Montserrat Milà

Penetrance of FMR1 premutation associated pathologies in fragile X syndrome families

Within the past few years, there has been a significant change in identifying and characterizing the FMR1 premutation associated phenotypes. The premutation has been associated with elevated FMR1 mRNA levels and slight to moderate reductions in FMRP levels. Furthermore, it has been established that ∼20% of female premutation carriers present primary ovarian insufficiency (POI) and that fragile X-associated tremor/ataxia syndrome (FXTAS) occurs in one-third of all male premutation carriers older than 50 years. Besides POI and FXTAS, new disorders have recently been described among individuals (especially females) with the FMR1 premutation. Those pathologies include thyroid disease, hypertension, seizures, peripheral neuropathy, and fibromyalgia. However there are few reports related to FXTAS penetrance among female premutation carriers or regarding these disorders recently associated to the FMR1 premutation. Therefore, we have evaluated 398 fragile X syndrome (FXS) families in an attempt to provide an estimation of the premutation associated phenotypes penetrance. Our results show that signs of FXTAS are detected in 16.5% of female premutation carriers and in 45.5% of premutated males older than 50 years. Furthermore, among females with the FMR1 premutation, penetrance of POI, thyroid disease and chronic muscle pain is 18.6, 15.9 and 24.4%, respectively. The knowledge of this data might be useful for accurate genetic counselling as well as for a better characterization of the clinical phenotypes of FMR1 premutation carriers.

A melanoma-associated germline mutation in exon 1β inactivates p14ARF

The INK4a/ARF locus encodes the cyclin dependent kinase inhibitor, p16INK4a and the p53 activator, p14ARF. These two proteins have an independent first exon (exon 1α and exon 1β, respectively) but share exons 2 and 3 and are translated in different reading frames. Germline mutations in this locus are associated with melanoma susceptibility in 20–40% of multiple case melanoma families. Although most of these mutations specifically inactivate p16INK4a, more than 40% of the INK4a/ARF alterations located in exon 2, affect both p16INK4a and p14ARF. We now report a 16 base pair exon 1β germline insertion specifically altering p14ARF, but not p16INK4a, in an individual with multiple primary melanomas. This mutant p14ARF, 60ins16, was restricted to the cytoplasm, did not stabilize p53 and was unable to arrest the growth of a p53 expressing melanoma cell line. This is the first example of an exon 1β mutation that inactivates p14ARF, and thus implicates a role for this tumour suppressor in melanoma predisposition.

Role of the CDKN2A Locus in Patients With Multiple Primary Melanomas

PURPOSE We have studied a consecutive case series of patients with multiple primary melanoma (MPM) for the involvement of the melanoma susceptibility loci CDKN2A and CDK4. PATIENTS AND METHODS One hundred four MPM patients (81 patients with two primary melanomas, 14 with three, five with four, one with five, two with six, and one with seven) were included. RESULTS Seven different CDKN2A germline mutations were identified in 17 patients (16.3%). In total, we identified 15 CDKN2A exon 2, one exon 1alpha missense mutation, and one exon 1beta frameshift mutation. The age of onset was significantly lower and the number of primary melanomas higher in patients with mutations. CDKN2A mutations were more frequent in patients with familial history of melanoma (35.5%) compared with patients without (8.2%), with a relative risk (RR) of 4.32 (95% CI, 1.76 to 10.64; P = .001), and in patients with more than two melanomas (39.1%) compared with patients with only two melanomas (10%) with an RR of 3.29 (95% CI, 1.7 to 6.3; P = .002). The A148T polymorphism was more frequent in patients with MPMs than in the control population (P = .05). A variant of uncertain significance, A127S, was also detected in one patient. No CDK4 mutations were identified, suggesting that it has a low impact in susceptibility to MPM. CONCLUSION MPM patients are good candidates for CDKN2A mutational screening. These patients and some of their siblings should be included in a program of specific follow-up with total body photography and digital dermoscopy, which will result in the early detection of melanoma in this subset of high-risk patients and improve phenotypic characterization.

