Colony-stimulating Factor 1 Receptor Mutations Research Articles

The Phenotypic and Genotypic Spectrum of CSF1R-Related Disorder in China.

Colony-stimulating factor 1 receptor (CSF1R)-related disorder (CRD) is a rare autosomal dominant disease. The clinical and genetic characteristics of Chinese patients have not been elucidated. The objective of the study is to clarify the core features and influence factors of CRD patients in China. Clinical and genetic-related data of CRD patients in China were collected. Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), and Sundal MRI Severity Score were evaluated. Whole exome sequencing was used to analyze the CSF1R mutation status. Patients were compared between different sexes, mutation types, or mutation locations. A total of 103 patients were included, with a male-to-female ratio of 1:1.51. The average age of onset was (40.75 ± 8.58). Cognitive impairment (85.1%, 86/101) and parkinsonism (76.2%, 77/101) were the main clinical symptoms. The most common imaging feature was bilateral asymmetric white matter changes (100.0%). A total of 66 CSF1R gene mutants (22 novel mutations) were found, and 15 of 92 probands carried c.2381 T > C/p.I794T (16.30%). The MMSE and MoCA scores (17.0 [9.0], 11.90 ± 7.16) of female patients were significantly lower than those of male patients (23.0 [10.0], 16.36 ± 7.89), and the white matter severity score (20.19 ± 8.47) of female patients was significantly higher than that of male patients (16.00 ± 7.62). There is no statistical difference in age of onset between male and female patients. The core manifestations of Chinese CRD patients are progressive cognitive decline, parkinsonism, and bilateral asymmetric white matter changes. Compared to men, women have more severe cognitive impairment and imaging changes. c.2381 T > C/p.I794T is a hotspot mutation in Chinese patients. © 2024 International Parkinson and Movement Disorder Society.

Primary microgliopathy presenting as degenerative dementias: A case series of novel gene mutations from India

Introduction Microglia exert a crucial role in homeostasis of white matter integrity and several studies highlight the role of microglial dysfunctions in neurodegeneration. Primary microgliopathy are disorders where the pathogenic abnormality of the microglia causes white matter disorder and leads to a neuropsychiatric diseases. Triggering Receptor Expressed on Myeloid Cells (TREM2), TYRO protein tyrosine kinase binding protein (TYROBP), Colony-stimulating factor 1 receptor (CSF1R) are genes implicated in primary microgliopathy. Clinical manifestations of primary microgliopathy are myriad ranging from neuropsychiatric syndrome, motor disability, gait dysfunction, ataxia, pure dementia, frontotemporal dementia, Alzheimer dementia and so on. It becomes imperative to establish diagnosis of microgliopathy masquerading as degenerative dementia, especially with promising therapies on horizon for the same. We aim to describe a case series of subjects with dementia harboring novel genes of primary microgliopathy, along with their clinical, neuropsychological, and cognitive profile and radiological patterns. Methods: The prospective study was conducted in a university referral hospital in South India, as a part of an ongoing clinic-genetic research on Dementia subjects and was approved by the institutional ethics committee. All patients underwent detailed assessment including socio demographic profile, clinical and cognitive assessment, pedigree analysis and comprehensive neurological examination. Subjects consenting for blood sampling underwent genetic testing by Whole exome sequencing (WES). Results: 100 patients of dementia underwent genetic analysis using whole exome sequencing and three pathogenic variants, one each of TREM2, TYROBP and CSF1R and two variants of uncertain significance in CSF1R were identified as cause of primary microgliopathy .TREM 2 and TYROBP presented as frontotemporal syndrome whereas CSF1R presented as frontotemporal syndrome and Alzheimer dementia. Conclusion :WES has widened the spectrum of underlying neuropathology of degenerative dementias and diagnosing primary microglial dysfunction with emerging therapeutic options is of paramount importance. Cases of primary microgliopathy due to Novel mutations in TREM2, TYROBP and CSF1R with phenotype of degenerative dementia are being first time reported from Indian cohort. Our study enriches the spectrum of genetic variants implicated in degenerative dementia, and provides the basis for exploring complex molecular mechanisms like microglial dysfunction, as underlying cause for neurodegeneration.

