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Maternal neglect induces depression symptoms in mice

This post has been written by Irene Gracia-Rubio and Olga Valverde from the Neurobiology of Behavior Research Group (GReNeC) at the CEXS-UPF.


The World Health Organization predicts that depressive disorders will be the greatest contributor to the global burden of disease by 2030. Major depression is thought to comprise a heterogeneous group of diseases caused by genetic, epigenetic and environmental factors. In humans, detrimental early life events, such as maternal neglect or abuse during childhood, are associated with increased risk of emotional disorders including major depression that may persist into adulthood. In fact, experimental and clinical studies have shown that the immaturity and plasticity of the central nervous system during childhood make it particular sensitive to stress at a young age, which may cause significant and permanent changes in brain structure and function.

On the other hand, recent clinical and experimental data suggest that the pathophysiology of several neuropsychiatric disorders, including depressive syndromes, involves activation of the immune system in response to inflammatory agents. In fact, pro-inflammatory cytokines alter tryptophan metabolism, affecting the activity of serotonin, a neurotransmitter with a key role in the modulation of mood. Therefore, the tryptophan metabolic route becomes imbalanced during depression, enhancing an alternative metabolic pathway, the kynurenine synthesis pathway, and decreasing the availability of tryptophan to be metabolized into serotonin. This metabolic change has been directly associated to the development of depressive symptoms in humans and in experimental animal models.



In a recent study published in Progress in Neuro-Psychopharmacology & Biological Psychiatry, we have shown that maternal separation indeed induces both neuroinflammation and long-lasting emotional alterations in mice. The study was developed during Irene Gracia-Rubio’s PhD training at the GReNeC and done in collaboration with other research teams: the group led by Roser Nadal in UAB for maternal behaviour evaluation, and also with Oscar Pozo and Josep Marcos, researchers of the Neuroscience Program at IMIM (Hospital del Mar Research Institute) for the analysis of the kynurenine pathways. To have the opportunity to work with all these researchers in a collaborative project has been a very positive experience.

Experimental settting

Our aim was to explore the interplay between depressive symptoms in behavioural models, neuroinflammation, and alterations in the tryptophan-kynurenine pathway since these mechanisms could lead to the discovery of new therapy approaches.

For that, we set up different behavioural models to induce conditions of early life adversity in male and female mice.  Although most studies are done only in males, we decided to study female mice since the risk of suffering depression is double in women than in men.

We used two conditions: the maternal separation paradigm in mice as a model of early life neglect, and the standard rearing condition (the ‘control’), in which offspring remained with their mothers for 21 days. We then looked at the effect of both conditions on emotional behaviour during adolescence and into adulthood.

To test these effects, we performed a range of tests of anxiety, depressive symptoms and other emotional-related behaviours. To test anxiety, we used the elevated plus maze, a test that evaluates the capability of a rodent to explore new and stressful environments. Anxiety-like behaviour is reflected by an attenuated exploratory behaviour in mice. For testing depressive-like symptoms, we used the tail-suspension test, a model to evaluate despair behaviour, in this case, the time spent immobile when a mouse is confronted to an inescapable stressful situation.



At the physiological level, we looked for signs of neuroinflammation in different brain areas, and analysed metabolites of the tryptophan-kynurenine pathway to explore the link between depressive symptoms and inflammatory reactions.

Our results showed that adverse events during early life in mice increase risk of long-lasting emotional alterations during adolescence and into adulthood. These emotional disturbances were particularly severe in females. Behavioural impairments, including depressive symptoms, were associated with neuroinflammatory reactions in the two brain regions evaluated (prefrontal cortex and hippocampus).

In conclusion, these findings support the preeminent role of neuroinflammation in emotional disorders. Our results lead us to propose that detrimental early life events such as maternal neglect reproduce most of the behavioural alterations associated with depressive symptoms in mice. These alterations seem to be long lasting since adult mice also showed these emotional alterations. We also found that females were more sensitive to adverse conditions than males since the detrimental effects observed were more intense and persisted longer in time in female mice. Our study also supports the notion that the imbalance of the tryptophan-kynurenine metabolism and the association of neuroinflammatory reactions underlie these emotional impairments under our experimental conditions.

