ATR regulates neuronal activity by modulating presynaptic firing

Abstract

Ataxia Telangiectasia and Rad3-related (ATR) protein, as a key DNA damage response (DDR) regulator, plays an essential function in response to replication stress and controls cell viability. Hypomorphic mutations of ATR cause the human ATR-Seckel syndrome, characterized by microcephaly and intellectual disability, which however suggests a yet unknown role for ATR in non-dividing cells. Here we show that ATR deletion in postmitotic neurons does not compromise brain development and formation; rather it enhances intrinsic neuronal activity resulting in aberrant firing and an increased epileptiform activity, which increases the susceptibility of ataxia and epilepsy in mice. ATR deleted neurons exhibit hyper-excitability, associated with changes in action potential conformation and presynaptic vesicle accumulation, independent of DDR signaling. Mechanistically, ATR interacts with synaptotagmin 2 (SYT2) and, without ATR, SYT2 is highly upregulated and aberrantly translocated to excitatory neurons in the hippocampus, thereby conferring a hyper-excitability. This study identifies a physiological function of ATR, beyond its DDR role, in regulating neuronal activity.

The Essential DNA Damage Response Complex MRN Is Dispensable for the Survival and Function of Purkinje Neurons

“…Furthermore, although the MRN complex and ATR are all essential DDR molecules and the functions of the MRN complex also on upstream of ATR in the DDR pathway depending on cell cycle status and physiological status, deletion of Atr in Purkinje cells (Atr-PC mice) does not compromise the development and survival of Purkinje cells. However, Atr-PC mice show ataxia due to a defect of intrinsic neuronal activity mediated by modulating presynaptic firing through interacting between ATR and synaptotagmin 2 (SYT2), rather than cerebellar degeneration (Kirtay et al, 2021). In this regard, it is interesting to note that Purkinje cells from Mre11-deleted mice do not show any electrophysiological defects in the current study (Figure 6).…”

“…Nbs1-PC or Mre11-PC mice with a specific deletion of Nbs1 or Mre11 in Purkinje cells were generated by crossing Nbs1 flox/flox (Frappart et al, 2005) or Mre11 flox/flox (Buis et al, 2008) mice with Pcp2-Cre transgenic mice (Kirtay et al, 2021). Nbs1-CNS ; P53-/-mice were generated previously described (Frappart et al, 2005).…”

“…TUNEL assay was performed as previously described (Kirtay et al, 2021). After the Tunel staining, sections were incubated by the first antibody rabbit anti-Calbindin (1:200, Swant) at 4 • C overnight.…”

“…Electrophysiological recording of Purkinje cells was performed as described previously (Kirtay et al, 2021). Briefly, the brains of 18-20-month-old mice were removed in ice-cold protective cutting artificial cerebrospinal fluid (aCSF1) containing: 95 mM of N-Methyl-D-glucamine, 30 mM of NaHCO 3 , 20 mM of HEPES, 25 mM of glucose, 2.5 mM of KCl, 1.25 mM of NaH 2 PO 4 , 2 mM of thiourea, 5 mM of sodium ascorbate, 3.0 mM of sodium pyruvate, 10 mM of MgSO 4 , 0.5 mM of CaCl 2 , 12 mM of N-acetylcysteine, adjusted to pH 7.3 and an osmolarity of 300-310 mOsmol, saturated with 95% O 2 /5% CO 2 .…”

An Eye in the Replication Stress Response: Lessons From Tissue-Specific Studies in vivo

“…Reports of retinal malformations and degeneration have been found in Seckel and Nijmegen breakage syndrome ( Figure 1B ). However, possible non-canonical functions of RSR genes in post-mitotic cells should not be overlooked, as it has been recently shown that ATR-CHK1 pathway can have a direct function on post-mitotic neurons activity and regeneration in model organisms ( Kirtay et al, 2021 ; Li et al, 2021 ). Clinical investigations performing follow up in RSR-related syndromes patients associated with molecular diagnosis can bring important insights on the eye manifestations of these disorders.…”