A genetic study of the FMR1 gene in a Sardinian multiple sclerosis population

Multiple sclerosis (MS) is a complex autoimmune disease originated from the interplay between genetic and environmental factors. An overlap of clinical and neuroradiological parameters has been described between MS and an adult-onset neurodegenerative disorder, the fragile-X-associated tremor/ataxia syndrome (FXTAS). This syndrome is caused by a trinucleotide premutation expansion of a CGG sequence in the 55-200 repeat range, which is located in the fragile-X mental retardation 1 (FMR1) gene. Female premutation carriers have an increased propensity for immune-mediated disorders. Recently, a case of co-occurrence of MS and FXTAS was reported. Assuming that the premutation expansion may play a role in the MS susceptibility, we evaluated its frequency in a cohort of MS patients from Sardinia, an island characterized by a very high frequency of MS. Nuclear DNA was extracted by standard methods, purified with bisulfite treatment and then amplified twice by PCR with specific primers. Microsatellite analysis was performed and emizogotic subjects were sequenced. Clinical data of patients were also collected. Only 1/755 MS patients exhibited the premutation expansion with a heterozygosis pattern (30/58). No pathogenic repeat expansions (>200 repeats) were found in the entire cohort. Repeats labeled as the gray zone (45-60 repeats) were observed in 15/755 patients. No specific clinical features concerning disease course, disease activity, and disability were reported for these patients. Our results do not support a possible role for premutation or gray zone alleles in MS Sardinian patients. Further studies are needed to better understand the relationship between FXTAS and MS.

Genetic counselling in ALS: facts, uncertainties and clinical suggestions

The clinical approach to patients with amyotrophic lateral sclerosis (ALS) has been largely modified by the identification of novel genes, the detection of gene mutations in apparently sporadic patients, and the discovery of the strict genetic and clinical relation between ALS and frontotemporal dementia (FTD). As a consequence, clinicians are increasingly facing the dilemma on how to handle genetic counselling and testing both for ALS patients and their relatives. On the basis of existing literature on genetics of ALS and of other late-onset life-threatening disorders, we propose clinical suggestions to enable neurologists to provide optimal clinical and genetic counselling to patients and families. Genetic testing should be offered to ALS patients who have a first-degree or second-degree relative with ALS, FTD or both, and should be discussed with, but not offered to, all other ALS patients, with special emphasis on its major uncertainties. Presently, genetic testing should not be proposed to asymptomatic at-risk subjects, unless they request it or are enrolled in research programmes. Genetic counselling in ALS should take into account the uncertainties about the pathogenicity and penetrance of some genetic mutations; the possible presence of mutations of different genes in the same individual; the poor genotypic/phenotypic correlation in most ALS genes; and the phenotypic pleiotropy of some genes. Though psychological, social and ethical implications of genetic testing are still relatively unexplored in ALS, we recommend multidisciplinary counselling that addresses all relevant issues, including disclosure of tests results to family members and the risk for genetic discrimination.

Mycobacterium avium subsp. paratuberculosis and multiple sclerosis in Sardinian patients: epidemiology and clinical features

BACKGROUND

Mycobacterium avium subspecies paratuberculosis (MAP) is an infectious factor recently found in association with multiple sclerosis (MS) in Sardinia.

OBJECTIVES

The objectives of this study were to confirm this association and evaluate its role in clinical features.

METHODS

A total of 436 patients and 264 healthy controls (HCs) were included. We examined the blood of each individual for MAPDNA and MAP2694 antibodies using IS900-specific PCR and ELISA, respectively. Differences in MAP presence between the MS group and HCs were evaluated. In MS patients, we considered: gender, age, age at onset, duration of disease, course, EDSS, therapy, relapse/steroids at study time, and oligoclonal bands (OBs).

RESULTS

MAPDNA and MAP2694 antibodies were detected in 68 MS and six HCs (p = 1.14 × 10(-11)), and 123 MS and 10 HCs (p = 2.59 × 10(-23)), respectively. OBs were found with reduced frequency in MAP-positive patients (OR = 0.52; p = 0.02). MAP2694 antibodies were detected more in patients receiving MS treatments (OR = 2.26; p = 0.01), and MAPDNA in subjects on steroids (OR = 2.65; p = 0.02).

CONCLUSION

Our study confirmed the association of MAP and MS in Sardinia. The low OB frequency in MAP patients suggests a peripheral role as a trigger in autoimmunity. MAP positivity might be influenced by steroids and MS therapy. Studies in other populations are needed to confirm the role of MAP in MS.

