Ian Maze

Histone H3 Gln 5 serotonylation (H3Q5ser) is a recently identified epigenetic modification in brain that modulates reader interactions with adjacent H3 Lys 4 trimethylation (H3K4me3) to promote transcriptional permissiveness ^1,2 . However, whether H3K4me3Q5ser and its associated binding proteins regulate neurodevelopmental gene expression programs remains unknown. Here, we identified the catalytically inactive Lysine methyltransferase 2E (KMT2E) as a reader of combinatorial H3K4me3Q5ser. KMT2E preferentially binds H3K4me3Q5ser over H3K4me3 alone, and enriches at broad chromatin domains marking actively transcribed neurodevelopmental loci. Notably, heterozygous variants in KMT2E have been implicated in ODLURO syndrome, a recently characterized neurodevelopmental disorder (NDD) ^3,4 . To identify the molecular mechanisms underlying ODLURO syndrome, we generated a Kmt2e transgenic mouse model that reproduces behavioral, physiological, and cellular endophenotypes associated with this and other NDDs. Furthermore, we observed that KMT2E mediates these effects by recruiting the NCoR/HDAC3 repressor complex to H3K4me3Q5ser-marked loci to restrict spreading of co-localized H3 Lys 9 acetylation (H3K9ac). Inhibition of aberrant H3K9ac spreading was sufficient to rescue transcriptional dysregulation in Kmt2e haploinsufficient neurons. These findings thus establish KMT2E as a critical reader of H3 serotonylation during neurodevelopment and provide mechanistic insights into the pathogenesis of ODLURO syndrome.

Transglutaminases (TGs) are a family of enzymes characterized by their calcium-dependent transamidation activity. In higher mammals, TG2 is the family member with the highest expression in the brain. Intriguingly, TG2 KO mice show no major neurodevelopmental abnormalities, which might be explained by compensation from the other members of the TG family also expressed in mammalian CNS. Thus, simpler animal models are likely better suited to study the contribution of TGs to brain formation and operation. The fruit fly Drosophila melanogaster contains a single TG gene ( dTg ), but its contribution to brain development and function remains poorly understood. Here, we show that dTg mutants display structural defects in the mushroom body (MB), an important associative area in Drosophila CNS, and in brain dopaminergic neurons both in vivo and in vitro. Furthermore, dTG-deficient animals show altered fly locomotion and strong asocial-like phenotype, two phenotypes associated with dopaminergic dysfunction. Consistent with these findings, brain transcriptomic experiments reveal changes in the expression of several genes associated with neurogenesis and neurodevelopment in dTG-deficient animals. Interestingly, expression of human TG6 (hTG6) under control of the endogenous dTg promoter rescues the social phenotype and the dopaminergic neurons loss. This manipulation partially reverts the changes in gene expression, and the motor defects. The partial reversion of phenotypes by hTG6 is consistent with a partial rescue of the epigenetic mark histone dopaminylation. Our data support the evolutionary conservation of TG functions across species and that TGs contribute to the maturation of brain neurons and circuits.

Mild traumatic brain injury (mTBI) is the most common form of central nervous system (CNS) injury and is often characterized by persistent neuroinflammation, metabolic dysregulation, and oxidative stress. Repetitive injuries compound these pathologies and lead to multifocal axonal injuries and long-term functional deficits. Despite the prevalence of mTBIs, the cellular mechanisms that facilitate or prevent recovery following injury remain poorly defined. Here, we extend our previous work on the role of the protein transglutaminase 2 (TG2) in CNS injury and we hypothesize that transcriptional regulation by TG2 restricts metabolic versatility in astrocytes following TBI, thereby impairing neuronal energetic support and worsening pathological outcomes. We utilized an established weight-drop model of repetitive mTBI followed by multi-parametric analysis of TBI pathology in complete TG2 knockout (TG2-/-) and wild type mice. At 28 days post-injury, TG2-/- mice showed marked attenuation of TBI pathology, compared to wild type mice, in vulnerable white matter and default mode network (DMN) regions, as assessed by diffusion magnetic resonance imaging (MRI), resting-state functional MRI, and immunohistochemistry. Integrated epigenomic, proteomic, and metabolomic profiling of cortical astrocytes isolated 28 days after injury revealed a pronounced metabolic restriction in wild type astrocytes which was remarkably attenuated in the TG2-/- mice. This rescue was associated with a de-repression of gene networks involved in glutamate recycling, lipid metabolism, and metabolic homeostasis. Together, these studies provide novel mechanistic insights into the metabolic dysregulation that characterizes persistent TBI pathology, and establish a foundation for evaluating TG2 as a therapeutic target for TBI.

