Mutation in an alpha1-antitrypsin enhancer results in an interleukin-6 deficient acute-phase response due to loss of cooperativity between transcription factors

We previously reported that a mutation in a 3' enhancer region of the alpha1-antitrypsin (AAT) gene is associated with chronic obstructive airways disease (COAD). During the acute-phase response the plasma concentration of AAT increases approximately 3-fold and this effect is mediated primarily by interleukin-6 (IL-6). We demonstrate, by transfection of Hep G2 cells, that the AAT gene contains at least two enhancers, one at the 5' end of the gene which is dominant under basal conditions, and another at the 3' end of the gene which exhibits weak basal activity. However, both enhancers must be present to modulate the IL-6-induced response which is diminished as a consequence of the 3' enhancer mutation. These results suggest that the 3' enhancer modulates the IL-6 response through an interaction with the 5' enhancer. The mutation occurs at a DNA binding site for the ubiquitous transcription factor octamer-1 (Oct-1) and results in a loss of cooperativity between Oct-1 and the tissue-specific transcription factor, NF-IL6 (C/EBPbeta), a member of the C/EBP family of transcription factors. NF-IL6 is a key transcription factor for a major pathway through which IL-6 mediates its effects. These observations provide a novel mechanism for a diminished IL-6-induced response.

A domain shared by the Polycomb group proteins Scm and ph mediates heterotypic and homotypic interactions

The Sex comb on midleg (Scm) and polyhomeotic (ph) proteins are members of the Polycomb group (PcG) of transcriptional repressors. PcG proteins maintain differential patterns of homeotic gene expression during development in Drosophila flies. The Scm and ph proteins share a homology domain with 38% identity over a length of 65 amino acids, termed the SPM domain, that is located at their respective C termini. Using the yeast two-hybrid system and in vitro protein-binding assays, we show that the SPM domain mediates direct interaction between Scm and ph. Binding studies with isolated SPM domains from Scm and ph show that the domain is sufficient for these protein interactions. These studies also show that the Scm-ph and Scm-Scm domain interactions are much stronger than the ph-ph domain interaction, indicating that the isolated domain has intrinsic binding specificity determinants. Analysis of site-directed point mutations identifies residues that are important for SPM domain function. These binding properties, predicted alpha-helical secondary structure, and conservation of hydrophobic residues prompt comparisons of the SPM domain to the helix-loop-helix and leucine zipper domains used for homotypic and heterotypic protein interactions in other transcriptional regulators. In addition to in vitro studies, we show colocalization of the Scm and ph proteins at polytene chromosome sites in vivo. We discuss the possible roles of the SPM domain in the assembly or function of molecular complexes of PcG proteins.

Evolutionary conservation and predicted structure of the Drosophila extra sex combs repressor protein

The Drosophila extra sex combs (esc) protein, a member of the Polycomb group (PcG), is a transcriptional repressor of homeotic genes. Genetic studies have shown that esc protein is required in early embryos at about the time that other PcG proteins become engaged in homeotic gene repression. The esc protein consists primarily of multiple copies of the WD repeat, a motif that has been implicated in protein-protein interaction. To further investigate the domain organization of esc protein, we have isolated and characterized esc homologs from divergent insect species. We report that esc protein is highly conserved in housefly (72% identical to Drosophila esc), butterfly (55% identical), and grasshopper (56% identical). We show that the butterfly homolog provides esc function in Drosophila, indicating that the sequence similarities reflect functional conservation. Homology modeling using the crystal structure of another WD repeat protein, the G-protein beta-subunit, predicts that esc protein adopts a beta-propeller structure. The sequence comparisons and modeling suggest that there are seven WD repeats in esc protein which together form a seven-bladed beta-propeller. We locate the conserved regions in esc protein with respect to this predicted structure. Site-directed mutagenesis of specific loops, predicted to extend from the propeller surface, identifies conserved parts of esc protein required for function in vivo. We suggest that these regions might mediate physical interaction with esc partner proteins.

