Axonal damage in acute multiple sclerosis lesions

One of the histological hallmarks of early multiple sclerosis lesions is primary demyelination, with myelin destruction and relative sparing of axons. On the other hand, it is widely accepted that axonal loss occurs in, and is responsible for, the permanent disability characterizing the later chronic progressive stage of the disease. In this study, we have used an antibody against amyloid precursor protein, known to be a sensitive marker of axonal damage in a number of other contexts, in immunocytochemical experiments on paraffin embedded multiple sclerosis lesions of varying ages in order to see at which stage of the disease axonal damage, in addition to demyelination, occurs and may thus contribute to the development of disability in patients. The results show the expression of amyloid precursor protein in damaged axons within acute multiple sclerosis lesions, and in the active borders of less acute lesions. This observation may have implications for the design and timing of therapeutic intervention, one of the most important aims of which must be the reduction of permanent disability.

A study of the quality of life and cost-utility of renal transplantation

The objective of this study was to assess the cost-utility of renal transplantation compared with dialysis. To accomplish this, a prospective cohort of pre-transplant patients were followed for up to two years after renal transplantation at three University-based Canadian hospitals. A total of 168 patients were followed for an average of 19.5 months after transplantation. Health-related quality of life was assessed using a hemodialysis questionnaire, a transplant questionnaire, the Sickness Impact Profile, and the Time Trade-Off Technique. Fully allocated costs were determined by prospectively recording resource use in all patients. A societal perspective was taken. By six months after transplantation, the mean health-related quality of life scores of almost all measures had improved compared to pre-transplantation, and they stayed improved throughout the two years of follow up. The mean time trade-off score was 0.57 pre-transplant and 0.70 two years after transplantation. The proportion of individuals employed increased from 30% before transplantation to 45% two years after transplantation. Employment prior to transplantation [relative risk (RR) = 23], graft function (RR 10) and age (RR 1.6 for every decrease in age by one decade), independently predicted employment status after transplantation. The cost of pre-transplant care ($66,782 Can 1994) and the cost of the first year after transplantation ($66,290) were similar. Transplantation was considerably less expensive during the second year after transplantation ($27,875). Over the two years, transplantation was both more effective and less costly than dialysis. This was true for all subgroups of patients examined, including patients older than 60 and diabetics. We conclude that renal transplantation was more effective and less costly than dialysis in all subgroups of patients examined.

The International Personality Disorder Examination. The World Health Organization/Alcohol, Drug Abuse, and Mental Health Administration international pilot study of personality disorders

BACKGROUND

One of the aims of the World Health Organization/Alcohol, Drug Abuse, and Mental Health Administration joint program on psychiatric diagnosis and classification is the development and standardization of diagnostic assessment instruments for use in clinical research worldwide. The International Personality Disorder Examination (IPDE) is a semistructured clinical interview compatible with the International Classification of Diseases, Tenth Revision, and the DMS-III-R classification systems. This is the first report of the results of a field trial to investigate the feasibility of using the IPDE to assess personality disorders worldwide.

METHODS

The IPDE was administered by 58 psychiatrists and clinical psychologists to 716 patients enrolled in clinical facilities at 14 participating centers in 11 countries in North America, Europe, Africa, and Asia. To determine interrater reliability, 141 of the IPDEs (20%) were independently rated by a silent observer. To determine temporal stability, 243 patients (34%) were reexamined after an average interval of 6 months.

RESULTS

The IPDE proved acceptable to clinicians and demonstrated an interrater reliability and temporal stability roughly similar to instruments used to diagnose the psychoses, mood, anxiety, and substance use disorders.

CONCLUSION

It is possible to assess personality disorders with reasonably good reliability in different nations, languages, and cultures using a semistructured clinical interview that experienced clinicians find relevant, meaningful, and user-friendly.

X-linked anhidrotic (hypohidrotic) ectodermal dysplasia is caused by mutation in a novel transmembrane protein

Ectodermal dysplasias comprise over 150 syndromes of unknown pathogenesis. X-linked anhidrotic ectodermal dysplasia (EDA) is characterized by abnormal hair, teeth and sweat glands. We now describe the positional cloning of the gene mutated in EDA. Two exons, separated by a 200-kilobase intron, encode a predicted 135-residue transmembrane protein. The gene is disrupted in six patients with X;autosome translocations or submicroscopic deletions; nine patients had point mutations. The gene is expressed in keratinocytes, hair follicles, and sweat glands, and in other adult and fetal tissues. The predicted EDA protein may belong to a novel class with a role in epithelial-mesenchymal signalling.

