Neural systems for choice and valuation with counterfactual learning signals

The purpose of this experiment was to test a computational model of reinforcement learning with and without fictive prediction error (FPE) signals to investigate how counterfactual consequences contribute to acquired representations of action-specific expected value, and to determine the functional neuroanatomy and neuromodulator systems that are involved. 80 male participants underwent dietary depletion of either tryptophan or tyrosine/phenylalanine to manipulate serotonin (5HT) and dopamine (DA), respectively. They completed 80 rounds (240 trials) of a strategic sequential investment task that required accepting interim losses in order to access a lucrative state and maximize long-term gains, while being scanned. We extended the standard Q-learning model by incorporating both counterfactual gains and losses into separate error signals. The FPE model explained the participants' data significantly better than a model that did not include counterfactual learning signals. Expected value from the FPE model was significantly correlated with BOLD signal change in the ventromedial prefrontal cortex (vmPFC) and posterior orbitofrontal cortex (OFC), whereas expected value from the standard model did not predict changes in neural activity. The depletion procedure revealed significantly different neural responses to expected value in the vmPFC, caudate, and dopaminergic midbrain in the vicinity of the substantia nigra (SN). Differences in neural activity were not evident in the standard Q-learning computational model. These findings demonstrate that FPE signals are an important component of valuation for decision making, and that the neural representation of expected value incorporates cortical and subcortical structures via interactions among serotonergic and dopaminergic modulator systems.

Successful endovascular repair of acute type B aortic dissection in undiagnosed Ehlers-Danlos syndrome type IV

A 61-year-old man presented with an acute type B aortic dissection for which a stent-graft was introduced. He remains complication-free 4 years onwards and has since been diagnosed with Ehlers-Danlos syndrome type IV (EDS IV). His particular mutation is predicted to result in lesser levels of normal collagen and may explain his favourable outcome from endovascular intervention. Understanding the genotype-phenotype correlation may influence the choice of therapy offered to patients with EDS IV.

Neurological presentation of Ehlers-Danlos syndrome type IV in a family with parental mosaicism

Ehlers-Danlos syndrome type IV (EDS-IV) is an autosomal-dominant disorder caused by a defect of type III collagen which leads to ruptures of arteries and hollow organs. Neurological presentation with muscle involvement and flexion contractures of the finger joints is uncommon. We clinically characterized seven members of a family with EDS-IV. The index patient, a young woman with an acrogeric face, suffered chronic muscle pain and cramps, Achilles tendon retraction, finger flexion contractures and seizures. The mother had similar features and had experienced an ischemic stroke. Biochemical study in cultured fibroblasts and molecular analysis of the COL3A1 gene led to the diagnosis of EDS-IV. A glycine substitution, p.G883V, within the triple helix of the alpha 1(III) chain, was found in the index patient and in the mother. The maternal grandfather and an aunt each had an abdominal aortic aneurysm, the rupture of which was the cause of death in the latter, at 40 years of age. Surprisingly, we found the mutation, as a mosaic, in the asymptomatic maternal grandmother. This expands the clinical spectrum of EDS type IV and confirms that in some families mosaicism can be identified as the source of the mutation.

A single amino acid substitution (D1441Y) in the carboxyl-terminal propeptide of the proalpha1(I) chain of type I collagen results in a lethal variant of osteogenesis imperfecta with features of dense bone diseases