Limb girdle muscular dystrophy in Manitoba Hutterites does not map to any of the known LGMD loci

Limb girdle muscular dystrophy (LGMD) is a heterogeneous group of disorders affecting primarily the shoulder and pelvic girdles. Autosomal dominant and recessive forms have been identified; 8 have been mapped and 1 more has been postulated on the basis of exclusion of linkage. An autosomal recessive muscular dystrophy was first described in 1976 in the Hutterite Brethren, a North American genetic and religious isolate [Shokeir and Kobrinsky, 1976; Clin Genet 9:197-202]. In this report, we discuss the results of linkage analysis in 4 related Manitoba Hutterite sibships with 21 patients affected with a mild autosomal recessive form of LGMD. Because of the difficulties in assigning a phenotype in some asymptomatic individuals, stringent criteria for the affected phenotype were employed. As a result, 7 asymptomatic relatives with only mildly elevated CK levels were assigned an unknown phenotype to prevent their possible misclassification. Two-point linkage analysis of the disease locus against markers linked to 7 of the known LGMD loci and 3 other candidate genes yielded lod scores of < or = -2 at theta = 0.01 in all cases and in most cases at theta = 0.05. This suggests that there is at least 1 additional locus for LGMD.

SMN(T) and NAIP mutations in Canadian families with spinal muscular atrophy (SMA): genotype/phenotype correlations with disease severity

Childhood-onset spinal muscular atrophy (SMA) is an autosomal recessive neuropathy characterized by selective degeneration of alpha-motor neuron cells of the spinal cord. Age of onset and motor development varies greatly among patients, but the molecular basis of this variability remains unclear. The SMA locus contains two copies of a 500-kb element and deletions within the telomeric element have been shown to be the most common cause of SMA. To study the relationship between genotype and phenotype, 60 SMA families, all but two of which are of French Canadian origin, were screened for deletions in the telomeric survival motor neuron (SMN(T)) and the intact neuronal apoptosis inhibitory protein (NAIP) genes. Combining these results with those obtained for the multicopy microsatellite marker Ag1-CA (D5S1556) indicated that there are at least two types of SMA alleles. Most type I SMA patients are homozygous for large scale deletions involving the entire SMN(T) gene as well as exons 5 and 6 of the NAIP gene. The strong association between the 100-bp allele of Ag1-CA and large scale deletions in populations of diverse ethnic origin suggests that this allele marks an unstable or founder SMA chromosome. In contrast, most chronic SMA patients have at least one SMA allele with either an intragenic SMN(T) deletion or a SMN(C):SMN(T) chimeric gene which replaces the normal SMN(T) gene. The broad continuum of disease presentation in chronic SMA is most likely a consequence of the interaction between different SMA alleles.

Chronic hepatitis C with normal aminotransferase levels: a clinical histologic study

OBJECTIVE

To define chronic hepatitis C virus (HCV) infection among patients with persistently normal aminotransferase levels (PNAL).

DESIGN

Retrospective chart review of all patients encountered during 1-yr with positive hepatitis C antibody (anti-C100-3 ELISA), no alternative cause for their liver disease and PNAL for 6 or more consecutive months prebiopsy. Blinded review of liver histology.

SETTING

Outpatient hepatology clinics of two academic centers.

PATIENTS

Fifty patients with PNAL among 303 with hepatitis C.

MEASUREMENTS

Epidemiologic profiles, reasons for seroscreening and confirmatory analyses were tabulated. Histology was reviewed and grading of inflammatory activity and stage of fibrosis was determined by protocol.

