Gemma Gadaleta

Acetylation and level of mitochondrial transcription factor A in several organs of young and old rats.

To gain further information on the role of mitochondrial transcription factor A (TFAM) in mitochondrial biogenesis, we studied the post-translational modifications of the protein in 6- and 28-month-old rat liver. Mass spectrometry and immunoblot analysis revealed that TFAM was acetylated at a single lysine residue and that the level of acetylation did not change with age. The measurement of the content of TFAM and of mitochondrial DNA (mtDNA) in several organs (cerebellum, heart, kidney, and liver) of young and old rats showed an age-related increase of mtDNA and TFAM in all the organs analyzed, except in heart. These data are discussed in the light of the multiple roles of TFAM in mitochondrial biogenesis and of the age-related change of the mitochondrial transcription.

Tissue-specific mtDNA abundance from exome data and its correlation with mitochondrial transcription, mass and respiratory activity.

Eukaryotic cells contain a population of mitochondria, variable in number and shape, which in turn contain multiple copies of a tiny compact genome (mtDNA) whose expression and function is strictly coordinated with the nuclear one. mtDNA copy number varies between different cell or tissues types, both in response to overall metabolic and bioenergetics demands and as a consequence or cause of specific pathological conditions. Here we present a novel and reliable methodology to assess the effective mtDNA copy number per diploid genome by investigating off-target reads obtained by whole-exome sequencing (WES) experiments. We also investigate whether and how mtDNA copy number correlates with mitochondrial mass, respiratory activity and expression levels. Analyzing six different tissues from three age- and sex-matched human individuals, we found a highly significant linear correlation between mtDNA copy number estimated by qPCR and the frequency of mtDNA off target WES reads. Furthermore, mtDNA copy number showed highly significant correlation with mitochondrial gene expression levels as measured by RNA-Seq as well as with mitochondrial mass and respiratory activity. Our methodology makes thus feasible, at a large scale, the investigation of mtDNA copy number in diverse cell-types, tissues and pathological conditions or in response to specific treatments.

Converging evidence for the association of functional genetic variation in the serotonin receptor 2a gene with prefrontal function and olanzapine treatment.

IMPORTANCE Serotonin (5-hydroxytryptamine) receptor 2a (5-HT2AR) signaling is important for modulation of corticostriatal pathways and prefrontal activity during cognition. Furthermore, newer antipsychotic drugs target 5-HT2AR. A single-nucleotide polymorphism in the 5-HT2AR gene (HTR2A rs6314, C>T; OMIM 182135) has been weakly associated with differential 5-HT2AR signaling and with physiologic as well as behavioral effects. OBJECTIVE To use a hierarchical approach to determine the functional effects of this single-nucleotide polymorphism on 5-HT2AR messenger RNA and protein expression, on prefrontal phenotypes linked with genetic risk for schizophrenia, and on treatment with olanzapine. DESIGN In silico predictions, in vitro, and case-control investigations. SETTING Academic and clinical facilities. PARTICIPANTS The postmortem study included 112 brains from healthy individuals; the in vivo investigation included a total sample of 371 healthy individuals and patients with schizophrenia. EXPOSURES Patients received olanzapine monotherapy for 8 weeks. MAIN OUTCOMES AND MEASURES In silico predictions, messenger RNA, and protein expression in postmortem human prefrontal cortex and HeLa cells, functional magnetic resonance imaging prefrontal activity and behavior during working memory and attention in healthy individuals, and response to an 8-week trial of olanzapine treatment in patients with schizophrenia. RESULTS Bioinformatic analysis predicted that rs6314 alters patterns of splicing, with possible effects on HTR2A expression. Moreover, the T allele was associated with reduced prefrontal messenger RNA expression in postmortem prefrontal cortex, with reduced protein expression in vitro, inefficient prefrontal blood oxygen level-dependent functional magnetic resonance imaging response during working memory and attentional control processing, and impaired working memory and attention behavior, as well as with attenuated improvement in negative symptoms after olanzapine treatment. CONCLUSIONS AND RELEVANCE Our results suggest that HTR2A rs6314 affects 5-HT2AR expression and functionally contributes to genetic modulation of known endophenotypes of schizophrenia-like higher-level cognitive behaviors and related prefrontal activity, as well as response to treatment with olanzapine.

The 25 kDa protein recognizing the rat curved region upstream of the origin of the L-strand replication is the rat homologue of the human mitochondrial transcription factor A

Mass spectrometry matrix‐assisted laser desorption ionization (MALDI) analysis and N‐terminus sequencing as well as immunoblotting experiments using human and mouse antibodies have allowed us to identify the 25 kDa protein, previously isolated from rat liver using magnetic beads coated with a rat liver mitochondrial (mt) DNA region upstream of the Ori‐L, as the homologue of human mt transcription factor A (mtTFA). We can therefore identify this DNA binding protein as the rat mtTFA. Furthermore, since we previously showed that the 25 kDa protein purified from rat liver was able to bind the curved mtDNA region upstream of the Ori‐L as well as the curved mtDNA in the D‐loop region, the results here reported lead us to state, for the first time, that mtTFA binds both the curved regions of mtDNA upstream of the two replication origins.

Isolation of a 25-kDa Protein Binding to a Curved DNA Upstream the Origin of the L Strand Replication in the Rat Mitochondrial Genome

The presence of a curved DNA sequence in the gene for the NADH-dehydrogenase subunit 2 of rat mitochondrial genome, upstream from the origin of the light strand replication have been demonstrated through theoretical analysis and experimental approaches. Gel retardation assays showed that this structure makes a complex with a protein component extracted from the mitochondrial matrix. The isolation and purification of this protein is reported. With a Sepharose CL-6B and magnetic DNA affinity chromatography a polypeptide was purified to homogeneity having 25-kDa mass as shown by gel electrophoresis. To functionally characterize this protein, its capability to bind to other sequences of the homologous or heterologous DNA and to specific riboprobes was also investigated. A role for this protein as a trans-acting agent required for the expression of the mammalian mitochondrial genome is suggested.