A novel Cx32 mutation causes X-linked Charcot-Marie-Tooth disease with brainstem involvement and brain magnetic resonance spectroscopy abnormalities

The objective of this study was to study genetic and phenotypic features of a family with X-linked Charcot-Marie-Tooth consisting of a healthy father, affected mother, two affected sons and one healthy one. A detailed electrophysiological and neuroimaging study, along with sequencing of the Cx32 gene, was performed in all family members. A novel Cx32 123 G>C mutation, determining an aminoacid variation (Glu41Asp), was found in the mother and the affected sons. An alteration in brainstem evoked potentials was found in the mother and one affected son. The affected son, who underwent magnetic resonance imaging, showed symmetrical hyperintensities in paratrigonal white matter, not found in his heterozygous mother, while both subjects exhibited alterations in brain metabolite ratios derived from localised proton-magnetic resonance spectroscopy. These data extend previous findings about central nervous system involvement in Cx32 mutated subjects and further support a functional role of the protein expression in oligodendrocytes.

HLA-DR,DQ and APOE genotypes and gender influence in Sardinian primary progressive MS

The authors examined the influence of APOE and human leukocyte antigen-DRB1-DQB1 polymorphisms on the course of multiple sclerosis in 871 patients, 773 with relapsing and 98 with primary progressive disease, and 348 control subjects. The risk of the primary progressive course was increased (odds ratio = 6.81, p = 0.002) in women carrying the APOE4 but not the DRB1-DQB1 predisposing genotype, suggesting in this subgroup of patients a reciprocal influence between these genes and gender in modulating clinical variability of the disease.

Interaction of loci within the HLA region influences multiple sclerosis course in the Sardinian population

We examined the influence of alleles at the HLA loci, previously found to be associated with multiple sclerosis (MS) in Sardinia, on the clinical course of the disease in 835 relapsing (R) and 100 primary progressive (PP) patients. Multivariate analysis was carried out on predisposing 0301 or non-associated DPB1 alleles, susceptible or non-associated DRB1-DQB1 haplotypes, both predisposing and non-predisposing, and negatively and non-negatively associated D6S1683 alleles, taking interaction between them into account. Intra-patient analysis showed that the presence of the susceptible or protective D6S1683 allele interacting with predisposing DP 0301 modulated risk of PP disease. These findings suggest that a locus telomeric to HLA class I exerts an effect on alleles at the DPB1 locus in modulating disease course.

Bias in parental transmission of the HLA-DR3 allele in Sardinian multiple sclerosis

The authors analyzed the female: male (F:M) ratio according to the HLA-DRB1-DQB1 genotype in a cohort of multiple sclerosis (MS) patients from Sardinia, where the disease is associated with DR3 and DR4. In the whole cohort of 1,097 patients, F:M ratio was 2.24; however, it was 2.88 in DR3/DR3 and 2.52 in DR3/DRX (X#DR3 and DR4) individuals. Parental transmission of DR3 and DR4, assessed in a set of 565 case-parent triads, showed evidence of paternal inheritance of DR3 in affected women, thus explaining the excess of females in the DR3 category.

Dissection of the HLA association with multiple sclerosis in the founder isolated population of Sardinia

Several studies have indicated that multiple sclerosis (MS) is associated and linked to the major histocompatibility complex (MHC)/human leukocyte antigen (HLA) region of chromosome 6p21.3, but the exact location and nature of the primarily associated locus within the HLA complex is still controversial and largely presumptive. By linkage disequilibrium mapping, we have systematically investigated this chromosome region in the founder population of Sardinia to determine the relative associations of the various loci with MS. An overall 11.4 Mb region, which encompasses the whole HLA complex, was scanned with 19 microsatellite markers and with single nucleotide polymorphisms within 12 functional candidate genes and assessed for MS association using the extended transmission disequilibrium test (ETDT). A peak of association represented by the three adjacent DRB1, -DQA1 and -DQB1 loci was detected in the class II region. Two additional less significant areas of association were detected, respectively, in the centromeric side of the class II region at the DPB1 locus and, telomeric of the classically defined class I loci, at the D6S1683 microsatellite. Conditional ETDT analysis indicated that these regions of association could be independent of each other. Within the main peak of association, DRB1 and DQB1 contribute to the disease association independently of each other whereas DQA1 had no detectable primary genetic effects. We evaluated the haplotype distribution at the region showing the strongest association and found five DQB1-DRB1 haplotypes positively associated with MS in Sardinia. These consistently included all the haplotypes previously found associated with MS in the various human populations, thus supporting a primary effect of the products of these loci in MS. Overall these results are consistent with a multilocus model of the MHC encoded susceptibility to MS.

