Molecular analysis of the SLC22A12 (URAT1) gene in patients with primary gout

OBJECTIVE

To analyse the SLC22A12 (URAT1) gene in primary gout patients, first-grade relatives and healthy controls and the possible association of them with demographic and clinical data.

SUBJECTS AND METHODS

We included 69 consecutive patients with diagnosis of primary gout, as well as 29 first-grade relatives and 120 healthy volunteers. Demographic and clinical data were obtained from the patients and relatives. DNA was purified from peripheral blood and all 10 exons of the SLC22A12 (URAT1) gene were sequenced.

RESULTS

We found six different mutations in the SLC22A12 gene in 16 out of 69 (23%) patients with primary gout. Five mutations were in exon 5 and one in exon 4; five out of six mutations were heterozygous (one compound heterozygous) and one homozygous. The C850G mutation (exon 5) was found in 11 gout patients, these patients have lower levels of triglycerides than the rest of the group: 160 +/- 56 vs 292 +/- 203 mg/dl (P = 0.038). In one family, we found SLC22A12 mutations in three relatives within exon 5. We did not find mutations in the other exons studied (1-3 and 6-10), nor in any of the 10 exons of the 120 healthy volunteers.

CONCLUSIONS

We found several mutations in SLC22A12 gene associated with primary gout, the definite role of these mutations in URAT1 activity needs to be further studied.

Analysis of the VCX3A, VCX2 and VCX3B genes shows that VCX3A gene deletion is not sufficient to result in mental retardation in X-linked ichthyosis

BACKGROUND

X-linked ichthyosis (XLI), an inborn error of metabolism, is due to steroid sulphatase (STS) deficiency. Most patients with XLI harbour complete deletion of the STS gene and flanking sequences. The presence of low copy number repeats on either side of the STS gene seems to have a major role in the high frequency of these deletions. Some patients with XLI with terminal deletions of Xp22.3 involving marker DXS1139 and the STS gene show mental retardation (MR); VCX3A is the only gene located on this critical region.

OBJECTIVES

To analyse the VCX3A, VCX, VCX2 and VCX3B genes in 80 unrelated Mexican patients with XLI with normal intelligence.

METHODS

STS activity was measured in the leucocytes using 7-[3H]-dehydroepiandrosterone sulphate as a substrate. Amplification of the regions from telomeric DXS89 to centromeric DXS1134 including both extremes of the STS and the VCX3A, VCX, VCX2 and VCX3B genes was performed using polymerase chain reaction.

RESULTS

No STS activity was detected in the patients with XLI (0.00 pmol mg(-1) protein h(-1)). We observed two different deletion patterns: the first group included 62 patients with deletion of VCX3A and VCX genes. The second group included 18 patients with breakpoints at several regions on either side of the STS gene not including the VCX3A gene.

CONCLUSIONS

These data indicate that more complex mechanisms, apart from possible VCX3A gene participation, are occurring in the genesis of MR in XLI, at least in the sample of Mexican patients analysed.

Gender-specific differences in clinical and metabolic variables associated with NAFLD in a Mexican pediatric population

INTRODUCTION AND OBJECTIVES

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease in children and it is more prevalent in Hispanic males. The gender differences can be explained by body fat distribution, lifestyle, or sex hormone metabolism. We evaluated anthropometric and metabolic differences by gender in children with and without NAFLD.

METHODS

We included 194 participants (eutrophic, overweight, and individuals with obesity). The presence of NAFLD was determined using ultrasonography, and we evaluated the association between this disease with metabolic and anthropometric variables by gender.

RESULTS

The mean age was 10.64±2.54 years. The frequency of NAFLD in boys was 24.51% and in girls was 11.96% (OR=2.39; 95%CI=1.10-5.19; p=0.025). For girls, NAFLD was significantly associated with triglycerides (p=0.012), homeostatic model assessment of insulin resistance (HOMA-IR) (p=0.048), and the visceral adiposity index (VAI) (p=0.024). The variables related to NAFLD in a gender-specific manner were body mass index (BMI) (p=0.001), waist circumference (WC) (p<0.001), HDL cholesterol (p=0.021), alanine aminotransferase (ALT) (p<0.001), and aspartate aminotransferase (AST) (p=0.002).

CONCLUSIONS

In our study NAFLD is more frequent in boys, only ALT, and no other clinical or metabolic variables, were associated with NAFLD in these patients. HOMA-IR, VAI, triglyceride levels, and ALT were associated with NAFLD only in girls. The ALT cut-off points for the development of NAFLD in our study were 28.5U/L in females and 27.5U/L in males. Our findings showed that NAFLD should be intentionally screened in patients with obesity, particularly in boys.

