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PubMed2006

Tuberous sclerosis complex: molecular pathogenesis and animal models.

Mutations in one of two genes, TSC1 and TSC2, result in a similar disease phenotype by disrupting the normal interaction of their protein products, hamartin and tuberin, which form a functional signaling complex. Disruption of these genes in the brain results in abnormal cellular differentiation, migration, and proliferation, giving rise to the characteristic brain lesions of tuberous sclerosis complex (TSC) called cortical tubers. The most devastating complications of TSC affect the central nervous system and include epilepsy, mental retardation, autism, and glial tumors. Relevant animal models, including conventional and conditional knockout mice, are valuable tools for studying the normal functions of tuberin and hamartin and the way in which disruption of their expression gives rise to the variety of clinical features that characterize TSC. In the future, these animals will be invaluable preclinical models for the development of highly specific and efficacious treatments for children affected with TSC.

Animals↗

PubMedDate not supplied

Rhebbing up mTOR: new insights on TSC1 and TSC2, and the pathogenesis of tuberous sclerosis.

Tuberous sclerosis is an autosomal dominant human genetic disorder in which distinctive tumors called hamartomas develop. Germline mutations in either TSC1 or TSC2 cause this syndrome, and hamartomas typically display second hit events with loss of the remaining normal allele. Studies initiated in Drosophila have identified a role for the Tsc1 and Tsc2 genes in the regulation of cell and organ size, and genetic interaction studies have placed them in the PI3K-Akt-mTOR-S6K pathway. Biochemical studies have shown that activated Akt phosphorylates TSC2 in the TSC1/TSC2 protein complex, inactivating it; while TSC1/TSC2 has GAP activity for the Rheb GTPase (a member of the ras family), and activated Rheb-GTP activates mTOR. Thus, in cells lacking TSC1 or TSC2 there are increased levels of Rheb-GTP which leads to activation of mTOR, leading to cell size increase and growth. These developments provide enhanced understanding of this signaling pathway and fundamental insights into the pathogenesis of tuberous sclerosis, and open the possibility of treatment for hamartomas by several pharmacologic approaches.

Drosophila Proteins↗

PubMed2005

Tuberous sclerosis and insulin resistance. Unlikely bedfellows reveal a TORrid affair.

The TSC1-TSC2 tumor suppressor complex serves as an interface between insulin and nutrient signaling pathways and the cell growth machinery. Recent work has indicated that the TSC1-TSC2 complex plays a role in the pathobiology of a number of tumor predisposition syndromes, including tuberous sclerosis (TSC1/2), Peutz-Jeghers syndrome (LKB1), and Cowden's syndrome (PTEN), in which the TSC/Rheb/mTOR axis is inappropriately active secondary to loss of tumor suppressor function. Recent work has demonstrated that TSC deficiency imposes a negative autoregulatory loop that suppresses insulin signaling at the post-receptor level, effectively resulting in cell autonomous insulin resistance. Exploitation of this insulin signaling deficiency may hold promise among tailored clinical therapies designed to manage tuberous sclerosis.

Animals↗

PubMed2000

[Clinical and molecular epidemiology of lymphangioleiomyomatosis and pulmonary pathology in tuberous sclerosis].

Pulmonary lymphangioleiomyomatosis is characterized by a proliferation of abnormal smooth muscle cells in peribronchial, perivascular and perilymphatic areas leading to cystic destruction of the pulmonary parenchyma. Recent clinical series of LAM have been helpful in better describing the various clinical and radiological forms of the disease, although our understanding of the pathophysiological mechanisms of LAM remains very limited. Significant progress has been noted in recent years with the discovery of probable antigenic and genetic similarities between pulmonary lymphangioleiomyomatosis, Bourneville tuberous sclerosis and renal angiomyolipoma. The proliferating cells in LAM share with normal smooth muscle cells their reactivity with desmine, vimentin and actin but certain are different by their reactivity with the monoclonal antibody HMB45, a common antigen marker of melanocyte differentiation cells, clear-cell lung carcinomas or renal angiomyolipomas. A loss heterozygosity in the region of the TSC2 gene in renal angiomyolipomas has been demonstrated in association with pulmonary lymphangioleiomyomatosis. The TSC2 gene is particularly implicated in the pathogenesis of Bourneville tuberous sclerosis.

