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Warburton L, Meniawy TM, Calapre L, Pereira M, McEvoy A, Ziman M, Gray ES, Millward M. Stopping targeted therapy for complete responders in advanced BRAF mutant melanoma. Sci Rep 2020; 10:18878. [PMID: 33139839 PMCID: PMC7606504 DOI: 10.1038/s41598-020-75837-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Accepted: 10/21/2020] [Indexed: 12/27/2022] Open
Abstract
BRAF inhibitors revolutionised the management of melanoma patients and although resistance occurs, there is a subgroup of patients who maintain durable disease control. For those cases with durable complete response (CR) it is not clear whether it is safe to cease therapy. Here we identified 13 patients treated with BRAF +/- MEK inhibitors, who cease therapy after prolonged CR (median = 34 months, range 20-74). Recurrence was observed in 3/13 (23%) patients. In the remaining 10 patients with sustained CR off therapy, the median follow up after discontinuation was 19 months (range 8-36). We retrospectively measured ctDNA levels using droplet digital PCR (ddPCR) in longitudinal plasma samples. CtDNA levels were undetectable in 11/13 cases after cessation and remained undetectable in patients in CR (10/13). CtDNA eventually became detectable in 2/3 cases with disease recurrence, but remained undetectable in 1 patient with brain only progression. Our study suggests that consideration could be given to ceasing targeted therapy in the context of prolonged treatment, durable response and no evidence of residual disease as measured by ctDNA.
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Affiliation(s)
- L Warburton
- Department of Medical Oncology, Sir Charles Gairdner Hospital, Nedlands, WA, Australia
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia
| | - T M Meniawy
- Department of Medical Oncology, Sir Charles Gairdner Hospital, Nedlands, WA, Australia
- School of Medicine and Pharmacology, University of Western Australia, Crawley, WA, Australia
| | - L Calapre
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia
| | - M Pereira
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia
| | - A McEvoy
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia
| | - M Ziman
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia
- School of Biomedical Science, University of Western Australia, Crawley, WA, Australia
| | - E S Gray
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia.
| | - M Millward
- Department of Medical Oncology, Sir Charles Gairdner Hospital, Nedlands, WA, Australia
- School of Medicine and Pharmacology, University of Western Australia, Crawley, WA, Australia
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Khattak M, Gray E, Reid A, Periera M, McEvoy A, Aya-Bonilla C, Meniawy T, Didan A, Millward M, Ziman M. PD-L1 expression on pre-treatment circulating tumour cells, but not serum VEGF, is predictive of response to pembrolizumab in melanoma. Ann Oncol 2018. [DOI: 10.1093/annonc/mdy269.080] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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3
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Marsavela G, Aya-Bonilla CA, Warkiani ME, Gray ES, Ziman M. Melanoma circulating tumor cells: Benefits and challenges required for clinical application. Cancer Lett 2018; 424:1-8. [PMID: 29548820 DOI: 10.1016/j.canlet.2018.03.013] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Revised: 02/01/2018] [Accepted: 03/09/2018] [Indexed: 02/07/2023]
Abstract
The implementation of novel therapeutic interventions has improved the survival rates of melanoma patients with metastatic disease. Nonetheless, only 33% of treated cases exhibit long term responses. Circulating tumor cell (CTC) measurements are currently of clinical value in breast, prostate and colorectal cancers. However, the clinical utility of melanoma CTCs (MelCTCs) is still unclear due to challenges that appear intrinsic to MelCTCs (i.e. rarity, heterogeneity) and a lack of standardization in their isolation, across research laboratories. Here, we review the latest developments, pinpoint the challenges in MelCTC isolation and address their potential role in melanoma management.