Abstract C160: HMPL-653, a highly potent and selective CSF-1R inhibitor, targeting both tumor cells and tumor microenvironment

Abstract Background: Colony stimulating factor 1 receptor (CSF-1R) and its ligand CSF-1 (CSF-1R/CSF-1) signaling regulates the function and survival of tumor-associated macrophages (TAM), which are involved in tumor progression and suppression of anti-tumor immunity. Moreover, activation of CSF-1R/CSF-1 axis including CSF-1 fusions or CSF-1R activating mutations has also been implicated in the pathogenesis of certain tumors such as tenosynovial giant cell tumor and histiocytic neoplasms. HMPL-653 is a highly potent and selective CSF-1R small molecule inhibitor, discovered and being currently developed in phase I clinical trial (NCT05277454) by HUTCHMED. Methods: The inhibition on CSF-1R kinase was determined using Z-LYTE™ kinase assay. The selectivity of HMPL-653 was assessed against a panel of 413 kinases by Eurofins. Cellular target inhibition on phosphorylation of CSF-1R (p-CSF-1R) was detected by ELISA. In vitro cell viability was measured by CCK-8 assay. Multiple CSF-1/CSF-1R driven tumor models in Nu/Nu nude mice were applied to determine the anti-tumor activity of HMPL-653 as a single agent. To demonstrate the immunoregulatory effect of HMPL-653, a murine tumor model, B16F10, was established in C57BL/6J mice, and the combination regimen, HMPL-653 plus PCP (poly (I:C)+CpG+anti-PD-1) was evaluated. Results: HMPL-653 strongly inhibited CSF-1R kinase with IC50 of 5 nM, showing >7-fold potency than that of the approved CSF-1R inhibitor pexidartinib (IC50=39 nM). And the selectivity profiling in 413 kinase panels revealed that HMPL-653 was highly potent only against CSF-1R, indicating a lower off-target risk than paxidatinib reported. HMPL-653 potently inhibited CSF-1 stimulated p-CSF-1R in THP-1 cells with IC50 of 5 nM. In CSF-1/CSF-1R-dependent cell lines, M-NFS-60 (mouse myelogenous leukemia) and three cell lines stably expressed BCR-CSF-1R or CSF-1R mutations (Ba/F3-BCR-CSF-1R, Ba/F3-CSF-1RW450-E456del, and Ba/F3-CSF-1RY546-K551del), HMPL-653 significantly down regulated p-CSF-1R and its downstream signaling p-ERK and p-AKT. As a consequence, HMPL-653 robustly inhibited the cell viability of above cell models (IC50s: 3~40 nM). Besides the direct anti-tumor effect, HMPL-653 also demonstrated strong inhibition on macrophage survival and M2 macrophage polarization, indicating a potential effect on targeting tumor microenvironment. In vivo, oral administration of HMPL-653 induced remarkable and dose-dependent anti-tumor efficacies in M-NFS-60 ascites model and subcutaneous tumor models harboring above mentioned CSF-1R alterations. And the PK/PD analysis revealed that the anti-tumor effect correlated well with p-CSF-1R inhibition. Moreover, HMPL-653 significantly improved the anti-tumor activity of PCP regimen in B16F10 model by reducing TAMs including M2 macrophages and increasing the ratio of M1/M2 macrophages. Conclusion: HMPL-653 is a highly potent and selective CSF-1R small molecule inhibitor which targets both CSF-1/CSF-1R-dependent tumors and tumor associated macrophages, warranting further clinical evaluation. Citation Format: Jia Hu, Liang Ge, Hui Zhang, An Jiang, Juntao Yu, Weifang Xue, Jian Wang, Yang Sai, Na Yang, Weiguo Qing, Yongxin Ren, Michael Shi, Weiguo Su. HMPL-653, a highly potent and selective CSF-1R inhibitor, targeting both tumor cells and tumor microenvironment [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C160.

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

Mutations leading to colony-stimulating factor-1 receptor (CSF-1R) loss-of-function or haploinsufficiency cause CSF1R-related leukoencephalopathy (CRL), an adult-onset disease characterized by loss of myelin and neurodegeneration, for which there is no effective therapy. Symptom onset usually occurs in the fourth decade of life and the penetrance of disease in carriers is high. However, familial studies have identified a few carriers of pathogenic CSF1R mutations that remain asymptomatic even in their seventh decade of life, raising the possibility that the development and severity of disease might be influenced by environmental factors. Here we report new cases in which long-term glucocorticoid treatment is associated with asymptomatic status in elder carriers of pathogenic CSF-1R mutations. The main objective of the present study was to investigate the link between chronic immunosuppression initiated pre-symptomatically and resistance to the development of symptomatic CRL, in the Csf1r+/- mouse model. We show that chronic prednisone administration prevents the development of memory, motor coordination and social interaction deficits, as well as the demyelination, neurodegeneration and microgliosis associated with these deficits. These findings are in agreement with the preliminary clinical observations and support the concept that pre-symptomatic immunosuppression is protective in patients carrying pathogenic CSF1R variants associated with CRL. Proteomic analysis of microglia and oligodendrocytes indicates that prednisone suppresses processes involved in microglial activation and alleviates senescence and improves fitness of oligodendrocytes. This analysis also identifies new potential targets for therapeutic intervention.

