Daughterless, the Drosophila orthologue of TCF4, is required for associative learning and maintenance of the synaptic proteome

Abstract

Mammalian transcription factor 4 (TCF4) has been linked to schizophrenia and intellectual disabilities, such as Pitt–Hopkins syndrome (PTHS). Here, we show that similarly to mammalian TCF4, fruit fly orthologue Daughterless (Da) is expressed widely in the Drosophila brain. Furthermore, silencing of da, using several central nervous system-specific Gal4 driver lines, impairs appetitive associative learning of the larvae and leads to decreased levels of the synaptic proteins Synapsin (Syn) and Discs large 1 (Dlg1), suggesting the involvement of Da in memory formation. Here, we demonstrate that Syn and dlg1 are direct target genes of Da in adult Drosophila heads, as Da binds to the regulatory regions of these genes and the modulation of Da levels alter the levels of Syn and dlg1 mRNA. Silencing of da also affects negative geotaxis of the adult flies, suggesting the impairment of locomotor function. Overall, our findings suggest that Da regulates Drosophila larval memory and adult negative geotaxis, possibly via its synaptic target genes Syn and dlg1. These behavioural phenotypes can be further used as a PTHS model to screen for therapeutics.This article has an associated First Person interview with the first author of the paper.

Isoform-Specific Reduction of the Basic Helix-Loop-Helix Transcription Factor TCF4 Levels in Huntington’s Disease

“…Furthermore, TCF4 regulates synaptic plasticity and memory, and overexpression of TCF4 results in abnormal distribution of layer 2/3 pyramidal neurons in prefrontal cortex and alters their intrinsic excitability ( Kennedy et al, 2016 ; Page et al, 2018 ; Thaxton et al, 2018 ). A recent study by Tamberg and colleagues ( Tamberg et al, 2020 ) showed that reduction of Daughterless ( Drosophila melanogaster homolog of TCF4) in larvae central nervous system impairs appetitive associative learning and downregulates synaptic protein encoding genes, therefore linking Daughterless, and possibly TCF4, to memory formation ( Tamberg et al, 2020 ).…”

Molecular and Cellular Function of Transcription Factor 4 in Pitt-Hopkins Syndrome

“…Along these lines, HDAC inhibitors, administered either with intraperitoneal injection of the broad-spectrum inhibitor SAHA or via intracerebroventricular injection of antisense oligonucleotide against Hdac2, were shown to be effective at rescuing contextual and trace-cued threat recognition memory in a PTHS mouse model [29]. Similarly, in fruit flies, feeding SAHA was able to rescue the negative geotaxis phenotype associated with silencing Da in female flies [41]. In addition, the dihydropyridine calcium channel inhibitor, nicardipine, was shown to be effective at rescuing a variety of behavioral deficits in the PTHS mouse model.…”

“…Beyond these ChIP-seq studies, several groups have identified specific downstream targets of TCF4 using a variety of cell and animal models. Manipulation of TCF4 expression in these models leads to altered expression of a variety of downstream targets which include two ion channels, Scn10a (Nav1.8) and Kcnq1 (Kv7.1) [26], Wnt7b [40], Gadd45g [31], Nrxn1 [27, 38], Syn , and Dlg1 [41]. The role of these downstream target genes in the generation of phenotypes will be discussed in greater detail below.…”

“…It is worth noting that some of these behavioral phenotypes are also present in fruit flies. Silencing of Da was shown to impair appetitive associative learning and memory in fly larvae and locomotion in adult flies [41].…”

Developmental disorders Journal Meeting: a collaboration between Development and Disease Models & Mechanisms

“…The fruit fly can be used to study associated phenotypes at molecular, cellular, brain and behavioural level with easy genetic manipulation, and there is an expanding array of techniques that allow in-depth and highthroughput research with this organism. These flies were utilised by Tamberg et al (2020), who show that silencing the fruit fly orthologue of the transcription factor TCF4that has been linked to intellectual disability and schizophreniacan impair larval memory and locomotive function, and causes loss of synaptic proteins. Behavioural anomalies have also been explored in mouse models of Down syndrome (Shaw et al, 2020) and of diseases related to the dysregulation of gap junction protein connexin 3, which more frequently affect the skin (Novielli-Kuntz et al, 2021).…”