Osteogenesis imperfecta (OI) is characterised by brittle bones and caused by mutations in the type I collagen genes, COL1A1 and COL1A2. We identified a mutation in the carboxyl-terminal propeptide coding region of one COL1A1 allele in an infant who died with an OI phenotype that differed from the usual lethal form and had regions of increased bone density. The newborn female had dysmorphic facial features, including loss of mandibular angle. Bilateral upper and lower limb contractures were present with multiple fractures in the long bones and ribs. The long bones were not compressed and their ends were radiographically dense. She died after a few hours and histopathological studies identified extramedullary haematopoiesis in the liver, little lamellar bone formation, decreased osteoclasts, abnormally thickened bony trabeculae with retained cartilage in long bones, and diminished marrow spaces similar to those seen in dense bone diseases such as osteopetrosis and pycnodysostosis. The child was heterozygous for a COL1A1 4321G-->T transversion in exon 52 that changed a conserved aspartic acid to tyrosine (D1441Y). Abnormal proalpha1(I) chains were slow to assemble into dimers and trimers, and abnormal molecules were retained intracellularly for an extended period. The secreted type I procollagen molecules synthesised by cultured dermal fibroblasts were overmodified along the full length but had normal thermal stability. These findings suggest that the unusual phenotype reflected both a diminished amount of secreted type I procollagen and the presence of a population of stable and overmodified molecules that might support increased mineralisation or interfere with degradation of bone.

Cyclosporin A and therapeutic plasma exchange in the treatment of severe systemic lupus erythematosus

Despite treatment with intensive immunosuppressive drug regimens, often the prognosis of patients suffering from systemic lupus erythematosus (SLE) is poor. Side effects such as infections and malignancies often occur. It was the aim of this trial to assess the effect of immunosuppression, in particular with cyclosporin, and the efficacy, safety, and clinical utility of intermittent treatment with therapeutic plasma exchange (TPE) in comparison to previous intensive therapy strategies using corticosteroids, azathioprine, and/or cyclophosphamide. In this prospective trial, 28 patients (24 women, 4 men, aged 36.3 +/- 11.8 years at the diagnosis of SLE) were treated for up to 10 years with drug regimens out of corticosteroids, azathioprine, and/or cyclophosphamide. Then, over a period of up to 8 years, in addition to conventional therapies, especially in active stages of the disease with extremely high concentrations of anti-DNA, anti-nuclear antibodies, and circulating immunocomplexes, TPE sessions were carried out depending on symptomatology. In addition, the patients received cyclosporin. Compared with previous treatment modalities, clinical symptoms improved more quickly and more effectively. During the study period of a mean of 5 years, corticosteroids, azathioprine, and cyclophosphamide were reduced by 40 to 100%. No severe side effects were seen. In acute stages of SLE and in forms with persistently high antibody levels, the addition of TPE sessions and cyclosporin as the basic immunosuppressive drug is mostly very effective with regard to improving clinical symptomatology.

Null alleles of the COL5A1 gene of type V collagen are a cause of the classical forms of Ehlers-Danlos syndrome (types I and II)

Ehlers-Danlos syndrome (EDS) types I and II, which comprise the classical variety, are well characterized from the clinical perspective, but it has been difficult to identify the molecular basis of the disorder in the majority of affected individuals. Several explanations for this failure to detect mutations have been proposed, including genetic heterogeneity, failure of allele expression, and technical difficulties. Genetic heterogeneity has been confirmed as an explanation for such failure, since causative mutations have been identified in the COL5A1, COL5A2, and tenascin X genes and since they have been inferred in the COL1A2 gene. Nonetheless, in the majority of families with autosomal dominant inheritance of EDS, there appears to be linkage to loci that contain the COL5A1 or COL5A2 genes. To determine whether allele-product instability could explain failure to identify some mutations, we analyzed polymorphic variants in the COL5A1 gene in 16 individuals, and we examined mRNA for the expression of both alleles and for alterations in splicing. We found a splice-site mutation in a single individual, and we determined that, in six individuals, the mRNA from one COL5A1 allele either was not expressed or was very unstable. We identified small insertions or deletions in five of these cell strains, but we could not identify the mutation in the sixth individual. Thus, although as many as one-half of the mutations that give rise to EDS types I and II are likely to lie in the COL5A1 gene, a significant portion of them result in very low levels of mRNA from the mutant allele, as a consequence of nonsense-mediated mRNA decay.

Clinical and genetic features of Ehlers-Danlos syndrome type IV, the vascular type

BACKGROUND

Ehlers-Danlos syndrome type IV, the vascular type, results from mutations in the gene for type III procollagen (COL3A1). Affected patients are at risk for arterial, bowel, and uterine rupture, but the timing of these events, their frequency, and the course of the disease are not well documented.

