José Fernández Piqueras

A pilot genetic study of the continuum between compulsivity and impulsivity in females: The serotonin transporter promoter polymorphism

According to some authors the obsessive-compulsive (OC) spectrum includes on one extreme, the Obsessive-Compulsive Disorder (OCD) and on the other extreme the most impulsive behaviors. This is a controversial idea and other authors define the OC spectrum in different ways. The serotonin transporter (5-HTT) gene is one of the main genes that control serotonergic function. A polymorphism in the promoter area of this gene classifies subjects with low expression as S individuals (s/s or s/l) and subjects with high expression as L individuals (l/l). This polymorphism was studied in female OCD patients (n = 24), non-impulsive controls (n = 112) and impulsive suicidal patients (n = 118) to support the OC spectrum hypothesis from a genetic perspective. A linear association exists among the serotonin transporter promoter functional genotypes (S versus L individuals) (chi2 linear by linear association = 8.9; df = 1; p = 0.003). The frequency of S individuals (s/l or s/s) was lowest in OCD (54%, 13/24); intermediate in non-impulsive controls (71%, 80/112) and highest in impulsive suicide attempters (82%, 96/117). More importantly, future studies need to consider that genetics may be related to behavioral dimensions (compulsivity to impulsivity) instead of to specific psychiatric disorders defined in clinical terms.

Hypermethylation of the cell cycle inhibitor p15 INK4b 3'-untranslated region interferes with its transcriptional regulation in primary lymphomas

The cyclin-dependent kinase inhibitor p15INK4b has been shown to be involved in human and rodent tumors and seems to act as a tumor suppressor gene in hematological malignancies. Alterations of this gene in tumors include mainly homozygous deletions and hypermethylation of the CpG island in the promoter region. In this work, we describe a new area sensitive to methylation in the 3′ untranslated region (UTR) of the murine p15INK4b gene. This region shows different levels of methylation depending on the tissues, being relatively highly methylated in brain and gut, and weakly methylated in liver, spleen or thymus. DNA methylation and expression is similar in both maternal and paternal alleles indicating no imprinting effect. Although methylation of the p15INK4b 3′-UTR is low in normal thymus, increased levels (up to 100%) of specific methylation in this region are found in up to 30% of radiation- or carcinogen-induced thymic lymphomas, correlating with decreased gene expression. Hypermethylation of the p15INK4b 3′-UTR frequently occurs in tumors with loss of heterozygosity (LOH) but without methylation of the promoter CpG island or intragenic mutations. Furthermore, in vitro CpG methylation of the 3′-UTR produces reduced levels of a luciferase reporter in cultured cells. Methylation of two CpG sites in a 120 bp region is sufficient to interfere with transcription of the reporter gene. These data suggest that although the levels of p15INK4b in normal tissues can be mainly determined by promoter regulatory elements, strong hypermethylation of the 3′-UTR can interfere with transcription. Thus, hypermethylation of the 3′-UTR may explain the lack of p15INK4b gene expression in a subset of tumors with no promoter methylation and could be a new alternative mechanism for tumor suppressor gene inactivation in tumorigenesis.

Multiplex–PCR of short amplicons for mtDNA sequencing from ancient DNA

Abstract We here describe a multiplex–PCR method to generate six overlapping short amplicons (100–130 bp) in two separate PCR reactions of non-overlapping fragments for full sequencing of the whole hypervariable region I (HV1). The performance of this multiplex system has been evaluated not only on ancient bone remains (5000–4000 BP) but also on different forensic samples with highly degraded DNA (bone remains, hair shafts, …) that yielded negative PCR results with the mtDNA amplification strategies usually employed in forensic genetics. The multiplex–PCR methodology described in this study also illustrates a potential high throughput strategy to reconstruct the sequence of both coding and non-coding regions of the mtDNA genome from ancient DNA.

Evidence for a new tumour suppressor gene locus for γ-radiation-induced thymic lymphoma located on the proximal part of mouse chromosome 18

IntroductionFive distinct thymic lymphoma suppressor regions have been identified on chromosome 4 (TLSR 1–5), and one on chromosome 19 (TLSR 8) through detection of loss of heterozygosity (LOH). Additionally, the involvement ofp16/INK4a, p15/INK4b, p73, Pten andFas had been reported in the most advanced stages of thymic lymphomagenesis.Material and methodsAdvanced thymic lymphomas (n=110) induced by gamma-irradiation in F1 hybrids from a BALB/c and C57BL/6J cross were analysed using micro-satellite markers on chromosomes 13, 14 and 18.ResultsOf the 110 tumours, 15 (14.5%) exhibited allelic losses on chromosome 18 atD18Mit21. Comparative analyses revealed significant differences (p<0.0001) for this marker and led us to define a new critical region of LOH on the proximal part of mouse chromosome 18, and named as TLSR9 according to the Mouse Nomenclature Committee.ConclusionsThe proposed TLSR9 region is orthologous with 18q11 region, which is affected in various types of human cancers (Mitelman Database of Chromosome Aberrations in cancer (2002) Mitelman F, Johansson B and Mertens F (eds), http://cgap.nci.nih.gov/Chromosomes/Mitelman), and containsN-cadherin as a possible candidate gene.ResumenIntroducciónHasta la fecha, han sido identificados 5locus supresores de linfomas tímicos en el cromosoma 4 de ratón (TLSR 1–5) y uno en el cromosoma 19 (TLSR 8) mediante la detección de pérdidas de heterocigosidad (LOH). Además, se ha descrito la implicación de los genesp16/INK4a, p15/INK4b, p73, Pten yFas en los estadios más avanzados de la linfomagénesis.Material y métodosSe analizaron 110 linfomas tímicos inducidos mediante radiación gamma en híbridos F1 del cruzamiento entre las cepas BALB/c y C57BL/6J utilizando marcadores polimórficos de tipo microsatélite repartidos a lo largo de los cromosomas 13, 14 y 18 de ratón.ResultadosDieciséis de 110 linfomas tímicos (14,5%) mostraron pérdidas alélicas en el cromosoma 18 para el marcadorD18Mit21. Un análisis comparativo reveló diferencias significativas (p<0,0001) para este marcador, por lo que se podría definir una nueva región de LOH en la parte proximal del cromosoma 18 de ratón denominada TLSR9 de acuerdo con el Comité de Nomenclatura del Ratón.ConclusionesLa región TLSR9 propuesta es ortóloga de la región 18q11, que se ve afectada en numerosos tipos de cánceres humanos (Mitelman Database of Chromosome Aberrations in cancer (2002) Mitelman F, Johansson B and Mertens F (eds), http://cgap.nci.nih.gov/Chromosomes/Mitelman), y contiene el genN-caderina como posible candidato.