Clinical, genetic, and molecular characteristics in a central-southern Chinese cohort of genetic leukodystrophies.

Leukodystrophies are a diverse group of rare inherited disorders that affect the white matter of the central nervous system with a wide phenotypic spectrum. We aimed to characterize the clinical and genetic features of leukodystrophies in a central-southern Chinese cohort. A cohort of 16 Chinese probands with leukodystrophy was recruited and performed genetic analysis by targeted panels or whole-exome sequencing. Further functional analysis of identified mutations in the colony stimulating factor 1 receptor (CSF1R) gene was explored. A total of eight pathogenic variants (3 novel, 5 documented) were identified in genes including AARS2, ABCD1, CSF1R, and GALC. Common symptoms of leukodystrophy such as cognitive decline, behavioral symptoms, bradykinesia, and spasticity were observed in mutation carriers as well as other rare features (e.g., seizure, dysarthric, and vision impairment). Overexpressing CSF1R mutants p.M875I and p.F971Sfs*7 in vitro showed pronounced cleavage CSF1R and suppressed protein expression, respectively, and reduced transcripts of both mutants were observed. CSF1 treatment revealed deficient and suppressed CSF1R phospho-activation with the mutants. In contrast to the plasma membrane and endoplasmic reticulum (ER) localized wild-type CSF1R, M875I mutant showed much less membrane association and greater detainment in the ER, whereas F971Sfs*7 mutation led to aberrant non-ER localization. Both mutations caused suppressed cell viability, which was partially resulted from deficient/suppressed CSF1R-ERK signaling. In summary, our findings expand the mutation spectrum of these genes in leukodystrophies. Supported by in vitro validation of the pathogenicity of heterozygous CSF1R mutations, our data also provide insights into the pathogenic mechanisms of CSF1R-related leukodystrophy.

Adult‐onset leukoencephalopathy with axonal spheroids and pigmented glia caused by a novel mutation of CSF1R gene

AbstractBackgroundAdult‐onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) is a rare autosomal dominant disorder caused by mutations in the colony‐stimulating factor 1 receptor (CSF1R) gene. As of 2022, more than 100 different CSF1R mutations were reported in patients with CSF1R‐related leukoencephalopathy.MethodIn this case report, we described ALSP in a previously healthy 46‐year‐old woman. The patient underwent detailed neurological examinations including cognitive assessment, brain magnetic resonance imaging (MRI) and whole‐exome sequencing.ResultThe patient manifested as memory impairment, poor interpersonal behavior and decreased verbal fluency. Brain MRI showed confluent white matter changes and atrophy of the corpus callosum. Whole‐exome sequencing identified a novel splice site mutation (C.1858 + 5G > A) in intron 13 of the CSF1R gene, which has not been reported worldwide.ConclusionALSP has a wide range of clinical manifestations and genetic heterogeneity. It should be considered when diagnosing rapidly progressive dementia with or without motor impairment. We recommend biopsy or genetic testing in these patients to avoid misdiagnosis and delayed diagnosis. We will continue to monitor this family in the future to improve our understanding of ALSP, so as to correctly diagnose ALSP in clinic and provide clinical data for better research on the pathogenesis and treatment of this disease.

Novel c.2654+1G>A mutation in the CSF1R gene in a family with CSF1R‐microglial encephalopathy

