Defective collagen VI α6 chain expression in the skeletal muscle of patients with collagen VI-related myopathies.

Collagen VI is a non-fibrillar collagen present in the extracellular matrix (ECM) as a complex polymer; the mainly expressed form is composed of α1, α2 and α3 chains; mutations in genes encoding these chains cause myopathies known as Ullrich congenital muscular dystrophy (UCMD), Bethlem myopathy (BM) and myosclerosis myopathy (MM). The collagen VI α6 chain is a recently identified component of the ECM of the human skeletal muscle. Here we report that the α6 chain was dramatically reduced in skeletal muscle and muscle cell cultures of genetically characterized UCMD, BM and MM patients, independently of the clinical phenotype, the gene involved and the effect of the mutation on the expression of the "classical" α1α2α3 heterotrimer. By contrast, the collagen VI α6 chain was normally expressed or increased in the muscle of patients affected by other forms of muscular dystrophy, the overexpression matching with areas of increased fibrosis. In vitro treatment with TGF-ß1, a potent collagen inducer, promoted the collagen VI α6 chain deposition in the ECM of normal muscle cells, whereas, in cultures derived from collagen VI-related myopathy patients, the collagen VI α6 chain failed to develop a network outside the cells and accumulated in the endoplasmic reticulum. The defect of the α6 chain points to a contribution to the pathogenesis of collagen VI-related disorders.

Intronic breakpoint definition and transcription analysis in DMD/BMD patients with deletion/duplication at the 5' mutation hot spot of the dystrophin gene.

Dystrophin mutations occurring at the 5' end of the gene frequently behave as exceptions to the "frame rule," their clinical severity being variable and often not related to the perturbation of the translation reading frame. The molecular mechanisms underlying the phenotypic variability of 5' dystrophin mutations have not been fully clarified. We have characterized the genomic breakpoints within introns 2, 6 and 7 and identified the splicing profiles in a cohort of DMD/BMD patients with deletion of dystrophin exons 3-7, 3-6 and duplication of exons 2-4. Our findings indicate that the occurrence of intronic cryptic promoter as well as corrective splicing events are unlikely to play a role in exons 3-7 deleted patients phenotypic variability. Our data suggest that re-initiation of translation could represent a major mechanism responsible for the production of a residual dystrophin in some patients with exons 3-7 deletion. Furthermore, we observed that the out-of-frame exon 2a is almost constantly spliced into a proportion of the dystrophin transcripts in the analysed patients. In the exons 2-4 duplicated DMD patient, producing both in-frame and out-of-frame transcripts, this splicing behaviour might represent a critical factor contributing to the severe phenotype. In conclusion, we suggest that multiple mechanisms may have a role in modulating the outcome of 5' dystrophin mutations, including recoding mechanisms and unusual splicing choices.

Characterization of a 4-Mb region at chromosome 6q21 harboring a replicative senescence gene.

A 4-Mb region containing a senescence gene was defined at 6q21 by fluorescence in situ hybridization and deletion mapping after transfer of a normal human chromosome 6 to a BK virus-transformed mouse cell line. By screening three different yeast artificial chromosome (YAC) libraries, a YAC contig was constructed that covers the deleted region at 6q21. The contig is composed of 18 overlapping YACs with a size of 250-1800 kb and contains 3 CpG islands and 10 expressed sequence tags. By sequencing YACs and P1 artificial chromosomes, nine new sequence tagged sites and three new expressed sequence tags were detected that enrich the genetic resources of the region. The contig may also contain a fragile site, FRA6F, located close to a CpG island, which could be a landmark to localize the senescence gene. This YAC contig will be used to detect expressed sequences to clone and characterize the senescence gene at 6q21.

Transfer of human chromosome 3 to an ovarian carcinoma cell line identifies three regions on 3p involved in ovarian cancer.

The molecular pathogenesis of ovarian carcinoma involves altered expression of growth factors, activation of oncogenes and loss of tumor suppressor genes. Loss of heterozygosity on chromosomes 3p, 6q, 11p, 17 and 18q was reported as a significant alteration in ovarian cancer. However, no functional proof has been provided of tumor suppressor activity located in these chromosomal regions. We therefore introduced normal human chromosomes 3 and 11 into an ovarian carcinoma cell line by microcell mediated chromosome transfer. Transfer of chromosome 3 induced senescence and growth arrest as well as suppression of tumorigenicity. Tumors induced by chromosome 3 monochromosomic hybrids consistently lost three small regions on 3p, two of which located in 3p23-24.2 and one located in 3p21.1-21.2, suggesting that these chromosomal regions are important for suppression of tumorigenicity of ovarian carcinoma cells. Transfer of chromosome 11 reduced the in vitro growth properties of ovarian cancer cells but did not significantly affect tumorigenicity. These results provide functional evidence for chromosome 3 tumor suppressor activity in ovarian cancer and define the chromosomal regions on 3p involved in the pathogenesis of this tumor. This experimental system, based on functional effects, may be useful for further delimitation and isolation of critical regions on 3p involved in tumor suppression.