Antibodies, Monoclonal↗

PubMed2002

[A case of intractable epilepsy: diagnosis of tuberous sclerosis based on histopathological findings and immunohistochemical expression of hamartin and tuberin].

We report here a 14-year-old boy suffering from intractable epilepsy since the age of 2. Neuroimaging showed a lesion in the left temporal lobe. He underwent resection of the left temporal lobe and multiple subpial transection of the left frontal lobe at the age of 8. Histopathological findings of surgical specimens were similar to those of tubers of tuberous sclerosis (TSC), although he had no other TSC stigmata. To discriminate from cortical dysplasia grade III, we examined the immunohistochemical expression of hamartin and tuberin, the TSC1 and TSC2 gene products. Based on results, we diagnosed this case as having TSC. He has been seizure free since the operation. Although lower than preoperatively, his intelligence quotient has not been declining progressively.

Adolescent↗

PubMed2006

[Prenatal diagnostics of tuberous sclerosis based on causal mutation knowledge].

BACKGROUND: Tuberous sclerosis is an autosomal-dominant disease characterised by development of benign growth - hamartomas in different organs. Disorder is caused by mutations affecting either of the tumor-suppressor genes, TSC1 or TSC2. Quest for causing mutations is very difficult due to their random distribution over the genes. METHODS AND RESULTS: Article refers on accomplishment of the first tuberous sclerosis prenatal diagnostics in Czech Republic based on knowledge of causing mutation. Foetal DNA sample, obtained in 13th week from Q435X family pregnant woman, was analyzed by DGGE method. CONCLUSIONS: Examination excluded presence of tested TSC1 gene defect in an offspring.

Female↗

PubMed1996

Changes in phenol oxidase and peroxidase levels in cocoyam tubers of different postharvest ages infected by Sclerotium rolfsii sacc.

Crude aqueous extracts from the peripheral rot zone of cocoyam tubers infected by Sclerotium rolfsii sacc were shown to be inhibitory to dialysed in vivo polygalacturonase (PG) of the pathogen. The PG inhibitory action, phenol oxidase and peroxidase activities were higher in cocoyam tubers of the Xanthosoma sagittifolium varieties than in those of the Coolocasia esculenta varieties. The levels of phenol oxidase, peroxidase and PG inhibitory activities also decreased as the postharvest age of the tubers increased.

Food Contamination↗

PubMed1994

Formation of new sensory cells in deafferented tuberous organs of the gymnotid fish Eigenmannia virescens.

The cutaneous electroreceptor "tuberous organs" of the lateral line system of Eigenmannia virescens were studied at light and electron microscopic levels with immunohistochemical and autoradiographic techniques after sectioning of the posterior branch of the lateral line nerve. After deafferentation total degeneration of the sensory cells was observed. The accessory cells of the basal platform, however, remain intact and undergo a process of differentiation. The cytoplasms and nuclei of these cells increase in volume, and the nuclei incorporate tritiated thymidine. In control tuberous organs with intact innervation, tritiated thymidine is absorbed by the nuclei of the elongated epidermal cells surrounding the sensory cavity. The newly formed sensory cells, but not those of the intact organs, are substance P immunoreactive. They have synaptic bars surrounded by vesicles and their free membrane surface is covered with microvilli. The new sensory cells are fully differentiated 35 days after the lateral line was cut. These results demonstrate that in the tuberous organs of E. virescens new sensory cells are formed in the absence of an innervation.

Afferent Pathways↗

PubMed2004

Determination of specific volatile organic compounds synthesised during Tuber borchii fruit body development by solid-phase microextraction and gas chromatography/mass spectrometry.

