[HPV-associated carcinomas of the female genital tract. Molecular mechanisms of development]. / HPV-assoziiertes Karzinom des weiblichen Genitaltrakts. Molekulare Mechanismen der Entstehung.

Infections with human papillomaviruses (HPV) are a common occurrence in both men and women. In contrast HPV-associated neoplasias are relatively rare and occur only in certain areas of the body. The virus has obviously developed efficient mechanisms for its persistence without inducing too much damage to the host. The formation of neoplasia seems to be more an exception. Epigenetic mechanisms play an important role in the regulation of viral gene expression. Investigations have indicated that exactly the transition from the permissive infection stage to a transformation stage, where neoplastic alterations can occur due to expression of the viral oncogenes, is associated with certain methylation patterns of the viral genome which promote the expression of the oncogenes E6 and E7. The transforming stage is seen as the actual carcinogenic event and can be immunohistochemically detected by the biomarker p16(INK4a).

Doxycycline control of prion protein transgene expression modulates prion disease in mice.

Conversion of the cellular prion protein (PrPC) into the pathogenic isoform (PrPSc) is the fundamental event underlying transmission and pathogenesis of prion diseases. To control the expression of PrPC in transgenic (Tg) mice, we used a tetracycline controlled transactivator (tTA) driven by the PrP gene control elements and a tTA-responsive promoter linked to a PrP gene [Gossen, M. and Bujard, H. (1992) Proc. Natl. Acad. Sci. USA 89, 5547-5551]. Adult Tg mice showed no deleterious effects upon repression of PrPC expression (>90%) by oral doxycycline, but the mice developed progressive ataxia at approximately 50 days after inoculation with prions unless maintained on doxycycline. Although Tg mice on doxycycline accumulated low levels of PrPSc, they showed no neurologic dysfunction, indicating that low levels of PrPSc can be tolerated. Use of the tTA system to control PrP expression allowed production of Tg mice with high levels of PrP that otherwise cause many embryonic and neonatal deaths. Measurement of PrPSc clearance in Tg mice should be possible, facilitating the development of pharmacotherapeutics.

Prion diseases.

There have been remarkably rapid advances in the understanding of prion diseases over the past year. The controversial notion that the transmissible agent may be an abnormal isoform of a host-encoded protein, the prion protein, is now gaining wide acceptance. The conundrum of how a disease can both be inherited as an autosomal dominant condition and also be experimentally transmissible by inoculation is beginning to make sense.

Auditory brain-stem response in zitter rats with genetic spongiform encephalopathy.

Zitter rats with genetic spongiform encephalopathy and hypomyelination developed an abnormal auditory brain-stem response (ABR) before the appearance of spongy lesions in the central nervous system (CNS). The ABR abnormalities were characterized by a dual peak of wave I, with a longer latency than in normal rats, and decreased or absent waves III and IV. Hypomyelination in both peripheral and central nerves may have been responsible for these abnormalities. The slow negative wave became wide and obscure with aging. These changes accompanied age-dependent progression of spongy changes in the CNS. These findings suggest that at least two mechanisms, one involving hypomyelination and the other causing spongy lesions, are responsible for the brain-stem auditory pathway dysfunction in zitter rats.

Fatal familial insomnia, a prion disease with a mutation at codon 178 of the prion protein gene.

BACKGROUND: We previously described two members of a family affected by an apparently genetically determined fatal disease characterized clinically by progressive insomnia, dysautonomia, and motor signs and characterized pathologically by severe atrophy of the anterior ventral and mediodorsal thalamic nuclei. Five other family members who died of this disease, which we termed "fatal familial insomnia," had broader neuropathologic changes suggesting that fatal familial insomnia could be a prion disease. METHODS: We used antibodies to prion protein (PrP) to perform dot and Western blot analyses, with and without proteinase K, on brain tissue obtained at autopsy from two patients with fatal familial insomnia, three patients with sporadic Creutzfeldt-Jakob disease, and six control subjects. The coding region of the PrP gene was amplified and sequenced in the samples from the two patients with fatal familial insomnia. Restriction-enzyme analysis was carried out with amplified PrP DNA from 33 members of the kindred. RESULTS: Protease-resistant PrP was found in both patients with fatal familial insomnia, but the size and number of protease-resistant fragments differed from those in Creutzfeldt-Jakob disease. In the family with fatal familial insomnia, all 4 affected members and 11 of the 29 unaffected members had a point mutation in PrP codon 178 that results in the substitution of asparagine for aspartic acid and elimination of the Tth111 I restriction site. Linkage analysis showed a close relation between the point mutation and the disease (maximal lod score, 3.4 when theta was zero). CONCLUSIONS: Fatal familial insomnia is a prion disease with a mutation in codon 178 of the PrP gene, but the disease phenotype seems to differ from that of previously described kindreds with the same point mutation.

A 'unified theory' of prion propagation.