Future investigations will explore the influence of maternal separation and neuroinflammation in other psychiatric disorders, in particular psychotic and drug use disorders.


Reference article:

Gracia-Rubio I, Moscoso-Castro M, Pozo OJ, Marcos J, Nadal R, Valverde O. Maternal separation induces neuroinflammation and long-lasting emotional alterations in mice. Prog Neuropsychopharmacol Biol Psychiatry. 65: 104-17, 2016. DOI: 10.1016/j.pnpbp.2015.09.003.

A roadmap for the implementation of the World Anti-Doping Code 2015

cyclingraceIn November 2013, a scientific multidisciplinary consensus meeting was held at the Home of FIFA in Switzerland to talk about Anti-Doping in Sport and to create a roadmap for the implementation of the 2015 World Anti-Doping Code. Jordi Segura, director of the Antidoping Laboratory at the IMIM, took part at the meeting and was one of the authors of a recent article explaining the strategy for the implementation of the 2015 World Anti-Doping Code.

According to the paper, published in the British Journal of Sports Medicine (BJSM), the key components of this strategy include: (1) sport-specific risk assessment, (2) prevalence measurement, (3) sport-specific test distribution plans, (4) storage and reanalysis, (5) analytical challenges, (6) forensic intelligence, (7) psychological approach to optimise the most deterrent effect, (8) the Athlete Biological Passport (ABP) and confounding factors, (9) data management system (Anti-Doping Administration & Management System (ADAMS), (10) education, (11) research needs and necessary advances, (12) inadvertent doping and (13) management and ethics: biological data.

The new code will be implemented in the near future.

In related news, Josep Antoni Pasqual, also at the IMIM, has been nominated President of the Antidoping Committee of the International Paralympic Committee (IPC) for the next 4 years. You can read the story here (in Catalan).


Dvorak J, Baume N, Botré F, Broséus J, Budgett R, Frey WO, Geyer H, Harcourt PR, Ho D, Howman D, Isola V, Lundby C, Marclay F, Peytavin A, Pipe A,Pitsiladis YP, Reichel C, Robinson N, Rodchenkov G, Saugy M, Sayegh S, Segura J, Thevis M, Vernec A, Viret M, Vouillamoz M, Zorzoli M. Time for change: a roadmap to guide the implementation of the World Anti-Doping Code 2015. Br J Sports Med. 2014 May;48(10):801-6. doi: 10.1136/bjsports-2014-093561. Epub 2014 Apr 24.

Understanding resistance to methadone treatment for opioid dependence

Methadone maintenance treatment (MMT) is the most widely-used therapy in opioid dependence, but it is not effective in some patients, who relapse or drop out from treatment. Researchers at the IMIM and Hospital del Mar led by Marta Torrens, in collaboration with colleagues at the CRG, have found a possible explanation of why some people may not respond well to this treatment.


As the authors explain in their paper published this month in the journal European Neuropsychopharmacology, they carried out a genetic analysis on several patients, focusing on the gene ALDH5A1. This enzyme is involved in the catabolism of the neurotransmitter gamma-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the mammalian central nervous system. ALDH5A1 comes in many forms, and the scientists found that subjects carrying the T variant allele had a higher risk to be nonresponders to methadone treatment. They hypothesized that this could be due to a reduction in the ALDH5A1 enzyme activity, which would increase endogenous GABA levels and therefore induce symptoms such as sedation and impaired psychomotor performance. These neuropsychological effects related with the reduction in enzyme activity could be responsible for a higher propensity to relapse in these genetically predisposed patients.

The findings could be helpful to predict which subjects with opioid dependence problems would probably not benefit from methadone maintenance treatment and could use other treatments instead, such as diamorphine.


Fonseca F, Gratacòs M, Escaramís G, De Cid R, Martín-Santos R, Farré M, Estivill X, Torrens M. ALDH5A1 variability in opioid dependent patients could influence response to methadone treatment. Eur Neuropsychopharmacol. 2013 Oct 18;

Common causes of complex diseases between Europeans and Asians

Genome-wide association studies (GWAS) have revolutionized the field of complex disease genetics in the last six years. Many disease associations (i.e. genetic variants that increase risk for a specific disease) have been detected using this technique, but the reported variants tend to explain only small fractions of risk. Also, the causal variants that generate the associations unveiled by GWAS have not been identified. And their frequency and degree of sharing across different ethnical populations remains unknown.

