Loss of the Er81 Transcription Factor in Cholinergic Cells Alters Striatal Activity and Habit Formation

Abstract

Highlights-The Er81 transcription factor is expressed in striatal cholinergic interneurons (CINs) -Conditional deletion of Er81 alters key molecular, morphological and electrophysiological properties of CINs in adult mice -Deletion of Er81 reduces the intrinsic excitability of CINs by upregulating delayed rectifier and hyperpolarization-activated currents -Deletion of Er81 alters in vivo striatal activity and habit formation SUMMARYThe finely-tuned activity of cholinergic interneurons (CINs) in the striatum is key for motor control, learning, and habit formation. Yet, the molecular mechanisms that determine their unique functional properties remain poorly explored. Using a combination of genetic and biochemical assays, in vitro and in vivo physiological characterisation, we report that selective ablation of the Er81 transcription factor leads to prominent changes in CIN molecular, morphological and electrophysiological features. In particular, the lack of Er81 amplifies intrinsic delayed-rectifier and hyperpolarization-activated currents, which subsequently alters the tonic and phasic activity of CINs. We further demonstrate that these alterations enhance their pause and time-locked responses to sensorimotor inputs in awake mice. Finally, this study reveals an Er81-dependent developmental mechanism in CINs essential for habit formation in adult mice. RESULTS Er81 is expressed in the striatal cholinergic interneuronsWe first analysed the expression of Er81 from birth to adulthood and found that both mRNA ( Figure 1A) and protein levels (Figure 1B) significantly drop from postnatal day 6 (P6) to P30 in the total striatum. In the CINs specifically, we observed similar decrease of Er81 protein levels from P6 to P30 (Figure 1C). To determine the proportion of CINs expressing Er81 at any stage during development, we analysed β-galactosidase staining, which perdures long after being synthesised (Dehorter et al., 2015). We found that most of CINs (62 ± 7 %) in the Er81 nlsLacZ/+ mice express β-galactosidase (and therefore Er81) in the striatum (Figure S1A), unlike cholinergic cells in the basal forebrain (6 ± 2%; Figure S1B). As Er81 can have an important role in cell function (Dehorter et al., 2015), we analysed the consequences of removing Er81 from CINs, using conditional knockout mice (cKO: ChAT-Cre; Er81 f/f ; comparing with control mice: ChAT-Cre; Er81 +/+ ). We did not observe any change in cholinergic cell density at P2 and P30 within the striatum between control and Er81 cKO conditions (Figure 1D-Fsuggesting that the specific deletion of Er81 does not affect CIN neurogenesis and migration. Cholinergic interneuron properties change in the absence of Er81To determine the role of Er81 in CIN specification and maturation, we assessed the molecular properties of these cells following Er81 deletion. The LIM homeodomain transcription factorLhx6 is expressed in about half of striatal CINs (Lozovaya et al., 2018)and is necessary for MGE-derived GABAergic interneuron specification (Liodis et al., 2007) (Fragkouli et al., ...

Recurrent Implication of Striatal Cholinergic Interneurons in a Range of Neurodevelopmental, Neurodegenerative, and Neuropsychiatric Disorders

“…Thus, ChINs display considerable molecular and functional heterogeneity that is likely imparted by differing developmental pathways [ 24 , 35 , 44 ]. A recent pre-print from Ranjbar-Slamloo et al suggests that the transcription factor Er81 is required for the proper anatomical and functional maturation of ChINs [ 45 ]. Going forward, it will be useful to identify additional transcription factors to help delineate different subpopulations of ChINs [ 46 ].…”