METHODS

We reviewed the clinical and family histories of and medical and surgical complications in 220 index patients with biochemically confirmed Ehlers-Danlos syndrome type IV and 199 of their affected relatives. We identified the underlying COL3A1 mutation in 135 index patients.

RESULTS

Complications were rare in childhood; 25 percent of the index patients had a first complication by the age of 20 years, and more than 80 percent had had at least one complication by the age of 40. The calculated median survival of the entire cohort was 48 years. Most deaths resulted from arterial rupture. Bowel rupture, which often involved the sigmoid colon, accounted for about a quarter of complications but rarely led to death. Complications of pregnancy led to death in 12 of the 81 women who became pregnant. The types of complications were not associated with specific mutations in COL3A1.

CONCLUSIONS

Although most affected patients survive the first and second major complications, Ehlers-Danlos syndrome type IV results in premature death. The diagnosis should be considered in young people who come to medical attention because of uterine rupture during pregnancy or arterial or visceral rupture.

Redefinition of exon 7 in the COL1A1 gene of type I collagen by an intron 8 splice-donor-site mutation in a form of osteogenesis imperfecta: influence of intron splice order on outcome of splice-site mutation

Most splice-site mutations lead to a limited array of products, including exon skipping, use of cryptic splice-acceptor or -donor sites, and intron inclusion. At the intron 8 splice-donor site of the COL1A1 gene, we identified a G+1-->A transition that resulted in the production of several splice products from the mutant allele. These included one in which the upstream exon 7 was extended by 96 nt, others in which either intron 8 or introns 7 and 8 were retained, one in which exon 8 was skipped, and one that used a cryptic donor site in exon 8. To determine the mechanism by which exon-7 redefinition might occur, we examined the order of intron removal in the region of the mutation by using intron/exon primer pairs to amplify regions of the precursor nuclear mRNA between exon 5 and exon 10. Removal of introns 5, 6, and 9 was rapid. Removal of intron 8 usually preceded removal of intron 7 in the normal gene, although, in a small proportion of copies, the order was reversed. The proportion of abnormal products suggested that exon 7 redefinition, intron 7 plus intron 8 inclusion, and exon 8 skipping all represented products of the impaired rapid pathway, whereas the intron-8 inclusion product resulted from use of the slow intron 7-first pathway. The very low-abundance cryptic exon 8 donor site product could have arisen from either pathway. These results suggest that there is commitment of the pre-mRNA to the two pathways, independent of the presence of the mutation, and that the order and rate of intron removal are important determinants of the outcome of splice-site mutations and may explain some unusual alterations.

Human Ehlers-Danlos syndrome type VII C and bovine dermatosparaxis are caused by mutations in the procollagen I N-proteinase gene

Ehlers-Danlos syndrome (EDS) type VIIC is a recessively inherited connective-tissue disorder, characterized by extreme skin fragility, characteristic facies, joint laxity, droopy skin, umbilical hernia, and blue sclera. Like the animal model dermatosparaxis, EDS type VIIC results from the absence of activity of procollagen I N-proteinase (pNPI), the enzyme that excises the N-propeptide of type I and type II procollagens. The pNPI enzyme is a metalloproteinase containing properdin repeats and a cysteine-rich domain with similarities to the disintegrin domain of reprolysins. We used bovine cDNA to isolate human pNPI. The human enzyme exists in two forms: a long version similar to the bovine enzyme and a short version that contains the Zn++-binding catalytic site but lacks the entire C-terminal domain in which the properdin repeats are located. We have identified the mutations that cause EDS type VIIC in the six known affected human individuals and also in one strain of dermatosparactic calf. Five of the individuals with EDS type VIIC were homozygous for a C-->T transition that results in a premature termination codon, Q225X. Four of these five patients were homozygous at three downstream polymorphic sites. The sixth patient was homozygous for a different transition that results in a premature termination codon, W795X. In the dermatosparactic calf, the mutation is a 17-bp deletion that changes the reading frame of the message. These data provide direct evidence that EDS type VIIC and dermatosparaxis result from mutations in the pNPI gene.

