AP-4 mediates vesicular transport of the 2-AG endocannabinoid producing enzyme DAGLB

Davies, Alexandra K; Ziegler, M. L.; Jumo, Hellen; Saber, Wardiya Afshar; Ebrahimi‐Fakhari, Darius; Borner, Georg H. H.

doi:10.1101/2020.10.25.353995

Cited by 3 publications

(4 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We also acknowledge that our assay relies on ATG9A distribution only and does not take into account other cargo proteins that are potentially important in neurons. 10 , 60 Thus, an interpretation of results from our fibroblast-based assay should integrate detailed clinical information, neuroimaging, molecular testing and in silico predictions, including those illustrated in Figs 1 and 2 and Supplementary Fig. 1 .…”

Section: Discussionmentioning

confidence: 99%

High-throughput imaging of ATG9A distribution as a diagnostic functional assay for adaptor protein complex 4-associated hereditary spastic paraplegia

Ebrahimi‐Fakhari

Alecu

Brechmann

et al. 2021

Brain Communications

Self Cite

View full text Add to dashboard Cite

Adaptor protein complex 4 (AP-4)-associated hereditary spastic paraplegia is caused by biallelic loss-of-function variants in AP4B1, AP4M1, AP4E1 or AP4S1, which constitute the four subunits of this obligate complex. While the diagnosis of AP-4-associated hereditary spastic paraplegia relies on molecular testing, the interpretation of novel missense variants remains challenging. Here we address this diagnostic gap by using patient-derived fibroblasts to establish a functional assay that measures the subcellular localization of ATG9A, a transmembrane protein that is sorted by AP-4. Using automated high-throughput microscopy, we determine the ratio of the ATG9A fluorescence in the trans-Golgi-network versus cytoplasm and ascertain that this metric meets standards for screening assays (Z’-factor robust > 0.3, strictly standardized mean difference > 3). The ‘ATG9A ratio’ is increased in fibroblasts of 18 well-characterized AP-4-associated hereditary spastic paraplegia patients (mean: 1.54 ± 0.13 vs. 1.21 ± 0.05 (standard deviation) in controls) and receiver-operating-characteristic analysis demonstrates robust diagnostic power (area under the curve: 0.85, 95% confidence interval: 0.849–0.852). Using fibroblasts from two individuals with atypical clinical features and novel biallelic missense variants of unknown significance in AP4B1, we show that our assay can reliably detect AP-4 function. Our findings establish the ‘ATG9A ratio’ as a diagnostic marker of AP-4-associated hereditary spastic paraplegia.

show abstract

Section: Discussionmentioning

confidence: 99%

High-throughput imaging of ATG9A distribution as a diagnostic functional assay for adaptor protein complex 4-associated hereditary spastic paraplegia

Ebrahimi‐Fakhari

Alecu

Brechmann

et al. 2021

Brain Communications

Self Cite

View full text Add to dashboard Cite

show abstract

“…Of note, recent work identified the 2-arachidonoylglycerol producing enzyme diacylglycerol lipase-beta (DAGLB) as a cargo of AP-4, 27 potentially linking loss of AP-4 function with abnormal endocannabinoid signaling and therefore to impaired axon growth, axon guidance, and myelination. 43 ATG9A, a second cargo of AP-4, 14,44,45 provides another compelling molecular link to impaired development of structures that arise from the commissural plate.…”

Section: Discussionmentioning

confidence: 99%

“…There is emerging evidence that loss of AP-4 function impairs neurite outgrowth and axon guidance. [14][15][16]27,28 To expand on previous reports of polymicrogyria in AP-4-HSP, 3,29 we systematically reviewed all MRI studies for developmental brain malformations. In our cohort, 19/73 patients (26%) were found to have polymicrogyria, classified as definite polymicrogyria (11/19) or possible polymicrogyria or dysgyria (8/19).…”

Section: Developmental Brain Malformations and Evidence Of Brain Iron...mentioning

confidence: 99%

Systematic Analysis of Brain MRI Findings in Adaptor Protein Complex 4–Associated Hereditary Spastic Paraplegia

Ebrahimi‐Fakhari¹,

Alecu²,

Ziegler³

et al. 2021

Neurology

Self Cite

View full text Add to dashboard Cite

Background and Objectives:AP-4-associated hereditary spastic paraplegia (AP-4-HSP: SPG47, SPG50, SPG51, SPG52) is an emerging cause of childhood-onset hereditary spastic paraplegia and mimic of cerebral palsy. This study aims to define the spectrum of brain MRI findings in AP-4-HSP and to investigate radio-clinical correlations.Methods:A systematic qualitative and quantitative analysis of 107 brain MRI studies from 76 individuals with genetically-confirmed AP-4-HSP and correlation with clinical findings including surrogates of disease severity.Results:We define AP-4-HSP as a disorder of gray and white matter and demonstrate that abnormal myelination is common and that metrics of reduced white matter volume correlate with severity of motor symptoms. We identify a common diagnostic imaging signature consisting of (1) a thin splenium of the corpus callosum, (2) an absent or thin anterior commissure, (3) characteristic signal abnormalities of the forceps minor (“ears of the grizzly sign”), and (4) periventricular white matter abnormalities. The presence of two or more of these findings has a sensitivity of ∼99% for detecting AP-4-HSP, while the combination of all four is found in ∼45% of cases. Compared to other HSP with a thin corpus callosum, the absent anterior commissure appears to be specific to AP-4-HSP. Our analysis further identified a subset of AP-4-HSP patients with polymicrogyria, underscoring the role of AP-4 in early brain development. Of clinical importance, these patients displayed a higher prevalence of seizures and status epilepticus, many at a young age.Discussion:Our findings define the MRI spectrum of AP-4-HSP providing opportunities for early diagnosis, identification of individuals at risk for complications, and a window into the role of the AP-4 complex in brain development and neurodegeneration.

show abstract

“…[ 11 ] Last but not least, over 150 human disorders are caused by impaired intracellular protein transport; [ 12 ] mapping the underlying protein mislocalization events will not only provide a better understanding of the disease mechanisms, but also afford insights into fundamental cell biology. [ 13,14 ]…”

mentioning

confidence: 99%

Spatial Proteomics: A Gateway to Understanding Cell Biology

Borner

2020

Proteomics

Self Cite

View full text Add to dashboard Cite

AP-4 mediates vesicular transport of the 2-AG endocannabinoid producing enzyme DAGLB

Cited by 3 publications

References 37 publications

High-throughput imaging of ATG9A distribution as a diagnostic functional assay for adaptor protein complex 4-associated hereditary spastic paraplegia

High-throughput imaging of ATG9A distribution as a diagnostic functional assay for adaptor protein complex 4-associated hereditary spastic paraplegia

Systematic Analysis of Brain MRI Findings in Adaptor Protein Complex 4–Associated Hereditary Spastic Paraplegia

Spatial Proteomics: A Gateway to Understanding Cell Biology

Contact Info

Product

Resources

About