AbstractBackgroundThe colony‐stimulating factor‐1 receptor (CSF1R) is a transmembrane tyrosine kinase receptor that is mainly expressed in the brain‐resident microglia. Thus, microglial dysfunction due to CSF1R mutation may play a primary and pivotal role in the pathogenesis of CSF1R‐microglial encephalopathy. Neither the functional consequences of all known CSF1R mutations nor the full genetic spectrum of mutations causing CSF1R‐microglial encephalopathy have been fully elucidated. We aimed to describe a novel heterozygous splicing variant of the CSF1R gene that caused CSF1R‐microglial encephalopathy in a Han Chinese family.MethodThe demographic data, detailed medical history, and clinical manifestations were collected from a family with CSF1R‐microglial encephalopathy. Some family members also underwent neuropsychological evaluation, structural and functional magnetic resonance imaging (MRI), and whole‐exome sequence analyses.ResultFour generations of this family, including 27 members, presented with a medical history of a dominant hereditary pattern (Figure 1). Seven of these 27 individuals had died, while five presented with similar cognitive impairments clinically, including the proband, and his sister, father, uncle, and grandmother during their life. Brain MRI of the proband (Figure 2) and his sister (Figure 3) depicted symmetric confluent and diffuse deep white matter changes, atrophy of the frontoparietal lobes, and thinning of the corpus callosum. The brother of the proband remained asymptomatic, and the structural brain MRI only revealed minimal white matter changes; however, pseudo‐continuous arterial spin labeling (pCASL) demonstrated marked reduction in the cerebral blood flow (CBF) in the bilateral deep white matter and corpus callosum (Figure 4). Whole‐exome sequencing was performed for seven family members, which identified a novel splice‐site heterozygous mutation (c.2319+1C>A) in intron 20 of the CSF1R gene in four members (Figure 5).ConclusionWe identified a novel splicing mutation (c.2319+1C>A) in intron 20 of CSF1R as the cause of CSF1R‐microglial encephalopathy in a Han Chinese family, which broadens the genetic spectrum of CSF1R‐microglial encephalopathy. We opine that clinically feasible pCASL techniques may be more sensitive to the alterations in CBF of associated with microglial density and cellular changes. This study highlights the potential value of pCASL techniques to improve the clinical diagnostic accuracy of CSF1R‐microglial encephalopathy.

Novel partial deletions, frameshift and missense mutations of CSF1R in patents with CSF1R-related leukoencephalopathy.

Colony-stimulating factor 1 receptor (CSF1R)-related leukoencephalopathy is an adult-onset leukoencephalopathy caused by mutations in CSF1R. The present study aimed to explore the broader genetic spectrum of CSF1R-related leukoencephalopathy in association with clinical and imaging features. Mutational analysis of CSF1R was performed for 100 consecutive patients with adult-onset leukoencephalopathy. Sequence and copy number variation (CNV) analyses of CSF1R were performed. The genomic ranges of the deletions were determined by long-read sequencing. Ligand-dependent autophosphorylation of CSF1R was examined in cells expressing the CSF1R mutants identified in this study. CSF1R mutations were identified in 15 patients, accounting for 15% of the adult-onset leukoencephalopathy cases. Seven novel and five previously reported CSF1R mutations were identified. The novel mutations, including three missense and one in-frame 3 bp deletion, were located in the tyrosine kinase domain (TKD) of CSF1R. Functional assays revealed that none of the novel mutations in the TKD showed autophosphorylation of CSF1R. Two partial deletions of CSF1R were identified that resulted in lack of the C-terminal region, including the distal TKD, in two patients. Various clinical features including cognitive impairment, psychiatric symptoms and gait disturbance were observed. Various degrees of the white matter lesions and corpus callosum abnormalities on magnetic resonance imaging and characteristic calcifications on computed tomography were observed as imaging features. Our results highlight the importance of examining the CNV of CSF1R even when Sanger or exome sequencing reveals no CSF1R mutations. Genetic examination of sequences and CNV analyses of CSF1R are recommended for an accurate diagnosis of CSF1R-related leukoencephalopathy.

Four Swedish cases of CSF1R-related leukoencephalopathy: Visualization of clinical phenotypes.

Colony stimulating factor 1 receptor (CSF1R)‐related leukoencephalopathy is a rare, genetic disease caused by heterozygous mutations in the CSF1R gene with rapidly progressive neurodegeneration, behavioral, cognitive, motor disturbances.ObjectiveTo describe four cases of CSF1R‐related leukoencephalopathy from three families with two different pathogenic mutations in the tyrosine kinase domain of CSF1R and to develop an integrated presentation of inter‐individual diversity of clinical presentations.MethodsThis is an observational study of a case series. Patients diagnosed with CSF1R encephalopathy were evaluated with standardized functional estimation scores and subject to analysis of cerebrospinal fluid biomarkers. Brain computed tomography (CT) and magnetic resonance imaging (MRI) were evaluated. We performed a functional phosphorylation assay to confirm the dysfunction of mutated CSF1R protein.ResultsTwo heterozygous missense mutations in the CSF1R gene were identified, c.2344C>T; p.Arg777Trp and c.2329C>T; p.Arg782Cys. A phosphorylation assay in vitro showed markedly reduced autophosphorylation in cells expressing mutations. According to ACMG criteria, both mutations were pathogenic. A radiological investigation revealed typical white matter lesions in all cases. There was inter‐individual diversity in the loss of cognitive, motor‐neuronal, and extrapyramidal functions.ConclusionsIncluding the present cases, currently three CSF1R mutations are known in Sweden. We present a visualization tool to describe the clinical diversity, with potential use for longitudinal follow‐up for this and other leukoencephalopathies.

