Schottlaender, LV;
Abeti, R;
Jaunmuktane, Z;
Macmillan, C;
Chelban, V;
O'Callaghan, B;
McKinley, J;
Maroofian, R;
Efthymiou, S;
Athanasiou-Fragkouli, A;
et al.
Schottlaender, LV; Abeti, R; Jaunmuktane, Z; Macmillan, C; Chelban, V; O'Callaghan, B; McKinley, J; Maroofian, R; Efthymiou, S; Athanasiou-Fragkouli, A; Forbes, R; Soutar, MPM; Livingston, JH; Kalmar, B; Swayne, O; Hotton, G; SYNAPS Study Group; Pittman, A; Mendes de Oliveira, JR; de Grandis, M; Richard-Loendt, A; Launchbury, F; Althonayan, J; McDonnell, G; Carr, A; Khan, S; Beetz, C; Bisgin, A; Tug Bozdogan, S; Begtrup, A; Torti, E; Greensmith, L; Giunti, P; Morrison, PJ; Brandner, S; Aurrand-Lions, M; Houlden, H
(2020)
Bi-allelic JAM2 Variants Lead to Early-Onset Recessive Primary Familial Brain Calcification.
Am J Hum Genet, 106 (3).
pp. 412-421.
ISSN 1537-6605
https://doi.org/10.1016/j.ajhg.2020.02.007
SGUL Authors: Maroofian, Reza
Abstract
Primary familial brain calcification (PFBC) is a rare neurodegenerative disorder characterized by a combination of neurological, psychiatric, and cognitive decline associated with calcium deposition on brain imaging. To date, mutations in five genes have been linked to PFBC. However, more than 50% of individuals affected by PFBC have no molecular diagnosis. We report four unrelated families presenting with initial learning difficulties and seizures and later psychiatric symptoms, cerebellar ataxia, extrapyramidal signs, and extensive calcifications on brain imaging. Through a combination of homozygosity mapping and exome sequencing, we mapped this phenotype to chromosome 21q21.3 and identified bi-allelic variants in JAM2. JAM2 encodes for the junctional-adhesion-molecule-2, a key tight-junction protein in blood-brain-barrier permeability. We show that JAM2 variants lead to reduction of JAM2 mRNA expression and absence of JAM2 protein in patient's fibroblasts, consistent with a loss-of-function mechanism. We show that the human phenotype is replicated in the jam2 complete knockout mouse (jam2 KO). Furthermore, neuropathology of jam2 KO mouse showed prominent vacuolation in the cerebral cortex, thalamus, and cerebellum and particularly widespread vacuolation in the midbrain with reactive astrogliosis and neuronal density reduction. The regions of the human brain affected on neuroimaging are similar to the affected brain areas in the myorg PFBC null mouse. Along with JAM3 and OCLN, JAM2 is the third tight-junction gene in which bi-allelic variants are associated with brain calcification, suggesting that defective cell-to-cell adhesion and dysfunction of the movement of solutes through the paracellular spaces in the neurovascular unit is a key mechanism in CNS calcification.
Item Type: |
Article
|
Additional Information: |
© 2020 The Authors. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) |
Keywords: |
Fahr disease, JAM2, JAM3, MYORG, OCLN, SLC20A2, familial idiopathic basal ganglia calcification, knock out mouse model, primary familial brain calcification, recessive brain calcification, SYNAPS Study Group, Genetics & Heredity, 06 Biological Sciences, 11 Medical and Health Sciences |
SGUL Research Institute / Research Centre: |
Academic Structure > Molecular and Clinical Sciences Research Institute (MCS) |
Journal or Publication Title: |
Am J Hum Genet |
ISSN: |
1537-6605 |
Language: |
eng |
Dates: |
Date | Event |
---|
5 March 2020 | Published | 10 February 2020 | Accepted |
|
Publisher License: |
Creative Commons: Attribution 4.0 |
Projects: |
|
PubMed ID: |
32142645 |
Web of Science ID: |
WOS:000519101800017 |
![](http://static.pubmed.gov/portal/portal3rc.fcgi/2745237/img/27842) |
Go to PubMed abstract |
URI: |
https://openaccess.sgul.ac.uk/id/eprint/111822 |
Publisher's version: |
https://doi.org/10.1016/j.ajhg.2020.02.007 |
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