An attempt of identifying MS-associated loci as a follow-up of a genomic linkage study in the Italian population

Subsequent to a genomic linkage study on Sardinian and Continental Italian families, we considered the possibility that some of the tested microsatellite markers showed association to MS. Markers selected on the basis of the data obtained in the original set of 70 multiplex families were tested for MS association in an additional set of 154 simplex families. A limited set of markers were further tested on an additional set of 100 simplex families. The results indicate the presence of a putative MS gene in 19q13.13.

DRB1-DQA1-DQB1 loci and multiple sclerosis predisposition in the Sardinian population

Multiple sclerosis (MS) is a common neurological disease caused by genetic and environmental factors. Previous genetic analyses have suggested that theMHC/HLA region on chromosome 6p21 contains an MS-predisposing component. Which of the many genes present in this region is primarily responsible for disease susceptibility is still an open issue. In this study, we evaluated, in a large cohort of MS families from the Mediterranean island of Sardinia, the role of allelic variation at the HLA-DRB1, DQA1 and DQB1 candidate loci in MS predisposition. Using the transmission disequilibrium test (TDT), we found significant evidence of association with MS in both the Sardinian-specific DRB1*0405(DR4)- DQA1*0501-DQB1*0301 haplotype and the DRB1* 0301(DR3)-DQA1*0501-DQB1*0201 haplotype. Detailed comparative analysis of the DRB1-DQA1- DQB1 haplotypes present in this data set did not identify an individual locus that could explain MS susceptibility. The predisposing effect is haplotype specific, in that it is confined to specific combinations of alleles at the DRB1, DQA1 and DQB1 loci. Cross-ethnic comparison between the two HLA haplotypes associated with MS in Sardinians and the DRB1*1501 (DR2)-DQA1*0102-DQB1* 0602 haplotype, associated with MS in other Caucasian populations, failed to identify any shared epitopes in the DR and DQ molecules that segregated with disease susceptibility. These results suggest that another MHC gene(s), in linkage disequilibrium with specific HLA-DRB1, DQA1, DQB1 haploypes, might be primarily responsible for genetic susceptibility to MS. Alternatively, the presence of complex interactions between different HLA haplotypes, other non-HLA predisposing genes and environmental factors may explain different associations in different populations.

HLA-DQA1 and -DQB1 associations with multiple sclerosis in Sardinia and French Canada: evidence for immunogenetically distinct patient groups

We analyzed the association of HLA-DQA1 and -DQB1 alleles with multiple sclerosis (MS) in a collaborative study of 116 Sardinian and 75 French Canadian MS patients by the relative predispositional effect method. In French Canadians, MS was positively associated with DQA1*0102 and DQB1*0602, but there was no positive association of either allele with Sardinian MS, which, by contrast, was positively associated with DQB1*0302 and *0201 and with DQA1*0301, whereas none of these alleles was MS-associated in French Canadians. In comparison with French Canadian results, DQA1*0102 was protective against MS in Sardinians. We suggest that DQA1*0102 has no MS predispositional role in French Canadians, but is MS-associated because it is in linkage disequilibrium with true predispositional alleles present within the DQB1*0602-bearing haplotype. Whereas DQB1 alleles encoding leucine (Leu) at residue 26 showed a strong MS association in French Canadians (relative risk = 24.7), there was no correlation with DQ beta Leu26 in Sardinian MS. No other DQA1 or DQB1 codons showed a positive disease correlation in both groups. Together the data suggest that the two MS patient groups are immunogenetically distinct, and it may be impossible to formulate a unifying hypothesis that explains the different MS-class II associations in these and other ethnic groups.

Role of predisposing and protective HLA-DQA and HLA-DQB alleles in Sardinian multiple sclerosis

OBJECTIVE

To study the role of HLA genes in susceptibility and resistance to multiple sclerosis (MS) in Sardinian patients. To verify whether HLA-DQA and HLA-DQB genes differed between unrelated (MSU) and related (MSR) patients, and whether relapsing-remitting and chronic progressive forms of MS are immunogenetically distinct entities.