Mutation analysis of the MECP2 gene in British and Italian Rett syndrome females.

Rett syndrome is an X-linked dominant neurological disorder, which appears to be the commonest genetic cause of profound combined intellectual and physical disability in Caucasian females. Recently, this syndrome has been associated with mutations of the MECP2 gene, a transcriptional repressor of still unknown target genes. Here we report a detailed mutational analysis of 62 patients from UK and Italian archives, representing the first comparative study among different populations and one of the largest number of cases so far analyzed. We review the literature on MECP2 mutations in Rett syndrome. This analysis has permitted us to produce a map of the recurrent mutations identified in this and previous studies. Bioinformatic analysis of the mutations, taking advantage of structural and evolutionary data, leads us to postulate the existence of a new functional domain in the MeCP2 protein, which is conserved among brain-specific regulatory factors.

Antiangiogenic, antitumoural and antimetastatic effects of two distamycin A derivatives with anti-HIV-1 Tat activity in a Kaposi's sarcoma-like murine model.

The antiangiogenic, antitumoural and antimetastatic effects of two novel sulphonic derivatives of distamycin A, PNU145156E and PNU153429, were studied in a Kaposi's sarcoma-like tumour model obtained by injecting nude mice with cells releasing extracellular HIV-Tat protein, derived from a tumour which developed in a BK virus/tat transgenic mouse. Both PNU145156E and PNU153429 were administered intraperitoneally every fourth day for three weeks at doses of 100 or 50 mg/kg of body weight respectively, starting one day after injecting the tumour cells. Both drugs delayed tumour growth in nude mice, preventing neovascularization induced by the Tat protein. PNU153429 also significantly reduced the number and size of spontaneous tumour metastases. Both effects on tumour growth and metastases were augmented by treating simultaneously nude mice with 7.5 mg/kg of body weight of minocycline given per os daily for four weeks starting four days after injecting the tumour cells. Neither acute nor chronic toxic side-effects were observed during the life span of treated nude mice. Due to their antiangiogenic and anti-Tat effects, these drugs are promising for the treatment of Kaposi's sarcoma in AIDS patients.

Prevalence of liver tumours in HIV-1 tat-transgenic mice treated with urethane.

The human immunodeficiency virus type 1 (HIV-1) Tat protein stimulates cell proliferation, inhibits apoptosis, displays angiogenic functions and is believed to be involved in the pathogenesis of Kaposi's sarcoma (KS) and other tumours arising in AIDS patients. Tat-transgenic (TT) mice, which constitutively express Tat in all tissues and organs, may therefore be predisposed to tumorigenesis. To test this hypothesis, we treated TT mice with urethane, a general carcinogen inducing tumours of various organs. The results indicate that, after injection of urethane, the incidence of lung tumours and lymphomas is not significantly different in the TT and control (CC) mice, whereas liver preneoplastic lesions and tumours show a significantly greater incidence in TT than in CC mice. This remarkable carcinogenic effect of urethane for the liver may be due to a tat-induced predisposition, manifested as a liver cell dysplasia (LCD), spontaneously affecting most of the TT mice. LCD may exert a promoting effect by stimulating proliferation of cell clones initiated by the mutagenic effect of urethane. In addition, LCD, which is associated with aneuploidy and chromosome instability, may enhance the progression to malignancy of the preneoplastic lesions induced by urethane. Interestingly, a significantly greater incidence of vascular ectasias and haemangiomas was detected in the liver of urethane-treated TT mice, most likely due to the marked angiogenic properties of Tat. This study suggests a role for Tat in the promotion and progression of tumours initiated by exogenous and endogenous carcinogens in HIV-1-infected patients, thereby contributing to the tumorigenesis in the course of AIDS.

Exploring the clinical and epidemiological complexity of GJB2-linked deafness.