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Affiliation(s)
- G Marsavela
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, Australia
| | - C A Aya-Bonilla
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, Australia.
| | - M E Warkiani
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, Australia; School of Biomedical Engineering, University of Technology Sydney, Sydney, Australia; Institute of Molecular Medicine, Sechenov First Moscow State University, Moscow, Russia
| | - E S Gray
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, Australia
| | - M Ziman
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, Australia; School of Pathology and Laboratory Medicine, University of Western Australia, Crawley, Australia
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4
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Cruickshank T, Thompson J, Dominguez J, Reyes A, Bynevelt M, Georgiou-Karistianis N, Barker R, Ziman M. J03 The Effect Of Multidisciplinary Rehabilitation On Brain Structure And Cognition In Huntington's Disease: An Exploratory Study. J Neurol Psychiatry 2014. [DOI: 10.1136/jnnp-2014-309032.186] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Reyes A, Cruickshank T, Nosaka K, Ziman M. J07 The Effects Of Respiratory Muscle Training On Pulmonary And Swallowing Function In Huntington's Disease Patients. Journal of Neurology, Neurosurgery & Psychiatry 2014. [DOI: 10.1136/jnnp-2014-309032.190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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6
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Reid AL, Millward M, Pearce R, Lee M, Frank MH, Ireland A, Monshizadeh L, Rai T, Heenan P, Medic S, Kumarasinghe P, Ziman M. Markers of circulating tumour cells in the peripheral blood of patients with melanoma correlate with disease recurrence and progression. Br J Dermatol 2012; 168:85-92. [PMID: 23013138 DOI: 10.1111/bjd.12057] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
BACKGROUND Multimarker quantitative real-time polymerase chain reaction (qRT-PCR) represents an effective method for detecting circulating tumour cells in the peripheral blood of patients with melanoma. OBJECTIVES To investigate whether the phenotype of circulating melanoma cells represents a useful indicator of disease stage, recurrence and treatment efficacy. METHODS Peripheral blood was collected from 230 patients with melanoma and 152 healthy controls over a period of 3years and 9months. Clinical data and blood samples were collected from patients with primary melanoma (early stages, 0-II, n=154) and metastatic melanoma (late stages, III-IV, n=76). Each specimen was examined by qRT-PCR analysis for the expression of five markers: MLANA, ABCB5, TGFβ2, PAX3d and MCAM. RESULTS In total, 212 of the patients with melanoma (92%) expressed markers in their peripheral blood. Two markers, MLANA and ABCB5, had the greatest prognostic value, and were identified as statistically significant among patients who experienced disease recurrence within our study period, being expressed in 45% (MLANA) and 49% (ABCB5) of patients with recurrence (P=0·001 and P=0·031, respectively). For patients administered nonsurgical treatments, MCAM expression correlated with poor treatment outcome. CONCLUSIONS Circulating tumour cells were detectable at all stages of disease and long after surgical treatment, even when patients were considered disease free. Specifically, expression of ABCB5 and MLANA had significant prognostic value in inferring disease recurrence, while MCAM expression was associated with poor patient outcome after treatment, confirming multimarker qRT-PCR as a potential technique for monitoring disease status.
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Affiliation(s)
- A L Reid
- School of Medical Sciences, Edith Cowan University, Perth, WA, Australia
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7
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Michalczyk K, Ziman M. Current concepts in human prion protein (Prp) misfolding, Prnp gene polymorphisms and their contribution to Creutzfeldt-Jakob Disease (CJD). Histol Histopathol 2007; 22:1149-59. [PMID: 17616941 DOI: 10.14670/hh-22.1149] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Transmissible spongiform encephalopathies are a group of neural degenerative diseases that may be infectious, sporadic, or hereditary and are associated with an abnormally folded prion protein. Unfortunately at the current time it is not at all clear what the normal structure of the prion protein actually is or how it is toxic to cells. Extensive research on prion diseases has led to a dramatic increase in understanding of the pathogenesis of prion disorders, which will hopefully lead to the development of effective treatments. The inability to detect the disease in blood using current technology has made screening difficult. While fortunately there has been a decline in the number of clinical cases of transmissible variant CJD, evidence indicates that very long incubation periods can occur in humans so there may be a long slow, gradual epidemic. In particular, clinical cases in genotypes other than those homozygous for methionine at codon 129 of PRNP have not yet occurred, but such cases might be expected to have longer incubation periods and show differences in pathology to those seen to date. Transgenic animal studies have shown that a large proportion of infected animals develop sub-clinical disease. Moreover, results from a large prevalence study in humans show that several cases test positive but do not develop clinical disease. It is possible therefore that further cases of secondary transmission could occur by iatrogenic spread, which could result in vCJD persisting in the UK at low levels for many years, highlighting the importance of continued vigilance.