Eosinophilic mucin rhinosinusitis: a distinct clinicopathological entity

BACKGROUND

Allergic fungal sinusitis (AFS) was recognized in 1981. Since 1983, a form of sinusitis histologically similar to AFS except for the absence of fungal hyphae has also been noted. The designation "eosinophilic mucin rhinosinusitis (EMRS)" is proposed. Its relationship to AFS is controversial and problematic.

OBJECTIVE

To determine whether distinctive clinical and immunological differences exist to differentiate the histological entity of EMRS from AFS.

STUDY DESIGN

Literature review and comparison of cases of AFS (n = 418) to EMRS (n = 40) from the literature, as well as cases of AFS (n = 13) and EMRS (n = 29) accrued in the present study.

RESULTS

A total of 431 AFS patients were compared with 69 EMRS patients. The mean age of patients with AFS was significantly younger than patients with EMRS (30.7 y compared with 48.0 y, respectively; P < .001). Male-to-female ratios were 1.03:1 and 1.26:1 for AFS and EMRS, respectively, and were not significantly different. Forty-one percent of patients with AFS were asthmatic compared with 93% of patients with EMRS (P < .0001). Thirteen percent of patients with AFS were aspirin sensitive compared with 54% of patients with EMRS (P < .0001). Polyp occurrence was almost 100% in both groups. Eighty-four percent of patients with AFS had allergic rhinitis (AR), while only 63% of patients with EMRS had AR (P = .004). Fifty-five percent of AFS patients had bilateral disease, in contrast to the 100% of EMRS patients with bilateral disease (P < .0001). Although average total immunoglobulin E (IgE) was elevated in both groups, it was significantly more elevated in AFS patients (range, 12-13,084 mg/ dL; mean, 1,941 mg/dL) compared with EMRS patients (range, 14-1,162 mg/dL; mean, 267 mg/dL; P < .001). Total immunoglobulin G (IgG) and IgG subclasses were seldom reported in the cases available from the literature of either AFS or EMRS. However, in the present series of EMRS, IgG1 deficiency occurred in 50% of evaluated patients (mean, 475 +/- 175 mg/dL; range, 250-869 mg/dL; normal, 422 to 1,200 mg/dL) but in no cases of AFS reported in the literature.

CONCLUSIONS

Significant clinical and immunological differences exist to distinguish AFS from EMRS. It is postulated that AFS is an allergic response to fungi in predisposed individuals, while EMRS occurs because of a systemic dysregulation of immunological controls. Because EMRS is a systemic disease, unilateral disease is not seen. In contrast, AFS, an allergic response to fungi, may occur unilaterally or bilaterally depending on the antigenic stimulation. EMRS also has a significantly higher association with asthma, an increased incidence of aspirin sensitivity, and an increased incidence of IgG1 deficiency. Therapy with a systemic steroid, a potent and indiscriminant anti-inflammatory agent, is a useful adjunct in both disorders. Fungal immunotherapy following surgical extirpation of AFS is useful in preventing AFS recurrence. It is predicted that fungal immunotherapy and antifungal agents will be ineffective in patients with EMRS. It is important to differentiate these two similar histopathological entities in future trials assessing therapeutic efficacy. Inclusion of both entities in a study could obscure recognition of the true effectiveness of intervention, because of the possible variable response differences between the two entities. This study shows that significant clinical and immunological differences exist between EMRS and AFS. The future awaits an exploration of the pathophysiological basis of these differences.

Effect of discussion and deliberation on the public's views of priority setting in health care: focus group study

OBJECTIVE

To investigate the extent to which people change their views about priority setting in health care as a result of discussion and deliberation.

DESIGN

A random sample of patients from two urban general practices was invited to attend two focus group meetings, a fortnight apart.

SETTING

North Yorkshire Health Authority.

SUBJECTS

60 randomly chosen patients meeting in 10 groups of five to seven people.

MAIN OUTCOME MEASURES

Differences between people's views at the start of the first meeting and at the end of the second meeting, after they have had an opportunity for discussion and deliberation, measured by questionnaires at the start of the first meeting and the end of the second meeting.

RESULTS

Respondents became more reticent about the role that their views should play in determining priorities and more sympathetic to the role that healthcare managers play. About a half of respondents initially wanted to give lower priority to smokers, heavy drinkers, and illegal drug users, but after discussion many no longer wished to discriminate against these people.

