Laboratory of Neuroepigenetics

 

General Description

 

Our laboratory is involved in deciphering the molecular mechanisms underlying neuronal gene expression regulation and their implications in regulating phenotypical and functional aspects of neuronal cells. Circuital functionality depends on single neuron physiology, which in turn influences complex behaviors. Cognitive and affective components of behaviors are significantly influenced by experiences and by the environment. In this regard, the epigenetic enzyme LSD1, whose discovery and initial characterization have been contributed by our lab, represents a unique example of a chromatin modifier that regulates its activity accordingly to environmental stimuli and experiences, favoring the process of organisms environmental adaptation.

 

Much of our interest is devoted to the comprehension of alternative splicing processes as a main source of LSD1 activity regulation. Some years ago, we identified a neurospecific LSD1 isoform which is only present in mammals, neuroLSD1. NeuroLSD1 differs from LSD1 for the addition of only 4 amino acids encoded by the microexon E8a and opposes to LSD1 activity representing a dominant negative isoform. Together, LSD1 and neuroLSD1 regulate neuroplasticity modulating chromatin structure of many genes, among which the Immediate Early Genes (IEGs). Thanks to splicing modulation, we observed that in mammals LSD1 modulates its activity within the perinatal window and during development and aging. Moreover, LSD1/neuroLSD1 relative ratio is also regulated by environmental stimuli like stressful experiences. Aberrant LSD1 splicing also characterizes epileptic neurodevelopmental disorders and possibly, psychiatric conditions. For these reasons, LSD1 splicing-related processes not only represent putative pathological mechanisms, but also possible new pharmacological targets.

 

LSD1 biology

 

Our group participated to LSD1 discovery, the first flavin-dependent histone demethylase. Such an enzyme represents an important component of a ubiquitous transcriptional corepressor complex also including CoREST and the histone deacetylases HDAC1 and 2. LSD1 is highly studied in tumor biology, where its upregulation often represents a negative prognostic marker, making it an interesting pharmacological target. Our discovery of a neurospecific LSD1 isoform (neuroLSD1) promoted the study of LSD1 in brain physiology. Through transcriptional regulation of synaptic and neuroplastic genes, the dual system LSD1-neuroLSD1 represents a powerful modifier of the mammalian neuronal epigenome in response to neuronal activity. The group developed a neuroLSD1^KO mouse model that is protected against pharmacological epilepsy (Rusconi et al., 2015 Cerebral Cortex) and features a peculiar low anxiety-like behavior (Rusconi et al., 2016 PNAS and Rusconi et al., 2017 TINS). This mouse model represents a new and unique tool to study environmental effects on the epigenome along with related behavioral outcomes. It has been also observed that LSD1 activity can be modified in vivo, in response to stressful experiences, and in vitro, in response to glutamatergic stimulation. In conclusion, LSD1 and neuroLSD1 participate in those epigenetic mechanisms that translate the effects of different environmental stimuli, including stress and aging, into a modification of memory-related gene transcription in the mammalian brain.

 

LSD1 principally regulates the glutamatergic compartment, where we characterized its function as involved in negative regulation of synaptic plasticity and memory consolidation (Longaretti et al., 2020 Neurobiology of Stress). The most relevant mechanism underlying this regulation is IEGs transcriptional repression, which opposes to morphofunctional neuronal modifications that are instrumental to synaptic formation and potentiation. However, LSD1 is also involved in the regulation of the endocannabinoid system (Longaretti et al., 2020 Journal of Neurochemistry) and positively regulates a homeostatic neuronal system based on the adhesion protein PCDH19 (Gerosa et al., 2022 Cell Reports). It is worth noting how mutations in the gene encoding this protein are causative of a neurodevelopmental disorder, the Developmental and Epileptic Encephalopathy-9 (DEE-9).

 

Research Lines

 

LSD1 implication in monogenic neurodevelopmental disorders

 

It has been recently discovered that monogenic disorders of the neurodevelopment with epileptic phenotypes, are caused by mutations in genes encoding for chromatin modifiers. In particular, mutations in genes encoding lysine-specific demethylases such as KDM5C, KDM6A and KDM6B are causative for epileptic neurological syndromes featuring intellectual disability and aberrant behaviors, respectively known as Cleaes-Jensen, Kabuki and NEDCFSA. These discoveries strongly support the importance of a correct histone methylation as instrumental to an appropriate nervous system development, besides a physiological regulation of neuronal excitability. Inherently, the first mutations of LSD1/KDM1A gene have been associated to a novel neurodevelopmental disorder of the nervous system called Cleft Palate with psychomotor retardation with distinctive facial features (CPRF, OMIM#616728). Our laboratory has contributed a biochemical and structural characterization of the LSD1 isoforms carrying CPRF patients’ mutations (Pilotto et al., 2016).