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Affiliation(s)
- K Michalczyk
- School of Exercise, Biomedical and Health Science, Edith Cowan University, Joondalup, Western Australia, Australia
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Abstract
In this paper, we discuss and critically analyse pre-hospital management of acute myocardial infarction (AMI). It is clear from several large studies that rapid diagnosis and application of thrombolysis reduces morbidity and mortality rates. Strategies that improve time to treatment in the pre-hospital setting are therefore of fundamental importance in the management of this fatal disease. The advantage of 12 lead electrocardiography use by paramedics to diagnose AMI and reduce time to treatment is discussed. Moreover, paramedic application of thrombolysis in the pre-hospital environment is examined. Several studies conducted worldwide support the notion that ambulance services can play a role in minimising time to treatment for patients with AMI. The contribution of early intervention by paramedics trained in critical care is potentially considerable, particularly in the important chain of survival that is often initiated by pre-hospital intervention.
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Affiliation(s)
- S Johnston
- St John's Ambulance, Western Australian Ambulance Service, Western Australia, Australia
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Abstract
Nestin is an intermediate filament protein expressed in dividing cells during the early stages of development in the CNS, PNS and in myogenic and other tissues. Upon differentiation, nestin becomes downregulated and is replaced by tissue-specific intermediate filament proteins. Interestingly, nestin expression is reinduced in the adult during pathological situations, such as the formation of the glial scar after CNS injury and during regeneration of injured muscle tissue. Although it is utilised as a marker of proliferating and migrating cells very little is known about its functions or regulation. In depth studies on the distribution and expression of nestin in mitotically active cells indicate a complex role in regulation of the assembly and disassembly of intermediate filaments which together with other structural proteins, participate in remodeling of the cell. The role of nestin in dynamic cells, particularly structural organisation of the cell, appears strictly regulated by phosphorylation, especially its integration into heterogeneous intermediate filaments together with vimentin or alpha-internexin.
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Affiliation(s)
- K Michalczyk
- School of Biomedical and Sports Science, Edith Cowan University, Joondalup, Western Australia, Australia
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10
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Abstract
Pax3 and Pax7 are powerful myogenic inducers and hence play a critical role in skeletal muscle development and regeneration. In this paper we discuss the role of Pax3 and Pax7 in dorsal patterning of the somite with subsequent determination of myogenic precursor cells for muscle formation within the developing embryo and in adult muscle. Recent evidence of the ability of stem cells to contribute to muscle regeneration in adult tissues, and the role of Pax7 in conversion of multipotent stem cells to the myogenic lineage are also discussed. Several tissue specific Pax7 transcripts that encode isoforms with different DNA binding characteristics and potentially distinct transactivation specificities are identified. The expression of a range of transcripts in the determination of different tissue lineages and distinct cell populations both in the embryo and in the adult indicates an extraordinary level of complexity. A detailed understanding of these molecules and their functions during embryogenesis and adult muscle formation is imperative for future stem cell therapies.
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Affiliation(s)
- T M Lamey
- School of Biomedical and Sports Science, Edith Cowan University, Joondalup, Western Australia, Australia
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Hughes TR, Mao M, Jones AR, Burchard J, Marton MJ, Shannon KW, Lefkowitz SM, Ziman M, Schelter JM, Meyer MR, Kobayashi S, Davis C, Dai H, He YD, Stephaniants SB, Cavet G, Walker WL, West A, Coffey E, Shoemaker DD, Stoughton R, Blanchard AP, Friend SH, Linsley PS. Expression profiling using microarrays fabricated by an ink-jet oligonucleotide synthesizer. Nat Biotechnol 2001; 19:342-7. [PMID: 11283592 DOI: 10.1038/86730] [Citation(s) in RCA: 829] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We describe a flexible system for gene expression profiling using arrays of tens of thousands of oligonucleotides synthesized in situ by an ink-jet printing method employing standard phosphoramidite chemistry. We have characterized the dependence of hybridization specificity and sensitivity on parameters including oligonucleotide length, hybridization stringency, sequence identity, sample abundance, and sample preparation method. We find that 60-mer oligonucleotides reliably detect transcript ratios at one copy per cell in complex biological samples, and that ink-jet arrays are compatible with several different sample amplification and labeling techniques. Furthermore, results using only a single carefully selected oligonucleotide per gene correlate closely with those obtained using complementary DNA (cDNA) arrays. Most of the genes for which measurements differ are members of gene families that can only be distinguished by oligonucleotides. Because different oligonucleotide sequences can be specified for each array, we anticipate that ink-jet oligonucleotide array technology will be useful in a wide variety of DNA microarray applications.