RESULTS

Among 50 patients with PNAL, 35 (70%) were female, 34 (68%) had parenterally acquired HCV, 44 (88%) abstained (> 2 yr) from ethanol, all were HIV-negative and none pharmacologically immunosuppressed. HCV infection was uniformly confirmed by RIBA II or HCV-RNA assay. The mean level of HCV-RNA by quantitative PCR was 3.79 x 10(5) copies/ml (range, 500 to 1.8 x 10(6) copies/ ml) and by B-DNA, 53 x 10(5) copies/ml (range, 3.5-230 x 10(5) copies/ml). Traditional histoevaluation yielded chronic hepatitis ("active", n = 15; "persistent", n = 25), cirrhosis (n = 7), and normal histology (n = 3). Blinded protocol review of histology (inflammatory grade/fibrotic stage) revealed 0/0 (n = 4), 1/0 (n = 6), 2/0 (n = 17), 2/1 (n = 3), 2/4 (n = 1), 3/0 (n = 2), 3/1 (n = 6), 3/2 (n = 2), and 3/3 (n = 9).

CONCLUSIONS

In chronic HCV infection, active inflammation, fibrosis, and variable circulating HCV-RNA levels may coexist with PNAL, particularly among female nondrinkers. Asymptomatic carriers with normal histology comprise 6 to 8% of chronic hepatitis C with PNAL. Management guidelines for this group of patients need to be developed.

Physical illness and disability among elderly people in England and Wales: the Medical Research Council Cognitive Function and Ageing Study. The Analysis Group

STUDY OBJECTIVE

This study was conducted as part of the MRC cognitive function and ageing study. It aimed to estimate the lifetime prevalence of self reported physical illnesses and other health related events, and the prevalence of limiting disability in people over 65 in six areas of England and Wales.

DESIGN

Screening phase of a two stage prevalence study.

SETTING

Geographically delimited areas in four urban and two rural areas including institutions.

PARTICIPANTS

Random population samples of people in their 65th year and above on the sample definition date, interviewed between 1989 and 1994. In Newcastle, Nottingham, and Oxford (urban) and in Cambridgeshire and Gwynedd(rural), the sample was stratified to provide equal numbers in the 65-74 and 75 years and over age groups. In Liverpool (urban), equal numbers in the five year age groups were taken.

MAIN RESULTS

Age standardised prevalences were calculated for each geographical area, sex, and age group (65-74, 75+). Many conditions were more prevalent in the older age group including stroke, Parkinson's disease, arthritis, diabetes, and shingles but hypertension was more common in the younger age group. Conditions that were more prevalent in men included angina, heart attack, stroke, head injury, and peptic ulcers while hypertension, shingles, pernicious anaemia, and thyroid disease were more common in women. There was a complex pattern of area differences for individual conditions. Cambridgeshire had generally low prevalences for many diseases, including vascular problems, Gwynedd and Newcastle had less healthy elderly populations, and Nottingham and Newcastle had the highest percentages of housebound.

CONCLUSIONS

This study provides the most robust available estimates for life-time prevalence of a variety of health conditions on a regional and national basis. It shows the greatly increased prevalence of disability in the very old population, particularly women.

Customary physical activity and survival in later life: a study in Nottingham, UK

OBJECTIVE

To assess the value of broadly based customary physical activity scores, derived from a questionnaire inventory, in predicting 10 year mortality among elderly people.

DESIGN

A 10 year survival analysis of participants in the first wave of the Nottingham longitudinal study of activity and ageing who, in face to face interviews in 1985, provided detailed information on customary physical activity, health, and lifestyle.

SETTING

Urban and suburban Nottingham

PARTICIPANTS

A total of 1042 people aged 65 years and over randomly sampled from general practitioner records.

MAIN RESULTS

On the basis of factor scores derived from the interview questionnaire, activity levels were graded as "high", "intermediate", or "low". In Cox regression models controlling for age, health status, and cigarette smoking at the time of the activity assessment, these gradings were significantly related to 10 year survival. Relative to the "high" activity groups, the risk of dying was significantly increased in both the "intermediate" (hazard ratio (HR) 1.53; 95% CI 1.12, 2.09) and "low" (HR 2.07; 95% CI 1.53, 2.79) groups for women, and in the "low" group (HR 1.59; 95% CI 1.12, 2.25) for men (p < 0.01 throughout).