REM sleep behavior disorder and vocal cord paralysis in Machado‐Joseph disease

We evaluated the occurrence of REM sleep behaviour disorder (RBD) and vocal cord abductor paralysis (VCAP) in a group of 9 Machado‐Joseph disease (MJD) patients. RBD was diagnosed by clinical history plus audiovisual polysomnography in 4 men and 1 woman (55%). While dreaming, 4 fell out of the bed and the other injured his arms. Laryngoscopy detected bilateral VCAP in 1 patient with stridor who required emergency tracheotomy, and partial vocal cord abductor restriction in 2. RBD and VCAP are two potentially injurious conditions that should be considered part of the clinical spectrum of MJD.

Influence of the ACE gene polymorphism in the progression of renal failure in autosomal dominant polycystic kidney disease

The recent description of a polymorphism in the gene for angiotensin-converting enzyme (ACE), with the D allele associated with greater plasma levels of ACE, allows us to perform studies of the relationship between this polymorphism and chronic renal diseases in which the renin-angiotensin system could be implicated. We examined 155 patients with autosomal dominant polycystic kidney disease (ADPKD) with linkage to the PKD1 locus. The ACE insertion/deletion (I/D) polymorphism was amplified with the previously published flanking primers, and the polymerase chain reaction product was separated, sized on a 2% agarose gel, and visualized by ultraviolet transillumination. The ACE genotype distributions were 11.6%, 63.8%, and 24.5% for II, ID, and DD, respectively. There were no significant differences among the three genotypes with respect to mean age, sex distribution, and prevalence of hypertension. The ACE genotype distribution in patients with end-stage renal failure at the time of data compilation was similar to that of the entire study population. In the subgroup of patients who received renal replacement therapy before the age of 50 years, we found a significant association between DD genotype and onset of end-stage renal disease (ESRD) before the age of 50 years compared with II and ID (P = 0.017). We calculated the estimated median renal survival time as 51 years for the II genotype, 53 years for the ID genotype, and 48 years for the DD genotype. There were statistically significant differences between DD and ID patients (P = 0.025). In conclusion, we found DD genotype implies a worse renal prognosis based on both the significantly lower median renal survival time and significantly greater percentage of patients who reach ESRD before the age of 50 years, without implying a greater prevalence of hypertension.

Structural variation in the human genome: the impact of copy number variants on clinical diagnosis

Over the past few years, the application of whole-genome scanning array technologies has catalyzed the appreciation of a new form of submicroscopic genomic imbalances, referred to as copy number variants. Copy number variants contribute substantially to genetic diversity and result from gains and losses of genomic regions that are 1000 base pairs in size or larger, sometimes encompassing millions of bases of contiguous DNA sequences. As genome-wide scanning techniques become more widely used in diagnostic laboratories, a major challenge is how to accurately interpret which submicroscopic genomic imbalances are pathogenic in nature and which are benign. Herein, we review the literature from the past 3 years on this new source of genomic variability and comment on factors that should be considered when trying to differentiate between a pathogenic and a benign copy number variant.

A novel mutation in JARID1C gene associated with mental retardation

X-linked mental retardation (XLMR) is an extremely heterogeneous condition that account for 15–25% of all mentally retarded patients. The number of genes newly reported in relation with this condition has been rapidly increased in the past years. One of the latest is called Jumonji AT-rich interactive domain 1C (JARID1C). This gene encodes for a member of a recently discovered protein family that harbours DNA-binding motifs, suggesting a possible role in transcriptional regulation and in the modification of chromatin structure. In this work we describe the results obtained by screening JARID1C gene in 24 mentally retarded males with history of at least two affected males. Remarkably, we have found a novel missense mutation in exon 10 of the gene that results in a Serine-to-arginine change at amino-acid 451 (S451R). This nucleotide change appears to be restricted to mentally retarded patients, since it has not been detected in control samples. Familial analysis has confirmed the segregation of this mutation with mental retardation. Furthermore, sequence alignment analysis with the different members of the human JARID1 family and with homologous proteins of mouse and fruit fly has revealed that the affected amino acid is conserved. Our data highlights the importance of reporting mutations in this gene since it might support the recent findings that implicates JARID1C with XLMR.