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Affiliation(s)
- T R Hughes
- Rosetta Inpharmatics, Inc., 12040 115th Avenue NE, Kirkland, WA 98034, USA
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Shoemaker DD, Schadt EE, Armour CD, He YD, Garrett-Engele P, McDonagh PD, Loerch PM, Leonardson A, Lum PY, Cavet G, Wu LF, Altschuler SJ, Edwards S, King J, Tsang JS, Schimmack G, Schelter JM, Koch J, Ziman M, Marton MJ, Li B, Cundiff P, Ward T, Castle J, Krolewski M, Meyer MR, Mao M, Burchard J, Kidd MJ, Dai H, Phillips JW, Linsley PS, Stoughton R, Scherer S, Boguski MS. Experimental annotation of the human genome using microarray technology. Nature 2001; 409:922-7. [PMID: 11237012 DOI: 10.1038/35057141] [Citation(s) in RCA: 332] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The most important product of the sequencing of a genome is a complete, accurate catalogue of genes and their products, primarily messenger RNA transcripts and their cognate proteins. Such a catalogue cannot be constructed by computational annotation alone; it requires experimental validation on a genome scale. Using 'exon' and 'tiling' arrays fabricated by ink-jet oligonucleotide synthesis, we devised an experimental approach to validate and refine computational gene predictions and define full-length transcripts on the basis of co-regulated expression of their exons. These methods can provide more accurate gene numbers and allow the detection of mRNA splice variants and identification of the tissue- and disease-specific conditions under which genes are expressed. We apply our technique to chromosome 22q under 69 experimental condition pairs, and to the entire human genome under two experimental conditions. We discuss implications for more comprehensive, consistent and reliable genome annotation, more efficient, full-length complementary DNA cloning strategies and application to complex diseases.
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Affiliation(s)
- D D Shoemaker
- Rosetta Inpharmatics, Inc., Kirkland, Washington 98034, USA
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Corrigall AV, Siziba KB, Maneli MH, Shephard EG, Ziman M, Dailey TA, Dailey HA, Kirsch RE, Meissner PN. Purification of and kinetic studies on a cloned protoporphyrinogen oxidase from the aerobic bacterium Bacillus subtilis. Arch Biochem Biophys 1998; 358:251-6. [PMID: 9784236 DOI: 10.1006/abbi.1998.0834] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The previously cloned and expressed protoporphyrinogen oxidase from Bacillus subtilis has been purified to homogeneity by Ni2+ affinity chromatography using a His6 tag and characterized. The enzyme has a molecular weight of approximately 56,000 daltons, a pI of 7.5, a pH optimum (protoporphyrinogen) of 8.7, and a noncovalently bound flavine adenine dinucleotide cofactor. The Michaelis constants (Km) for protoporphyrinogen-IX, coproporphyrinogen-III, and mesoporphyrinogen-IX are 1.0, 5.29, and 4.92 microM, respectively. Polyclonal antibody to B. subtilis protoporphyrinogen oxidase demonstrated weak cross-reactivity with both human and Myxococcus xanthus protoporphyrinogen oxidase. B. subtilis protoporphyrinogen oxidase is not inhibited by the diphenyl ether herbicide acifluorfen at 100 microM and is weakly inhibited by methylacifluorfen at the same concentration. Bilirubin, biliverdin, and hemin are all competitive inhibitors of this enzyme.