Contiguous gene syndrome due to deletion of the first three exons of the Kallmann gene and complete deletion of the steroid sulphatase gene

OBJECTIVE

Large terminal or interstitial deletions of the 22.3 region on the short arm of the X chromosome cause contiguous gene syndromes. Kallmann syndrome (hypogonadotrophic hypogonadism with anosmia or hyposmia) associated with X-linked ichthyosis, due to a contiguous gene syndrome, is an uncommon finding. Genetic defects have been demonstrated in the Xp22.3 region, explaining the presence of one or both entities in affected individuals. In this report we describe the molecular findings of a patient with Kallmann syndrome and X-linked ichthyosis.

PATIENT

A 20-year-old subject with hypogonadism, anosmia and generalized ichthyosis was studied endocrinologically, biochemically and molecularly.

MEASUREMENTS

Levels of LH, FSH, GH, testosterone, oestradiol and cortisol were determined basally and after specific stimulation tests. Enzymatic activity of steroid sulphatase was measured in leucocytes. Polymerase chain reaction of the 14 exons of the Kallmann gene and of the 5' and 3' extremes of the steroid sulphatase gene was performed in genomic DNA.

RESULTS

A partial deletion from exon 1 to exon 3 of the Kallmann gene, as well as a complete deletion of the steroid sulphatase gene were observed.

CONCLUSIONS

A patient bearing a contiguous gene syndrome with partial deletion of the Kallmann syndrome gene and complete deletion of the steroid sulphatase gene is described. This is the first time a mutation in the conserved cysteine-rich N-terminal region which corresponds to the whey acidic protein motif of the Kallmann gene has been characterized, thus demonstrating the importance of this specific region for the function of the gene.

Unusual clinical presentation in two cases of multiple sulfatase deficiency

Multiple sulfatase deficiency (MSD) is an inborn error of metabolism that combines the clinical features of late infantile metachromatic leukodystrophy and mucopolysaccharidosis. The characteristic biochemical abnormality is a reduction in the activities of several sulfatases, with consequent tissue accumulation of sulfatides, sulfated glycosaminoglycans, sphingolipids, and steroid sulfates. In this study we present two unusual cases of MSD with variable enzymatic deficiency of arylsulfatases A, B, and C. Both patients had ichthyosis, broad thumbs and index fingers, an unusually slow progression of the neurologic symptoms, and lacked the hepatosplenomegaly that is typical of MSD. Olivopontocerebellar atrophy was present and one patient had a large retrocerebellar cyst. Mucopolysaccharides were not detected in the urine from either subject. Leukocyte arylsulfatase A activity in patient 1 was 0.46 nmol/mg protein/hr and in patient 2 was 0.0 nmol/mg protein/hr (normal 0.7-5.0 nmol/mg protein/hr). Leukocyte arylsulfatase B activity in patient 1 was 24 nmol/mg protein/hr and in patient 2 was 22 nmol/mg protein/hr (normal 115-226 nmol/mg protein/hr). Leukocyte arylsulfatase C in patient 1 was 0.30 pmol/mg protein/hr and in patient 2 was 0.28 pmol/mg protein/hr (normal 0.84 pmol/mg protein/hr). In conclusion, these two patients with MSD had mild clinical presentations not previously reported and variable enzymatic deficiency of arylsulfatases A, B, and C.

Mutation report: a novel partial deletion of exons 2-10 of the STS gene in recessive X-linked ichthyosis

X-linked ichthyosis is an inherited disease due to steroid sulfatase deficiency. Onset is at birth or early after birth with dark, regular, and adherent scales of skin. Approximately 85%-90% of X-linked ichthyosis patients have large deletions of the STS gene and flanking sequences. Three patients have been identified with partial deletions of the gene. Two deletions have been found at the 3' extreme and the other one implicating exons 2-5. This study describes a novel partial deletion of the STS gene in an X-linked ichthyosis patient. The subject was classified through steroid sulfatase assay in leukocytes using 7-[3H]-dehydroepiandrosterone sulfate as a substrate. Exons 1, 2, 5, and 7-10, and 3' flanking sequences DXS1131, DXS1133, DXS237, DXS1132, DXF22S1, and DXS278 of the STS gene were analyzed through polymerase chain reaction. The DNA analysis showed that exon 1 and 3' flanking sequences from DXS237 to DXS278 were present. In this study we report the fourth partial deletion of the STS gene and the first spanning exons 2-10 in X-linked ichthyosis patients.