Large kindred with Ehlers-Danlos syndrome type IV due to a point mutation (G571S) in the COL3A1 gene of type III procollagen: low risk of pregnancy complications and unexpected longevity in some affected relatives

Ehlers-Danlos syndrome (EDS) type IV is an autosomal dominant connective tissue disorder. Early morbidity and mortality results from rupture of vessels and internal organs. A large kindred with EDS type IV was studied clinically, and the biochemical defects and underlying mutation in the COL3A1 gene that encodes the chains of type III procollagen were identified. A G-->A transition results in a single amino acid substitution, G571S, in the triple helical domain of the products of one COL3A1 allele. Although the clinical findings seen on examination are characteristic of EDS type IV, longevity is longer than that seen in many families and there is less pregnancy-associated morbidity or mortality than in some families. This suggests that some clinical aspects of EDS type IV may be related to the nature of the mutation and its effect on the behavior of the protein.

Multiple vascular and bowel ruptures in an adolescent male with sporadic Ehlers-Danlos syndrome type IV

Ehlers-Danlos syndrome (EDS) type IV is a heritable disorder resulting from mutations in the COL3A1 gene that cause deficient production of type III collagen. Clinical manifestations of EDS type IV include hypermobility of small joints, excessive bruisability, thin translucent skin, poor wound healing, bowel rupture, and vascular rupture that is often fatal. A 14-year-old male without a family history of EDS died following multiple bowel and abdominal blood vessel ruptures. Even in areas apart from rupture sites, the bowel wall was thin because of diminished submucosa and muscularis propria. Similarly, the walls of blood vessels in bowel submucosa and elsewhere in the abdomen varied in thickness, and contained frayed and fragmented elastic tissue fibers. Fibroblasts cultured from the patient's skin secreted reduced quantities of type III collagen that was explained by a point mutation in one copy of the COL3A1 gene. EDS type IV should be strongly suspected in any patient with otherwise unexplainable bowel and/or vessel rupture.

Splicing defects in the COL3A1 gene: marked preference for 5' (donor) spice-site mutations in patients with exon-skipping mutations and Ehlers-Danlos syndrome type IV

Ehlers-Danlos syndrome (EDS) type IV results from mutations in the COL3A1 gene, which encodes the constituent chains of type III procollagen. We have identified, in 33 unrelated individuals or families with EDS type IV, mutations that affect splicing, of which 30 are point mutations at splice junctions and 3 are small deletions that remove splice-junction sequences and partial exon sequences. Except for one point mutation at a donor site, which leads to partial intron inclusion, and a single base-pair substitution at an acceptor site, which gives rise to inclusion of the complete upstream intron into the mature mRNA, all mutations result in deletion of a single exon as the only splice alteration. Of the exon-skipping mutations that are due to single base substitutions, which we have identified in 28 separate individuals, only two affect the splice-acceptor site. The underrepresentation of splice acceptor-site mutations suggests that the favored consequence of 3' mutations is the use of an alternative acceptor site that creates a null allele with a premature-termination codon. The phenotypes of those mutations may differ, with respect to either their severity or their symptomatic range, from the usual presentation of EDS type IV and thus have been excluded from analysis.

Ehlers-Danlos syndrome type VIIA and VIIB result from splice-junction mutations or genomic deletions that involve exon 6 in the COL1A1 and COL1A2 genes of type I collagen

Ehlers-Danlos syndrome (EDS) type VII results from defects in the conversion of type I procollagen to collagen as a consequence of mutations in the substrate that alter the protease cleavage site (EDS type VIIA and VIIB) or in the protease itself (EDS type VIIC). We identified seven additional families in which EDS type VII is either dominantly inherited (one family with EDS type VIIB) or due to new dominant mutations (one family with EDS type VIIA and five families with EDS type VIIB). In six families, the mutations alter the consensus splice junctions, and, in the seventh family, the exon is deleted entirely. The COL1A1 mutation produced the most severe phenotypic effects, whereas those in the COL1A2 gene, regardless of the location or effect, produced congenital hip dislocation and other joint instability that was sometimes very marked. Fractures are seen in some people with EDS type VII, consistent with alterations in mineral deposition on collagen fibrils in bony tissues. These new findings expand the array of mutations known to cause EDS type VII and provide insight into genotype/phenotype relationships in these genes.