CONCLUSION

The public's views about setting priorities in health care are systematically different when they have been given an opportunity to discuss the issues. If the considered opinions of the general public are required, surveys that do not allow respondents time or opportunity for reflection may be of doubtful value.

Identification of a new splice form of the EDA1 gene permits detection of nearly all X-linked hypohidrotic ectodermal dysplasia mutations

X-linked hypohidrotic ectodermal dysplasia (XLHED), the most common of the ectodermal dysplasias, results in the abnormal development of teeth, hair, and eccrine sweat glands. The gene responsible for this disorder, EDA1, was identified by isolation of a single cDNA that was predicted to encode a 135-amino-acid protein. Mutations in this splice form were detected in <10% of families with XLHED. The subsequent cloning of the murine homologue of the EDA1 gene (Tabby [Ta]) allowed us to identify a second putative isoform of the EDA1 protein (isoform II) in humans. This EDA1 cDNA is predicted to encode a 391-residue protein, of which 256 amino acids are encoded by the new exons. The putative protein is 94% identical to the Ta protein and includes a collagen-like domain with 19 repeats of a Gly-X-Y motif in the presumptive extracellular domain. The genomic structure of the EDA1 gene was established, and the complete sequence of the seven new exons was determined in 18 XLHED-affected males. Putative mutations, including 12 missense, one nonsense, and four deletion mutations, were identified in approximately 95% of the families. The results suggest that EDA1 isoform II plays a critical role in tooth, hair, and sweat gland morphogenesis, whereas the biological significance of isoform I remains unclear. Identification of mutations in nearly all of the XLHED families studied suggests that direct molecular diagnosis of the disorder is feasible. Direct diagnosis will allow carrier detection in families with a single affected male and will assist in distinguishing XLHED from the rarer, clinically indistinguishable, autosomal recessive form of the disorder.

Prevalence of speech and language disorders in 5-year-old kindergarten children in the Ottawa-Carleton region

A representative sample of 5-year-old kindergarten children was assessed for speech and/or language disorder. Of the 1,655 children tested, 180 were identified as having speech or language impairment. It is estimated that within the total reference population, between 16.2% and 21.8% would show some impairment; for the boys, the rate would be 15.5% to 20.7% and for the girls, between 19.1% and 25.1%. Most of these children would show some language impairment as opposed to speech problems only. Approximately 36% of the identified boys and 30% of the girls would have speech problems only, the remainder having speech and language problems or language problems only. Followup studies of these children are needed to ascertain their outcome and language status in middle childhood.

Definitions of fungal rhinosinusitis

Classification of fungal rhinosinusitis is important for the accurate prediction of prognosis and direct therapy. The most important distinction is between invasive and noninvasive fungal rhinosinusitis. Within the invasive division are acute invasive and chronic invasive (granulomatous and nongranulomatous forms) rhinosinusitis. Within the noninvasive division are saprophytic colonization, fungus balls, and allergic fungal rhinosinusitis. This article briefly outlines the definition and management of each of these manifestations.

Randomized controlled trial of brief cognitive behaviour therapy versus treatment as usual in recurrent deliberate self-harm: the POPMACT study

BACKGROUND

We carried out a large randomized trial of a brief form of cognitive therapy, manual-assisted cognitive behaviour therapy (MACT) versus treatment as usual (TAU) for deliberate self-harm.

METHOD

Patients presenting with recurrent deliberate self-harm in five centres were randomized to either MACT or (TAU) and followed up over 1 year. MACT patients received a booklet based on cognitive behaviour therapy (CBT) principles and were offered up to five plus two booster sessions of CBT from a therapist in the first 3 months of the study. Ratings of parasuicide risk, anxiety, depression, social functioning and global function, positive and negative thinking, and quality of life were measured at baseline and after 6 and 12 months.

RESULTS

Four hundred and eighty patients were randomized. Sixty per cent of the MACT group had both the booklet and CBT sessions. There were seven suicides, five in the TAU group. The main outcome measure, the proportion of those repeating deliberate self-harm in the 12 months of the study, showed no significant difference between those treated with MACT (39%) and treatment as usual (46%) (OR 0.78, 95% CI 0.53 to 1.14, P=0.20).

CONCLUSION

Brief cognitive behaviour therapy is of limited efficacy in reducing self-harm repetition, but the findings taken in conjunctin with the economic evaluation (Byford et al. 2003) indicate superiority of MACT over TAU in terms of cost and effectiveness combined.