There is now very persuasive evidence that the transmissible agent for spongiform encephalopathies such as scrapie, consists of a modified form of the normal host protein PrPc, devoid of any nucleic acid. On the other hand, because there are many different strains of scrapie agent with distinct phenotypes which can be propagated in animals homozygous for the PrPc gene, it has been suggested that a nucleic acid must be a component of the agent. Can the two views be reconciled?

Molecular biology and transgenetics of prion diseases.

Considerable progress has been made deciphering the role of an abnormal isoform of the prion protein (PrP) in scrapie of animals and Gerstmann-Sträussler syndrome (GSS) of humans. Some transgenic (Tg) mouse (Mo) lines that carry and express a Syrian hamster (Ha) PrP gene developed scrapie 75 d after inoculation with Ha prions; non-Tg mice failed to show symptoms after greater than 500 d. Brains of these infected Tg(HaPrP) mice featured protease-resistant HaPrPSc, amyloid plaques characteristic for Ha scrapie, and 10(9) ID50 units of Ha-specific prions upon bioassay. Studies on Syrian, Armenian, and Chinese hamsters suggest that the domain of the PrP molecule between codons 100 and 120 controls both the length of the incubation time and the deposition of PrP in amyloid plaques. Ataxic GSS in families shows genetic linkage to a mutation in the PrP gene, leading to the substitution of Leu for Pro at codon 102. Discovery of a point mutation in the Prp gene from humans with GSS established that GSS is unique among human diseases--it is both genetic and infectious. These results have revised thinking about sporadic Creutzfeldt-Jakob disease, suggesting it may arise from a somatic mutation. These findings combined with those from many other studies assert that PrPSc is a component of the transmissible particle, and the PrP amino acid sequence controls the neuropathology and species specificity of prion infectivity. The precise mechanism of PrPSc formation remains to be established. Attempts to demonstrate a scrapie-specific nucleic acid within highly purified preparations of prions have been unrewarding to date. Whether transmissible prions are composed only of PrPSc molecules or do they also contain a second component such as small polynucleotide remains uncertain.

Prion dementia without characteristic pathology.

Gerstmann-Sträussler syndrome (GSS) was diagnosed in a family with presenile dementia by prion protein gene analysis. Extensive histological examination of the brain of an affected individual from this family showed no characteristic features of GSS or Creutzfeldt-Jakob disease (CJD). Thus "spongiform encephalopathy" (GSS or CJD) cannot always be excluded on neuropathological grounds in an individual dying of a dementing condition, and the true prevalence of these diseases is likely to be underestimated. Screening by prion protein gene analysis will help to determine the full clinical and neuropathological phenotype in familial cases. This observation may be relevant to the assessment of possible transmission of bovine spongiform encephalopathy to man.

Creutzfeldt-Jakob disease and kuru patients lack a mutation consistently found in the Gerstmann-Sträussler-Scheinker syndrome.

We and others have recently reported that patients with the Gerstmann-Sträussler-Scheinker syndrome have a mutation at codon 102 of the gene coding for amyloid protein that accumulates in this disease. We report here that this mutation was not found in 5 familial and 27 sporadic cases of Creutzfeldt-Jakob disease or in 3 patients with kuru, so that although this mutation may be responsible for amyloidogenesis and transmissibility in Gerstmann-Sträussler-Scheinker syndrome, it cannot be the only cause of human spongiform encephalopathy.

Creutzfeldt-Jakob disease patients with congophilic kuru plaques have the missense variant prion protein common to Gerstmann-Sträussler syndrome.

Congophilic kuru plaques, one of the pathological hallmarks in kuru and Gerstmann-Sträussler syndrome, are sometimes present in patients with Creutzfeldt-Jakob disease (CJD). The congophilic kuru plaques are composed partly of a host-encoded prion protein, and a missense variant prion protein with the codon 102 proline-to-leucine change (Leu102) is commonly present in patients with Gerstmann-Sträussler syndrome. To investigate the relationship between this syndrome and CJD with congophilic kuru plaques, we made a sequence analysis of the prion protein gene from patients with CJD, with or without congophilic kuru plaques. We found no alterations other than the Leu102 change, common to Gerstmann-Sträussler syndrome, in one of the prion protein alleles of the patient with congophilic kuru plaques. In the prion protein genotype analysis of other patients with CJD, the Leu102 allele was revealed to be carried heterozygously by 6 of 7 patients who had CJD with congophilic kuru plaques, yet no patient with CJD without congophilic kuru plaques had this allele. Interestingly, the Leu102 allele was also carried by some unaffected relatives of 3 patients with CJD with congophilic kuru plaques but with no apparent familial occurrence of a similar neurological disorder. Our findings show that CJD with congophilic kuru plaques should be categorized as belonging to Gerstmann-Sträussler syndrome, not CJD, and also suggest that the variant prion protein with Leu102 is closely related to the amyloidogenesis seen in subjects with congophilic kuru plaques.