Mutations in the COL3A1 gene result in the Ehlers-Danlos syndrome type IV and alterations in the size and distribution of the major collagen fibrils of the dermis

Ehlers-Danlos syndrome type IV (EDS type IV) results from heterozygosity for mutations in the COL3A1 gene that encodes the chains of type III procollagen. By using light, transmission, and scanning electron microscopy, we examined skin biopsies from 22 individuals with EDS type IV in whom the COL3A1 mutations had been identified. The most striking changes in EDS type IV were correlated with point mutations that substituted a residue for a glycine near the carboxyl-terminal end of the triple-helical domain of pro alpha1(III). In three cases with the mutation G1012R, G1018V, or G1021E, cells in the dermis had extremely dilated rough endoplasmic reticulum (RER), the dermis was thin, and there was a reduced proportion of collagen although the proportion of elastic fibers appeared increased. In these tissues, collagen fibrils were small (65-80 nm) compared to normal (95-110 nm). Fibrils 80-90 nm in diameter and moderately dilated RER were found with mutations G769R, G373R, and G061E and with exon-skipping mutations of exons 34 and 45. With mutations G034R and G016C and exon-skipping mutations that deleted the sequences of exons 7, 8, 14, 18, 24, and 27, fibrils were more variable in size (85-120 nm). The composite collagen fibrils characteristic of EDS types I and II were not found in EDS type IV. These findings indicate that mutations in the COL3A1 gene have effects on secretion, fibrillogenesis, and skin architecture that reflect the position and nature of the mutation.

The deletion of six amino acids at the C-terminus of the alpha 1 (II) chain causes overmodification of type II and type XI collagen: further evidence for the association between small deletions in COL2A1 and Kniest dysplasia

We have identified an 18 bp deletion in exon 49 of the type II procollagen gene (COL2A1) in a patient with Kniest dysplasia. The deletion is located at the very C-terminus of the helical domain and removes two of three Gly-Pro-Pro triplets at positions 1007-1012, which are thought to be involved in helix formation and stability. Morphological investigation of an iliac crest biopsy showed large inclusions in the endoplasmic reticulum of chondrocytes, reflecting impaired secretion of type II collagen. Electrophoretic analysis of collagens extracted from cartilage or synthesised by cultured chondrocytes showed that type II and also type XI procollagen molecules containing mutant alpha 1 (II) chains showed post-translational overmodification. These observations provide further evidence for the general association of Kniest dysplasia with small deletions in the helical domain of type II collagen.

Non-radioactive multiplex-SSCP analysis: detection of a new type II procollagen gene (COL2A1) mutation

We have developed a protocol that allows fast and efficient mutation screening of the 54 exons from the type II procollagen (COL2A1) gene. The protocol is based on the multiple non-radioactive hybridization of blotted single-strand conformation polymorphism gels. Using this screening procedure we have been able to identify a new (Gly895 to Ser) mutation in the COL2A1 gene of a patient with a mild form of spondyloepiphyseal dysplasia congenita.

Autosomal dominant spondylarthropathy due to a type II procollagen gene (COL2A1) point mutation

Osteoarthrosis represents a very common disease with heterogeneous etiology. In some pedigrees linkage of the condition with the type II collagen gene (COL2A1) has been established, but information on the underlying gene defect is still incomplete as only one mutation causing this phenotype has been identified. We analyzed the COL2A1 gene in a 27-year-old woman and her 47-year-old mother presenting with severe premature osteoarthrosis and X-ray signs compatible with mild spondyloepiphyseal dysplasia. Examination of the complete gene in both patients was done by amplification of all 54 exons, screening of the PCR products by SSCP-analysis, and subsequent sequencing. In mother and daughter a G to A transition at the 5'-end of exon 21 was detected, leading to a substitution of serine for glycine at position 274 of the triple helical domain. The mutation was not present in unaffected family members or in healthy control individuals. The autosomal dominant spondylarthropathies may represent the less severe entities of the clinical spectrum of type II collagenopathies.