Pregnancy and postpartum experiences represent transformative physiological states that impose lasting demands on the maternal body and brain, resulting in lifelong neural adaptations ^1–6 . However, the precise molecular mechanisms that drive these persistent alterations remain poorly understood. Here we used brain-wide transcriptomic profiling to define the molecular landscape of neuroplasticity induced by reproductive experience, identifying the dorsal hippocampal formation (dHF) as a key site of transcriptional remodelling. Combining single-cell RNA sequencing with a maternal–pup separation paradigm, we additionally found that chronic postpartum stress significantly disrupts dHF adaptations by altering dopamine dynamics, leading to changes in the dopamine-dependent histone post-translational modification, H3 dopaminylation, which causally mediates downstream alterations in gene expression and behaviour. In human dorsal subiculum, a brain structure within the dHF, we uncovered conserved patterns of parity-dependent alterations in H3 dopaminylation and transcription. We further established the sufficiency of dopamine modulation in regulating these adaptations via chemogenetic suppression of dopamine release into the dHF, which recapitulated key epigenomic and behavioural features of reproductive experience in virgin female mice. In sum, our findings establish dopamine as a central regulator of parity-induced neuroadaptations in humans and mice, revealing a fundamental transcriptional mechanism by which female reproductive experience remodels the brain to sustain long-term behavioural adaptations.

Histone H3 Gln5 serotonylation (H3Q5ser) is a posttranslational modification that guides transcriptional permissiveness in the brain and periphery. Because it can co-occur with H3K4me3, prior studies focused on its modulation of H3K4me3 readers , leaving open whether H3Q5ser acts as an autonomous chromatin mark. Using proteomic, structural, molecular, epigenomic, and cellular approaches, we show that Quinone reductase 2 (QR2), previously known only as a cytosolic enzyme, reads H3Q5ser independently of H3K4me3. QR2 recognizes the serotonyl group through its FAD-dependent quinone-binding pocket, discriminating against unmodified H3, H3K4me3, and other monoaminyl marks. In human iPSC-derived neurons, CRISPR-Cas9 disruption of H3 serotonylation or QR2 binding impairs transcriptional programs, synaptic connectivity, and electrophysiological maturation. In cortical organoids, these disruptions cause progenitor over-proliferation at the expense of excitatory neurons and uncouple POU2F1-linked regulatory elements from the excitatory neuron maturation program. Together, these findings reveal an H3 serotonylation-QR2 signaling axis essential for human neurodevelopment.

Ventral hippocampus (vHPC) CA1 pyramidal neurons send glutamatergic projections to nucleus accumbens (NAc), and this vHPC-NAc circuit mediates cocaine seeking and reward, but it is unclear whether vHPC-NAc neuron properties are modulated by cocaine exposure to drive subsequent behavior. The immediate early gene transcription factor FosB/ΔFosB is induced throughout the brain by cocaine and is critical for cocaine seeking, but its function in vHPC-NAc neurons is not understood. We now show that circuit-specific knockout of FosB/ΔFosB in vHPC-NAc neurons impaired cocaine reward expression and forced abstinence–induced seeking. We also found that vHPC-NAc excitability was decreased by experimenter-administered repeated cocaine and cocaine self-administration, and this cocaine-induced excitability decrease was mediated by ΔFosB expression. To uncover the mechanism of this change in circuit function, we used circuit-specific translating ribosome affinity purification to assess cocaine-induced, FosB/ΔFosB-dependent changes in gene expression in vHPC-NAc. We found that cocaine causes a FosB/ΔFosB-dependent increase in the expression of calreticulin, an endoplasmic reticulum–resident calcium-buffering protein. Calreticulin expression mediated vHPC-NAc excitability and was necessary for cocaine reward. These findings uncover a noncanonical mechanism by which cocaine increases calreticulin in vHPC leading to decreased vHPC-NAc excitability and drives cocaine seeking and reward.

Pregnancy and postpartum experiences represent transformative physiological states that impose lasting demands on the maternal body and brain, resulting in lifelong neural adaptations ^1–6 . However, the precise molecular mechanisms driving these persistent alterations remain poorly understood. Here, we used brain-wide transcriptomic profiling to define the molecular landscape of parity-induced neural plasticity, identifying the dorsal hippocampal formation (dHF) as a key site of transcriptional remodeling. Combining single-cell RNA sequencing with a maternal-pup separation paradigm, we additionally demonstrated that chronic postpartum stress significantly disrupts dHF adaptations by altering dopamine dynamics, leading to changes in the dopamine-dependent histone post-translational modification – H3 dopaminylation, with further alterations in transcription, cellular plasticity, and behavior. In human dorsal subiculum, a brain structure within the dHF, we uncovered conserved patterns of parity-dependent alterations in H3 dopaminylation and transcription. We further established the sufficiency of dopamine modulation in regulating these parity-induced adaptations via chemogenetic suppression of dopamine release into the dHF, which recapitulated key epigenomic and behavioral features of parity in virgin female mice. In sum, our findings establish dopamine as a central regulator of parity-induced neuroadaptations in humans and mice, revealing a fundamental transcriptional mechanism by which female reproductive experiences remodel the brain to sustain long-term behavioral adaptations.