Stickler syndrome in children: a radiological review

AIM

To review the radiological findings of the largest cohort to date of paediatric patients with Stickler syndrome, all with confirmed molecular genetic analysis and sub-typing.

PATIENTS AND METHODS

It is understood that the National Health Service (NHS) commissioned service at Addenbrookes Hospital, Cambridge, UK has the largest cohort of Stickler syndrome patients in the paediatric age group worldwide with 240 registered children. Fifty-nine were assessed radiologically and for their genotypes. These radiographs were reviewed and 74 knee, 45 pelvic, and 47 spinal examinations were evaluated.

RESULTS

Radiological features were noted in 45.9% of knee radiographs, 11.1% of pelvic radiographs, and 42.6% of spinal radiographs. The findings were reviewed in the light of each patient's specific genetic Stickler syndrome subtype.

CONCLUSION

The prevalence of orthopaedic abnormalities overall in the present series is substantially below those published in previous smaller case series. This would support the more recent findings of an array of ocular only phenotypes of Stickler syndrome described in the literature.

Bilateral giant retinal tears in Osteogenesis Imperfecta

Background

Osteogenesis imperfecta (OI) is a rare primarily autosomal dominant condition in which the connective tissues of bones, ligaments and sclerae do not form properly. Typically, mutations in COL1A1 and COL1A2 genes lead to the defective formation or quantity of type I collagen, the principle matrix in these tissues. Molecular genetic studies have now elucidated multiple genetic subtypes of the disorder but little literature exists on the risk of retinal tears and detachments in OI.

Case presentation

We report the first case of a child with a rare recessive type of OI, subtype VIII, resulting from a P3H1 (also known as LEPRE1) gene mutation presenting with bilateral giant retinal tears and the surgical challenges encountered in performing retinal detachment repair due to scleral thinning. The P3H1 gene encodes for prolyl 3-hydroxylase 1 which is involved in the post-translational modification of not only collagen type I but also types II and V which when mutated may result in pathological posterior vitreous detachment (PVD) and giant retinal tear detachments.

Conclusions

Genetic analyses are increasingly important in such cases and may guide patient monitoring and potential prophylactic treatment, known to significantly reduce the probability of giant retinal tear detachments in other high-risk collagenopathies such as Stickler Syndrome Type I.

Ophthalmic and molecular genetic findings in Kniest dysplasia

PURPOSE

To study the variability of the ophthalmic phenotype in Kniest dysplasia. Kniest dysplasia is an inherited disorder associated with defects in type II collagen and characterised by short-trunked dwarfism, kyphoscoliosis, and enlarged joints with restricted mobility. Other features include marked hand arthropathy, cleft palate, hearing loss, and ocular abnormalities (myopia, abnormal vitreous, and high risk of developing retinal detachment).

METHODS

Data from eight unrelated individuals with a clinical and molecular diagnosis of Kniest dysplasia are reported. Clinical assessment included an audiogram and ophthalmological examination in all but one patient who died in the immediate postnatal period. Sanger sequencing of the COL2A1 gene was performed.

RESULTS

Six of the seven patients tested were high myopes with one patient being an emmetrope. Bilateral quandratic cataracts and subluxed lenses were noted in one subject. Variable but abnormal vitreous architecture was observed in all seven individuals tested. Six of the seven patients had significant hearing impairment and five of the seven patients exhibited clefting abnormalities. One patient had bilateral retinal detachments in his twenties. Six dominant disease-causing COL2A1 variants were detected. In three cases, testing of parental samples revealed that the disease-causing variant was not present in either parent.

CONCLUSION

The ophthalmic features in Kniest dysplasia are very similar to those in other disorders of type II collagen such as Stickler syndrome. It is likely that different type II collagenopathies have a similar level of ocular morbidity and regular ophthalmologic examination is recommended. Kniest dysplasia is associated with heterozygous COL2A1 mutations that are frequently de novo.

Chronic wound and postamputation claudication pain in a diabetic patient

Underlying ischaemic disease should be excluded in patients with delayed wound healing. Contrast angiography is a useful imaging method for assessing the specific cause of wound chronicity and may also be helpful in assessing the aetiology of unexplained pain symptoms. Angioplasty provides a practical alternative to more invasive techniques in addressing peripheral ischaemia. Our patient suffered claudication-type pain in his thigh and a non-healing stump wound following below-knee amputation. Magnetic resonance angiography confirmed the presence of arterial stenoses and an angioplasty was successfully performed to improve patency of the profunda femoris vessel. Following the operation, the claudication pain symptoms were significantly reduced and the stump wound went on to heal.

Topical steroids for chronic wounds displaying abnormal inflammation

INTRODUCTION

Chronic, non-healing wounds are often characterised by an excessive, and detrimental, inflammatory response. We review our experience of using a combined topical steroid, antibiotic and antifungal preparation in the treatment of chronic wounds displaying abnormal and excessive inflammation.

METHODS

A retrospective review was undertaken of all patients being treated with a topical preparation containing a steroid (clobetasone butyrate 0.05%), antibiotic and antifungal at a tertiary wound healing centre over a ten-year period. Patients were selected as the primary treating physician felt the wounds were displaying excessive inflammation. Healing rates were calculated for before and during this treatment period for each patient. Changes in symptom burden (pain, odour and exudate levels) following topical application were also calculated.

