TMX2 Is a Crucial Regulator of Cellular Redox State, and Its Dysfunction Causes Severe Brain Developmental Abnormalities

Scientific paper - Original scientific paper

• Author: Laura V. Vandervore
• Author: ...
• Author: Nataša Jovanov Milošević
• Author: ...
• Author's institution: University of Zagreb; School of Medicine; (Croatian Institiute for Brain Research)
• Author's institution: University of Zagreb; School of Medicine; (Department of Medical Biology)
• Scientific / art field, discipline and subdiscipline: BIOMEDICINE AND HEALTHCARE; Clinical Medical Sciences; Clinical Cytology
• Scientific / art field, discipline and subdiscipline: BIOMEDICINE AND HEALTHCARE; Clinical Medical Sciences; Neurology

Abstract (english)

The redox state of the neural progenitors regulates physiological processes such as neuronal differentiation and dendritic and axonal growth. The relevance of endoplasmic reticulum (ER)-associated oxidoreductases in these processes is largely unexplored. We describe a severe neurological disorder caused by bi-allelic loss-of-function variants in thioredoxin (TRX)-related transmembrane-2 (TMX2); these variants were detected by exome sequencing in 14 affected individuals from ten unrelated families presenting with congenital microcephaly, cortical polymicrogyria, and other migration disorders. TMX2 encodes one of the five TMX proteins of the protein disulfide isomerase family, hitherto not linked to human developmental brain disease. Our mechanistic studies on protein function show that TMX2 localizes to the ER mitochondria-associated membranes (MAMs), is involved in posttranslational modification and protein folding, and undergoes physical interaction with the MAM-associated and ER folding chaperone calnexin and ER calcium pump SERCA2. These interactions are functionally relevant because TMX2-deficient fibroblasts show decreased mitochondrial respiratory reserve capacity and compensatory increased glycolytic activity. Intriguingly, under basal conditions TMX2 occurs in both reduced and oxidized monomeric form, while it forms a stable dimer under treatment with hydrogen peroxide, recently recognized as a signaling molecule in neural morphogenesis and axonal pathfinding. Exogenous expression of the pathogenic TMX2 variants or of variants with an in vitro mutagenized TRX domain induces a constitutive TMX2 polymerization, mimicking an increased oxidative state. Altogether these data uncover TMX2 as a sensor in the MAM-regulated redox signaling pathway and identify it as a key adaptive regulator of neuronal proliferation, migration, and organization in the developing brain.

• Keywords (english): Adolescent; Adult; Brain / abnormalities; Brain Diseases / genetics; Brain Diseases / metabolism; Brain Diseases / pathology; Child; Child, Preschool; Cohort Studies; Developmental Disabilities / genetics; Developmental Disabilities / metabolism; Developmental Disabilities / pathology; Female; Fibroblasts / metabolism; Fibroblasts / pathology; Follow-Up Studies; Humans; Infant; Infant, Newborn; Male; Membrane Proteins / genetics; Membrane Proteins / metabolism; Mitochondria / metabolism; Mitochondria / pathology; Oxidation-Reduction; Prognosis; Skin / metabolism; Skin / pathology; Thioredoxins / genetics; Thioredoxins / metabolism; Transcriptome
• Language: english
• Publication type: Scientific paper - Original scientific paper
• Publication status: Published
• Peer review: Peer review
• Publication version: Published version
• Journal title: The American Journal of Human Genetics
• Numbering: vol. 105, no. 6, pp. 1126-1147
• p-ISSN: 0002-9297
• e-ISSN: 1537-6605
• DOI: https://doi.org/10.1016/j.ajhg.2019.10.009
• URN:NBN: urn:nbn:hr:105:093095
• Publication: 2019-12-05
• Document URL: https://linkinghub.elsevier.com/retrieve/pii/S0002929719303970
• Type of resource: Text
• Access conditions: Open access
• Created on: 2021-01-12 10:16:35