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Affiliation(s)
- A V Corrigall
- MRC/UCT Liver Research Centre, University of Cape Town Medical School, Observatory, 7925, South Africa
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Ziman M, Chuang JS, Tsung M, Hamamoto S, Schekman R. Chs6p-dependent anterograde transport of Chs3p from the chitosome to the plasma membrane in Saccharomyces cerevisiae. Mol Biol Cell 1998; 9:1565-76. [PMID: 9614194 PMCID: PMC25385 DOI: 10.1091/mbc.9.6.1565] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/1998] [Accepted: 03/23/1998] [Indexed: 11/11/2022] Open
Abstract
Chitin synthase III (CSIII), an enzyme required to form a chitin ring in the nascent division septum of Saccharomyces cerevisiae, may be transported to the cell surface in a regulated manner. Chs3p, the catalytic subunit of CSIII, requires the product of CHS6 to be transported to or activated at the cell surface. We find that chs6Delta strains have morphological abnormalities similar to those of chs3 mutants. Subcellular fractionation and indirect immunofluorescence indicate that Chs3p distribution is altered in chs6 mutant cells. Order-of-function experiments using end4-1 (endocytosis-defective) and chs6 mutants indicate that Chs6p is required for anterograde transport of Chs3p from an internal endosome-like membrane compartment, the chitosome, to the plasma membrane. As a result, chs6 strains accumulate Chs3p in chitosomes. Chs1p, a distinct chitin synthase that acts during or after cell separation, is transported normally in chs6 mutants, suggesting that Chs1p and Chs3p are independently packaged during protein transport through the late secretory pathway.
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Affiliation(s)
- M Ziman
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, California 94720, USA
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15
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Kay PH, Harmon D, Fletcher S, Robertson T, Ziman M, Papadimitriou JM. Pax7 includes two polymorphic homeoboxes which contain rearrangements associated with differences in the ability to regenerate damaged skeletal muscle in adult mice. Int J Biochem Cell Biol 1998; 30:261-9. [PMID: 9608680 DOI: 10.1016/s1357-2725(97)00108-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Pax7 is a paired-type homeobox gene which has previously been shown to play an important role in skeletal muscle formation. It is expressed in skeletal muscle of the limbs during embryogenesis and in adulthood. The aims of this study were firstly to determine the degree of polymorphism of Pax7 amongst inbred laboratory mice using Southern blotting and Pax7 regional specific sub-probes. Secondly, functional studies were performed on mice with each of the different structural forms of Pax7 to determine whether they were associated with differences in the ability to regenerate damaged skeletal muscle. Four different allelic forms of Pax7 have now been identified in laboratory mice indicating that the previously reported DNA sequence of Pax7 is not applicable to all laboratory mice. Hybridisation patterns of TaqI digested DNA representing each of the different Pax7 alleles with the Pax7 specific sub-probes suggested that in contrast to previous findings, Pax7 is associated with two highly polymorphic homeoboxes. The presence of two homeoboxes in BALB/c mice has been confirmed by DNA sequencing. Results of functional studies have also shown that the ability to regenerate damaged skeletal muscle in adult mice is strongly associated with the presence of a 0.15-kb TaqI fragment derived from one of the homeoboxes.
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Affiliation(s)
- P H Kay
- Department of Pathology, University of Western Australia, Nedlands, Australia
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16
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Kay PH, Harmon D, Fletcher S, Ziman M, Jacobsen PF, Papadimitriou JM. Variation in the methylation profile and structure of Pax3 and Pax7 among different mouse strains and during expression. Gene 1997; 184:45-53. [PMID: 9016952 DOI: 10.1016/s0378-1119(96)00572-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Structural alterations within the myogenic and neurogenic developmental gene Pax7 which involve TaqI recognition sequences have previously been reported. These alterations are associated with differences in the efficiency of regrowth of damaged skeletal muscle. To identify other structural features of Pax genes which may influence skeletal muscle regrowth, variation in the structure and methylation status of Pax7 and the closely related gene Pax3 has been sought among different mouse strains and during gene expression using the restriction endonucleases MspI and HpaII. Following MspI digestion, RFLPs within Pax7 have been found which most likely reflect intron size variability within the paired box. Differences in the size of MspI and HpaII fragments hybridising with Pax7 and Pax3 region specific sub-probes indicate that the paired boxes are hypomethylated, whereas the region encoding the homeodomain of each gene is highly methylated in the spleen and other tissues from adult mice. In the skeletal muscle precursor cell line C2C12, which expresses Pax7 but not Pax3, the homeodomain encoding region of Pax7 is hypomethylated. In spleen cells, the Pax7 paired box is transcribed but the homeodomain encoding region is not. By contrast, both the paired box and the homeobox of Pax3 are hypermethylated in C2C12 cells indicating that generation of alternate transcripts from Pax genes may be controlled by DNA methylation. In contrast to Pax3, reference to the size of fragments hybridising with a Pax7 homeobox specific probe provides evidence for CpNpG methylation within and immediately downstream from the region encoding the homeodomain. Interestingly, CpNpG methylation remains when the Pax7 homeobox is expressed. Structural variation recognised by MspI digestion and differences in the methylation profile of Pax7 are not associated with the ability to regrow damaged skeletal muscle.