RESULTS

Overall, 34 ulcers were identified from 25 individual patients (mean age: 65 years, range: 37-97 years) and 331 clinic visits were analysed, spanning a total time of 14,670 days (7,721 days 'before treatment' time, 6,949 days 'during treatment' time). Following treatment, 24 ulcers demonstrated faster rates of healing, 3 ulcers showed no significant change in healing rates and 7 were healing more slowly (p=0.0006). Treatment generally reduced the burden of pain and exudate, without affecting odour.

CONCLUSIONS

In normal wound healing, inflammation represents a transient but essential phase of tissue repair. In selected cases, direct application of a steroid containing agent has been shown to improve healing rates, presumably by curtailing this phase. Further evaluation is required to establish the role of preparations containing topical steroids without antimicrobials in the management of chronic wounds.

Type 1 Stickler syndrome: a histological and ultrastructural study of an untreated globe

AIMS

To present a histological and ultrastructural study of an untreated globe in a patient with genetically confirmed type 1 Stickler syndrome.

METHODS

Histological and electron microscopic examinations were performed on the enucleated globe from the proband of a pedigree with type 1 Stickler syndrome. Linkage analysis was carried out using polymorphic markers flanking the COL2A1 gene and the mutation was identified by direct sequencing.

RESULTS

The significant retinal abnormality was incarceration of vitreous collagen within glial strands on the inner surface of an atrophic and gliotic detached retina. The incarcerated collagenous layers contained glial cells and extended from the retina to form strands, some of which contributed to a retrolental membrane. Mutation screening detected a C to T mutation in exon 47 that inserted a premature termination codon into the reading frame of the mRNA. Sequence analysis of three of the four affected children confirmed that they were also heterozygous for the base change. The youngest child's DNA was not analysed.

CONCLUSIONS

The study represents the first evidence of abnormal interactions between pathological vitreous collagen and the inner retina in a patient with type 1 Stickler syndrome with a confirmed mutation in the COL2A1 gene.

Clinical features and surgical management of retinal detachment secondary to round retinal holes

AIMS

The majority of rhegmatogenous retinal detachments result from pathological posterior vitreous detachment (PVD) and secondary horseshoe or giant retinal tears. Retinal detachment without PVD is usually associated with either retinal dialysis or round retinal holes. This study characterises the features, surgical outcome, and incidence of bilateral involvement of detachment associated with round retinal holes.

METHODS

In all, 110 retinal detachments from 96 consecutive patients with retinal detachment secondary to round retinal holes were studied. Analysis of patient age, sex, refraction, preoperative visual acuity, presented symptoms, position and extent of detachment, number and distribution of holes present, posterior hyaloid membrane status, surgical management, outcome of surgery, and postoperative visual acuity were studied.

RESULTS

The mean age for patients was 34 years with a marked female preponderance (64%) and myopia (83%). The posterior hyaloid membrane remained attached in 95 eyes (86%). In all, 45% patients had bilateral pathology, of which 33% had 'mirror image' distribution. Detachments were predominantly shallow (93%) and slow in progression (17%). A total of 100 detachments were repaired with cryotherapy and scleral buckling, eight with cryotherapy alone, and one with laser retinopexy. In all, 99% detachments were successfully reattached with a single procedure. The mean follow-up period was 2 years. There were no instances of redetachment.

CONCLUSIONS

Round hole detachments are slowly evolving detachments with attached vitreous gel in young, predominantly female myopes. Examination of the fellow eye should be mandatory as there is a high incidence of bilateral pathology. Scleral buckling procedures remained highly effective in this selected group of patients.

Hyperconvolution of the inner limiting membrane in vitreomaculopathies

BACKGROUND

This study investigates the similarities and differences between epiretinal membranes in four clinically distinct types of vitreomaculopathy. We propose a hypothesis on the origin of the predominant cell type and its potential role in causing these conditions.

METHODS

Epiretinal membranes (ERMs) surgically removed from a prospective, consecutive series of vitrectomies for macular pucker associated with an untreated peripheral horseshoe tear (MP), cellophane maculopathy (CM), stage 4 macular hole (MH) and vitreomacular traction syndrome (VMT) were examined by light microscopy and by immunocytochemistry (ICC) using antibodies marking type IV collagen, type II collagen, glial fibrillary acidic protein (GFAP), and low- and high-molecular-weight cytokeratin (MNF116). These specimens were compared with post-mortem control eyes with and without physiological posterior vitreous detachment (PVD). Light microscopy was carried out on 5-microm-thick sections cut from formalin-fixed, paraffin-embedded tissue blocks. Appropriate autoclave or enzyme pre-digestion steps were deployed to retrieve antigens for ICC. No patient had undergone previous vitreoretinal surgery or peripheral retinopexy.

RESULTS

From a series of 38 patients, (13 CM, 8 MP, 16 MH and 1 VMT) a total of 20 specimens contained sufficient tissue for histology and immunocytochemistry. All specimens contained portions of inner limiting membrane (ILM) coated by GFAP-positive cells. Specimens from patients with MP and CM exhibited hyperconvolution of the ILM, which was not found in the specimens from patients with MH or VMT or in the control eyes. Hyperconvolution was associated with increased glial cell density, GFAP staining intensity and duplication of ILM basement membrane. Three cases of ERMs from the MP group contained, in addition, cytokeratin-positive cells. In the control group; post-mortem eyes with PVDs showed patchy staining of the posterior hyaloid membrane for GFAP and type 4 collagen. Post-mortem eyes with attached gel showed weak positivity of the ILM for type 4 collagen, and a monolayer of GFAP-positive cells lined the vitreous aspect of the ILM.