Tinea imbricata: autosomal dominant pattern of susceptibility in a polygamous indigenous family of the Nahuatl zone in Mexico. Tinea imbricata: Autosomal dominierendes Anfalligkeitsmuster in einer poligamen Eingeborenen-Familie in Nahuatl, Mexiko

We report on 9 confirmed cases of tinea imbricata (Tokelau, infection due to Trichophyton concentricum) out of 16 family members. They had a common mother with three different fathers. The genetic analysis of the family suggests an autosomal dominant pattern of susceptibility. Most cases (8/9) were presented as concentric and lamellar forms. One patient also had onychomycosis due to T. concentricum. Only two out of nine cases had a positive response to trichophytin.

Carrier identification by FISH analysis in isolated cases of X-linked ichthyosis

X-linked ichthyosis (XLI) is an inborn error of metabolism due to steroid sulfatase (STS) deficiency. STS assay and FISH are useful in diagnosing carrier status of XLI. Biochemical analysis appears to indicate that most sporadic cases are inherited. Since this method does not seem to be completely reliable in recognizing XLI-carriers, the aim of the present study was to corroborate by FISH whether or not most sporadic cases of XLI had de novo mutations. XLI patients were classified through STS assay and PCR amplification of 5'-3' ends of the STS gene. XLI patients had undetectable levels of STS activity and complete deletion of the STS gene. Patients' mothers were studied through STS assay and FISH. Nine out of 12 mothers presented an STS activity compatible with XLI-carrier state. These mothers also had only one copy of the STS gene, indicating that they carry the primary gene defect. One mother had normal STS activity but only one copy of the STS gene. This data corroborated that most sporadic cases do not represent de novo mutations, and that FISH must be included in the analysis of mothers of sporadic cases when they present with normal STS activity, in order to correctly diagnose the XLI carrier state.

Most "sporadic" cases of X-linked ichthyosis are not de novo mutations

X-linked ichthyosis is an inherited disease with dark, regular and adherent scales as clinical characteristics. It is caused by a deficiency of the steroid sulphatase enzyme. Steroid sulphatase assay is a relative easy tool that enables correct diagnosis of X-linked ichthyosis patients and carriers. A large number of X-linked ichthyosis patients correspond to non-familial cases that seem to represent de novo mutations. In this study, we examined the X-linked ichthyosis carrier state of the mothers of 42 non-familial cases to determine whether their children corresponded to de novo mutations. To classify patients and carriers, a steroid sulphatase assay was performed in leukocytes using 7-[3H]-dehydroepiandrosterone sulphate as substrate. In 36 mothers (85%) we found steroid sulphatase activity compatible with the carrier state of X-linked ichthyosis. This data suggest that most of the mothers of these patients present the primary gene defect, excluding de novo mutations in the patients.

Whole sequence of the mitochondrial DNA genome of Kearns Sayre Syndrome patients: Identification of deletions and variants

Mitochondria both produce the energy of the cell as ATP via respiration and regulate cellular metabolism. Accordingly, any deletion or mutation in the mitochondrial DNA (mtDNA) may result in a disease. One of these diseases is Kearns Sayre syndrome (KSS), described for the first time in 1958, where different large-scale deletions of different sizes and at different positions have been reported in the mitochondrial genome of patients with similar clinical symptoms. In this study, sequences of the mitochondrial genome of three patients with clinic features of KSS were analyzed. Our results revealed the position, heteroplasmy percentage, size of deletions, and their haplogroups. Two patients contained deletions reported previously and one patient showed a new deletion not reported previously. These results display for the first time a systematic analysis of mtDNA variants in the whole mtDNA genome of patients with KSS to help to understand their association with the disease.

Segregation analysis in X-linked ichthyosis: paternal transmission of the affected X-chromosome

BACKGROUND

Steroid sulphatase (STS) deficiency has been described in a diversity of ethnic populations. The phenotype of STS deficiency, X-linked ichthyosis (XLI), is a genodermatosis characterized by dark scaly skin. About 90% of patients with XLI have complete deletion of the entire STS gene and flanking sequences. The variable number tandem repeats, on either side of the STS gene, appear to play an important role in these interstitial deletions due to nonallelic homologous recombination (NAHR). It is difficult to establish if this NAHR occurs between two chromosomes, between sister chromatids or between the same chromatid.

OBJECTIVES

To identify the parental origin of the affected X-chromosome in seven unrelated sporadic cases of XLI.