CONCLUSION

Since the survival model controlled for age, health status, and cigarette smoking, it is unlikely that the activity gradings used here are simple proxies for physical health. It is concluded, therefore, that within the elderly population, recall based survey assessments covering a wide range of customary or habitual physical activities, can provide indices showing both cross sectional utility and predictive validity.

Lack of association between bipolar disorder and tyrosine hydroxylase: a meta-analysis

Tyrosine hydroxylase (TH) is a candidate gene extensively explored in several association studies of bipolar disorder (BD). However, because of conflicting results of independent studies and low statistical power of individual studies to detect small differences between cases and controls, reliable conclusions are difficult to formulate. A method to obtain more reliable conclusions about the involvement of the TH locus in the etiology of BD is meta-analysis. We undertook a meta-analysis of studies that investigated the association between BD and TH genetic markers. The studies were identified by means of computerized searches of several databases, and the scanning of review articles and the reference lists of the primary articles identified. More than 60 publications were reviewed, and 9 relevant articles were included in this meta-analysis, with an overall sample of 1,069 subjects (547 cases and 522 normal controls). The overall odds ratio (and confidence interval) based on combining the results of the studies was 1.02 (0.68-1.54). Test of the null hypothesis that the mean log odds ratio equals zero (chi2 = 0.11; 5 df; P > 0.05) indicated that there was no overall association between bipolar disorder and tyrosine hydroxylase.

Resistance to salmonellosis in the chicken is linked to NRAMP1 and TNC

Natural resistance to infection with Salmonella typhimurium in mice is controlled by two major loci, Bcg and Lps, located on mouse chromosomes 1 and 4, respectively. Both Bcg and Lps exert pleiotropic effects and contribute to cytostatic/cytocidal activities of the macrophage. Bcg encodes for a membrane phosphoglycoprotein designated Nrampl (natural resistance-associated macrophage protein 1), which belongs to an ancient family of membrane proteins, Lps has not been cloned yet, but its location on mouse chromosome 4 has been refined for positional cloning. As in mice, chicken inbred lines differ in their susceptibility to infection with Salmonella typhimurium. We have tested the candidacy of the chicken homologs of Nrampl and Tnc (a locus closely linked to Lps), in the differential resistance of chicken inbred lines to infection with S. typhimurium. We have first analyzed six inbred chicken lines of Salmonella-resistant or Salmonella-susceptible phenotypes for the presence of nucleotide sequence variations within the coding portion of NRAMP1. We have identified 11 sequence variations within NRAMP1 in the chicken inbred lines tested: 10 of these represented either silent mutations or conservative changes. However, one G-->A substitution at nucleotide 696 resulted in the nonconservative replacement of Arg223 to Gln223 within the predicted TM5-6 region. This allelic variant was specific to the susceptible line C and not observed in any of the resistant strains. To investigate the effect of NRAMP1 and TNC on resistance to infection with S. typhimurium, 425 (W1 x C)F1 x C chicken progeny were examined during a period of 15 days postinfection. Together, NRAMP1 and TNC explain 33% of the early differential resistance to infection with S. typhimurium of parental lines C and W1. Our data established that resistance to infection with S. typhimurium in chickens is inherited as a complex trait and that comparative mapping has proven to be useful to identify Salmonella-resistance genes in the chicken.

T cell responses to human type II collagen in patients with rheumatoid arthritis and healthy controls

OBJECTIVE

To study the prevalence of T cell responses to human type II collagen (CII) in patients with rheumatoid arthritis (RA) with or without antibodies to CII, and in healthy controls.

METHODS

Assays were performed to study T cell proliferative responses to CII in peripheral blood from 69 patients with RA (11 with anti-CII antibodies and 58 without) and 28 healthy controls. Further analysis was made of the time course of the response and the epitopic specificity, using peptides derived from the cyanogen bromide 11 (CB11) fragment of CII.