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Affiliation(s)
- P H Kay
- Department of Pathology, University of Western Australia, Nedlands.
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Abstract
There is now considerable evidence suggesting that alterations in the DNA methylating machinery play an important role in tumorigenesis and tumour progression. For example, focal hypermethylation and generalised genomic demethylation are features of many different types of neoplasms. It is thought that tumorigenesis and tumour progression may be caused by hypermethylation induced mutational events and silencing of genes which control cellular proliferation and/or demethylation induced reactivation of genes which may only be required during embryological development. Consequently, we have begun to investigate the role of DNA methylation and developmental genes in malignant lymphoproliferative diseases. Previously, in all cases of non-Hodgkins lymphoma and leukemia studied, we have shown that the myogenic developmental gene Myf-3 is abnormally hypermethylated. In this review we discuss the possible significance of these findings since in vitro studies suggest that Myf-3 may play an important role in control of the cell cycle and therefore lymphomagenesis. In vitro and in vivo evidence suggests that PAX genes may also have oncogenic potential. The PAX family of developmental genes are involved in cellular differentiation, proliferation and cell migration. Expression of PAX3 in particular is associated with cellular mobility. Our previous studies have indicated that alternate regional expression of PAX genes may be controlled by DNA methylation. Therefore, we have proposed that abnormal methylation profiles of PAX3 may be associated with neoplastic transformation and/or metastatic potential. Results thus far reveal that the paired box of PAX3 is abnormally hypermethylated and the homeobox abnormally hypomethylated in lymphomas and leukemias. These new findings are consistent with our postulate and support the idea that inappropriate methylation induced activation or inactivation of developmental genes such as Myf-3 and PAX3 play an important role in lymphomagenesis and disease progression and that inspection of the methylation status of other developmental genes is warranted.
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Affiliation(s)
- P H Kay
- Department of Pathology, University of Western Australia, Nedlands, Australia
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18
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Ziman M, Chuang JS, Schekman RW. Chs1p and Chs3p, two proteins involved in chitin synthesis, populate a compartment of the Saccharomyces cerevisiae endocytic pathway. Mol Biol Cell 1996; 7:1909-19. [PMID: 8970154 PMCID: PMC276039 DOI: 10.1091/mbc.7.12.1909] [Citation(s) in RCA: 123] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
In Saccharomyces cerevisiae, the synthesis of chitin, a cell-wall polysaccharide, is temporally and spatially regulated with respect to the cell cycle and morphogenesis. Using immunological reagents, we found that steady-state levels of Chs1p and Chs3p, two chitin synthase enzymes, did not fluctuate during the cell cycle, indicating that they are not simply regulated by synthesis and degradation. Previous cell fractionation studies demonstrated that chitin synthase I activity (CSI) exists in a plasma membrane form and in intracellular membrane-bound particles called chitosomes. Chitosomes were proposed to act as a reservoir for regulated transport of chitin synthase enzymes to the division septum. We found that Chs1p and Chs3p resided partly in chitosomes and that this distribution was not cell cycle regulated. Pulse-chase cell fractionation experiments showed that chitosome production was blocked in an endocytosis mutant (end4-1), indicating that endocytosis is required for the formation or maintenance of chitosomes. Additionally, Ste2p, internalized by ligand-induced endocytosis, cofractionated with chitosomes, suggesting that these membrane proteins populate the same endosomal compartment. However, in contrast to Ste2p, Chs1p and Chs3p were not rapidly degraded, thus raising the possibility that the temporal and spatial regulation of chitin synthesis is mediated by the mobilization of an endosomal pool of chitin synthase enzymes.