METHODS

Amplification of the regions from DXS89 to DXS1134 (telomeric-centromeric) including the 5' and 3' ends of the STS gene was performed through polymerase chain reaction. GeneScan analysis was performed using the DXS987, DXS8051 and DXS1060 markers located on the short arm of the X-chromosome. Fluorescence in situ hybridization analysis was performed with a digoxigenin-labelled cDNA STS probe.

RESULTS

STS gene deletion in patients with XLI involved the sequences DXS1139 and DXF22S1. In five families segregation analysis showed paternal transmission of the affected X-chromosome in the XLI carrier. It was not possible to determine the parental origin of the affected X-chromosome in two families.

CONCLUSIONS

These data strongly suggest that STS gene deletion occurred in the male meiosis probably due to an intrachromosomal event, recombination between S232 sequences on the same DNA molecule, or during the process of DNA replication.

X-linked ichthyosis in Mexico: high frequency of deletions in the steroid sulfatase encoding gene

The present study analyzes the frequency of molecular deletions in the steroid sulfatase (STS) encoding gene in a sample of 50 Mexican subjects with biochemical diagnosis of X-linked ichthyosis (XLI). To establish the correct diagnosis, STS activity was determined in leukocytes using 7-(3)H-dehydroepiandrosterone sulfate as the substrate. No amplification of the 3' and 5' ends of the STS gene by PCR was detected in the DNA of 49 patients, whereas only one sample of 50 presented a normal amplification. This report shows a very high frequency of deletions in the human STS encoding gene in a representative sample of the Mexican population, and it defines the characteristics of XLI in patients whose STS gene has a complete deletion as a major molecular defect.

An atypical contiguous gene syndrome: molecular studies in a family with X-linked Kallmann's syndrome and X-linked ichthyosis

BACKGROUND AND OBJECTIVE

Kallmann's syndrome (KS) is characterized by hypogonadotrophic hypogonadism in association with anosmia or hyposmia. This entity can be associated with X-linked ichthyosis (XLI) in a contiguous gene syndrome. Genetic defects have been demonstrated on the Xp22.3 region explaining the presence of one or both entities in affected individuals. In this report we describe the molecular findings in four patients, pertaining to a three generation family, with KS which was associated with XLI in two of them.

MEASUREMENTS

Enzymatic activity of steroid sulphatase was measured in leucocytes. Polymerase chain reaction of the 14 exons of the Kallmann gene (KAL) and of the 5' and 3' extremes of the steroid sulphatase gene was performed in genomic DNA. PCR products of the 14 exons of the KAL gene were purified and sequenced.

RESULTS

Absence of steroid sulphatase activity and a complete deletion of the STS gene were demonstrated in both patients with XLI. In all subjects, the 14 KAL gene exons amplified in a normal fashion; no mutation was documented after sequencing all exons.

CONCLUSIONS

Although it has been proposed recently that the X-linked form of the disease accounts for the minority of patients with Kallman's syndrome, the pedigree chart of this family demonstrates this inheritance pattern. Various possibilities are mentioned in order to explain the absence of mutation in the KAL gene. The coexistence, in this family, of Kallman's syndrome individuals and patients with Kallman's syndrome and X-linked ichthyosis is discussed.

Molecular Analysis of the CYP1B1 Gene: Identification of Novel Truncating Mutations in Patients with Primary Congenital Glaucoma

BACKGROUND

Mutations and polymorphisms have been identified in the CYP1B1 gene; while mutations that affect the conserved core structures of cytochrome P4501B1 result in primary congenital glaucoma (PCG), mutations in other regions hold the potential to define differences in estrogen metabolism. In the present study, we analyzed the CYP1B1 gene in Mexican patients with PCG and described four novel mutations.

MATERIALS AND METHODS

The sample included 12 nonrelated cases with PCG. Analysis of coding regions of the CYP1B1 gene was performed through PCR and DNA sequencing analysis from genomic DNA.