Arcadi Navarro, from the Institute of Evolutionary Biology (UPF-CSIC), set out to study the degree of sharing of disease-associated variants across populations, in order to help solving these issues. Together with Urko Marigorta, they did a comprehensive survey of GWAS replicability across 28 diseases. As they report in their paper in PLOS Genetics, most loci and SNPs discovered in Europeans for these conditions had been extensively replicated using peoples of European and East Asian ancestry, while replication with individuals of African ancestry proved to be much less common.


The authors found a strong and significant correlation across Europeans and East Asians, indicating that underlying causal variants are common and shared between the two ancestries and that they tend to map close to the associated marker SNPs.

They also observed that GWAS with larger sample sizes have detected variants with weaker effects but not with lower frequencies. This indicates that most GWAS results are due to common variants.



Marigorta UM, Navarro A. High Trans-ethnic Replicability of GWAS Results Implies Common Causal Variants. PLoS Genet. 2013 Jun;9(6):e1003566

Female sex control: a third way

Females have an extra X chromosome as compared to males, and this can mean trouble – think of what happens when someone has an extra copy of any other chromosome, 21 being the most (in)famous! Dosage compensation is therefore essential, and there’s different ways of dealing with it. In humans, women inactivate one of their X chromosomes, while in the fruifly the opposite happens: males overactivate their only copy of X.

The complex in charge of doing so is called MSL and male-specific-lethal-2 (msl2) is one of its subunits. Female flies must inhibit this gene in order to survive, and Sex-lethal (SXL) is the protein which orchestrates this repression. So far, it was known that SXL binds to the 5′ and 3′ untranslated regions (UTRs) of the msl2 mRNA, inhibiting splicing in the nucleus and subsequent translation in the cytoplasm.


But Fatima Gebauer and colleagues at the CRG have now found a third way SXL can repress msl2: by inhibition of nucleocytoplasmic transport of msl2 mRNA.

To identify SXL cofactors in msl2 regulation, the researchers from the Regulation of Protein Synthesis in Eukaryotes group devised a two-step purification method termed GRAB (GST pull-down and RNA affinity binding) and identified Held-Out-Wings (HOW) as a component of the msl2 5′ UTR-associated complex.

Their experiments showed that HOW directly interacts with SXL and binds to two sequence elements in the msl2 5′ UTR. Depletion of HOW reduced the capacity of SXL to repress the expression of msl2 reporters without affecting SXL-mediated regulation of splicing or translation. Instead, HOW was required for SXL to retain msl2 transcripts in the nucleus.

These results, published in Genes & Development uncover a novel function of SXL in (msl2) nuclear mRNA retention – a third way for female control of sex-specific gene expression.

Graindorge A, Carré C, Gebauer F. Sex-lethal promotes nuclear retention of msl2 mRNA via interactions with the STAR protein HOW. Genes Dev. 2013 Jun 15;27(12):1421-33

DNA isolation method may affect methylation results

Researchers from the neurovascular research group at the IMIM have recently published a paper showing that, when studying DNA methylation, the protocol used for DNA isolation can affect the results.

In the paper published in the Open Access journal PLoS One, Jaume Roquer and the rest of the authors – all part of the Spanish Stroke Genetics Consortium – used three different commercial kits for DNA extraction for each sample, and then quantified the global DNA methylation (GDM) by a luminometric methylation assay (LUMA). In the 580 samples analysed, they found significant differences in GDM in the same samples between the three DNA isolation methods.

Large epidemiological studies, such as those carried out by the Spanish Stroke Genetics Consortium, are susceptible to accumulate variability by differences in the protocols, sample cohorts, reagent lots, and technologies used. This study demonstrates for the first time that the method of DNA extraction is indeed an important source of variability in LUMA methylation measurements.