DESIGN

Case-control study of HLA-DQA and HLA-DQB gene frequency.

SETTING

All patients investigated were followed up by our MS referral centers.

PATIENTS

The study involved 116 MSU patients, 67 of whom had a relapsing-remitting form (MSr), 28 of whom had a chronic progressive from-the-onset form (MSc), and 21 of whom had a benign form (MSb), 32 patients with MSR, 19 parents and 27 healthy siblings of patients with MSR, and 86 controls. Selection of patients was random, while control subjects came from families without known immunologic diseases. All patients had definite MS.

MAIN OUTCOME MEASURE

Statistical analysis of gene frequencies was conducted with the chi 2 test with correction (Pc) for the alleles investigated, as was decided before the study began.

RESULTS

The DQA1*0301 allele was found to be increased in patients (MSU vs controls, Pc = .008; patients with MSc vs controls, Pc = .001; patients with MSR vs controls, Pc = .02; and parents vs controls, Pc = .04), while the DQA1*0102 allele was found to be diminished in patients with MSr vs controls (Pc = .001). Among the DQB genes, the DQB1*0502 allele was diminished in patients with MSr vs controls (Pc = .04), while the sum of DQB1*0201 and *0302 alleles was significantly increased in patients with MSR vs controls (Pc = .003).

CONCLUSION

Both HLA-DQA and HLA-DQB genes influence genetic susceptibility and resistance to MS. The roles of these genes differ in the various forms of MS. Patients with MSU and MSR both share HLA-DQA susceptibility genes.

HLA-DQB1 genotype in Sardinian multiple sclerosis: evidence for a key role of DQB1 *0201 and *0302 alleles

We studied HLA-DQB1 haplotypes in 103 unrelated multiple sclerosis (UMS) patients and in 26 related (RMS) patients from 12 families from Sardinia, Italy, where the disease was associated with the HLA-DR4 allele. Using polymerase chain reaction and allele-specific oligonucleotide probes, we found in UMS an increased frequency of the DQB1 *0201 (p = 0.010) and DQB1 *0302 (p = 0.025) alleles, whereas the DQB1 *0301 allele was significantly decreased (p = 0.027). In RMS, only the DQB1 *0302 allele was increased (p = 0.047), and no difference was found in the DQB1 *0301 allele. For DQB haplotypes, an increased frequency of DQB1 *0302/*0502 (p = 0.026) and a decreased frequency of DQB1 *0201/*0601 (p = 0.009) and DQB1 *0502/*0502 (p = 0.025) was found in UMS patients, whereas RMS patients showed an increased frequency of DQB1 *0301/*0302 (p = 0.005). Because DQB1 *0201 and *0302 alleles are increased in Caucasian MS patients, where the disease is related to HLA-DR2 and where a primary association with the HLA-DR2, DQB1 *0602 allele has been reported, we conclude that Caucasian and Sardinian populations share HLA-DQB1 *0201 and *0302 alleles in genetic susceptibility to MS.

A PvuII RFLP at D6S114E locus in the HLA region (RING4 locus)

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Sardinian multiple sclerosis is associated with HLA-DR4: a serologic and molecular analysis

HLA haplotypes in 45 unrelated Sardinian multiple sclerosis patients and in six multiplex families were defined, using both serologic and restriction fragment length polymorphism (RFLP) analysis. In unrelated MS patients, we found an association with HLA-DR4 (p less than 0.01, relative risk = 2.5) and DQw3 (p less than 0.04, relative risk = 2.2). Using a beta-DR cDNA probe, we observed no variation of the DR4 RFLP profile in sporadic or related MS patients compared with DR4-specific pattern in controls. Using a beta-DQ cDNA probe, we identified two DQw3 patterns (DQw3.1 and DQw3.2) with similar frequency in patients and in controls. No specific RFLPs were observed in association with different disease courses. The frequency of haplotype sharing in affected members of multiplex families was not different from that expected by chance. This study shows that Sardinian MS patients carry predominantly the HLA-DR4 allele, in contrast to the DR2 prevalence reported in Caucasian populations. The lack of association with HLA haplotypes in affected members of multiplex families may indicate that genetic factors outside the HLA system play a substantial role in families with MS.