Fruit body development is a particular phase of the Tuber life cycle, characterised by the aggregation of different types of hyphae, i.e., vegetative hyphal cells and highly specialised reproductive hyphae (asci). In order to identify the volatile organic compounds (VOCs) produced in different stages of the Tuber borchii ripening fruit body, solid-phase microextraction with gas chromatography and mass spectrometry was used. The volatile organic compounds were extracted using a DVB/CAR/PDMS 50/30 microm fiber placed for 10 min at room temperature in the truffle headspace. The results obtained reveal 49 compounds each of which was present only in a particular stage of maturation. 1-octen-3-ol, aromadendrene, alpha-farnesene and other terpenoid compounds were of particular interest, and their possible biological roles are discussed. The production of aromadendrene in the completely unripe fruit body suggests the existence of communication events in the early stage of ascomata formation between the fungus and the host plant. alpha-Farnesene could represent a chemotactic attractant to saprophytic organisms in order to disperse the fungal spores in the environment. The identification of the VOCs produced by truffles during their maturation could give information about the processes underlying this phase of Tuber life cycle.

Ascomycota↗

PubMed1991

Comparison of the expression of several stress-responsive genes in potato tubers.

Changes in gene expression induced by mechanical injury and heat shock were studied by comparing the expression of several stress-responsive gene families in potato tubers. The steady-state levels of mRNA-encoding ubiquitin, HSP70, and phenylalanine ammonia-lyase (PAL) increased and patatin transcript levels decreased within 45 minutes of impact injury. Nuclear runoff assays were used to demonstrate that the changes in steady-state transcript levels were due, at least in part, to changes in the rate of transcription for these genes. The observed changes in transcript levels were confined to the injured portion of the tuber. Treatment of tubers with exogenous ethylene elicited the same changes in the steady-state transcript levels as impact injury, indicating a potential role for this hormone in the injury-induced regulation of these genes. Two other forms of physical stress, heat shock and cutting injury, resulted in patterns of gene expression that are different from those induced by impact injury. The stress-induced regulation of these four gene families is complex, even though several characteristics of their expression are similar.

Blotting, Northern↗

PubMed1996

A novel MADS-box gene of potato (Solanum tuberosum L.) expressed during the early stages of tuberization.

A potato MADS-box gene cDNA (POTM1-1) from an early tuber cDNA library has been isolated and characterized. The deduced amino acid sequence of POTM1-1 cDNA encodes 250 amino acids of a putative transcription factor containing a MADS-box domain and a K-box domain. These conserved domains share high homologies to those of flower-specific homeotic proteins, TM4 of tomato and AP1 of Arabidopsis, indicating that POTM1-1 gene is a homologue of the AP1 gene family. The levels of POTM1-1 transcripts were high in axillary buds, underground stolen tips, and newly formed tubers, but relatively low in mature tubers. During axillary bud development in a model petiole-leaf cutting system, the levels of POTM1-1 transcripts were abundant in actively growing shoots and during the early stages of microtuber development. It is possible that POTM1-1 functions as a transcription factor that regulates plant developmental processes in a number of tissue types.

Base Sequence↗

PubMed2004

Transfer of tuber soft rot and early blight resistances from Solanum brevidens into cultivated potato.

Tuber soft rot and early blight are serious potato diseases. Development of potato varieties resistant to these diseases has been hindered by the scarcity of resistant germplasm. A diploid wild species, Solanum brevidens, shows significant resistance to both diseases. Numerous potato breeding lines have been developed from a potato- S. brevidens somatic hybrid, A206. A BC(3) clone, C75-5+297, derived from this somatic hybrid as well as its BC(1) and BC(2) parental lines showed resistance to both tuber soft rot and early blight. Clone C75-5+297 has consistently out-yielded common varieties under disease stress. Using both molecular and cytogenetic approaches we demonstrated that a single copy of chromosome 8 from S. brevidens replaced a potato chromosome 8 in C75-5+297. Thus, C75-5+297 represents a potato- S. brevidens chromosome substitution line. Our results suggest that the presence of a single chromosome from S. brevidens may significantly impact the resistance to multiple potato diseases. The high yield potential of C75-5+297 makes it an excellent parent for developing potato varieties with resistances to both tuber soft rot and early blight.