The problem of this ‘batch effect’ becomes even more pronounced in collaborative studies, where different cohorts and differences in sample processing may threaten comparability of data and results. That is why the authors – which include Roberto Elosua’s group, also at the IMIM – recommend that methylation studies that apply multiple DNA extraction methods or in cross study comparisons should report the method used, and adjust their methylation results by this variable in order to avoid possible bias, be comparable and reach biologically meaningful conclusions.


Soriano-Tárraga C, Jiménez-Conde J, Giralt-Steinhauer E, Ois A, Rodríguez-Campello A, Cuadrado-Godia E, Fernández-Cadenas I, Montaner J, Lucas G, Elosua R, Roquer J, GeneStroke “The Spanish Stroke Genetics Consortium”. DNA Isolation Method Is a Source of Global DNA Methylation Variability Measured with LUMA. Experimental Analysis and a Systematic Review. PLoS One. 2013;8(4):e60750

Assessing a new test for cervical cancer

Continuing with the issue of cervical cancer (you can read a previous post about virus-like particle (VLP)-based vaccines against this type of cancer), which is caused by high-risk human papillomavirus (HR-HPV), a group of researchers from the Pathology department of the Hospital del Mar (Parc de Salut MAR Biobanc), a reference laboratory for cervical cytology in Barcelona, have recently evaluated the clinical performance of a new HPV test (the cobas HPV Test).

Although the most widespread screening technique for cervical cancer is cytology (also called Papanicolaou test, or Pap smear), HPV detection has been proposed as an alternative, since it is more sensitive for the detection of precancerous lesions. However, compared to cytology, HPV testing has the risk of an excessive number of women without relevant lesions being referred for colposcopy.

 Hybrid capture 2 (HC2) is the current gold standard in HPV testing in cervical samples, but other tests have been recently launched, such as the cobas HPV Test. Since clinical sensitivity and specificity are decisive factors before the introduction of a new screening tool, the authors decided to evaluate the applicability of the new cobas HPV Test in the Catalan opportunistic screening protocol, which presently is based on cytology and HC2.

The study included samples from 958 women. According to the authors of this paper, published in PLoS One, the cobas HPV test system showed excellent results regarding both sensitivity and specificity, being at least as good as HC2. Both intralaboratory and interlaboratory reproducibility values were in the category considered almost perfect, overcoming the minimal requirements for a clinical test. The cobas HPV test has also proved to be a user-friendly system with high reproducibility and easy interpretation of results. It also has some advantages compared to HC2: it doesn’t require a specific procedure which takes time and increases the risk of contamination, and it contains an internal positive control (DNA amplification of cellular beta-globin).

“We feel confident that our results confirm a reliable clinical performance of cobas HPV Test allowing its introduction in cervical cancer screening protocols”, concludes correspondent author Sergi Serrano.


Lloveras B, Gomez S, Alameda F, Bellosillo B, Mojal S, Muset M, Parra M, Palomares JC, Serrano S. HPV Testing by cobas HPV Test in a Population from Catalonia. PLoS One. 2013;8(3):e58153

Therapeutic virus-like particle- based vaccines against cervical cancer

Cervical cancer represents the second most frequent gynecological malignancy in the world. It is caused by a persistent virus infection by the high-risk human papillomavirus (HR-HPV) but no cervical cancer vaccine has been marketed to date. In a paper published in PLoS, Juan Martin Caballero, director of the PRBB animal facility, together with colleagues from a pharmaceutical company have generated a virus-like particle (VLP)-based vaccine to treat this cancer and have tested it in humanized transgenic mice.

The researchers took a long C-terminal fragment of the HPV-16 E7 protein – one of the two viral proteins necessary for induction and maintenance of malignant transformation – and introduced it into the infectious bursal disease virus (IBDV) VLP. The combination of tumor antigens and IBDV-VLPs has been shown as a good strategy to boost the immune response and direct it against different types of cancer.

The authors tested the therapeutic potential of their new vaccine, VLP-E7, in HLA-A2 humanized transgenic mice grafted with TC1/A2 tumor cells. They performed a series of tumour challenge experiments demonstrating a strong immune response against already formed tumors, including its complete eradication. Remarkably, therapeutic efficacy was obtained with a single dose without adjuvant and it persisted when the mice were re-challenged with a second tumor cell inoculation. As the authors state, this indicates a high immunogenic potential and in vivo efficacy of  their cervical cancer candidate vaccine, VLP-E7, although further studies will be necessary to investigate the potential of the IBDV VLP carrier and its applications to other human diseases.


