Diana Valverde

Influence of glutathione S-transferase M1 and T1 homozygous null mutations on the risk of antituberculosis drug-induced hepatotoxicity in a Caucasian population.

Objectives: Genetic variations in enzymes of isoniazid metabolism confer an increased risk for antituberculosis drug‐induced hepatotoxicity in Asian populations. The present study was aimed at investigating the possible association of antituberculosis drug‐induced hepatotoxicity with polymorphisms at the glutathione S‐transferase (GST) gene in a Caucasian population.

Retinitis pigmentosa in Spain

Retinitis pigmentosa is a term commonly given to a group of inherited and progressive disorders which affect the photoreceptors of the retina. As part of an ongoing research programme throughout Spain, clinical, epide‐miological, and genetic studies have been carried out on these diseases. Here, we report the relative frequencies of the different genetic types in 503 non‐syndromic and 89 syndromic RP families of Spanish origin. The most frequent syndromic RP forms were Usher syndrome type 1 (20/ 89 families=30%) and Usher syndrome type 2 (44 families=49%). Among non‐syndromic RP forms, 12% were autosomal dominant, 39% autosomal recessive and 4% X‐linked. Forty‐one percent were isolated or simplex cases and in 4% the genetic type could not be established.

Identification of 14 novel mutations in the long isoform of USH2A in Spanish patients with Usher syndrome type II

Mutations in USH2A gene have been shown to be responsible for Usher syndrome type II, an autosomal recessive disorder characterised by hearing loss and retinitis pigmentosa. USH2A was firstly described as consisting of 21 exons, but 52 novel exons at the 3’ end of the gene were recently identified. In this report, a mutation analysis of the new 52 exons of USH2A gene was carried out in 32 unrelated patients in which both disease-causing mutations could not be found after the screening of the first 21 exons of the USH2A gene. On analysing the new 52 exons, fourteen novel mutations were identified in 14 out of the 32 cases studied, including 7 missense, 5 frameshift, 1 duplication and a putative splice-site mutation.

Discovery and Functional Analysis of a Retinitis Pigmentosa Gene, C2ORF71

Retinitis pigmentosa is a genetically heterogeneous group of inherited ocular disorders characterized by progressive photoreceptor cell loss, night blindness, constriction of the visual field, and progressive visual disability. Homozygosity mapping and gene expression studies identified a 2 exon gene, C2ORF71. The encoded protein has no homologs and is highly expressed in the eye, where it is specifically expressed in photoreceptor cells. Two mutations were found in C2ORF71 in human RP patients: A nonsense mutation (p.W253X) in the first exon is likely to be a null allele; the second, a missense mutation (p.I201F) within a highly conserved region of the protein, leads to proteosomal degradation. Bioinformatic and functional studies identified and validated sites of lipid modification within the first three amino acids of the C2ORF71 protein. Using morpholino oligonucleotides to knockdown c2orf71 expression in zebrafish results in visual defects, confirming that C2ORF71 plays an important role in the development of normal vision. Finally, localization of C2ORF71 to primary cilia in cultured cells suggests that the protein is likely to localize to the connecting cilium or outer segment of photoreceptor cells.

N-acetyltransferase 2 polymorphisms and risk of anti-tuberculosis drug-induced hepatotoxicity in Caucasians.

OBJECTIVE To analyse slow-acetylation N-acetyltransferase 2 (NAT2) polymorphisms for their association with the risk of anti-tuberculosis drug-induced hepatotoxicity (ATDH). DESIGN A case-control study including Caucasian patients with tuberculosis (TB) treated with isoniazid, rifampicin and pyrazinamide. NAT2 genotype results were compared between ATDH cases and controls and with a healthy Spanish control population of Caucasian origin. RESULTS Fifty cases and 67 controls were included in the study. Slow, intermediate and rapid NAT2 genotypes were found in respectively 72%, 18% and 10% of cases compared with 65.7%, 25.4% and 9% of controls (P> 0.05). On comparing NAT2 genotypes among cases with those among healthy controls (n = 1312), we found more slow NAT2 genotypes and fewer intermediate genotypes among cases (respectively 72% and 18% in cases vs. 54.8% and 38.1% in controls; OR 2.07, 95%CI 1.12-2.79, P = 0.016 and OR 0.37, 95%CI 0.18-0.75, P = 0.003). CONCLUSIONS We could not demonstrate an increased risk of ATDH related to the presence of slow NAT2 polymorphisms among this Caucasian TB cohort. However, we found a significantly greater frequency of slow and a significantly lower frequency of intermediate NAT2 genotypes among the ATDH cases compared with the healthy control population.

Clinical and genetic studies in Spanish patients with Usher syndrome type II: description of new mutations and evidence for a lack of genotype--phenotype correlation.

Patients with Usher syndrome type II (USH2) show moderate‐to‐severe hearing loss (HL), retinitis pigmentosa and normal vestibular function. The progression of HL remains controversial. To evaluate whether a phenotype–genotype correlation exists regarding the issue of progression of HL, only USH2 patients with a defined genotype were selected. Ophthalmologic, vestibular and audiometric examination along with a mutation analysis of the USH2A gene (exons 1–21) was performed in twenty‐eight Spanish USH2 patients. Ten different pathogenic mutations and 17 sequence variants not associated with the disease were found. Six of the 10 mutations are novel. Disease alleles were identified in 13 of the 28 families tested. Eight of these 13 families had a mutation found in both alleles. In the other five families, only one mutation was identified. The phenotypic data provide evidence for the existence of phenotypic differences between patients with the same genotype. These differences were observed at both the interfamilial and intrafamilial levels.