Agriculture↗

PubMed2006

Detection of a quantitative trait locus for both foliage and tuber resistance to late blight [Phytophthora infestans (Mont.) de Bary] on chromosome 4 of a dihaploid potato clone (Solanum tuberosum subsp. tuberosum).

Linkage analysis, Kruskal-Wallis analysis, interval mapping and graphical genotyping were performed on a potato diploid backcross family comprising 120 clones segregating for resistance to late blight. A hybrid between the Solanum tuberosum dihaploid clone PDH247 and the long-day-adapted S. phureja clone DB226(70) had been crossed to DB226(70) to produce the backcross family. Eighteen AFLP primer combinations provided 186 and 123 informative maternal and paternal markers respectively, with 63 markers in common to both parents. Eleven microsatellite (SSR) markers proved useful for identifying chromosomes. Linkage maps of both backcross parents were constructed. The results of a Kruskal-Wallis analysis, interval mapping and graphical genotyping were all consistent with a QTL or QTLs for blight resistance between two AFLP markers 30 cM apart on chromosome 4, which was identified by a microsatellite marker. The simplest explanation of the results is a single QTL with an allele from the dihaploid parent conferring resistance to race 1, 4 of P. infestans in the foliage in the glasshouse and to race 1, 2, 3, 4, 6, 7 in the foliage in the field and in tubers from glasshouse raised plants. The QTL was of large effect, and explained 78 and 51% of the variation in phenotypic scores for foliage blight in the glasshouse and field respectively, as well as 27% of the variation in tuber blight. Graphical genotyping and the differences in blight scores between the parental clones showed that all of the foliage blight resistance is accounted for by chromosome 4, whereas undetected QTLs for tuber resistance probably exist on other chromosomes. Graphical genotyping also explained the lack of precision in mapping the QTL(s) in terms of lack of appropriate recombinant chromosomes.

Chromosome Mapping↗

PubMed2005

Decision making in the treatment of tuberous and tubular breasts: volume adjustment as a crucial stage in the surgical strategy.

Tuberous and tubular breasts, two distinct deformities based on the same anatomic anomaly, are characterized by several morphologic alterations with a wide spectrum of expression. The classifications reported in the literature are based primarily on deformity of shape, but other parameters such as breast volume and symmetry often are underrated. This study aimed to define tuberous and tubular breasts and their management accurately on the basis of multiple anatomic alterations involving breast volume and symmetry as well as shape. The records of 30 patients affected by tubular and tuberous breast were reviewed. Surgical strategy included correction of breast shape through areola and gland alterations, correction of volume asymmetry through parenchyma resection, and volume augmentation through permanent expandable breast implant insertion. All the patients were treated bilaterally. Evaluation using a visual analogic scale confirmed high patient satisfaction with a mean value of 92.6% in the assessment of shape, volume, and symmetry. Correct diagnosis, careful preoperative evaluation, and a comprehensive surgical strategy can achieve, in one surgical procedure, good and long-lasting outcomes in terms of breast shape and volume symmetry.

Adult↗

PubMed2006

Surgical reconstruction of tuberous breasts.

BACKGROUND: Tuberous breast deformity is a rare entity affecting young women bilaterally or unilaterally. It requires surgical correction, depending on the severity of the clinical expression, because of its aesthetic appearance. Since the presentation of the malformation by Rees and Aston in 1976, many surgical procedures have been developed, but the deformity still is one of the most challenging congenital breast anomalies. METHODS: Between September 1999 and September 2005, eight patients with tuberous breast deformity underwent surgery in our department. A two-stage approach was used to manage 14 tuberous breasts. We used a combination of anatomic textured tissue expanders with magnetic injection sites and silicone gel implants. Other reconstructive procedures such as mastopexy, breast reduction, and areolar reduction can be considered. RESULTS: Our long-term results, with a maximum follow-up of 6 years, were satisfying. They have been uniformly good and compare favorably with those presented in the literature when the use of other methods. CONCLUSIONS: This two-stage approach is a relatively simple, safe, and technically easy procedure that is easy to learn. The results achieved with this approach seem to be reliable and gratifying.