Evaluation of CSF1R-related adult onset leukoencephalopathy with axonal spheroids and pigmented glia diagnostic criteria.

Diagnostic criteria for adult onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) due to colony-stimulating factor 1 receptor (CSF1R) mutation have recently been proposed. Our objective was to assess their accuracy in an independent multicenter cohort. We evaluated the sensitivity and specificity of the diagnostic criteria for ALSP (including the "probable" and "possible" definitions) in a national cohort of 22 patients with CSF1R mutation, and 59 patients with an alternative diagnosis of adult onset inherited leukoencephalopathy. Overall, the sensitivity of the diagnostic criteria for ALSP was 82%, including nine of 22 patients diagnosed as probable and nine of 22 diagnosed as possible. Twenty of the 59 CSF1R mutation-negative leukoencephalopathies fulfilled the diagnostic criteria, leading to a specificity of 66%. Diagnostic criteria for ALSP have an overall limited sensitivity along with a modest specificity. We suggest that in patients suspected of genetic leukoencephalopathy, a comprehensive magnetic resonance imaging pattern-based approach is warranted, together with white matter gene panel or whole exome sequencing.

From HDLS to BANDDOS: fast-expanding phenotypic spectrum of disorders caused by mutations in CSF1R

Colony-stimulating factor 1 receptor (CSF1R) plays key roles in the development and function of the cells in the monocyte/macrophage lineage, including microglia and osteoclasts. It is well known that mono-allelic mutations of CSF1R cause hereditary diffuse leukoencephalopathy with spheroids (HDLS, OMIM # 221820), an adult-onset progressive neurodegenerative disorder. Recently, a more severe phenotypic spectrum has been identified in individuals with bi-allelic mutations of CSF1R. In addition to leukoencephalopathy of earlier onset than HDLS, the new disease shows brain malformations and skeletal dysplasia compatible with dysosteosclerosis (DOS), thus named "brain abnormalities, neurodegeneration, and dysosteosclerosis" (BANDDOS, OMIM # 618476). In addition, some individuals with bi-allelic missense mutations of CSF1R have been found to present with incomplete BANDDOS where skeletal dysplasia is absent. In this review, we summarize the monogenic disorders caused by mutations in CSF1R and their mutational spectra, and propose a dose-dependent model to explain the complex genotype-phenotype association.

Characterization of a novel CSF1R mutation causing hereditary diffuse leukoencephalopathy with spheroids in a case presenting with young-onset dementia

ObjectiveThis poster aims to report an unregistered mutation CSF1R gene in a patient presenting young-onset dementia.Hypothesis: Novel heterozygous deletion–insertion mutation in the Colony-Stimulating Factor 1 Receptor (CSF1R) gene is linked to a case of hereditary diffuse leukoencephalopathy with spheroids (HDLS), presenting with young-onset dementia.BackgroundCSF1R mediates proliferation, differentiation, and survival of monocytes/ macrophages and microglia. Pathogenic variants in the CSF1R gene cause autosomal dominant diffuse hereditary leukoencephalopathy with spheroids characterized by variable behavioural, cognitive, and motor changes, usually presenting with young-onset dementia. The average lifespan after the start of the symptoms is often 6 years.Case reportMolecular genetic analysis of whole-exome sequencing (WES) was carried out for a 49-year-old male patient presenting with rapid cognitive decline, behavioural symptoms and impaired sphincteric control.DiscussionWES identified the heterozygous deletion–insertion variant c.2356_2357delinsAC p.(Leu786Thr) (chr5:149435867-49435868; hg19) in the CSF1R gene. To the best of our knowledge the variant has not been described in the literature so far (HGMD 2019.3). No allele frequencies in the general population have been documented.ConclusionWe believe that we have identified a novel mutation in the CSF1R gene. This mutation is likely to be linked to this patient presenting with young-onset dementia.