Kniest and Stickler dysplasia phenotypes caused by collagen type II gene (COL2A1) defect

Kniest and Stickler dysplasia are two chondrodysplasias characterized by specific phenotypes. No basic defect has been found in patients with Kniest dysplasia, whereas Stickler dysplasia is one of four chondrodysplasias for which mutations of type II procollagen gene (COL2A1) have been identified. We studied a 2-year-old girl presenting with manifestations of Kniest dysplasia and her mother showing a Stickler phenotype. Analysing COL2A1 in both patients, we detected the same 28 basepair deletion spanning the 3'-exon/intron boundary of exon 12 in mother and daughter. We were able to prove a somatic mosaic status for this mutation in the mother which accounts for her milder Stickler-like phenotype.

[Clinical importance of hepatitis B virus DNA detection in serum of children with chronic hepatitis B]

206 sera from 172 children with chronic hepatitis B infection were tested for HBV DNA by dot blot hybridization. 111 were positive and 95 negative for HBV DNA. 103 (78.6%) of the positive patients had HBeAg and 5 (7.7%) anti-HBe. In 60 (92.3%) of the anti-HBe positive sera no HBV DNA could be detected. Children with elevated liver enzymes had HBV DNA in 80.1%, whereas in 71.6% of the chronic HBsAg carriers with normal liver enzymes no HBV DNA was found. In 87 of the 95 dot blot negative patients polymerase chain reaction was performed. 73 (83.9%) children of this group were HBV DNA positive. All HBeAg positive patients and those with elevated aminotransferases had HBV DNA in their serum. 56 anti-HBe-positive HBsAg carriers were also positive; 14 were negative for HBV DNA. Our results demonstrate that viral sequences can be found in all HBeAg positive and in most of the anti-HBe positive children. Patients with ongoing virus replication have to be considered infectious and recommendation for vaccination of close relatives of these patients must be stressed.

[Retinoschisis with a giant central outer layer retinal tear and concomitant detachment]

The authors report on 2 cases with a special form of senile retinoschisis with retinal detachment. In both cases, a typical retinoschisis was combined with a giant tear of the outer retinal layer and a sickle-shaped retinal detachment extending almost to the macula. In contrast to previously published cases, which were treated by a conventional scleral buckling procedure or vitrectomy with fluid air exchange, it was decided to demarcate the retinal detachment by argon laser photocoagulation. The authors consider this non-invasive procedure sufficiently safe and effective.

Bioassay for determination of nystatin in faeces after oral application

An optimized bioassay (agar diffusion assay) using a defined Candida albicans strain as tester strain for determination of nystatin excreted with the faeces during and after oral application is presented. The sensitivity of the test achieves 39 IU nystatin/g faeces relating to the total amount of nystatin (using dimethylformide for solution of nystatin in the faeces) and 78 IU nystatin/g faeces relating to the biologically active portion (using aqua dest for suspension of nystatin from the faeces). Precision and reproducibility of the bioassay are assured by standardized procedures. By means of the bioassay, doses and application intervals for orally administered nystatin can be optimized.

[Temporal arteritis with hypotension syndrome and necrosis of the scalp]

An 80-year-old male patient with histologically confirmed temporal arteritis presented with two very rare complications: ocular hypotony and bilateral scalp necrosis. The intraocular pressure gradually normalized on high-dose cortisone therapy. Scalp necrosis was surgically removed and covered with a split-skin graft with good incorporation of the transplant. Scalp necrosis as well as ocular hypotony are serious complications of temporal arteritis, indicating a poor prognosis. To date three similar cases have been reported in the literature.