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Ophthalmology
Published in Stephan Strobel, Lewis Spitz, Stephen D. Marks, Great Ormond Street Handbook of Paediatrics, 2019
It is often associated with hypermetropia, colobomas of the iris, cataracts, persistent hyperplastic primary vitreous, retinopathy of prematurity, angle closure glaucoma, infantile glaucoma and chronic open angle glaucoma. Systemic associations include Ehlers–Danlos syndrome, Marfan syndrome, Rieger syndrome, Norrie syndrome, Trisomy 21 (Down syndrome), progeria, rubella, Turner syndrome, Waardenburg syndrome, Weil–Marchesani syndrome, Warburg micro syndrome, cataract microcornea syndrome and acroreno-ocular syndrome.
Identification of novel cis-mutations in the GJA8 gene in a 3-generation Iranian family with autosomal dominant congenital nuclear cataract
Published in Ophthalmic Genetics, 2022
Neda Jabbarpour, Hassan Saei, Mohammad Hossein Jabbarpoor Bonyadi, Mortaza Bonyadi
Congenital cataracts are clinically and genetically diverse. There are more than 300 genes identified to be involved in the development of congenital cataract, including syndromic and non-syndromic cataracts (1). Non-syndromic cataracts are inherited in 8.3 to 25% of cases, of which 76–89% are inherited as autosomal dominant, 7% as autosomal recessive, and 2–10% as X-linked. Congenital cataract, which could lead to blindness or amblyopia in infants, is estimated to have an incidence of 1 to 6 in 10,000 live birth (2). The C × 50 and C × 46‘s N-terminal domains are hotspots for genetic variants related to congenital cataracts (1). Gap junction proteins, encoded by connexin family of genes (abbreviated CX), are frequently identified by their molecular weights, for example, C × 50 (GJA8) is the 50 kDa connexin protein. An alternative nomenclature is the gap junction protein system, which classifies connexins according to their α (GJA) and β (GJB) forms (3). These proteins provide a pathway for the intercellular exchanges of ions, small metabolites, and second messengers which are essential for cell synchronization, growth and development (4). Three connexin isoforms known as C × 43, C × 46, and C × 50 are reported to be expressed in mammalian lens (5). Gap Junction protein alpha-8 (GJA8) gene encodes a transmembrane connexin protein (CX50) essential for the maturation of lens fiber cells and their growth. This protein is a connexin of the ocular lens, which maintains ionic and water balance and transparency and optical properties of the lens (6). Several previous studies have shown the association of this gene with zonular pulverulent cataracts, nuclear progressive cataracts, and cataract-microcornea syndrome with autosomal dominant pattern in the pedigree (7–10).