Relationships between novel nucleotide variants within the colony-stimulating factor 1 receptor (CSF1R) gene and mastitis indicators in sheep

Colony-stimulating factor 1 receptor (CSF1R) plays an important role in the process of innate immunity and inflammation, thus it was hypothesized that the CSF1R gene might affect the occurrence of mammalian mastitis. The purpose of this study was to investigate the association between nucleotide variations of CSF1R gene and mastitis in Australian white sheep (AUWs). Two indel variants (Intron5-27 bp and Intron5-22 bp) within the CSF1R gene have been found in AUWs. The Chi-square test for different mastitis symptoms demonstrated that individuals without symptoms of mastitis had higher ‘I’ allele frequencies and ‘II’ genotype frequencies (p < 0.01). We found strong correlation between mastitis and lactation score through Pearson correlation analysis. Therefore, we also analyzed the relationship between the two indel loci and lactation, we found that the lactation ability of individuals with type II was stronger than that of DD genotype at the Intron5-22 bp (p < 0.05). Additionally, we found that the combined genotype of the two loci was significantly associated with mastitis (p < 0.01). These findings indicated that CSF1R mutations were significantly associated with mastitis, and could affect lactation performance, suggesting that two deletion sites could be used as the effective molecular markers against mastitis in sheep breeding.

Sporadic Japanese case of adult‐onset leukoencephalopathy with axonal spheroids and pigmented glia caused by a de novo p.Phe849del mutation in CSF1R

AbstractAdult‐onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) is an autosomal dominant neurodegenerative disorder caused by mutations in the colony‐stimulating factor 1 receptor (CSF1R) gene. We, herein, report the first Japanese case of ALSP caused by a de novo p.Phe849del mutation in CSF1R: a 44‐year‐old man who presented callosal disconnection symptoms. Brain MRI revealed dilation of the lateral ventricles, periventricular white matter hyperintensities, and thinning of the corpus callosum with hyperintensities on T2‐weighted and FLAIR images. Brain single photon emission computed tomography (SPECT) showed hypoperfusion in the anterior corpus callosum. White matter lesions in MRI and hypoperfusion in SPECT increased with age. A brain biopsy at 44 years revealed axonal spheroids. Callosal disconnection symptoms and hypoperfusion in the anterior corpus callosum may be important indicators of ALSP, especially when caused by a p.Phe849del CSF1R mutation.

Clinical features and genetic characteristics of hereditary diffuse leukoencephalopathy with spheroids due to CSF1R mutation: a case report and literature review.

Hereditary diffuse leukoencephalopathy with spheroid (HDLS) is an autosomal dominant white matter disease characterized by adult-onset cognitive impairment, behavioral or emotional changes, paresis, Parkinsonism, and seizures. Mutations in the gene encoding colony-stimulating factor 1 receptor (CSF1R) have been identified as the cause of HDLS. Detail medical history, clinical features and brain imaging of a patient with adult-onset leukoencephalopathy, cognitive impairment and motor dysfunction was reviewed and next generation sequencing was performed. An extensive literature research was then performed to identify all patients with HDLS previously reported. The clinical characteristics, brain imaging and genetic features of patients with HDLS were reviewed. A novel CSF1R mutation, c.1952G>A p.G651E was identified in the patient. Extensive review showed that HDLS typically presents with broad phenotypic variability. The most common symptoms of HDLS were cognitive impairment, followed by psychiatric symptoms, Parkinsonism, gait disorder, and dysphagia. The most common brain imaging findings of HDLS were bilateral white matter lesion, mostly around the ventricles, frontal lobe, and parietal lobe. Calcifications in white matter on CT, cerebral atrophy and thinning of corpus callosum were also common features. Although HDLS demonstrates an autosomal dominant pattern, sporadic cases are not uncommon. Early recognition of clinical and neuroradiographical characteristics of HDLS is key for the correct diagnosis of the disease.