RESULTS

Significant proliferative responses to CII were found in 50% of patients with anti-CII, 5.3% of RA patients without these antibodies, and 35.7% of healthy controls. Responses in RA patients differed from those in healthy controls; the former had kinetics suggestive of a recall response and the latter that of a primary response. Some common epitopes within CB11 were recognized by T cells from patients and controls.

CONCLUSION

Proliferative T cell responses to CII occur in some healthy individuals, suggesting that thymic tolerance for this antigen may be incomplete. Most patients with RA have no evidence of a T cell response to CII, possibly indicating the development of peripheral tolerance to this antigen as a consequence of cartilage breakdown. However, in a minority of patients, T and B cell responses to CII persist, and may contribute to joint damage.

Phenotypic variability in Friedreich ataxia: role of the associated GAA triplet repeat expansion

We studied genotype-phenotype correlations in a group of 100 patients with typical Friedreich ataxia (FRDA), and in three groups of patients with atypical clinical presentations, including 44 Acadian FRDA, 8 late-onset FRDA (LOFA), and 6 FRDA with retained reflexes (FARR). All patients, except 3 with typical FRDA, carried two copies of the FRDA-associated GAA triplet repeat expansion. Overall, the phenotypic spectrum of FRDA appeared to be wider than defined by the currently used diagnostic criteria. Our study indicated the existence of several sources of variability in FRDA. Patients with larger GAA expansions tended to have earlier onset and were more likely to show additional manifestations of the disease. Mitotic instability of the expanded GAA repeats may partially account for the limited degree of correlation between expansion sizes as determined in lymphocytes and clinical parameters. Some clinical variants associated with specific FRDA haplotypes, such as Acadian FRDA and FARR, turned out to be unrelated to expansion sizes. No polymorphism in the frataxin coding sequence could be associated with these clinical variants.

Longitudinal trends in late-life insomnia: implications for prescribing

OBJECTIVE

To assess trends in insomnia and hypnotic drug use in a representative sample of elderly general practice patients.

DESIGN

Longitudinal study with three interview waves--1985, 1989 and 1993.

SETTING

Urban and suburban Nottingham.

PARTICIPANTS

1042 patients originally aged 65 and over randomly sampled from general practitioner lists.

MAIN OUTCOME MEASURES

Point prevalence estimates, status (case/non-case/died) at 4-year follow-up, episode incidence and survival functions.

RESULTS

At baseline (1985) 221 respondents met the survey criteria for insomnia. Of these, 36.1% continued to report severely disrupted sleep in 1989. Within this period 84 new cases of insomnia were identified (an incidence rate of 3.1% per person-year at risk). Controlling for age and sex, insomnia was unrelated to survival among prevalent cases, but significantly related to survival among incident cases (odds ratio = 1.7; 95% confidence interval = 1.1-2.5). Of 166 respondents using prescription hypnotics in 1985, 31.7% continued to report usage in 1989. Similarly, out of 41 new hypnotic drug users identified in 1989, 29.3% continued to report usage in 1993.

CONCLUSIONS

Important clinical differences in the natural history of insomnia are evident when incident and prevalent cases are compared. Nevertheless, outcomes at 4-year follow-up suggest that, for the majority of surviving cases identified in a prevalence screen and for a substantial minority of incident cases, late-life insomnia shows a level of chronicity incompatible with hypnotic drug therapy as currently recommended.