CONCLUSIONS

These results indicate that glial cells are fundamentally important in the formation of ERMs found in this group of vitreomaculopathies. The hyperconvolution and duplication of the ILM in CM and MP were striking and distinctive features and suggest a mechanism by which these membranes exert tractional forces on the retina. Post-mortem control eyes contained a similar (but more dispersed) population of GFAP-positive cells in the region of the ILM, suggesting the primary aetiology for CM and MP may originate within the ILM. ERMs from MP cases may, in addition, contain cytokeratin-positive cells, of probable RPE origin.

Relationships between soil heavy metal concentration and mycorrhizal colonisation in Thymus polytrichus in northern England

A study was conducted to establish whether the wild thyme [ Thymus polytrichus A. Kerner ex Borbás ssp. britannicus (Ronn.) Kerguelen (Lamiaceae)] growing in the metal-contaminated soils along the River South Tyne, United Kingdom, is colonised by arbuscular mycorrhizal (AM) fungi, and whether the degree of colonisation increases (perhaps suggesting increasing mycorrhizal dependence) or decreases (indicating possible inhibition of AM growth) with increasing degree of soil contamination. Seasonal changes in AM colonisation were also assessed. The AM fungal communities colonising T. polytrichus were also investigated, using the polymerase chain reaction with restriction fragment length polymorphism and sequencing of fungal DNA to establish whether AM species richness varied between sites, and whether fungal ecotypes specific to sites with different amounts of metal contamination could be identified. All plants examined were heavily colonised by AM fungi, and mean percentage root length colonised did not increase significantly with increasing soil metal contamination. However, AM vesicle abundance (percentage of mycorrhizal root length containing vesicles) at the most contaminated site was significantly greater than at the other sites. No significant seasonal variation in degree of colonisation or vesicle abundance was found. Glomus was the predominant AM genus detected at all sites. The number of AM genotypes colonising T. polytrichus roots was similar at all sites but, although some were common to all sites, certain strains appeared to be specific to either the most- or the least-contaminated site. This variation in species may account for the difference in vesicle abundance between sites. The consistently heavy AM colonisation of T. polytrichus found suggests that these fungi are not inhibited by soil heavy metals at these sites, and that the host derives some benefit from its AM symbiont.

Effects of mycorrhizal colonisation on Thymus polytrichus from heavy-metal-contaminated sites in northern England

A study was performed to establish whether colonisation with arbuscular mycorrhizal (AM) fungi is beneficial to wild thyme [ Thymus polytrichus A. Kerner ex Borbás ssp. britannicus (Ronn.) Kerguelen (Lamiaceae)] growing in the heavy-metal-contaminated soils along the River South Tyne, United Kingdom. T. polytrichus plants of the same genotype were grown under controlled conditions with and without Zn contamination, and differences between AM-colonised and -uncolonised plants in mean shoot and root growth (dry weight) and Zn concentration were assessed. When grown in the heavy-metal-contaminated, low-P soil from one of the South Tyne sites, AM-colonised plants grew significantly larger than uncolonised plants; however, there was no significant difference in growth between AM and non-AM plants grown in an artificial substrate with a larger available P concentration, with or without Zn contamination. Mycorrhizal colonisation increased tissue Zn concentrations during the experiments. It is concluded that AM fungi are beneficial, if not essential, to T. polytrichus growing in the low-nutrient soils along the River South Tyne, because of their role in enhancing plant uptake of P (and possibly other nutrients). There was no evidence from this study that the fungi reduce plant uptake of heavy metals at these sites, but rather increase Zn uptake. However, the resulting tissue metal concentrations do not appear to be large enough to be detrimental to plant growth.

Apomixis in flowering plants: an overview

Apomixis is a common feature of perennial plants, which occurs in ca. 60% of the British flora, but has been largely ignored by reproductive theoreticians. Successful individuals may cover huge areas, and live to great ages, favoured by 'symmetrical' selection. Apomixis is favoured by colonizing modes, for instance post-glacially. Despite its theoretical advantages, apomixis usually coexists with sexuality, suggesting 'hidden' disadvantages. Agamospermy (apomixis by seed) is relatively uncommon, but gains from the attributes of the seed. It pays agamospermy genes, which discourage recombination, to form co-adapted linkage groups, so that they become targets for disadvantageous recessive mutant accumulation. Consequently, agamospermy genes cannot succeed in diploids and agamosperms are hybrid and highly heterotic. Agamospermous endosperm may suffer from genomic imbalance, so that nutritious ovules, which can support embryos without endosperm, may be preadapted for agamospermy. When primary endosperm nucleus fertilization ('pseudogamy') continues as a requirement for many aposporous agamosperms, selfing sex becomes preadaptive and archesporial sex remains an option. Apomictic populations can be quite variable although apomictic families are much less variable than sexuals. Only in some diplosporous species does sex disappear completely, and in those species some release of variability may persist through somatic recombination. The search for an agamospermy gene suitable for genetic modification should target fertile sexuals with a single localized agamospermy (A) gene, which therefore lack a genetic load. The A gene should coexist alongside sexuality, so that it would be easy to select seedlings of sexual and asexual origins. Plants with sporophytic agamospermy provide all these attributes.