Clinicopathologic characterization and abnormal autophagy of CSF1R-related leukoencephalopathy

BackgroundCSF1R-related leukoencephalopathy, also known as hereditary diffuse leukoencephalopathy with spheroids (HDLS), is a rare white-matter encephalopathy characterized by motor and neuropsychiatric symptoms due to colony-stimulating factor 1 receptor (CSF1R) gene mutation. Few of CSF1R mutations have been functionally testified and the pathogenesis remains unknown.MethodsIn order to investigate clinical and pathological characteristics of patients with CSF1R-related leukoencephalopathy and explore the potential impact of CSF1R mutations, we analyzed clinical manifestations of 15 patients from 10 unrelated families and performed brain biopsy in 2 cases. Next generation sequencing was conducted for 10 probands to confirm the diagnosis. Sanger sequencing, segregation analysis and phenotypic reevaluation were utilized to substantiate findings. Functional examination of identified mutations was further explored.ResultsClinical and neuroimaging characteristics were summarized. The average age at onset was 35.9 ± 6.4 years (range 24–46 years old). Younger age of onset was observed in female than male (34.2 vs. 39.2 years). The most common initial symptoms were speech dysfunction, cognitive decline and parkinsonian symptoms. One patient also had marked peripheral neuropathy. Brain biopsy of two cases showed typical pathological changes, including myelin loss, axonal spheroids, phosphorylated neurofilament and activated macrophages. Electron microscopy disclosed increased mitochondrial vacuolation and disorganized neurofilaments in ballooned axons. A total of 7 pathogenic variants (4 novel, 3 documented) were identified with autophosphorylation deficiency, among which c.2342C > T remained partial function of autophosphorylation. Western blotting disclosed the significantly lower level of c.2026C > T (p.R676*) than wild type. The level of microtubule associated protein 1 light chain 3-II (LC3-II), a classical marker of autophagy, was significantly lower in mutants expressed cells than wild type group by western blotting and immunofluorescence staining.ConclusionsOur findings support the loss-of-function and haploinsufficiency hypothesis in pathogenesis. Autophagy abnormality may play a role in the disease. Repairing or promoting the phosphorylation level of mutant CSF1R may shed light on therapeutic targets in the future. However, whether peripheral polyneuropathy potentially belongs to CSF1R-related spectrum deserves further study with longer follow-up and more patients enrolled.Trial registrationChiCTR, ChiCTR1800015295. Registered 21 March 2018.

Factors predictive of the presence of a CSF1R mutation in patients with leukoencephalopathy.

Background and purposeThe purpose was to identify statistically factors that correlate with the presence of a colony‐stimulating factor 1 receptor (CSF1R) mutation and to reevaluate the accuracy of the current diagnostic criteria for CSF1R‐related leukoencephalopathy.Methods CSF1R testing was conducted on 145 consecutive leukoencephalopathy cases who were clinically suspected of having adult‐onset leukoencephalopathy with axonal spheroids and pigmented glia. From these, 135 cases whose detailed clinical information was available were enrolled. Forward logistic stepwise regression was performed to generate a probability model to predict a positive CSF1R mutation result. The current diagnostic criteria were also applied to our cohort and their sensitivity and specificity were calculated.ResultsTwenty‐eight CSF1R‐mutation‐positive cases and 107 CSF1R‐mutation‐negative cases were identified. Our probability model suggested that factors raising the probability of a CSF1R‐mutation‐positive result were younger onset, parkinsonism, thinning of the corpus callosum and diffusion‐restricted lesions. It also showed that involuntary movements and brainstem or cerebellar atrophy were negative predictors of a CSF1R‐mutation‐positive result. In our cohort, the sensitivity and specificity for ‘probable’ or ‘possible’ CSF1R‐related leukoencephalopathy were 81% and 14%, respectively.ConclusionsClinical and brain imaging features predictive of the presence of a CSF1R mutation are proposed. Consideration of these factors will help prioritize patients for CSF1R testing.

Homozygous Mutations in CSF1R Cause a Pediatric-Onset Leukoencephalopathy and Can Result in Congenital Absence of Microglia

Microglia are CNS-resident macrophages that scavenge debris and regulate immune responses. Proliferation and development of macrophages, including microglia, requires Colony Stimulating Factor 1 Receptor (CSF1R), a gene previously associated with a dominant adult-onset neurological condition (adult-onset leukoencephalopathy with axonal spheroids and pigmented glia). Here, we report two unrelated individuals with homozygous CSF1R mutations whose presentation was distinct from ALSP. Post-mortem examination of an individual with a homozygous splice mutation (c.1754-1G>C) demonstrated several structural brain anomalies, including agenesis of corpus callosum. Immunostaining demonstrated almost complete absence of microglia within this brain, suggesting that it developed in the absence of microglia. The second individual had a homozygous missense mutation (c.1929C>A [p.His643Gln]) and presented with developmental delay and epilepsy in childhood. We analyzed a zebrafish model (csf1rDM) lacking Csf1r function and found that their brains also lacked microglia and had reduced levels of CUX1, a neuronal transcription factor. CUX1+ neurons were also reduced in sections of homozygous CSF1R mutant human brain, identifying an evolutionarily conserved role for CSF1R signaling in production or maintenance of CUX1+ neurons. Since a large fraction of CUX1+ neurons project callosal axons, we speculate that microglia deficiency may contribute to agenesis of the corpus callosum via reduction in CUX1+ neurons. Our results suggest that CSF1R is required for human brain development and establish the csf1rDM fish as a model for microgliopathies. In addition, our results exemplify an under-recognized form of phenotypic expansion, in which genes associated with well-recognized, dominant conditions produce different phenotypes when biallelically mutated.