Characterization of the mtTFA gene and identification of a processed pseudogene in rat.

Mitochondrial DNA replication and transcription are regulated from essential nucleus-encoded components that interact with the mitochondrial (mt) D-loop region. Among these there is the mitochondrial transcription factor A (mtTFA or Tfam). We have determined the sequence of the cDNA mtTFA in rat and have demonstrated that the gene has a mosaic organization with six introns whose sizes we have calculated. A differential splicing transcript lacking exon 5 has been detected in all assayed tissues and represents 9.85% of the full length transcript. Beside the gene which is homologous to the one found in man and mouse, rat nuclear genome contains at least 12 copies of this gene or genome fragments with high similarity to mtTFA. We have determined the sequence of one of these copies. This resulted to have 76.26% similarity to the active gene but to lack introns, suggesting it might be a processed pseudogene. RT-PCR experiments have demonstrated that this pseudogene (psi mtTFA) is transcribed in liver tissue.

A 67-kDa protein binding to the curved DNA in the main regulatory region of the rat mitochondrial genome

We have purified, by sequence-specific affinity chromatography, a mitochondrial (mt) matrix protein which binds to the curved DNA located between the replication origin (ori) of the leading strand (ori-H) and the two transcription promoters in the rat mt genome. The protein was characterized by gel electrophoresis as a 67-kDa polypeptide and seems to be involved in the DNA contact on the mt light strand. This protein differs (in the size and location of its DNA-binding site) from other DNA-binding proteins studied so far in animal mt systems. We suggest a role for the 67-kDa protein, assisted by other proteins, in regulating the initiation of leading-strand replication.

Association of functional genetic variation in PP2A with prefrontal working memory processing

HighlightsRs959627, a SNP in PPP2R2B modulates postmortem prefrontal cortex gene expression.The same SNP affects prefrontal cortex function during Working Memory processing.Putative mechanism relies on modulation on D2 cAMP‐independent dopamine signaling. ABSTRACT Variation in prefrontal dopaminergic signaling mediated by D2 receptor has been implicated in cognitive phenotypes of schizophrenia, including working memory. Molecular cascades downstream of D2 receptor include a cAMP‐dependent‐ and a cAMP‐independent‐pathway. Protein‐Phosphatase‐2A (PP2A) is a key partner of D2 receptor in cAMP‐independent signaling. This enzyme comprises a regulatory subunit that is coded by PPP2R2B gene. Given the molecular relationship between PP2A and D2 signaling, we hypothesized genetic variation in PPP2R2B affecting mRNA expression of this gene in prefrontal cortex to be associated with prefrontal processing during working memory. In order to probe such a hypothesis we investigated SNPs associated with PPP2R2B expression in two independent samples of human postmortem prefrontal cortex. Then, we tested SNPs for which association was replicated as predictors of prefrontal activity during WM as probed by functional magnetic resonance (fMRI) in a sample of healthy humans. We found that a SNP associated with PPP2R2B expression (rs959627) predicted prefrontal activity during the N‐Back working memory task. In particular, individuals carrying rs959627T allele, a condition associated with lower PPP2R2B expression in postmortem prefrontal cortex, showed greater activity in right inferior frontal gyrus (IFG) during N‐Back compared to CC subjects. Furthermore, such an activity was negatively correlated with behavioral performance at the task. Consistently with previous studies, these findings suggest reduced right IFG efficiency during working memory processing in rs959627 T‐carriers, as indexed by their greater need to activate this brain region in order to achieve similar levels of behavioral proficiency as compared to CC individuals.

Analysis of cystic fibrosis gene mutations in children with cystic fibrosis and in 964 infertile couples within the region of Basilicata, Italy: a research study.

IntroductionCystic fibrosis is the most common autosomal recessive genetic disease in the Caucasian population. Extending knowledge about the molecular pathology on the one hand allows better delineation of the mutations in the CFTR gene and the other to dramatically increase the predictive power of molecular testing.MethodsThis study reports the results of a molecular screening of cystic fibrosis using DNA samples of patients enrolled from January 2009 to December 2013. Patients were referred to our laboratory for cystic fibrosis screening for infertile couples. In addition, we identified the gene mutations present in 76 patients affected by cystic fibrosis in the pediatric population of Basilicata.ResultsIn the 964 infertile couples examined, 132 subjects (69 women and 63 men) resulted heterozygous for one of the CFTR mutations, with a recurrence of carriers of 6.85%. The recurrence of carriers in infertile couples is significantly higher from the hypothetical value of the general population (4%).ConclusionsThis study shows that in the Basilicata region of Italy the CFTR phenotype is caused by a small number of mutations.Our aim is to develop a kit able to detect not less than 96% of CTFR gene mutations so that the relative risk for screened couples is superimposable with respect to the general population.

Primer directed poly(A) synthesis in rat liver mitochondria.

Abstract Rat liver mitochondria contain an endogenous factor highly specific in stimulating the homologous poly(A) polymerase. By using an in vivo labelling with [32P] orthophosphate it is possible to prepare a labelled factor and to demonstrate that it is stably incorporated in an acid insoluble molecule. This suggests that the factor probably acts as a primer in the polymerization of ATP molecules, being involved in the recognition between the mitochondrial poly(A) polymerase and the homologous RNA molecules which have to be polyadenylated.