Fungus balls of the paranasal sinuses

Fungus balls of the paranasal sinuses represent a noninvasive manifestation of fungal sinusitis. Patients are immunocompetent but no more allergic than the general population. There is little tissue reaction to the tangled mat of hyphae. If the patient becomes immunocompromised, then the fungus ball may become invasive, as illustrated by an included case report. One hundred sixty-three additional cases of patients with paranasal sinus fungus balls are reviewed from the literature.

Mucormycosis of the nose and paranasal sinuses

Rhinocerebral mucormycosis is an invasive fungal infection initiated in the paranasal sinuses that frequently progresses to orbital and brain involvement. If recognized early, involvement is limited to the nasal cavity and paranasal sinuses. Diabetics in poor control are at greatest risk, however, any immunocompromised individual may be infected. The mainstays of therapy are reversal of immunosuppression, systemic amphortericin B, and surgical débridement. Survival has improved dramatically, yet deaths still occur if the infection is not recognized and not treated early in its course or if the source of immunocompromise is not reversible. Several case examples illustrate the clinical course of this unusual, but potentially fatal, fungal infection. Taxonomy, clinical presentation, diagnosis, and management of mucormycosis of the paranasal sinuses are reviewed in detail.

Geographic variation in allergic fungal rhinosinusitis

Allergic fungal rhinosinusitis (AFRS) has a worldwide distribution. This survey of 20 otolaryngologic practices throughout the United States confirmed a variation in the frequency of AFRS relative to endoscopic sinus procedures performed for all other diagnoses. The highest incidence occurred in Memphis, Tennessee at 23%, with three other southern practices reporting a frequency of at least 10%. In the northern locations the frequency ranged from 0 to 4%. No correlation with mould counts was demonstrated, possibly because of incomplete mould data relative to most of the surgical locations.

The Nottingham study of neurotic disorder: comparison of drug and psychological treatments

210 psychiatric outpatients with generalised anxiety disorder (71), or panic disorder (74), or dysthymic disorder (65) diagnosed by an interview schedule for DSM-III were allocated by constrained randomisation to one of five treatments: diazepam (28), dothiepin (28), placebo (28), cognitive and behaviour therapy (84), and a self-help treatment programme (42). All treatments were given for 6 weeks and then withdrawn by 10 weeks. Ratings of psychopathology were made by psychiatric assessors blind to both treatment and diagnosis before treatment and at 2, 4, 6, and 10 weeks after randomisation. 18 patients had insufficient data for analysis because of early drop-out. There were no important differences in treatment response between the diagnostic groups, but diazepam was less effective than dothiepin, cognitive and behaviour therapy, or self-help, these three treatments being of similar efficacy. Significantly more patients in the placebo group took additional psychotropic drugs in the 10 week period, and those allocated to dothiepin and cognitive and behaviour therapy took the least.

Adjunctive hyperbaric oxygen for treatment of rhinocerebral mucormycosis

The therapy of rhinocerebral mucormycosis includes aggressive surgical debridement, administration of high-dose amphotericin B, and control of underlying predisposing conditions, especially diabetes and immunosuppression or immunodeficiency. Hyperbaric oxygen suppresses fungal growth in vitro and has theoretical value in treating mucormycosis because it reduces the tissue hypoxia and acidosis that accompany vascular invasion by the fungus. In a retrospective review of patients at Duke University Medical Center with rhinocerebral mucormycosis, six patients were treated with hyperbaric oxygen and seven cases (involving six patients) were treated without hyperbaric oxygen. All patients received surgical debridement and amphotericin B. Two of six patients receiving hyperbaric oxygen therapy died, and four of seven patients not receiving hyperbaric oxygen therapy died. Adverse effects from hyperbaric oxygen were minimal. Because mucormycosis occurs infrequently, this retrospective review involved a small number of patients. Despite this limitation, adjunctive hyperbaric oxygen appears to be a promising clinical modality for the treatment of rhinocerebral mucormycosis and warrants further investigation.

Adenovirus E1a gene product expressed at high levels in Escherichia coli is functional

The human type C adenovirus E1a 13S messenger RNA encodes a gene product, that positively regulates the transcription of viral genes and certain cellular genes and is involved in the transformation of primary mammalian cells. The E1a gene product was expressed at high levels in Escherichia coli. In a Xenopus oocyte microinjection assay, the purified Escherichia coli-produced protein activated the E1a-responsive adenovirus E3 promoter and functioned as efficiently as the E1a gene itself.