Schizophrenia and chromosome 6p

Several studies have recently reported genetic linkage between markers located on the short arm of chromosome 6 and schizophrenia. Valid conclusions, however, are difficult to formulate because chromosomal markers that yielded positive results span a relatively large region of chromosome 6, and studies did not necessarily obtain consistent results with regard to the particular loci tested. Here, we report a meta-analysis of the results of linkage studies of schizophrenia that used chromosome 6p markers. After conducting a systematic search, nine different studies were selected for the analysis using defined criteria. Pooled P values were obtained for all common markers investigated and provided additional support for a major susceptibility locus for schizophrenia in this region. In addition, two markers located 2 cM apart, D6S274 and D6S285, provided the most significant results. These findings may help narrow the chromosomal region in the search for a major gene implicated in schizophrenia.

Risk factors for late-life insomnia in a representative general practice sample

BACKGROUND

Insomnia is widely reported and widely treated in general practice, yet relatively little research has focused on the natural history of the condition in primary care settings. As a result, there is at present little information to enable clinicians to assess insomnia risk, or anticipate outcomes in older general practice populations.

AIM

To estimate, using 8-year longitudinal data, the risk of insomnia onset associated with selected health and lifestyle factors.

METHOD

Survivors from a nationally representative sample (n = 1042) of elderly people originally interviewed in 1985 were reassessed in 1989 (n = 690) and 1993 (n = 410). At the first follow up in 1989, 84 new cases of insomnia were identified (a weighted incidence rate per person per year at a risk of 3.1%; 95% CI = 2.7-3.5). In logistic regression analyses controlling for age and sex, the risk of insomnia onset was then assessed in relation to the selected factors.

RESULTS

Three factors assessed in 1985 were significantly and independently related to incident insomnia: psychometric ratings consistent with depressed mood odds ratio (OR) = 4.41; 95% CI = 3.32-5.43); health index scores indicating lower physical health status (OR = 1.19; 95% CI = 1.06-1.31 per unit change in scale score); and moderate and low levels of physical activity (OR = 1.91 and 2.14; 95% CI = 1.91-3.62 and 2.14-3.64 respectively). However, although depressed mood represented a major risk factor, the most likely source of risk was physical rather than mental ill-health.

CONCLUSIONS

Psychiatric, somatic and lifestyle factors significantly and independently increase the risk of insomnia in older general practice patients. In predicting incident sleep disturbance, these factors exceed in importance the age and sex of patients.

Microsatellite polymorphism of the alpha 1-antichymotrypsin gene locus associated with sporadic Alzheimer's disease

A variant of the apolipoprotein E gene, APOE*4, is associated with both sporadic Alzheimer's disease (AD) and a subset of familial AD and this association is stronger with early as opposed to late onset AD. Both APOE*4 and alpha 1-antichymotrypsin (ACT) will accelerate the rate of amyloid filament formation and are major constituents of the plaques associated with AD. We now show that a dinucleotide microsatellite allele in the 5'-flanking sequence of the ACT gene, designated A10, in association with APOE*4 significantly increases the risk of developing sporadic AD, which accounts for the majority of AD cases.

Neuroendocrine activation after myocardial infarction: causes and consequences

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Epidemiology of gonococcal and chlamydial infections in Harrow and Brent

OBJECTIVE

To describe the epidemiology and associated clinical features of gonorrhoea and chlamydial infection and to develop a profile of sexually transmitted diseases (STDs) in an outer London health district.

DESIGN

Hospital-based retrospective study.

SETTING

Genitourinary medicine clinic, Northwick Park Hospital, Harrow and Brent Health Authority.

SUBJECTS

70 male and female individuals with gonorrhoea and 129 with chlamydial infection, diagnosed consecutively over 28 months in 1992-94.