Vitreoretinopathy with phalangeal epiphyseal dysplasia, a type II collagenopathy resulting from a novel mutation in the C-propeptide region of the molecule

A large family with dominantly inherited rhegmatogenous retinal detachment, premature arthropathy, and development of phalangeal epiphyseal dysplasia, resulting in brachydactyly was linked to COL2A1, the gene encoding proalpha1(II) collagen. Mutational analysis of the gene by exon sequencing identified a novel mutation in the C-propeptide region of the molecule. The glycine to aspartic acid change occurred in a region that is highly conserved in all fibrillar collagen molecules. The resulting phenotype does not fit easily into pre-existing subgroups of the type II collagenopathies, which includes spondyloepiphyseal dysplasia, and the Kniest, Strudwick, and Stickler dysplasias.

Clinical, histological and ultrastructural studies of the posterior hyaloid membrane

AIMS

To investigate the histological, immunohistochemical and ultrastructural features of the posterior hyaloid membrane (PHM) in its naturally separated state in patients without previous surgery and slit-lamp documentation of antemortem posterior vitreous detachment (PVD).

METHODS

A prospective study was commenced in 1992 to recruit patients with physiological PVD from an unselected group of general medical inpatients and ascertain the prevalence of PVD. Postmortem specimens subsequently available were studied to analyse the clinicopathological correlation and processed using standard techniques for histology, immunohistochemistry and electron microscopy.

RESULTS

Eighty-five patients were examined with ages ranging from 68 to 98 yrs (mean 83.4 yrs). The posterior hyaloid membrane had clearly separated from the retina in 66% of eyes. Twenty-nine eyes from 15 patients were subsequently studied pathologically. The posterior hyaloid membrane exhibited a uniform cellular component, most densely populated around the Weiss' ring. The cells were characterised by oval or round nuclei, indistinct cytoplasm and were only seen within, or abutting, the weakly eosinophilic posterior hyaloid membrane. The posterior aspect of the posterior hyaloid membrane showed a convoluted appearance staining lightly with haematoxylin and eosin. The detached posterior hyaloid membrane exhibited focal positivity for GFAP and type IV collagen. Electron microscopy demonstrates both fibres and basement membrane associated with the cellular component including hemi-desmosome attachment plaques between the cells and basement membrane.

CONCLUSIONS

This study illustrates some of the structural differences between the posterior hyaloid membrane and the cortical vitreous gel it envelopes and demonstrates the presence of cells intimately associated with the posterior hyaloid membrane in its naturally separated state. We propose the cellular population integral to the PHM to be designated as laminocytes in order to emphasise their type IV collagen/basement membrane association and planar array within the membrane which separates at posterior vitreous detachment.

Molecular genetics of rhegmatogenous retinal detachment

Rhegmatogenous retinal detachment (RRD) most commonly occurs as a spontaneous event resulting from posterior vitreous detachment, typically between the ages of 40-70 yrs. It is also a feature in some inherited disorders, most commonly Stickler syndrome. The relationship between these inherited disorders and the spontaneous cases is unclear. Here in particular we review Stickler syndrome, and discuss the differential diagnosis of Stickler, Wagner and Marshall syndromes. Other rare inherited disorders associated with RRD are also briefly reviewed.

The effects of altitude, aspect, grazing and time on the proportion of cyanogenics in neighbouring populations of Trifolium repens L. (white clover)

The proportion of cyanogenic individuals of white clover amongst 200 individuals in each of 32 neighbouring populations in Northumberland, UK were recorded. Sites differed for four altitude zones, two aspects, and were either sheep pasture or ungrazed meadow. The proportion of cyanogenics showed a striking reduction with increasing altitude. Below 100 m, north-facing sites contained more cyanogenics than south-facing sites, but aspect did not affect higher sites. Grassland management had no effect on the proportion of cyanogenics. A 24-year study of one population showed highly significant changes in the proportion of cyanogenics over time, suggesting that a significant turnover of individuals occurs. In some cases, different size class cohorts varied for the proportion of cyanogenics within a year, and the same cohort varied between years. We conclude that environment at birth may determine the proportion of cyanogenics for that cohort, so that this proportion persists in that cohort as it matures. Comparisons of the proportion of cyanogenics with mean monthly averages for January minimum temperature, July maximum temperature and August rainfall showed a significant association only with mean January minima 2 1/2 years previously. We hypothesise that the 2 to 3-year cohort may predominate in this population. We suggest that winter cold and summer drought may both select against cyanogenics. Grazing by large herbivores does not favour cyanogenesis, but some invertebrate herbivory may do so. Most selection probably occurs at birth and will be greatest in populations with a high turnover.

Basilar artery aneurysm: an unusual cause of intractable hiccups

A70-year-old retired lorry driver was admitted as an emergency with a 2-day history of moderate amount of haematemesis, nausea, vomiting and intractable hiccups. He was a known hypertensive and 5 years previously had an episode of subarachnoid haemorrhage. Complications required the insertion of a Rickman reservoir shunt. Since the time of the subarachnoid haemorrhage, his hiccups had been almost constant despite taking chlorpromazine tablets 25 mg three times a day.

On examination, he had intractable hiccups. Cardiovascular, respiratory and abdominal examination were normal. Neurological examination revealed a right-sided partial third nerve palsy (with ptosis and pupillary sparing). He also had a right-sided squint operation during childhood. More detailed examination of the cranial nerves revealed mild right-sided glossopharyngeal and hypoglossal nerve palsies. Routine full blood count, blood biochemistry, chest X-ray and abdominal ultrasound scan were normal. Upper gastrointestinal endoscopy revealed a hiatus hernia with mild oesophagitis. He was started on omeprazole.