Mutation of RGA1, which encodes a putative GTPase-activating protein for the polarity-establishment protein Cdc42p, activates the pheromone-response pathway in the yeast Saccharomyces cerevisiae

We have selected yeast mutants that exhibit a constitutively active pheromone-response pathway in the absence of the beta subunit of the trimeric G protein. Genetic analysis of one such mutant revealed that it contained recessive mutations in two distinct genes, both of which contributed to the constitutive phenotype. One mutation identifies the RGA1 locus (Rho GTPase activating protein), which encodes a protein with homology to GAP domains and to LIM domains. Deletion of RGA1 is sufficient to activate the pathway in strains lacking the G beta subunit. Moreover, in wild-type strains, deletion of RGA1 increases signaling in the pheromone pathway, whereas over-expression of RGA1 dampens signaling, demonstrating that Rga1p functions as a negative regulator of the pheromone response pathway. The second mutation present in the original mutant proved to be an allele of a known gene, PBS2, which encodes a putative protein kinase that functions in the high osmolarity stress pathway. The pbs2 mutation enhanced the rga1 mutant phenotype, but by itself did not activate the pheromone pathway. Genetic and two-hybrid analyses indicate that an important target of Rga1p is Cdc42p, a p21 GTPase required for polarity establishment and bud emergence. This finding coupled with recent experiments with mammalian and yeast cells indicating that Cdc42p can interact with and activate Ste20p, a protein kinase that operates in the pheromone pathway, leads us to suggest that Rga1p controls the activity of Cdc42p, which in turn controls the magnitude of signaling in the pheromone pathway via Ste20p.

E1A 13S and 12S mRNA products made in Escherichia coli both function as nucleus-localized transcription activators but do not directly bind DNA

We previously purified and characterized functionally the Escherichia coli-expressed product of the human subgroup C adenovirus E1A 13S mRNA (B. Ferguson, N. Jones, J. Richter, and M. Rosenberg, Science 224:1343-1346, 1984; B. Krippl, B. Ferguson, M. Rosenberg, and H. Westphal, Proc. Natl. Acad. Sci. USA 81:6988-6992, 1984). We have now expressed in E. coli and purified the protein product encoded by the human subgroup C adenovirus E1A 12S mRNA and have compared the functional properties of this protein with those of the E1A 13S mRNA product. Using microinjection techniques to introduce these proteins into mammalian cells, we found that the E1A 12S mRNA product, like the 13S mRNA product, localized rapidly to the cell nucleus and induced adenovirus gene expression. Although both E1A gene products localized to the nucleus and stimulated adenovirus gene transcription, these proteins did not directly bind to DNA under conditions in which a known DNA-binding protein, the human c-myc gene product, bound DNA efficiently. Thus, the E1A and myc gene products, which have been related both structurally and functionally, exhibit distinctly different biochemical properties.

Nurse-patient relationships: the context of nurse prescribing

Nurse prescribing was initiated in the United Kingdom in October 1994 in eight demonstration sites. The evaluation of this extension to the community nurses' role explored both economic and qualitative benefits to patients, carers, nurses and other health care professionals. In this paper the impact of nurse prescribing on patients is explored. Benefits experienced by patients are described along with the difficulties encountered. The patients' views regarding nurses as prescribers are also explored. Data were collected by means of interviews with patients/carers, the focus of which was to evaluate changes associated with nurse prescribing. Patients raised a number of issues associated with their relationship with nurses. Patients valued nurses for both their accessibility and approachability, which led them to discuss health issues which would not otherwise have been brought to the attention of the general practitioner. The arguments which support the incorporation of these qualities into an expanded nursing role are presented.

T-ray Imaging and Tomography

We demonstrate two algorithms used forreconstructing the target's structure basedon the diffracted pulses and additionallyshow that a three-dimensional target can bereconstructed using the broadband pulsesand a Fresnel lens by virtue of itsfrequency dependent focal length. Oneadvantage of T-ray imaging is the abilityto measure the far-infrared spectralresponse of the target. To highlight theimportance of this spectral information, wedemonstrate T-ray classification imagingwith different biological samples using asimple classification algorithm and twodimensional T-ray spectroscopic images.

Allergic fungal sinusitis: allergic, infectious, or both?