RESULTS

More men than women had gonorrhoea (43 versus 27) but more women than men had chlamydial infection (84 versus 45), p < 0.001. There was a clear tendency for cases with either infection to locate along major road and rail transport routes. Foci of gonococcal infection were concentrated mainly in the densely populated areas, whereas chlamydial cases were more evenly spread. There was no significant effect of gender or type of STD on the odds ratio for residence in Harrow, single marital status or attendance for test of cure. However, the odds ratios for women having sexual intercourse with a regular partner only or previous STD were 5 (95% CI 2.4 to 10.2), p < 0.001 and 0.3 (95% CI 0.18 to 0.69), p = 0.002 times the odds for men, respectively. The odds ratios for patients with gonococcal infection being employed or having sex with a regular partner only were 0.5 (95% CI 0.27 to 0.98), p = 0.04 and 0.30 (95% CI 0.15 to 0.60), p < 0.001 times the odds for patients with chlamydial infection, respectively. Of the women with gonorrhoea and previous pregnancy, 68% gave a history of abortion compared with 44% of those with chlamydial infection (p = 0.03).

CONCLUSION

The identification of foci gonococcal and chlamydial infection and apparent location of these infections along the major transport routes in our health district require further study. That chlamydial infection, unlike gonorrhoea, is evenly distributed irrespective of population concentration and deprivation, suggests urgent need for a comprehensive local effort to control both STDs.

Limb-girdle muscular dystrophy and Miyoshi myopathy in an aboriginal Canadian kindred map to LGMD2B and segregate with the same haplotype

We report the results of our investigations of a large, inbred, aboriginal Canadian kindred with nine muscular dystrophy patients. The ancestry of all but two of the carrier parents could be traced to a founder couple, seven generations back. Seven patients presented with proximal myopathy consistent with limb girdle-type muscular dystrophy (LGMD), whereas two patients manifested predominantly distal wasting and weakness consistent with Miyoshi myopathy (distal autosomal recessive muscular dystrophy) (MM). Age at onset of symptoms, degree of creatine kinase elevation, and muscle histology were similar in both phenotypes. Segregation of LGMD/MM is consistent with autosomal recessive inheritance, and the putative locus is significantly linked (LOD scores >3.0) to six marker loci that span the region of the LGMD2B locus on chromosome 2p. Our initial hypothesis that the affected patients would all be homozygous by descent for microsatellite markers surrounding the disease locus was rejected. Rather, two different core haplotypes, encompassing a 4-cM region spanned by D2S291-D2S145-D2S286, segregated with the disease, indicating that there are two mutant alleles of independent origin in this kindred. There was no association, however, between the two different haplotypes and clinical variability; they do not distinguish between the LGMD and MM phenotypes. Thus, we conclude that LGMD and MM in our population are caused by the same mutation in LGMD2B and that additional factors, both genetic and nongenetic, must contribute to the clinical phenotype.

Friedreich ataxia in Acadian families from eastern Canada: clinical diversity with conserved haplotypes

The gene for Friedreich ataxia (FRDA), an autosomal-recessive neurodegenerative disease, remains elusive. The current candidate region of about 150 kb lies between loci FR2 and F8101 near the D9S15/D9S5 linkage group at 9q13-21.1. Linkage homogeneity between classical FRDA and a milder, slowly progressive Acadian variant (FRDA-Acad) has been demonstrated. An extended D9S15-D9S5 haplotype (C6) predominates in FRDA-Acad chromosomes from Louisiana. We studied 10 Acadian families from New Brunswick, Canada. In eight families, affected individuals conformed to the clinical description of FRDA-Acad; in one, 2 sibs presented with spastic ataxia (SPA-Acad). In the last family, 2 sibs had FRDA-Acad, and one had SPA-Acad. We found that SPA-Acad is linked to the FRDA gene region. The C6 haplotype and a second major haplotype (B7) were identified. The same ataxia-linked haplotypes segregated with both FRDA-Acad and SPA-Acad in two unrelated families. The parental origins of these haplotypes were different. Our observation of different phenotypes associated with the same combination of haplotypes may point to the influence of the parent of origin on gene expression, indicate the effect of modifier genes, or reflect the presence of different mutations on the same haplotypes. Our findings underline the need to investigate families with autosomal-recessive ataxias for linkage to the FRDA region, despite lack of key diagnostic manifestations such as cardiomyopathy or absent deep-tendon reflexes.