Elevated granulocyte colony stimulating factor (CSF) causes cerebellar deficits and anxiety in a model of CSF‐1 receptor related leukodystrophy

Abstract

Colony stimulating factor (CSF) receptor-1 (CSF-1R)-related leukoencephalopathy (CRL) is an adult-onset, demyelinating and neurodegenerative disease caused by autosomal dominant mutations in CSF1R, modeled by the Csf1r +/À mouse. The expression of Csf2, encoding granulocyte-macrophage CSF (GM-CSF) and of Csf3, encoding granulocyte CSF (G-CSF), are elevated in both mouse and human CRL brains. While monoallelic targeting of Csf2 has been shown to attenuate many behavioral and histological deficits of Csf1r +/À mice, including cognitive dysfunction and demyelination, the contribution of Csf3 has not been explored. In the present study, we investigate the behavioral, electrophysiological and histopathological phenotypes of Csf1r +/À mice following monoallelic targeting of Csf3. We show that Csf3 heterozygosity normalized the Csf3 levels in Csf1r +/À mouse brains and ameliorated anxiety-like behavior, motor coordination and social interaction deficits, but not the cognitive impairment of Csf1r +/À mice. Csf3 heterozygosity failed to prevent callosal demyelination. However, consistent with its effects on behavior, Csf3 heterozygosity normalized microglial morphology in the cerebellum and in the ventral, but not in the dorsal hippocampus. Csf1r +/À mice exhibited altered firing activity in the deep cerebellar nuclei (DCN) associated with increased engulfment of glutamatergic synapses by DCN microglia and increased deposition of the complement factor C1q on glutamatergic synapses. These phenotypes were significantly ameliorated by monoallelic deletion of Csf3. Our current and earlier findings indicate that G-CSF and GM-CSF play largely non-overlapping roles in CRL-like disease development in Csf1r +/À mice.

Prophylactic effect of chronic immunosuppression in a mouse model of CSF‐1 receptor‐related leukoencephalopathy

“…At 12 months of age Csf1r +/− male mice exhibited autistic–like behavior which was attenuated by prednisone treatment (Figure 1b). This phenotype was not observed in females of this age (data not shown), although in a previous study (Biundo et al, 2023a), it was detected in older (13–16 months‐old) females. Similarly, there was a positive effect of prednisone treatment in preventing the development of motor coordination deficits in Csf1r +/− mice, detected by evaluating the number of slips on a balance beam (Figure 1c).…”

“…Behavioral studies involved both male and female mice. Because hallmark histopathological features of the disease (demyelination, neurodegeneration, increased densities and morphological change of microglia) were reproducibly detected in both male and female mice (Biundo et al, 2023a; Chitu et al, 2015, Chitu et al, 2020), we have conducted the histopathological evaluation in female mice and proteomic analysis in male mice. The age and sex of mice used in each experiment are indicated in the figures and figure legends.…”

“…Behavioral studies were conducted in mice between 11 and 15 months of age as described (Biundo et al, 2023a). Social interaction deficits were assessed at 11 months of age using the three‐chamber sociability test (Kana et al, 2019).…”

“…Microglial expansion occurs in the cortex and white matter of CRL patients in a stage-dependent manner and is accompanied by gradual loss of membrane processes, indicative of activation (Oyanagi et al, 2017). Csf1r +/À mice reproduce the increase in microglial densities in multiple brain regions including the motor cortex, hippocampus and corpus callosum (Figure 3a-d) (Biundo et al, 2023a;Chitu et al, 2015). This phenotype is prevented by prednisone treatment (Figure 3a-d).…”

“…These findings suggested that the development of CRL might be delayed by modulating microglia function. Indeed, using mouse models, we have shown that granulocyte‐macrophage colony stimulating factor (GM‐CSF) and granulocyte colony stimulating factor (G‐CSF) contribute to microglia dyshomeostasis in non‐overalpping manner and that their genetic targeting improves several aspects of CRL pathology and behavior (Biundo et al, 2023a; Chitu et al, 2020). Furthermore, treatment of 6‐month‐old Csf1r +/− mice for 6–8 weeks with a dosage of the CSF‐1R inhibitor PLX5622 that eliminates <25% of microglia resulted in an improvement in cognitive function in the novel object recognition test (Arreola et al, 2021).…”