Absence of Activating Mutations in the EGFR Kinase Domain in Spanish Head and Neck Cancer Patients

The discovery of kinase domain mutations in the epidermal growth factor receptor gene (EGFR) in never-smoker patients, associated with an increased sensitivity to tyrosine kinase inhibitors (TKIs) such as gefitinib or erlotinib, has been one of the most relevant findings ever in non-small cell lung carcinomas (NSCLC). Since treatment with TKIs has furthermore shown a clinical benefit in head and neck squamous cell carcinoma (HNSCC) patients, we hypothesized that these mutations could also be present in this neoplasia. Current studies looking for EGFR mutations in HNSCC are limited and results are still controversial. In this work, we screened for EGFR tyrosine kinase mutations in tumour DNA obtained from 31 Spanish patients with HNSCC by PCR-single-strand conformational polymorphism analysis. None of the patients displayed a somatic EGFR mutation, previously described in NSCLC, but other DNA sequence variations were found in 9 of 31 HNSCC patients. Accordingly, activating EGFR mutations in HNSCC patients seem to be a rare event in Spanish patients, suggesting that there is little room for the administration of TKIs in HNSCC based on the presence of these mutations. Additional investigations about EGFR amplification are indicated to establish a potential relationship between EGFR overexpression and the response to anti-EGFR therapies.

Arrayed primer extension technology simplifies mutation detection in Bardet-Biedl and Alstrom syndrome.

Bardet–Biedl syndrome (BBS; OMIM no. 209 900) and Alström syndrome (ALMS; OMIM no. 203 800) are rare, multisystem genetic disorders showing both a highly variable phenotype and considerable phenotypic overlap; they are included in the emerging group of diseases called ciliopathies. The genetic heterogeneity of BBS with 14 causal genes described to date, serves to further complicate mutational analysis. The development of the BBS–ALMS array which detects known mutations in these genes has allowed us to detect at least one mutation in 40.5% of BBS families and in 26.7% of ALMS families validating this as an efficient and cost-effective first pass screening modality. Furthermore, using this method, we found two BBS families segregating three BBS alleles further supporting oligogenicity or modifier roles for additional mutations. We did not observe more than two mutations in any ALMS family.

Novel Mutations in BMPR2, ACVRL1 and KCNA5 Genes and Hemodynamic Parameters in Patients with Pulmonary Arterial Hypertension

Background Pulmonary arterial hypertension (PAH) is a rare and progressive vascular disorder characterized by increased pulmonary vascular resistance and right heart failure. The aim of this study was to analyze the Bone Morphogenetic Protein Receptor 2 (BMPR2), Activin A type II receptor like kinase 1 (ALK1/ACVRL1) and potassium voltage-gated channel, shakerrelated subfamily, member 5 (KCNA5) genes in patients with idiopathic and associated PAH. Correlation among pathogenic mutations and clinical and functional parameters was further analyzed. Methods and Results Forty one patients and fifty controls were included in this study. Analysis of BMPR2, ACVRL1 and KCNA5 genes was performed by polymerase chain reaction (PCR) and direct sequencing. Fifty one nucleotide changes were detected in these genes in 40 of the 41 patients; only 22 of these changes, which were classified as pathogenic, have been detected in 21 patients (51.2%). Ten patients (62.5%) with idiopathic PAH and 10 (40%) with associated PAH showed pathogenic mutations in some of the three genes. Several clinical and hemodynamics parameters showed significant differences between carriers and non-carriers of mutations, being more severe in carriers: mean pulmonary artery pressure (p = 0.043), pulmonary vascular resistence (p = 0.043), cardiac index (p = 0.04) and 6 minute walking test (p = 0.02). This differences remained unchanged after adjusting for PAH type (idiopathic vs non idiopathic). Conclusions Pathogenic mutations in BMPR2 gene are frequent in patients with idiopathic and associated PAH group I. Mutations in ACVRL1 and KCNA5 are less frequent. The presence of these mutations seems to increase the severity of the disease.

Autosomal recessive retinitis pigmentosa in Spain: evaluation of four genes and two loci involved in the disease

Autosomal recessive retinitis pigmentosa (ARRP) is a genetically heterogeneous form of retinal degeneration. The genes for the β‐subunit of rod phosphodiesterase (PDEB), rhodopsin (RHO), peripherin/RDS (RDS) and the rod outer segment membrane protein 1 (ROM1), as well as loci at 6p and 1q, have previously been reported as the cause of ARRP. In order to determine whether they are responsible for the disease in Spanish pedigrees, linkage and homozygosity studies using markers at these loci were carried out on 47 Spanish ARRP families. SSCP analysis was performed to search for mutations in the genes cosegregating with the disease in particular pedigrees. Three homozygous mutations in the PDEB gene were found, thus accounting for 6% of the cases. No other disease‐causing mutation was observed in the other genes analysed, nor was significant evidence found for the involvement of the loci at 6p or 1q. On the basis of these data, it is unlikely that these genes and loci account for a considerable proportion of ARRP cases.