In view of the neurological findings and past history of subarachnoid bleed, a magnetic resonance imaging brain scan was performed. This revealed a large basilar artery aneurysm with a significant mass effect on the brainstem at the level of the border of fourth ventricle (Figures 1–3).

Alternative drug treatment in the form of nifedipine 10 mg three times a day was initiated instead of chlorpromazine and the hiccups resolved completely. On follow-up in the clinic a few months later, there was no recurrence of the hiccups.

Seed weight and seed number affect subsequent fitness in outcrossing and selfing Primula species

Using the outcrossing Primula farinosa and its autogamous selfing relatives P. scotica, P. scandinavica and P. stricta, we compared the fitness of light and heavy seeds. Heavy seeds germinated in greater numbers and more quickly. In competition with seedlings grown from lighter seeds, heavy seeds produced larger rosettes. In P. farinosa such seedlings went on to produce more seeds, and in two populations heavier seeds, than plants from lighter seeds. After transplantation to natural populations, seedlings of P. farinosa derived from heavy seeds produced larger rosettes, more flowers and seeds than those from lighter seeds in certain populations so that seedlings born of heavy seeds were much fitter than seedlings from lighter seeds. Average seed weight varied in inverse proportion to seed number per capsule. The autogamous species produced on average about twice as many seeds per capsule as P. farinosa. In P. scotica and P. stricta this difference appears to be due in part to assured fertilization, but this high fecundity did not cause disadvantageously light seeds. As these species produced fewer capsules per scape, their overall seed production was on average no greater than for P. farinosa. P. farinosa traded-off fitness between capsules with large seed numbers, which donated more offspring to the next generation, and those with small seed numbers, whose heavy seeds would be more likely to reproduce themselves in the next generation. We conclude that low fecundity in outcrossing species might at times be advantageous.

Anaemia, diarrhoea and opportunistic infections in Fell ponies

This report summarises clinical and pathological observations on Fell pony foals with a range of signs that included ill thrift, anaemia, respiratory infection, glossal hyperkeratosis and diarrhoea. Some of the foals had normochromic, normocytic anaemia and some had low levels of plasma proteins, including immunoglobulin G. Antibiotic and supportive treatment was ineffective and all affected foals died or were killed on humane grounds. Postmortem examination of 12 foals and tissues from 2 other foals revealed a range of lesions that included glossal hyperkeratosis, typhlocolitis, intestinal cryptosporidiosis, granulomatous enteritis, proliferative and necrotising bronchiolitis consistent with adenovirus infection; lesions similar to those in the respiratory tract were present in the salivary gland and pancreas of individual foals. Lymphoid tissue was judged to be smaller than expected. These observations suggest the possibility of opportunistic infections secondary to some form of undefined immunocompromised state.

COL2A1 exon 2 mutations: relevance to the Stickler and Wagner syndromes

AIMS

To compare the clinical and molecular genetic features of two phenotypically distinct subgroups of families with type 1 Stickler syndrome.

BACKGROUND

Stickler syndrome (hereditary arthro-ophthalmopathy, McKusick Nos 108300 and 184840) is a dominantly inherited disorder of collagen connective tissue, resulting in an abnormal vitreous, myopia, and a variable degree of orofacial abnormality, deafness, and arthropathy. Stickler syndrome is the commonest inherited cause of rhegmatogenous retinal detachment in childhood with a risk of giant retinal tear (GRT) which is commonly bilateral and a frequent cause of blindness.

METHOD

Pedigrees were identified from the vitreoretinal service database and subclassified according to vitreoretinal phenotype. Ophthalmic, skeletal, auditory, and orofacial features were assessed. Linkage analysis was carried out with markers for the candidate genes COL2A1, COL11A1, and COL11A2. The COL2A1 gene was amplified as five overlapping PCR products. Direct sequencing of individual exons identified mutations.

RESULTS

Eight families exhibiting the type 1 vitreous phenotype were studied. Seven were consistent for linkage to COL2A1, with lod scores ranging from 2.1 to 0.3. In most instances linkage to COL11A1 and COL11A2 could be excluded. One family was analysed without prior linkage analysis. Three of the families exhibited a predominantly ocular phenotype with minimal or absent systemic involvement and were found to have mutations in exon 2 of COL2A1. Five other pedigrees with an identical ocular phenotype plus orofacial, auditory, and articular involvement had mutations in others regions of the COL2A1 gene. None of the pedigrees exhibited the characteristic lenticular, retinal pigment epithelial, or choroidal changes seen in Wagner syndrome.

CONCLUSIONS

These data confirm that type 1 Stickler syndrome is caused by mutations in the gene encoding type II collagen (COL2A1). In addition, data are submitted showing that mutations involving exon 2 of COL2A1 are characterised by a predominantly ocular variant of this disorder, consistent with the major form of type II procollagen in non-ocular tissues having exon 2 spliced out. Such patients are all at high risk of retinal detachment. This has important implications for counselling patients with regard to the development of systemic complications. It also emphasises the importance and reliability of the ophthalmic examination in the differential diagnosis of this predominantly ocular form of Stickler syndrome from Wagner's vitreoretinopathy.