RESULTS AND DISCUSSION

Molecular analysis of the CYP1B1 gene showed the following molecular defects: (1) a novel single-base pair deletion within codon 370 (1454delC) that produces a substitution of leucine instead of proline and a premature stop codon 57 amino acids after the last original amino acid; this family also harbored a novel polymorphic variant of the cytochrome P4501B1 with six single-nucleotide polymorphisms (142C-->G; 355G-->T; 729G-->C; 4326C-->G; 4360C-->G and 4379C-->T); (2) a novel single-base pair deletion within codon 277 (1176delT) that results in a premature stop codon; (3) a novel single-base pair deletion within codon 179 (880delG) that produces a substitution of arginine instead of alanine and a premature stop codon 17 amino acids downstream from the last original amino acid, and (4) a duplication (or insertion) of ten base pairs within codon 404 (1556dupATGCCACCAC) that results in a premature stop codon 26 amino acids after the last original amino acid. We also observed in 2 nonrelated patients a deletion of 13 bp (1410_1422delGAGTGCAGGCAGA) previously reported for other populations.

CONCLUSION

We reported four novel mutations and a novel polymorphic variant in the CYP1B1 gene in PCG in the Mexican population; it has important implications in diagnosis and genetic counseling.

Familial pycnodysostosis: identification of a novel mutation in the CTSK gene (cathepsin K)

BACKGROUND

Pycnodysostosis, an autosomal recessive skeletal dysplasia, is characterized by short stature, osteosclerosis, delayed cranial suture closure, hypoplastic mandible, acro-osteolysis, hypoplastic clavicle, and dental anomalies. The disorder is caused by CTSK gene defects, a gene localized on 1q21.

PURPOSE

To describe the clinical, radiological, and molecular findings in a family with pycnodysostosis.

METHODS

The CTSK gene was analyzed from genomic DNA in a nonconsanguinity Mexican family with 3 affected members with pycnodysostosis and 100 healthy controls.

RESULTS AND INTERPRETATION

We identified the novel homozygous mutation c.908G>A within exon 8 of the CTSK gene. This missense mutation leads to the substitution of the amino acid glycine at position 303 by glutamic acid (G303E) in cathepsin K protease. No genotype/phenotype correlation was present in affected members of the family with pycnodysostosis.

Satoyoshi syndrome with unusual skeletal abnormalities and parental consanguinity

Satoyoshi syndrome (SS) (OMIM 600705) is a rare multisystemic disorder of unknown etiology characterized by progressive painful intermittent muscle spasm, alopecia universalis, diarrhea, short stature, amenorrhea, and secondary skeletal abnormalities mimicking a metaphyseal chondrodysplasia. To date all reported cases have been sporadic. We describe a 26-year-old Mexican woman, a product of consanguineous parents with clinical characteristics of SS. Our patient, also showed skeletal anomalies not previously reported that seems to be a coincidental finding.

Novel mutation and white matter involvement in an Indian child with pycnodysostosis

Pycnodysostosis (OMIM # 265800) is an inherited lysosomal disorder due to affection of cathepsin K gene, localised to 1q21. Pycnodysostosis can present with both skeletal and extraskeletal features. The index patient presented with cardinal features of short stature, dental and digital anomalies with history of multiple fractures. He, in addition had an unreported finding of white matter hyperintensity suggesting dysmyelination on neuroimaging. Molecular analysis revealed a homozygous insertion of single nucleotide in exon 5 of the CTSK gene that produces the substitution of phenylalanine instead of leucine at position 160 of protein and a premature termination of protein synthesis due to insertion of a stop codon. This mutation (c.480_481insT), (p.L160fsX173) is a novel frameshift mutation. The index case extends the phenotypic spectrum and the list of previously reported mutations in the CTSK gene.

Particular distribution of the GJB2/GJB6 gene mutations in Mexican population with hearing impairment

BACKGROUND

Hereditary sensorineural hearing loss (SNHL) is a genetically heterogeneous disorder worldwide. Mutations in the GJB2 gene are a frequent cause of hereditary SNHL. There is a prevalence of certain mutations in various populations which suggests that specific mutations may be influenced by ethnic background.

OBJECTIVE

To analyze the prevalence of GJB2, GJB6 mutations in several geographic areas of Mexico in patients with hereditary SNHL.

MATERIALS AND METHODS

One hundred and forty Mexican unrelated propositi with prelingual SNHL were included in the study. All patients had three previous generations born in Mexico and belonged to no specific ethnic group. Analyses of the GJB2 and GJB6 genes and mt.1555A

RESULTS

Twenty-three homozygous mutations, 57 heterozygous mutations, 1 double heterozygous (GJB2/GJB6) and 59 wild-type genotypes in the GJB2 gene were observed. Three patients had the homozygous c.del35 mutation whereas 26 patients were heterozygous for this gene defect. Only one patient with the GJB6 gene deletion was present (it includes the double heterozygous GJB2/GJB6). The mt.1555A>G mutation was not detected.