 

We are also interested in understanding how, besides specific LSD1 mutations, quantitative alterations in LSD1/neuroLSD1 ratio could emerge into pathological phenotypes, indeed:

 

1)      In at least two monogenic epileptic disorders of the neurodevelopment, namely the Rett Syndrome (OMIM#312750) and the DEE-9 (OMIM#300088), LSD1 expression levels are decreased.

2)      LSD1 plays a role as a hippocampal circuitry protector, as neuroLSD1^KO mice show increased epileptic thresholds.

 

Main ongoing projects:

• To deepen the knowledge about epigenetic and transcriptional mechanisms involving LSD1 in the modulation of neuronal excitability
• To design novel pharmacological strategies aimed at normalizing LSD1 activity in the hippocampus

 

LSD1 implications in psychiatric disorders

 

One of our most interesting recent results describe increased LSD1 levels in the mammalian hippocampus (neuroLSD1^KO mice) as related to a significant reduction of the anxiety-like profile. This peculiar behavioral phenotype is coupled to obvious alterations in memory consolidation. Moreover, traumatic experiences elicit, in the mouse hippocampus and frontocortical areas, as a stress response, a significant increase of LSD1 levels.

 

This context opens interesting perspectives about mnemonic correlates of psychiatric disorders.

We are thus interested in understanding:

 

1)      Whether and how LSD1 could mediate a peculiar typology of learning and memory consolidation of traumatic events, within a specific temporal window that follows the stressful experience.

2)      If LSD1 could be involved in protecting excitatory circuits not only in the face of hyperexcitability, but also from developing environmental stress vulnerability.

3)      If, within some psychiatric disorders such as post-traumatic syndromes, that can be referred to, as memory and overgeneralizing disorders, and within avoidance disorders, LSD1 alterations could contribute to the behavioral drift, making it an interesting option as a potential therapeutic target in modifying the pathological trajectory of the disease.

 

Main ongoing projects:

• To understand hippocampal epigenetic mechanisms in stress response and how their implications could be protective or detrimental, inducing trauma-related psychiatric disorders in vulnerable individuals
• To study the contribution of intronic genetic polymorphisms in LSD1/KDM1A gene splicing regulatory regions, to interindividual variability of stress susceptibility.

 

Granted Projects

 

• Fondazione Telethon GGP20016 (2021-2024)
• Competitive Research Grants (CRG) from KAUST 2020-2023
• Seed Seal of Excellence (UNIMI) 2020
• PSR 2019
• Progetto Fondazione Cariplo 2016-0908 (2017-2022)
• Progetto Giovani Fondazione Cariplo 2014-0972 (2015-2018)
• Fondazione Telethon GGP14072 (2015-2018)

• Progetto Bandiera CNR-EPIGEN (2012-2019)

• Progetto Fondazione Cariplo (2009-2012)

• PRIN 2009-2011

• PRIN 2004-2006

• PRIN 2006-2008.
• PUR 2009

• Fondazione Telethon GGP07078, 2007-2009.
• MINISTERO DEGLI ESTERI (MAE), JOINT MOBILITY PROJECTS FOR THE EXCHANGE OF RESEARCHERS 2008-2010 

 

Research Group Composition

 

Elena Battaglioli (Full Professor of Applied Biology), Francesco Rusconi (RTD-B), Emanuela Toffolo (D-type Technician), Chiara Forastieri (Postdoc), Elena Romito (PhD Student). In the lab we have currently two undergraduate students from the master’s degree course in Medical Biotechnology and Molecular Medicine.

 

Contacts

 

Elena Battaglioli (E-mail elena.battaglioli@unimi.it)

Francesco Rusconi (E-mail francesco.rusconi@unimi.it)

 

Phone 0039 02 503 30445 – 30469

 

Location

 

LITA, Via F.lli Cervi 93, 20054 Segrate, Milano