Differentiation of murine premigratory primordial germ cells in culture

In the mouse embryo, primordial germ cells first appear in the extraembryonic mesoderm and divide rapidly while migrating to the fetal gonad. Shortly after their arrival in the gonad, germ cells sexually differentiate as proliferation ceases. Previous studies have established that primordial germ cells proliferate and migrate in feeder layer culture. To explore cellular regulation of fetal germ cell development, we have used germ cell nuclear antigen 1 (GCNA1), a marker normally expressed only in postmigratory germ cells, to investigate the developmental potency of both pre- and postmigratory cells in this culture system. We found that explanted premigratory germ cells will initiate expression of this marker and are, therefore, capable of undertaking some aspects of gonocyte differentiation without intimate exposure to the fetal gonad. We have also tested whether postmigratory gonocytes are stable in culture. As detected by either alkaline phosphatase or GCNA1, we did not detect long-term survival of either prospermatogonia or oogonia under conditions that support the survival, proliferation, and differentiation of earlier premigratory cells. These observations are consistent with an autonomous cellular mechanism governing the initial stages of gonocyte differentiation, and suggest that differentiation towards gonocytes is accompanied by a change in requirements for cell survival.

Stickler syndrome: further mutations in COL11A1 and evidence for additional locus heterogeneity

Stickler syndrome (hereditary arthro-ophthalmopathy) is a dominantly inherited connective tissue disorder with ocular, oro-facial, auditory and skeletal manifestations. It is genetically and phenotypically heterogeneous with the majority of families having mutations in the gene encoding type II collagen (COL2A1) and exhibiting a characteristic 'membranous' or type 1 vitreous phenotype. More recently a novel mutation in the gene encoding the alpha1 chain of type XI collagen (COL11A1) was reported in a Stickler syndrome pedigree with a different 'beaded' or type 2 vitreous phenotype. In the present study five more families with the type 2 vitreous phenotype were examined for linkage to four candidate genes: COL2A1, COL5A2, COL11A1 and COL11A2. Two families were linked to COL11A1 and sequencing identified mutations resulting in shortened alphal(XI) collagen chains, one via exon skipping and the other via a multiexon deletion. One of the families showed weak linkage to COL5A2 but sequencing the open reading frame failed to identify a mutation. In the remaining two families all four loci were excluded by linkage analysis. These data confirm that mutations in COL11A1 cause Stickler syndrome with the type2 vitreous phenotype and also reveal further locus heterogeneity.

Activin and TGFbeta limit murine primordial germ cell proliferation

Mammalian primordial germ cells (PGCs) proliferate as they migrate from their initial location in the extraembryonic mesoderm to the genital ridge, the gonadal anlage. Once in the genital ridge, PGCs cease dividing and differentiate according to their gender. To identify ligands that might limit PGC proliferation, we analyzed growth factor receptors encoded in RNA obtained from purified germ cells shortly after their arrival in the genital ridge. Receptors for two members of the TGFbeta superfamily were found, TGFbeta1 and activin. As the signal-transducing domains of both receptor systems are highly conserved, the effects of both TGFbeta1 and activin on PGCs would be expected to be similar. We found that both ligands limited the accumulation of germ cells in primary PGC cultures. BrdU incorporation assays demonstrated that either ligand inhibits PGC proliferation. These results suggest that these signal transduction pathways are important elements of the mechanism that determines germ cell endowment.

A single base mutation in COL5A2 causes Ehlers-Danlos syndrome type II

Ehlers-Danlos syndrome (EDS) is a heterogeneous group of connective tissue disorders. Recently mutations have been found in the genes for type V collagen in a small number of people with the most common forms of EDS, types I and II. Here we characterise a COL5A2 mutation in an EDS II family. Cultured dermal fibroblasts obtained from an affected subject synthesised abnormal type V collagen. Haplotype analysis excluded COL5A1 but was concordant with COL5A2 as the disease locus. The entire open reading frame of the COL5A2 cDNA was directly sequenced and a single base mutation detected. It substituted a glycine residue within the triple helical domain (G934R) of alpha2(V) collagen, typical of the dominant negative changes in other collagens, which cause various other inherited connective tissue disorders. All three affected family members possessed the single base change, which was absent in 50 normal chromosomes.

A point mutation in an intronic branch site results in aberrant splicing of COL5A1 and in Ehlers-Danlos syndrome type II in two British families

Ehlers-Danlos syndrome (EDS) is a heterogeneous group of connective-tissue disorders characterized by skin fragility, joint laxity, and skeletal deformities. Type V collagen appears to have a causal role in EDS types I and II, which show phenotypic overlap and may sometimes be allelic. Type V collagen can exist as a heterotrimer, [alpha1(V)]2alpha2(V), and it both coassembles with and regulates type I collagen-fibril diameter. Using an intragenic COL5A1 polymorphism, we have demonstrated linkage, at zero recombination, to the same allele in two large British EDS type II families (LOD scores 4.1 and 4.3). Affected members from each family were heterozygous for a point mutation in intron 32 (IVS32:T-25G), causing the 45-bp exon 33 to be lost from the mRNA in approximately 60% of transcripts from the mutant gene. This mutation lies only 2 bp upstream of a highly conserved adenosine in the consensus branch-site sequence, which is required for lariat formation. Although both families shared the same marker allele, we have been unable to identify a common genealogy. This is the first description of a mutation at the lariat branch site, which plays a pivotal role in the splicing mechanism, in a collagen gene. Very probably, the resulting in-frame exon skip has a dominant-negative effect due to incorporation of the mutant proalpha chain into the triple-helical molecule. These findings further confirm the importance of type V collagen in the causation of EDS type II, and the novel collagen mutation indicates the importance of the lariat branch site in splicing.