GJB2 mutation analysis was performed in 179 unrelated subjects with sporadic or familial hearing loss (HL). Among 57 families, 18 showed a vertical transmission of HL, the disease being present in two or three generations. Besides 155 nonsyndromic cases, 24 patients presenting with extra-auditory clinical signs were included in the molecular study. GJB2 mutation analysis was also performed in 19 subjects with an anamnestic history of perinatal risks factors for acquired HL. The 35delG mutation accounted for 22.1% of analyzed chromosomes in sporadic cases and 39.4% in familial cases; 35delG prevalence reached 41% in autosomal recessive and 44.4% in pseudodominant pedigrees. Two novel GJB2 mutations were identified in compound heterozygosity with 35delG allele (D159V, 284ins/dup[CACGT]). Two 35delG homozygous subjects were identified among HL cases classified as environmental in origin. Four patients 35delG heterozygous (35delG/V95M, 35delG/L90P, 35delG/167delT, and 35delG/?) and two homozygous presented with extra-auditory clinical signs involving different organs (skin, vascular system, hemopoietic lineages, and thyroid). In a high proportion of 35delG heterozygous HL patients (52%), no second GJB2 mutation was detected. The reported data highlight the complexity of the genetic epidemiology of GJB2-linked deafness, further enlarging the spectrum of situations in which GJB2 mutation analysis should be performed. The presence of extra-auditory signs in a significant portion of GJB2-mutated patients suggests the possibility that GJB2 loss of function could contribute to clinical phenotypes presenting in association with deafness. This hypothesis deserves further investigation. The failure to identify a presumed partnering GJB2 mutation in a high proportion of deaf patients remains a challenging problem to be clarified.

MECP2 gene mutation analysis in the British and Italian Rett Syndrome patients: hot spot map of the most recurrent mutations and bioinformatic analysis of a new MECP2 conserved region.

Rett syndrome (RTT) is an X-linked dominant neurological disorder, which appears to be the most common genetic cause of profound combined intellectual and physical disability in Caucasian females. This syndrome has been associated with mutations of the MECP2 gene, a transcriptional repressor of unknown target genes. We report a detailed mutational analysis of a large cohort of RTT patients from the UK and Italy. This study has permitted us to produce a hot spot map of the mutations identified. Bioinformatic analysis of the mutations, taking advantage of structural and evolutionary data, leads us to postulate the existence of a new functional domain in the MeCP2 protein, conserved among brain-specific regulatory factors.

[SV40 as a possible cofactor in the etiopathogenesis of mesothelioma and other human tumors]. / SV40 come possible cofattore nell'eziopatogenesi del mesotelioma e di altri tumori umani.

Simian virus 40 (SV40) has been introduced into the human population with contaminated polio vaccines between 1955 and 1963. Previous research conducted by southern blot hybridization and recent analysis by PCR have shown the presence of SW0 sequences in human brain tumors, mesotheliomas and osteosarcomas as well as in normal tissues such as blood and sperm fluids. SV40 RNA and T antigen were detected in the same tissues. All the samples were coinfected by BK Virus (BKV), suggesting that BKV may have a helper function for SV40 replication in human cells. The presence of SV40 in human tumors suggests that the virus may be a cofactor in the etiopathogenesis of human neoplasia. In addition, blood and semen may represent the vectors for transmission of SV40 by horizontal infection in the human population.

A patient with limb girdle muscular dystrophy carries a TRIM32 deletion, detected by a novel CGH array, in compound heterozygosis with a nonsense mutation.

Limb girdle muscular dystrophy 2H is a rare autosomal recessive muscular dystrophy, clinically highly variable, caused by mutations in the TRIM32 gene. Here we describe a 35-years-old who experienced progressive muscle weakness. The muscle biopsy revealed an unspecific pattern of atrophic and hypertrophic fibers; the immunohistochemistry for several proteins was normal. Comparative genomic hybridization (CGH) analysis showed a heterozygous deletion of the entire TRIM32 gene. On the other allele we identified the R316X nonsense mutation. The genetic diagnosis of LGMD2H in this case was reached by using a novel high throughput diagnostic tool.

Prenatal UPD testing survey in Robertsonian translocations.

A systematic search was made for uniparental disomy (UPD) in familial or de novo balanced Robertsonian translocations, identified by prenatal cytogenetic investigations. Parent-of-origin studies were performed using molecular markers for both chromosomes involved in the translocation. No UPD cases were identified out of 23 analysed cases. The results presented here, combined with other available data, provide preliminary elements for genetic counselling in these common chromosomal rearrangements.

Growth arrest and suppression of tumorigenicity of bladder-carcinoma cell lines induced by the P16/CDKN2 (p16INK4A, MTS1) gene and other loci on human chromosome 9.

