no obvious homology to the sequences in GenBank. One clone had over 95% homology to a Ca2+/calmodulin-insensitive adenylyl cyclase, a recently cloned gene that was isolated from rat brain and was shown to be expressed only in adult brain and lung. Two novel cDNAs were investigated further by Northern blot analysis and were found to be expressed differentially during development; their expression was confined to the forebrain in the adult mouse. Further characterization by in situ hybridization showed that the mRNA corresponding to one clone was localized to a limited number of differentiating functional structures in the developing nervous system. In the adult brain, this message is confined to the forebrain with the highest level of expression in the cortex. These data suggest that the product of this gene is involved in the establishment of neuronal networks during brain development and in synaptic plasticity in the mature cortex. This work demonstrates that RAP-PCR is a powerful method for the simultaneous detection of differences between multiple RNA populations and, as such, can be used to study differential gene expression in the brain.

Animals↗
PubMed1994

Mini-mouse: phenotypic characterization of a transgenic insertional mutant allelic to pygmy.

A phenotypic analysis was performed on two alleles at the pygmy locus which arose by insertional mutagenesis in transgenic mice. Similar to the spontaneous mutant pygmy, the adult insertional transgenic mutants are 40% of the size of wild-type litter-mates whereas adult heterozygotes are 80% of wild-type litter-mates. An analysis of the various organs revealed that, in general, there was a reduction in weight of each organ commensurate with the overall reduction in body size. However, two organs did not follow this pattern, the brain being disproportionately larger and the adrenals disproportionately smaller in the mutant mice. In addition, mini-mice have less adipose tissue than their wild-type or heterozygous litter-mates. A developmental analysis determined that mutants could first be identified on the basis of reduced body weight at day 15.5 of gestation. The small size is not due to a growth hormone deficiency so these mice differ from other known dwarf mouse mutants. Therefore they should provide insight into the growth hormone-resistant human dwarfisms and help in furthering our knowledge of mammalian growth and development.

Adipose Tissue↗
PubMed1994

Expression of the helix-loop-helix protein, Id, during branching morphogenesis in the kidney.

Id, a member of the helix-loop-helix protein family, is an inhibitor of transcriptional activation by basic-helix-loop-helix proteins. In the developing mouse kidney, Id mRNA was observed as early as 12.5 days post-coitum (dpc) specifically in the condensed mesenchyme surrounding the ureteric buds by in situ hybridization. At 14.5 dpc, Id mRNA was localized to the collecting tubules and developing glomeruli while the surrounding mesenchyme lacked Id hybridization. From birth to day 10 postnatal, Id mRNA is localized to the collecting tubules, immature glomeruli and renal pelvis. In the adult kidney, Id mRNA was detectable by Northern blot analysis but no cell type-specific localization was noted by in situ hybridization. These results indicate a role for HLH-bHLH proteins in the differentiation of the epithelial structures of the kidney.

Acute Kidney Injury↗
PubMed1993

Arbitrary primed PCR fingerprinting of RNA applied to mapping differentially expressed genes.

Differential gene expression between various tissues and developmental stages or between cells in vitro under different growth conditions can be rapidly and efficiently compared using the RNA arbitrarily primed polymerase chain reaction (RAP) fingerprinting method (Welsh et al., 1992b; Liang and Pardee, 1992). In RAP, a primer of arbitrary sequence primes both first and second strand cDNA synthesis. The mixture of products is then PCR amplified and resolved electrophoretically, yielding highly reproducible fingerprints that are tissue-specific or growth condition-specific. Differences between fingerprints arise from differentially expressed genes, as verified by Northern blot analysis. RAP can be performed on the RNA samples using various DNA primers. Each two day experiment yields a sample of approximately twenty cDNA products per lane making the identification of differentially or developmentally regulated genes no longer rate limiting. Those PCR products representing genes that are regulated can be cloned from the gel and sequenced. Sequences can be compared to the DNA and protein sequence databases to identify homologs, motifs and members of gene families. The clones can be placed on the genetic map as Expression Tagged Sites (ETS, Adams et al., 1991a).

Animals↗
PubMed1993

Germ cell deficient (gcd) mouse as a model of premature ovarian failure.

Premature ovarian failure (POF) in women is characterized as menopause commencing before age 35. Although some cases of POF appear to be inherited, no experimental animal models of familial POF are available. Recently a mouse mutation has been identified that results in infertility due to a lack of primordial germ cells arising in early embryonic development. It was observed that shortly after puberty, females homozygous for this mutation entered reproductive senescence as defined by high levels of circulating gonadotropins, inability to respond either hormonally or functionally to superovulation, and a disrupted estrous cycle. Also, the ovaries completely lacked developing follicles and the endometrium was inactive. However, these mice had undergone complete sexual development as determined by age of vaginal opening, mammary gland histology, and sexual behavior. Thus, these animals closely mimic familial premature ovarian failure and may be useful models for study of the pathogenesis and treatment of this condition.

Animals↗