Hydroxychloroquine myopathy

A woman with systemic lupus erythematosus developed severe myopathy after a septicemic episode, and her treatment before admission was hydroxychloroquine sulfate and prednisolone. A muscle biopsy revealed no evidence of vasculitis and creatine kinase was normal. She continued taking maintenance prednisolone and with intensive physiotherapy her muscle strength slowly returned. It is possible that the hydroxychloroquine was responsible for the myopathy.

Genetic linkage to the collagen alpha 1 (V) gene (COL5A1) in two British Ehlers-Danlos syndrome families with variable type I and II phenotypes

To investigate the role of COL5A1 as a candidate gene for Ehlers-Danlos syndrome (EDS), we have carried out linkage studies in two large British families with EDS type I/II and type II, respectively. Fourteen living, affected individuals were identified by family history, clinical examination and ultrastructural analysis. A polymorphic intragenic simple sequence repeat at the COL5A1 locus showed linkage to EDS without recombination to give a combined lod score of 5.7. We have previously reported linkage to COL5A1 in an EDS type I/II family which brings the total lod score to 9.8 at zero recombination. Taken together, these data implicate COL5A1 as an important cause of EDS and confirm that types I and II are allelic.

A family with Stickler syndrome type 2 has a mutation in the COL11A1 gene resulting in the substitution of glycine 97 by valine in alpha 1 (XI) collagen

Stickler syndrome (hereditary arthro-ophthalmopathy) is the commonest inherited cause of retinal detachment and one of the commonest autosomal dominant connective tissue dysplasias. There is clinical and locus heterogeneity with about two thirds of families linked to the gene encoding type II procollagen (COL2A1). Families with Sticklers syndrome type 1 have a characteristic congenital vitreous anomaly and are linked without recombination to markers at the COL2A1 locus. In contrast families with the type 2 variety have a different vitreo-retinal phenotype and are not linked to the COL2A1 gene. Type XI collagen is a quantitatively minor fibrillar collagen related to type V collagen and associated with the more abundant type II collagen fibrils. A mutation in COL11A2, the gene for alpha 2 (XI) procollagen, has recently been found in a family described as having Stickler syndrome, although there was no ocular involvement. Here we show for the first time that a family with the full Type 2 Stickler syndrome including vitreous and retinal abnormalities is linked to the COL11A1 gene and characterise the mutation as a Glycine to Valine substitution at position 97 of the triple helical domain caused by a single base G-->T mutation. These results are the first to provide confirmation that type XI collagen is an important structural component of human vitreous. They also support previous work suggesting that mutations in the genes encoding collagen XI can give rise to some manifestations of Stickler syndrome, but of these, only mutations in COL11A1 will give the full syndrome including the vitreo-retinal features.

COL3A1 mutations cause variable clinical phenotypes including acrogeria and vascular rupture

We have recently analysed by histological, protein and molecular DNA techniques 23 mutations of the collagen III gene (COL3A1), most of which cause premature arterial fragility, thin skin and variants of vascular Ehlers-Danlos syndrome. There were 14 glycine substitutions between residues 637 and 1021, eight exon skips between exons 7 and 45 and one small inframe deletion. The glycine substitutions produce a gradient of increasingly abnormal clinical phenotypes from exons 36 to 49 while the clinical severity of exon skips is much more variable. Each mutation is private for the affected family or individual concerned having the potential for early prenatal diagnosis and prevention.

Clinicopathological correlations of compound heterozygous COL7A1 mutations in recessive dystrophic epidermolysis bullosa

Recessive dystrophic epidermolysis bullosa is an inherited mechano-bullous disorder of skin and mucous membranes. Ultrastructurally, the disease is characterized by abnormalities of anchoring fibrils, attachment structures below the epidermal basement membrane, composed of type VII collagen. Mutations in the type VII collagen gene (COL7A1) have been shown conclusively to underlie dystrophic epidermolysis bullosa. Since there is variation of the phenotype, accompanied by heterogeneous anchoring fibril morphology and type VII collagen immunostaining, it is conceivable that different types and combinations of COL7A1 mutations correlate with different phenotypes. We therefore screened recessive dystrophic epidermolysis bullosa patients for COL7A1 mutations. Three unrelated patients showed the same premature termination codon mutation in exon 13 of one allele, yet they were all compound heterozygotes, each having a different mutation in the second allele. The first patient had a premature termination codon within the collagenous region of COL7A1 associated with severe disease, absent anchoring fibrils and undetectable type VII collagen immunostaining. The second had a premature termination codon in the non-collagenous NC-2 region associated with severe disease, wispy anchoring fibrils, and patchy type VII collagen immunostaining. The third had a glycine-to-aspartic acid substitution within the collagenous region, associated with milder disease, no identifiable anchoring fibrils, but near normal type VII collagen immunostaining. We conclude that the nature and position of mutations within COL7A1 correlate with specific disease features and may provide an insight into the molecular mechanisms of anchoring fibril formation and epidermal-dermal adhesion.

High purity, recovery, and selection of human blood cells with a novel high gradient magnetic separator

The selective isolation of cell subpopulations from previously cryopreserved human blood mononuclear cells was achieved magnetically using a novel, well-characterized conical funnel filter containing a variety of ordered wire arrays. Tetrameric antibody complexes targeted against the CD8 antigen were used to bind colloidal superparamagnetic dextran-iron particles to the desired cells with very low nonspecific binding. The novel design of the filter was such that the retention of cells at zero magnetic field was on average 0.9%. After two successive magnetic separations, an average purity of 98% was obtained for the desired labeled cells. A third separation gave > 99% purity. Purity was affected by the unlabeled cells, which expressed high intercellular adhesion (0.5% of the total cells). The ultimate recovery of the labeled cells was limited by the degree of nonmagnetic labeling of the cells expressing very low levels of targeted antigen. Recoveries could be as low as 78%, depending on the donor. The separation system described was believed suitable for difficult large-scale separations, that is, cells expressing the CD34 antigen.