Breast↗

PubMed2004

Expression of the hepatitis B surface S and preS2 antigens in tubers of Solanum tuberosum.

In an attempt to develop an edible vaccine, we transformed a recombinant hepatitis B virus (HBV) gene encoding the middle protein of HBV that contains the surface S and preS2 antigen into potato by Agrobacterium-mediated transformation. The HBV gene was under control of either the CaMV 35S promoter, the double 35S promoter with the AlMV 5' non-translated leader sequence, or the tuber-specific patatin promoter. HBV mRNA levels were higher with the 35S promoter than with the double 35S and patatin promoters; however, the levels of the S and preS2 antigen in the transformed tubers were higher with the patatin promoter than with the CaMV 35S and double promoters. The levels of preS2 antigen produced are the highest reported to date. Transgenic potato tubers were fed to mice, and the mice showed an immune response against the HBV S antigen.

Animal Feed↗

PubMed2006

Artificial synthesis of interspecific chimeras between tuber mustard (Brassica juncea) and cabbage (Brassica oleracea) and cytological analysis.

Interspecific chimeras between tuber mustard and red cabbage were obtained by in vitro graft-culture method. Before grafting, 6-day-old seedlings of tuber mustard and red cabbage were vertically half-cut and treated with different concentrations of 6-BA and NAA for 1 min, then, they were symmetrically fit together. As a result, sectorial chimeras were initially produced from the united shoot tips. The maximum frequency of chimeral bud formation reached 6.33% when the vertical sections of tuber mustard and cabbage were treated with 2 mg/l 6-BA and 1 mg/l NAA. When sectorial chimeras were propagated on MS medium containing 1 mg/l 6-BA, periclinal and mericlinal chimeras gradually developed. Chimeral shoots were rooted on half-strength MS medium containing 0.1 mg/l NAA. The rooted chimeras were acclimatized and transferred to the field for cytological and morphological analysis. The results showed that stomata density in the chimeras was significantly higher than that of their parents, while chloroplast size, starch grain size and number were intermediate between the two parents. The chimeras were further analyzed by flow cytometry, and the results indicated that they contained both sets of parental chromosomes. Moreover, chimeral plants possessed valuable characters from the two parents.

Brassica↗

PubMed2002

Antisense repression of cytosolic phosphoglucomutase in potato (Solanum tuberosum) results in severe growth retardation, reduction in tuber number and altered carbon metabolism.

The aim of this work was to investigate the role of cytosolic phosphoglucomutase (PGM; EC 5.4.2.2) in the regulation of carbohydrate metabolism. Many in vitro studies have indicated that PGM plays a central role in carbohydrate metabolism; however, until now the importance of this enzyme in plants has not been subject to reverse-genetics investigations. With this intention we cloned the cytosolic isoform of potato PGM (StcPGM) and expressed this in the antisense orientation under the control of the CaMV 35 S promoter in potato plants. We confirmed that these plants contained reduced total PGM activity and that loss in activity was due specifically to a reduction in cytosolic PGM activity. These plants were characterised by a severe phenotype: stunted aerial growth combined with limited root growth and a reduced tuber yield. Analysis of the metabolism of these lines revealed that leaves of these plants were inhibited in sucrose synthesis whereas the tubers exhibited decreased levels of sucrose and starch as well as decreased levels of glycolytic intermediates but possessed unaltered levels of adenylates. Furthermore, a broader metabolite screen utilising GC-MS profiling revealed that these lines contained altered levels of several intermediates of the TCA cycle and of amino acids. In summary, we conclude that cytosolic PGM plays a crucial role in the sucrose synthetic pathway within the leaf and in starch accumulation within the tuber, and as such is important in the maintenance of sink-source relationships.

Amino Acids↗