Influence of dehydroepiandrosterone on G-6-PD activity and 3H-thymidine uptake of human lymphocytes in vitro

Dehydroepiandrosterone (DHEA) was found to inhibit experimental cancer development in mouse and rat lung, colon and mammary gland. Since DHEA is a potent inhibitor of mammalian G-6-PD, the hypothesis that the compound could inhibit cell proliferation through an inhibition of the pentose phosphate pathway has been formulated. We studied the effects of DHEA on the proliferation in vitro of human lymphocytes induced by several mitogens (PHA, ConA and PWM), measuring 3H-thymidine uptake. DHEA inhibited 3H-thymidine uptake of mitogen-stimulated cells from both G-6-PD+ and G-6-PD- (mediterranean type deficiency) individuals in a dose-dependent and reversible fashion. The inhibitory effect was found even if DHEA was added to cells in the last hours of culture, simultaneously with the addition of 3H-thymidine. These data suggest that the inhibition of thymidine uptake induced by DHEA on human lymphocytes probably does not depend on the inhibition of G-6-PD.

Lymphocyte subsets in human adenoids and tonsils. Rosette formation, alpha-naphthyl acetate esterase cytochemistry, monoclonal antibodies and peanut lectin reactivity

The distribution of mononuclear cell subsets has been studied in human adenoids, tonsils and peripheral blood (PB) by evaluating the presence of surface immunoglobulins, E-rosette formation, receptors for IgG Fc and for complement, alpha-naphthyl acetate esterase (ANAE) cytochemistry, reactivity with peanut lectin (PNA) and with monoclonal antibodies (McAb) (OK panel). Adenoids and tonsils, compared to PB, contain (1) fewer macrophages and T cells but more B cells; (2) higher proportions of ANAE negative, complement receptors and Ia-like antigens bearing T lymphocytes; (3) higher percentages of cells reacting with the McAbs OKT9 and OKT10 ("immature" lymphoid cells). In both adenoids and tonsils, clusters, formed by a central heavily ANAE stained interdigitating cell surrounded by lymphocytes with a sickle-shaped ANAE reaction, were found. Analogous clusters have been previously described in mice and human thymus. Two major hypotheses could be put forward: (1) adenoids and tonsils contain "immature" lymphoid cells undergoing education process, or (2) the above organs contain lymphocytes activated by a constant exposure to bacterial antigens or mitogens.

Surface markers on lymphocytes from human cerebrospinal fluid. Identification by monoclonal antibodies

Lymphocyte subpopulations in cerebrospinal fluid (CSF) and peripheral blood (PB) were studied using monoclonal antibodies and the common membrane markers. The results in three groups of patients were compared: 36 subjects with 'non-immunological disorders' (NID), 14 subjects with multiple sclerosis (MS) and 6 with subacute sclerosing panencephalitis (SSPE). It was found that, in patients with NID, (1) 90% of cells were T lymphocytes, reactive with OKT3; (2) the helper/suppressor (T4/T8) ratios were the same in the CSF and the PB; (3) the OKIa1 percentage was lower in the CSF than in the PB; and (4) only a few cells were 'immature', reacting with OKT10. Using the membrane markers (E rosettes, Fc IgG receptors and surface immunoglobulins), on the other hand, it was noted that the majority of cells in the CSF were identified as suppressor T lymphocytes and surface immunoglobulin-positive B cells were less common than the Ia1 marker suggested. There were no significant differences between the CSF results in patients with NID and MS but the OKT3 lymphocytes were reduced in CSF samples from patients with SSPE.

Lymphocyte subpopulations in blood and cerebrospinal fluid from patients with subacute sclerosing panencephalitis

Lymphocyte subpopulations in peripheral blood (PB) and cerebrospinal fluid (CSF) from 26 children affected with subacute sclerosing panencephalitis (SSPE) and from 13 controls with various neurological diseases without any immunological implication were examined for surface markers. SSPE patients were found to have significantly lower %s of E-rosette forming cells (RFC) (T lymphocytes) and of EA-RFC (TG lymphocytes, suppressor T cells) in both CSF and PB. No difference was found in EAC-RFC (B lymphocytes) either in CSF or PB. The low EA-RFC values can be explained by genetic factors, immune complexes or virus infection, and they could account for the hypersynthesis of oligoclonal immunoglobulins in the central nervous system. Longitudinal studies performed in 6 SSPE patients during isoprinosine therapy revealed a time-dependent decrement of the %s of E- and EA-RFC in CSF. It cannot be affirmed whether this is related to the disease or to the therapy.