{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nSTRA6 is a multi‐transmembrane cell surface receptor that functions primarily as a high‐affinity transporter for vitamin A by binding circulating retinol–binding protein (RBP) to mediate retinol uptake. This activity initiates retinoic acid–dependent transcriptional cascades that are essential for normal embryogenesis and organogenesis, including the development of the eye, heart, lungs, and other tissues. Mutations in STRA6 lead to complex, pleiotropic developmental malformations such as anophthalmia/microphthalmia, cardiac defects, diaphragmatic hernia, and pulmonary dysgenesis, as described in several patient cohorts."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "4"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nStructural and mechanistic studies of STRA6 have revealed that its function not only depends on proper transmembrane orientation and integrity of extracellular loops but also on post‐translational modifications such as phosphorylation that are intimately linked to its ligand‐transfer activity. Detailed mutagenesis experiments have identified an essential RBP–binding domain and even provided evidence consistent with the existence of a transmembrane pore required for retinol transport. Disruption of these functional domains has been implicated in isolated ocular malformations and syndromic conditions."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "5", "end_ref": "10"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nBeyond its developmental role, STRA6 is increasingly recognized as an important mediator in metabolic and oncogenic processes. Its ability to function as a cytokine receptor—activating intracellular JAK/STAT signaling upon retinol uptake—has been linked to disturbances in insulin signaling and the development of insulin resistance, with interactions involving RBP4 and transthyretin modulating these effects. Moreover, up‐regulation of STRA6 is associated with enhanced tumorigenesis in colon cancer, and its genetic polymorphisms are correlated with gestational diabetes and type 2 diabetes, highlighting its involvement in metabolic disease."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "11", "end_ref": "16"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nSTRA6’s regulatory influence extends to multiple other physiological systems. In the skin, for example, STRA6 expression in keratinocytes governs retinoid homeostasis, affecting proliferation and differentiation essential for normal epidermal architecture. In mesenchymal stem cells, altered STRA6 levels have been implicated in the skewing of cell fate decisions toward adipogenesis at the expense of osteoblastogenesis, thereby contributing to the pathogenesis of osteoporosis. In the decidualizing endometrium, SRC-2–dependent induction of STRA6 underscores its role in reproductive biology. These studies underscore the broad impact of STRA6 in tissue-specific homeostasis."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "17", "end_ref": "21"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nEmerging evidence also reveals a role for STRA6 in cardiac development and further implicates its dysregulation in congenital heart defects through disrupted retinoic acid signaling. In addition, aberrant STRA6 expression has been identified as a potential prognostic marker and therapeutic target in cancers such as colorectal carcinoma, where it contributes to tumor cell proliferation and chemoresistance. These novel insights expand the functional repertoire of STRA6 beyond vitamin A transport, linking it to both developmental and disease‐related signaling networks."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "22"}]}, {"type": "t", "text": "\n"}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Francesca Pasutto, Heinrich Sticht, Gerhard Hammersen, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Mutations in STRA6 cause a broad spectrum of malformations including anophthalmia, congenital heart defects, diaphragmatic hernia, alveolar capillary dysplasia, lung hypoplasia, and mental retardation."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Am J Hum Genet (2007)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1086/512203"}], "href": "https://doi.org/10.1086/512203"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "17273977"}], "href": "https://pubmed.ncbi.nlm.nih.gov/17273977"}]}, {"type": "r", "ref": 2, "children": [{"type": "t", "text": "Christelle Golzio, Jelena Martinovic-Bouriel, Sophie Thomas, et al. 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