Wild-type P16/CDKN2 (p16INK4A, MTS1) cDNA, directed by the cytomegalovirus (CMV) immediate early promoter, was transfected into RT4 and RT112 bladder-carcinoma cell lines bearing a mutated endogenous P16/CDKN2 gene and lacking endogenous P16/CDKN2 respectively. In both cases, only transfected clones with rearranged exogenous P16/CDKN2 cDNA could be grown and propagated in cell culture. This result is reminiscent of transfection of wild-type p53 into cells with a deleted or mutated endogenous gene and suggests that P16/CDKN2, over-expressed under control of the strong CMV promoter, induces growth arrest in RT4 and RT112 cells. Transfer of human chromosome 9 to RT4 cells produced RT4/H9 hybrid clones retaining the P16/CDKN2 gene, since in RT4/H9 cell clones P16/CDKN2-gene expression is modulated by the physiological control of chromosomal regulatory sequence. All the RT4/H9 clones lost the entire chromosome 9, except clone 4 and clone 5, which maintained a deleted and an intact chromosome 9 respectively. Loss of several loci in 9p21, including P16/CDKN2, in tumors induced in nude mice by clone 4 and clone 5 suggests that P16/CDKN2 or other genes in 9p21 suppress tumorigenicity in bladder-carcinoma cells. Tumors induced by clone 4 and clone 5 show loss of markers in 9q. The regions 9q22.3, 9q32-33 and 9q34.2, which were maintained in the 2 clones and lost in their derived tumors, may contain tumor-suppressor genes relevant in bladder carcinoma. The results of this study suggest that the P16/CDKN2 gene controls growth of bladder-carcinoma cells when it is over-expressed, and may be involved in the development of bladder carcinoma, but other genes in 9p21 and 9q may participate in bladder-cancer progression.

Morphological, histochemical, immunohistochemical, and ultrastructural characterization of tumors and dysplastic and non-neoplastic lesions arising in BK virus/tat transgenic mice.

To study the role in AIDS pathogenesis of the human immunodeficiency virus type 1 (HIV-1) Tat protein, a transactivator of viral and cellular genes, we generated transgenic mice with a recombinant DNA containing BK virus (BKV) early region and the HIV-1 tat gene, directed by its own promoter-enhancer. DNA hybridization revealed that the transgene is stably maintained in all organs of transgenic mice as a tandem insertion in a number of copies ranging from 5 to 20 per cell. In addition, tat and BKV RNA were expressed in all tissues. Transgenic mice developed three types of lesions: 1) tumors, 2) hyperplastic and dysplastic lesions, and 3) non-neoplastic lesions. Tumors of different histotypes, such as lymphomas, adenocarcinomas of skin glands, leiomyosarcomas, skin squamous cell carcinomas, hepatomas, hepatocarcinomas, and cavernous liver hemangiomas, developed in 29% of transgenic animals. The majority of tumors were malignant, invasive, and producing metastases. Conversely, tumors of only two histotypes (lymphomas and adenocarcinomas of skin glands) appeared in control mice. Hyperplastic and dysplastic lesions were more frequent in transgenic than in control mice and involved the skin or its adnexes, the liver and the rectum, indicating multiple targets for the activity of the transgene. Pyelonephritis, frequently complicated with hydronephrosis, inflammatory eye lesions, and amyloid depositions represented the most frequent non-neoplastic lesions detected in transgenic mice. Many of the pathological findings observed in this animal model are comparable to similar lesions appearing in AIDS patients, suggesting a relevant role for Tat in the pathogenesis of such lesions during the course of AIDS.

Simian virus 40 footprints in normal human tissues, brain and bone tumours of different histotypes.

SV40 footprints were investigated by PCR in normal human tissues and tumours of different histotypes, followed by Southern blot hybridization with a specific internal oligoprobe for SV40 DNA. Specific SV40 amplification products were detected at high prevalence in primary human brain tumours: 83% of choroid plexus papillomas, 75% ependymomas, 47% astrocytomas and 37% glioblastomas. SV40 footprints were also revealed in primary bone tumours: 35% osteosarcomas and Ewing's tumours. Positive normal tissue samples ranged from 45% of sperm fluids to 8% of brain tissue. Normal bone tissue specimens were SV40 negative. These results indicate that SV40 is associated with human brain and bone neoplasms, whereas normal bone and brain tissues were either SV40 negative or positive at low grade. SV40 footprints were found in other normal samples such as PBC, B- and T-lymphocytes and sperm fluids, indicating that SV40 is latent in these cells. Therefore, these cells may be vectors of SV40 in other host tissues and may spread SV40 infection by blood transfusion and sexual transmission in the human population.

Chromosomal aberrations induced by BK virus T antigen in human fibroblasts.

Human fibroblasts, transfected with a recombinant DNA containing the neo gene and BK virus (BKV) early region, which expresses BPV large T antigen (TAg), show cytogenetic alterations characterized by dicentric chromosomes and other structural aberrations such as deletions, duplications, translocations, and ring chromosomes. Such alterations were absent or significantly less frequent in human fibroblasts transfected with a plasmid expressing only the neo gene. The chromosome damage in BKV-transfected cells was evident before the appearance of the morphologically transformed phenotype and therefore seems to be a primary effect of TAg expression in human cells. The specific pattern of chromosome aberrations suggests the prevalence of an indirect clastogenic effect, determined by the inhibition of p53 regulatory functions on genome stability by BKV TAg. Due to the widespread distribution of BKV in the human population and to the latent state of BKV DNA in many human organs, the clastogenic activity of BKV TAg may potentially participate in an oncogenic process involving BKV latently infected cells.