Allergic fungal sinusitis is a benign noninvasive sinus disease related to a hypersensitivity reaction to fungal antigens. A wide variety of fungal agents has been implicated, with the vast majority belonging to the Dematiaceae family. Allergic fungal sinusitis should be suspected in any atopic patient with refractory nasal polyps. Sinus computed tomograms and magnetic resonance imaging findings can be quite distinctive, but not diagnostic. Diagnosis requires histopathologic examination, which shows characteristic allergic mucin. Hyphae can be demonstrated on special fungal stains or confirmed by a positive fungal culture. At surgery, the diagnosis should be considered if thick, tenacious allergic mucin is encountered in the atopic patient with nasal polyps. Fungal cultures should then be obtained, and the pathologist alerted to the possible diagnosis of allergic fungal sinusitis. Current recommendations for therapy include conservative but complete exenteration of all allergic mucin. This can often be accomplished endoscopically. Adjunctive short-term systemic steroids are often helpful, and nasal steroid sprays should be continued long term. The length and dose of steroid therapy is controversial. Persistence of allergic fungal sinusitis with recurrence of sinonasal symptoms is common, particularly when there has been incomplete eradication of allergic fungal mucin. Even when the patient is clinically disease free, recurrence can occur, presumably from reexposure to fungal antigens. Therefore close clinical, endoscopic, and radiographic follow-up is important.

New insights into the role of PML in tumour suppression

The PML gene is involved in the t(15;17) translocation of acute promyelocytic leukaemia (APL), which generates the oncogenic fusion protein PML (promyelocytic leukaemia protein)-retinoic acid receptor alpha. The PML protein localises to a subnuclear structure called the PML nuclear domain (PML-ND), of which PML is the essential structural component. In APL, PML-NDs are disrupted, thus implicating these structures in the pathogenesis of this leukaemia. Unexpectedly, recent studies indicate that PML and the PML-ND play a tumour suppressive role in several different types of human neoplasms in addition to APL. Because of PML's extreme versatility and involvement in multiple cellular pathways, understanding the mechanisms underlying its function, and therefore role in tumour suppression, has been a challenging task. In this review, we attempt to critically appraise the more recent advances in this field and propose new avenues of investigation.

Seven-year follow-up of speech/language impaired and control children: psychiatric outcome

This study examined the 7-year psychiatric outcome of 202 speech/language (S/L) impaired and control children selected from a community sample at age 5 years. Children with S/L at age 5 years were more likely to be psychiatric cases at age 12.5 years than were normal controls, even if their S/L improved. Controlling for concurrent psychiatric disorder, S/L impairment at age 5 years was still associated with an increased rate of psychiatric disorder at 12.5 years. Psychiatric disorder at age 12.5 years was more likely to co-occur with language disorder than with speech disorder.

Mutations within a furin consensus sequence block proteolytic release of ectodysplasin-A and cause X-linked hypohidrotic ectodermal dysplasia

X-linked hypohidrotic ectodermal dysplasia (XLHED) is a heritable disorder of the ED-1 gene disrupting the morphogenesis of ectodermal structures. The ED-1 gene product, ectodysplasin-A (EDA), is a tumor necrosis factor (TNF) family member and is synthesized as a membrane-anchored precursor protein with the TNF core motif located in the C-terminal domain. The stalk region of EDA contains the sequence -Arg-Val-Arg-Arg156-Asn-Lys-Arg159-, representing overlapping consensus cleavage sites (Arg-X-Lys/Arg-Arg( downward arrow)) for the proprotein convertase furin. Missense mutations in four of the five basic residues within this sequence account for approximately 20% of all known XLHED cases, with mutations occurring most frequently at Arg156, which is shared by the two consensus furin sites. These analyses suggest that cleavage at the furin site(s) in the stalk region is required for the EDA-mediated cell-to-cell signaling that regulates the morphogenesis of ectodermal appendages. Here we show that the 50-kDa EDA parent molecule is cleaved at -Arg156Asn-Lys-Arg(159 downward arrow)- to release the soluble C-terminal fragment containing the TNF core domain. This cleavage appears to be catalyzed by furin, as release of the TNF domain was blocked either by expression of the furin inhibitor alpha1-PDX or by expression of EDA in furin-deficient LoVo cells. These results demonstrate that mutation of a functional furin cleavage site in a developmental signaling molecule is a basis for human disease (XLHED) and raise the possibility that furin cleavage may regulate the ability of EDA to act as a juxtacrine or paracrine factor.