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Affiliation(s)
- M Ziman
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, USA
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Meissner PN, Dailey TA, Hift RJ, Ziman M, Corrigall AV, Roberts AG, Meissner DM, Kirsch RE, Dailey HA. A R59W mutation in human protoporphyrinogen oxidase results in decreased enzyme activity and is prevalent in South Africans with variegate porphyria. Nat Genet 1996; 13:95-7. [PMID: 8673113 DOI: 10.1038/ng0596-95] [Citation(s) in RCA: 150] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Variegate porphyria (VP), a low-penetrant autosomal dominant inherited disorder of haem metabolism, is characterised by photosensitivity (Fig. 1) and a propensity to develop acute neuropsychiatric attacks with abdominal pain, vomiting, constipation, tachycardia, hypertension, psychiatric symptoms and, in the worst cases, quadriplegia. Acute attacks, often precipitated by inappropriate drug therapy, are potentially fatal. While earlier workers thought the distal haem biosynthetic enzyme ferrochelatase may be involved in the genesis of VP, it was shown in the early 1980's, and is now accepted, that VP is associated with decreased protoporphyrinogen oxidase activity (PPO) (E.C.1.3.3.4). VP prevalence is much higher in South Africa than elsewhere; probably due to a founder effect with patients descending from a 17th century Dutch immigrant. PPO cDNAs from Bacillus subtilis, Myxococcus xanthus, human placenta and mouse liver have been cloned, sequenced and expressed. Human and mouse cDNAs consist of open reading frames 1431 nucleotides long, encoding a 477 amino acid protein. The human PPO gene contains thirteen exons, spanning approximately 4.5 kb. We have identified a C to T transition in codon 59 (in exon 3) resulting in an arginine to tryptophan substitution (R59W). A protein expressed from an in vitro-mutagenized PPO construct exhibits substantially less activity than the wild type. The R59W mutation was present in 43 of 45 patients with VP from 26 of 27 South African families investigated, but not in 34 unaffected relatives or 9 unrelated British patients with PPO deficiency. Since at least one of these families is descended from the founder of South African VP, this defect may represent the founder gene defect associated causally with VP in South Africa.
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Affiliation(s)
- P N Meissner
- Lennox Eales Porphyria Laboratories, MRC/UCT Liver Research Centre, University of Cape Town Dept. of Medicine, South Africa
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Posada J, Miller PJ, McCullough J, Ziman M, Johnson DI. Genetic and biochemical analysis of Cdc42p function in Saccharomyces cerevisiae and Schizosaccharomyces pombe. Methods Enzymol 1995; 256:281-90. [PMID: 7476442 DOI: 10.1016/0076-6879(95)56032-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- J Posada
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington 05405, USA
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Abstract
Cdc24p and Cdc42p are involved in the control of cell polarity during the Saccharomyces cerevisiae cell cycle. Cdc42p is a member of the Ras superfamily of GTPases and Cdc24p displays limited amino-acid sequence similarity with the Dbl proto-oncoprotein, which acts to stimulate guanine-nucleotide exchange on human Cdc42p. We have performed several genetic experiments to test whether Cdc24p and Cdc42p interact within the cell. First, overexpression of Cdc24p suppressed the dominant-negative cdc42D118A allele. Second, overexpression of wild-type CDC24 and CDC42 genes together was a lethal event resulting in a morphological phenotype of large, round, unbudded cells, indicating a loss of cell polarity. Third, a cdc24ts cdc42ts double mutant exhibited a synthetic-lethal phenotype at the semi-permissive temperature of 30 degrees C. These data suggest that Cdc24p and Cdc42p interact within the cell and that Cdc24p may be involved in the regulation of Cdc42p activity.