Bi-allelic CSF1R Mutations Cause Skeletal Dysplasia of Dysosteosclerosis-Pyle Disease Spectrum and Degenerative Encephalopathy with Brain Malformation

Colony stimulating factor 1 receptor (CSF1R) plays key roles in regulating development and function of the monocyte/macrophage lineage, including microglia and osteoclasts. Mono-allelic mutations of CSF1R are known to cause hereditary diffuse leukoencephalopathy with spheroids (HDLS), an adult-onset progressive neurodegenerative disorder. Here, we report seven affected individuals from three unrelated families who had bi-allelic CSF1R mutations. In addition to early-onset HDLS-like neurological disorders, they had brain malformations and skeletal dysplasia compatible to dysosteosclerosis (DOS) or Pyle disease. We identified five CSF1R mutations that were homozygous or compound heterozygous in these affected individuals. Two of them were deep intronic mutations resulting in abnormal inclusion of intron sequences in the mRNA. Compared with Csf1r-null mice, the skeletal and neural phenotypes of the affected individuals appeared milder and variable, suggesting that at least one of the mutations in each affected individual is hypomorphic. Our results characterized a unique human skeletal phenotype caused by CSF1R deficiency and implied that bi-allelic CSF1R mutations cause a spectrum of neurological and skeletal disorders, probably depending on the residual CSF1R function.

Discriminative clinical and neuroimaging features of motor-predominant hereditary diffuse leukoencephalopathy with axonal spheroids and primary progressive multiple sclerosis: A preliminary cross-sectional study

BackgroundHereditary diffuse leukoencephalopathy with axonal spheroids (HDLS) is a rare autosomal-dominant white matter disease, typically characterized by juvenile cognitive decline and frontoparietal white matter lesions. A portion of HDLS patients exhibit preferential motor dysfunctions as their initial symptoms, mimicking multiple sclerosis (MS). However, there is no study comparing this phenotype of HDLS and primary progressive multiple sclerosis (PPMS), which greatly resemble each other. This is the first preliminary study to clarify the clinical and neuroimaging features of motor-predominant HDLS, and compare it with PPMS, using cases whose colony stimulating factor 1 receptor (CSF1R) were sequenced. MethodsClinical and radiological data from Japanese patients at the Department of Neurology, Kyushu University Hospital, Fukuoka, Japan, were evaluated retrospectively and cross-sectionally. Twenty-nine brain and 18 spinal cord magnetic resonance imaging (MRI) scans from four motor-predominant HDLS patients with CSF1R mutations and 15 PPMS patients without CSF1R mutations, were evaluated using an HDLS MRI scoring system. ResultsTwo patients with HDLS were initially diagnosed with MS and received immunotherapy. Clinically, motor-predominant HDLS and PPMS patients resembled each other in onset age and disability. However, motor-predominant HDLS patients had a significantly higher frequency of frontal release signs, lower positivity rates of oligoclonal IgG bands (OCB), and lower IgG index values. Total HDLS MRI scores, total white matter lesions (WMLs), and brain atrophy were similar between the diseases. However, motor-predominant HDLS patients had more marked atrophy of the corpus callosum (CC) body, more WMLs in the deep and subcortical regions of the frontoparietal lobes, fewer WMLs in the occipitotemporal periventricular regions, and more restricted diffusivity lesions on MRI than PPMS patients. There was a stronger association between disease duration and CC index in HDLS, suggesting more rapid progression compared with PPMS. ConclusionsMotor-predominant HDLS has characteristic frequent frontal release signs, normal findings for OCB and the IgG index, severe CC body atrophy, abundant deep and subcortical WMLs in the frontoparietal lobes, subtle occipitotemporal lobe periventricular WMLs, and more restricted diffusivity lesions on MRI. Although the present study was limited by the small number of HDLS cases, we propose that immunotherapy should be avoided in such cases.