Variation in seed production and germinability in common reed (Phragmites australis) in Britain and France with respect to climate

Northern populations of Phragmites australis (Cav.) Trin. ex Steud. (common reed) often flower so late that the ability to produce viable seeds before winter dieback can be limited. If climate changes as predicted, the reed may become able to set seed further north in its range. This would have implications for the ability of reed to colonize new sites as well as for the distribution of animals which eat reed seeds in winter. A survey of 34 British populations in 1993 and 1994 showed that seed production is highly variable between sites, ranging from 0 to 100%. Southern and western populations tended to show the highest seed sets, although some southern populations were infertile and some northern sites set seed. Average seed weight tended to be higher in sites which showed good seed set. Seeds from sites with high average seed weight tended to germinate more readily. The seed-setting capability of populations was successfully associated with climatic conditions at the time of flowering. However, seed weight was not found to relate to climate, but depended on seed production and overall plant height. Logistic regression modelling indicated that the best seed sets should occur in P. australis when: (i) August rainfall is low; (ii) the combined rainfalls of September and October are high; and (iii) the combined temperatures of these months are high. The model accounts for approximately one third of the variation in observed seed sets between sites, indicating that other, unmeasured, factors might also play a part in determining seed set in P. australis. At three northern populations which were studied in more detail, a number of genotypes coexisted, and legitimate pollen germination and pollen-tube growth was observed in each case. As no seed set occurred in two of these, self-incompatibility cannot explain poor seed setting.

Use of type VII collagen gene (COL7A1) markers in prenatal diagnosis of recessive dystrophic epidermolysis bullosa

Generalised recessive dystrophic epidermolysis bullosa (EB) is a severe inherited disease in which patients suffer from blistering and scarring of the skin and mucous membranes after minor mechanical trauma. Tight genetic linkage has been established to the type VII collagen gene (COL7A1) at 3p21, with no evidence of locus heterogeneity. Several COL7A1 mutations have now been identified in recessive dystrophic EB patients. Prenatal diagnosis has been performed by examination of a fetal skin biopsy taken at about 16 weeks' gestation, and relies on identification of characteristic ultrastructural and immunohistochemical changes. We have now achieved a first trimester prenatal diagnosis using intragenic and flanking COL7A1 markers in a pregnancy at risk for recessive dystrophic EB. Segregation of the informative markers predicted the baby would be an unaffected carrier. The pregnancy continued to term and a healthy baby was born, confirming this result.

Modeling cation/anion-water interactions in functional aluminosilicate structures

A need for the computer simulation of hydration/dehydration processes in functional aluminosilicate structures has been noted. Full and realistic simulations of these systems can be somewhat ambitious and require the aid of interactive computer graphics to identify key structural/chemical units, both in the devising of suitable water-ion simulation potentials and in the analysis of hydrogen-bonding schemes in the subsequent simulation studies. In this article, the former is demonstrated by the assembling of a range of essential water-ion potentials. These span the range of formal charges from +4e to -2e, and are evaluated in the context of three types of structure: a porous zeolite, calcium silicate cement, and layered clay. As an example of the latter, the computer graphics output from Monte Carlo computer simulation studies of hydration/dehydration in calcium-zeolite A is presented.

Efficient strategy for the detection of mutations in acrogeric Ehlers-Danlos syndrome type IV

cDNA encoding the C-terminal domain (nt2283 to 3714) of type III collagen was amplified by PCR in five overlapping products and examined for mutations in 13 patients with Ehlers-Danlos syndrome type IV (EDS IV) with uncharacterised lesions and in five control patients with known single base mutations. Six different point mutations were detected by denaturing gradient gel electrophoresis (DGGE), in addition to those in the known controls. Four of seven patients who had no point mutations in this region were shown to lack complete exons from their amplified cDNA. Mutations were detected in all patients with typical or acrogeric EDS IV, but only in one of four individuals with the atypical form of the disease.

Fitness constraints on flower number, seed number and seed size in the dimorphic species Primula farinosa L. and Armeria maritima (Miller) Willd

Using two dimorphic species with diallelic incompatibility, Primula farinosa L. and Armeria maritima (Miller) Willd., we tested the hypothesis that an association of seedling performance with seed size, and an inverse association of seed size with seed number, might, contrary to most fitness models, select for plants which set relatively few seeds. In P. farinosa we discovered positive relationships between seed number per capsule and capsule number per inflorescence. As capsules are formed in most flowers, scapes with few flowers set the fewest seeds per capsule. This suggests that conspicuousness to pollinators and/or plant resource play an important role in reproductive success in this species. Seed size and seedling performance were also positively associated. For P. farinosa, which has multi-seeded fruits, we discovered an inverse association between seed size and seed number for capsules containing more than 65 seeds. We suggest that stabilizing selection may occur for flower number per inflorescence in this species, as inflorescences with 8-11 capsules tend to set many seeds which may be inefficiently small. This tends to confirm our hypothesis. However, for A. maritima there is a positive association between seed size and seed number per inflorescence. For such plants with single-seeded fruits there should be directional selection for large flower number pet-inflorescence, a trend which may have led to the evolution of the capitulum.