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Affiliation(s)
- M Ziman
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington 05401
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Ziman M, Preuss D, Mulholland J, O'Brien JM, Botstein D, Johnson DI. Subcellular localization of Cdc42p, a Saccharomyces cerevisiae GTP-binding protein involved in the control of cell polarity. Mol Biol Cell 1993; 4:1307-16. [PMID: 8167411 PMCID: PMC275766 DOI: 10.1091/mbc.4.12.1307] [Citation(s) in RCA: 212] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The Saccharomyces cerevisiae Cdc42 protein, a member of the Ras superfamily of low-molecular-weight GTP-binding proteins, is involved in the control of cell polarity during the yeast cell cycle. This protein has a consensus sequence (CAAX) for geranylgeranyl modification and is likely to be associated, at least in part, with cell membranes. Using cell fractionation and immunolocalization techniques, we have investigated the subcellular localization of Cdc42p. Cdc42p was found in both soluble and particulate pools, and neither its abundance nor its distribution varied through the cell cycle. The particulate form of Cdc42p could be solubilized with detergents but not with NaCl or urea, suggesting that it is tightly associated with membranes. An increase in soluble Cdc42p was observed in a geranylgeranyltransferase mutant strain (cdc43-2ts) grown at the restrictive temperature. In addition, Cdc42p from a cdc42C188S mutant strain (that has an alteration at the prenylation consensus site) was almost exclusively in the soluble fraction, suggesting that membrane localization is dependent on geranylgeranyl modification at Cys-188. Immunofluorescence and immunoelectron microscopy experiments demonstrated that Cdc42p localizes to the plasma membrane in the vicinity of secretory vesicles that were found at the site of bud emergence, at the tips and sides of enlarging buds, and within mating projections (shmoo tips) in alpha-factor-arrested cells. These results indicate that Cdc42p is localized to the bud site early in the cell cycle and suggest that this localization is critical for the selection of the proper site for bud emergence and for polarized cell growth.
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Affiliation(s)
- M Ziman
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington 05405
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Ziman M, O'Brien JM, Ouellette LA, Church WR, Johnson DI. Mutational analysis of CDC42Sc, a Saccharomyces cerevisiae gene that encodes a putative GTP-binding protein involved in the control of cell polarity. Mol Cell Biol 1991; 11:3537-44. [PMID: 1904541 PMCID: PMC361094 DOI: 10.1128/mcb.11.7.3537-3544.1991] [Citation(s) in RCA: 94] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The Saccharomyces cerevisiae CDC42 gene product, a member of the ras superfamily of low-molecular-weight GTP-binding proteins, is involved in the control of cell polarity. We have analyzed the effects of three CDC42 mutations (Gly to Val-12, Gln to Leu-61, and Asp to Ala-118) in the putative GTP-binding and hydrolysis domains and one mutation (Cys to Ser-188) in the putative isoprenylation site. The first three mutations resulted in either a dominant-lethal or dose-dependent dominant-lethal phenotype when present on plasmids in haploid cdc42-1ts or wild-type strains. Both wild-type and cdc42-1ts cells carrying plasmids (pGAL) with either the CDC42Val-12 or CDC42Leu-61 alleles under the control of a GAL promoter were arrested with a novel phenotype of large cells with elongated or multiple buds. Cells carrying pGAL-CDC42Ala-118 were arrested as large, round, unbudded cells reminiscent of cdc42-1ts arrested cells. The different phenotype of the CDC42Ala-118 mutant versus the CDC42Val-12 and CDC42Leu-61 mutants was unexpected since the phenotypes of all three analogous ras mutants were similar to each other. This suggests that aspects of the biochemical properties of the Cdc42 protein differ from those of the Ras protein. The cdc42Ser-188 mutant gene was incapable of complementing the cdc42-1ts mutation and was recessive to both wild-type and cdc42-1ts. In double-mutant alleles, the cdc42Ser-188 mutation was capable of suppressing the dominant lethality associated with the three putative GTP-binding and hydrolysis mutations, suggesting that isoprenylation is necessary for the activity of the wild-type and mutant proteins.
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Affiliation(s)
- M Ziman
- Cell and Molecular Biology Program, University of Vermont, Burlington 05405
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