Martin Caballero J, Garzón A, González-Cintado L, Kowalczyk W, Jimenez Torres I, Calderita G, Rodriguez M, Gondar V, Bernal JJ, Ardavín C, Andreu D, Zürcher T, von Kobbe C. Chimeric Infectious Bursal Disease Virus-Like Particles as Potent Vaccines for Eradication of Established HPV-16 E7-Dependent Tumors. PLoS One. 2012;7(12):e52976

How much pollution are you exposed to? Ask your smartphone!


Exposure assessment in epidemiological studies is a tricky issue, because of the difficulty of constantly tracking people’s activity and location, both of which can affect the exposure to pollution. Researchers at CREAL have shown how using smartphone technology can help to reduce this bias in health effects estimates.

Audrey de Nazelle, a postdoc at Mark Nieuwenhuijsen’s lab who has currently started her own group at the Centre for Environmental Policy, Imperial College in London, used the CalFit smartphone technology to track person-level time, geographic location, and physical activity patterns for improved air pollution exposure assessment. CalFit is a ubiquitous sensing technology developed at UC Berkeley. It consists on using a GPS and an accelerometer in a smartphone to record the location and physical activity of the carrier through energy expenditure and activity tracking algorithms. de Nazelle and her colleagues at CREAL distributed CalFit-equipped smartphones to 36 subjects in Barcelona to obtain information on physical activity and geographic location. This information was then linked to space-time air pollution mapping.

The authors of the paper, published in Environmental Pollution, found that information from CalFit could substantially alter exposure estimates. For instance, travel activities – which wouldn’t have been measurable without the use of the mobiles – accounted on average for 6% of people’s time and 24% of their daily inhaled NO(2).

The potential of this technology for epidemiological studies is enormous. As the authors state, the large number of mobile phone users makes this technology a potential unobtrusive means of enhancing epidemiologic exposure data at low cost. In fact, they are now using it in several epidemiological projects they are involved in, such as the ERC-funded BREATHE study, the EC-funded PHENOTYPE, and the HELIX and EXPOsOMICs studies.


You can read a related interview to de Nazelle here.


de Nazelle A, Seto E, Donaire-Gonzalez D, Mendez M, Matamala J, Nieuwenhuijsen MJ, Jerrett M. Improvingestimates of airpollutionexposurethroughubiquitoussensingtechnologies.EnvironPollut. 2013 Feb 13;176C:92-99

Understanding cannabis

Cannabis has a long history of use as medicine, with historical evidence dating back more than 4000 years.  The potential therapeutic benefits of cannabinoid compounds are huge, but this substance can also have negative effects. A recent paper by Andrés Ozaita and colleagues at the Neurophar laboratory of Rafael Maldonado (CEXS-UPF) has given new insights into the molecular mechanisms that underlie cannabinoid-mediated effects.

Using mice as a model system, the authors had previously shown that blocking the mTOR pathway prevented the amnesic-like effects of THC (a synthetic form of cannabinoid). In the present study, published in the journal Neuropsychopharmacology, they have gone further, proving that the inhibition of the mTOR pathway by the rapamycin derivative temsirolimus, prevents both the anxiogenic- and the amnesic-like effects produced by acute THC, but has no effect on THC-induced anxiolysis, hypothermia, hypolocomotion, and antinociception (lack of pain perception).

Therefore, treatment with temsirolimus could segregate the potentially beneficial effects of cannabinoid agonists, such as the decrease of pain and anxiety, from the negative effects, such as amnesia and an increase of anxiety. As the authors say, these results could help targeting the endocannabinoid system in order to prevent possible side effects.


Puighermanal E, Busquets-Garcia A, Gomis-González M, Marsicano G, Maldonado R, Ozaita A. Dissociation of the Pharmacological Effects of THC by mTOR Blockade. Neuropsychopharmacology. 2013 Jan 28;

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