CONCLUSION

We found a great variety of mutations depending on the analyzed region in patients with SNHL; 57.86% of patients had affection in one or two alleles in GJB2 or GJB6 genes whereas 42.14% were wild-type. In some cases, allele distribution depended on region. Molecular studies of more genes involved in hereditary non-syndromic SNHL are required to completely confirm the molecular basis of hearing loss in Mexican population.

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Key Words

• Connexins
• GJB2 gene
• GJB6 gene
• Gene mutations
• Hypoacusia

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MESH Headings

• Adolescent
• Adult
• Child
• Child, Preschool
• Connexin 26
• Connexin 30
• Connexins/genetics
• Female
• Gene Frequency
• Hearing Loss, Sensorineural/genetics
• Heterozygote
• Homozygote
• Humans
• Infant
• Infant, Newborn
• Male
• Mexico
• Mutation
• Sequence Analysis, DNA
• Young Adult

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Expression of metalloproteinases MMP-2 and MMP-9 is associated to the presence of androgen receptor in epithelial ovarian tumors

BACKGROUND

The current study evaluated the metalloproteinases MMP-2 and MMP-9 expression in epithelial cells and the surrounding stroma in ovarian tumors and the association of MMPs with the histological subtypes, the clinical stage and the presence of steroid hormone receptors. Tumor samples were obtained from 88 patients undergoing surgical cytoreduction of primary ovarian tumors in Instituto Nacional de Cancerología, from México City. The formalin fixed and paraffin embedded samples were processed in order to demonstrate the presence of androgen receptor,estrogen receptor alpha, progesterone receptor, MMP-2,MMP-9 and collagen IV by immunohistochemistry and/or immunofluorescence.

RESULTS

MMP-2 and MMP-9 were differentially expressed in the epithelium and the stroma of ovarian tumors associated to histological subtype, clinical stage and sexual steroid hormone receptor expression. Based on Cox proportional hazard regression model we demonstrated that MMP-2 located in the epithelium and the stroma are independent prognostic biomarkers for overall survival in epithelial ovarian tumors. Kaplan Meir analysis of the combination of AR (+) with MMP-2 (+) in epithelium and AR (+) with MMP-2 (-) in stroma displayed a significant reduction of survival.

CONCLUSIONS

The presence of MMP-2 in the stroma of the tumor was a protective factor while the presence of MMP-2 in the epithelium indicated an adverse prognosis. The presence of AR associated with MMP-2 in the tumor cells was a risk factor for overall survival in epithelial ovarian cancer.

Two different PABPN1 expanded alleles in a Mexican population with oculopharyngeal muscular dystrophy arising from independent founder effects

BACKGROUND

Oculopharyngeal muscular dystrophy (OPMD) is a late onset hereditary myopathy of autosomal dominant transmission characterised by ptosis, dysphagia and limb weakness. The disease is caused by short heterozygous expansions of a (GCN)(10) triplet located in the first exon of the PABPN1 gene at chromosome 14q11.1. Most affected individuals from North America and Europe carry a mutant (GCN)(13) allele. Although evidence for a founder mutation effect has been shown in several populations with OPMD, analysis of large groups of patients from different ethnic backgrounds will help to identify the relative contribution of each allele to the disease and a possible genotype-phenotype correlation.

METHODS

22 unrelated patients with OPMD from Mexico, a previously uncharacterised population, were clinically and molecularly analysed. Detailed ophthalmological and clinical examinations were performed in each proband and molecular analysis of the PABPN1 gene was carried out by PCR amplification and allele-specific cloning/sequencing. Two single nucleotide polymorphisms (SNPs) linked to PABPN1 were determined in each individual and in a number of affected first-degree relatives.

RESULTS

15 subjects (68%) carried a mutant (GCN)(15) or (GCG)(11)(GCA)(3)(GCG) PABPN1 allele; the remaining 7 (32%) exhibited an abnormal (GCN)(13) or (GCG)(9)(GCA)(3)(GCG) allele. Analysis of two SNPs linked to PABPN1 strongly suggests that both expanded alleles originate from two independent founder effects. In addition, in this particular population the (GCN)(15) allele was associated with an earlier onset of the disease (mean 46.5 years) compared with the (GCN)(13) allele (mean 54.7 years).

CONCLUSION

The results of this study suggest that OPMD in the Mexican population is mostly due to (GCG)(11) or (GCG)(9) PABPN1 expanded alleles arising from two independent founder effect mutations. These findings add to the definition of the genetic features of the disease and to the establishment of a probable genotype-phenotype correlation.