Dosage-Dependent Severity of the Phenotype in Patients with Mental Retardation Due to a Recurrent Copy-Number Gain at Xq28 Mediated by an Unusual Recombination

We report on the identification of a 0.3 Mb inherited recurrent but variable copy-number gain at Xq28 in affected males of four unrelated families with X-linked mental retardation (MR). All aberrations segregate with the disease in the families, and the carrier mothers show nonrandom X chromosome inactivation. Tiling Xq28-region-specific oligo array revealed that all aberrations start at the beginning of the low copy repeat LCR-K1, at position 153.20 Mb, and end just distal to LCR-L2, at 153.54 Mb. The copy-number gain always includes 18 annotated genes, of which RPL10, ATP6AP1 and GDI1 are highly expressed in brain. From these, GDI1 is the most likely candidate gene. Its copy number correlates with the severity of clinical features, because it is duplicated in one family with nonsyndromic moderate MR, is triplicated in males from two families with mild MR and additional features, and is present in five copies in a fourth family with a severe syndromic form of MR. Moreover, expression analysis revealed copy-number-dependent increased mRNA levels in affected patients compared to control individuals. Interestingly, analysis of the breakpoint regions suggests a recombination mechanism that involves two adjacent but different sets of low copy repeats. Taken together, our data strongly suggest that an increased expression of GDI1 results in impaired cognition in a dosage-dependent manner. Moreover, these data also imply that a copy-number gain of an individual gene present in the larger genomic aberration that leads to the severe MECP2 duplication syndrome can of itself result in a clinical phenotype as well.

Associated features in females with an FMR1 premutation

Changes in the fragile X mental retardation 1 gene (FMR1) have been associated with specific phenotypes, most specifically those of fragile X syndrome (FXS), fragile X tremor/ataxia syndrome (FXTAS), and fragile X primary ovarian insufficiency (FXPOI). Evidence of increased risk for additional medical, psychiatric, and cognitive features and conditions is now known to exist for individuals with a premutation, although some features have been more thoroughly studied than others. This review highlights the literature on medical, reproductive, cognitive, and psychiatric features, primarily in females, that have been suggested to be associated with changes in the FMR1 gene. Based on this review, each feature is evaluated with regard to the strength of evidence of association with the premutation. Areas of need for additional focused research and possible intervention strategies are suggested.

Evidence of depressive symptoms in fragile-x syndrome premutated females

Objectives Fragile-X premutation carriers have been considered asymptomatic patients for a long time. It has been, however, demonstrated that the premutation is also involved in clinical pathology, such as premature ovarian failure, the fragile-X-associated tremor/ataxia syndrome, and a distinct neurocognitive and behavioral phenotype, which includes psychiatric problems. To define better this neuropsychiatric phenotype associated with premutation carriers and to minimize a possible environmental effect, we examined psychiatric and depressive symptoms in 34 FMR1 premutation carrier mothers of children with fragile-X syndrome in comparison with two control groups (39 mothers with a non-fragile-X syndrome mentally retarded child and 39 mothers from the general population). Methods All participants completed both questionnaires, which assess psychiatric symptoms (the symptom checklist-90-revised) and depression (Beck Depression Inventory). Results Both groups of mothers with a mentally retarded child showed greater susceptibility to psychological problems than the control group without a mentally retarded child, but FMR1 premutated mothers evidenced a higher tendency to depression. These results suggest that, despite the stress of caring for a child with mental retardation, the premutation by itself could be responsible for some psychiatric traits. Conclusion Our findings reinforce the hypothesis of a pathogenic gene-brain-behavior mechanism in the premutation range.