Expanding the clinical spectrum of COL1A1 mutations in different forms of glaucoma

Abstract

BackgroundPrimary congenital glaucoma (PCG) and early onset glaucomas are one of the major causes of children and young adult blindness worldwide. Both autosomal recessive and dominant inheritance have been described with involvement of several genes including CYP1B1, FOXC1, PITX2, MYOC and PAX6. However, mutations in these genes explain only a small fraction of cases suggesting the presence of further candidate genes.MethodsTo elucidate further genetic causes of these conditions whole exome sequencing (WES) was performed in an Italian patient, diagnosed with PCG and retinal detachment, and his unaffected parents. Sanger sequencing of the complete coding region of COL1A1 was performed in a total of 26 further patients diagnosed with PCG or early onset glaucoma. Exclusion of pathogenic variations in known glaucoma genes as CYP1B1, MYOC, FOXC1, PITX2 and PAX6 was additionally done per Sanger sequencing and Multiple Ligation-dependent Probe Amplification (MLPA) analysis.ResultsIn the patient diagnosed with PCG and retinal detachment, analysis of WES data identified compound heterozygous variants in COL1A1 (p.Met264Leu; p.Ala1083Thr). Targeted COL1A1 screening of 26 additional patients detected three further heterozygous variants (p.Arg253*, p.Gly767Ser and p.Gly154Val) in three distinct subjects: two of them diagnosed with early onset glaucoma and mild form of osteogenesis imperfecta (OI), one patient with a diagnosis of PCG at age 4 years. All five variants affected evolutionary, highly conserved amino acids indicating important functional restrictions. Molecular modeling predicted that the heterozygous variants are dominant in effect and affect protein stability and thus the amount of available protein, while the compound heterozygous variants act as recessive alleles and impair binding affinity to two main COL1A1 binding proteins: Hsp47 and fibronectin.ConclusionsDominant inherited mutations in COL1A1 are known causes of connective tissues disorders such as OI. These disorders are also associated with different ocular abnormalities, although recognition of the common pathology for both features is seldom being recognized. Our results expand the role of COL1A1 mutations in different forms of early-onset glaucoma with and without signs of OI. Thus, we suggest including COL1A1 mutation screening in the genetic work-up of glaucoma cases and detailed ophthalmic examinations with fundus analysis in patients with OI.Electronic supplementary materialThe online version of this article (doi:10.1186/s13023-016-0495-y) contains supplementary material, which is available to authorized users.

Generation of a Matrix Gla (Mgp) floxed mouse, followed by conditional knockout, uncovers a new Mgp function in the eye

“…As reasoned in Buie et al 67 , besides provoking an increase in calcification 68 , 69 , BMP2 could influence IOP by its consequent increases in Col1A1 67 , a trabecular meshwork ECM component, originally reported to be enhanced under glaucomatous conditions 70 . More recently Col1A1 has been found to be genetically linked to glaucoma cohorts 71 . In the same Buie’s paper 67 , it was also discussed the well-known crosstalk between BMP2 and the Wnt/β-catenin pathways and the activation of each of the pathways by the other 72 , 73 .…”

Updates on the molecular genetics of primary congenital glaucoma (Review)

“…Mutations in the COL1A1 gene are typically associated with skeletal and dermatological conditions, including Ehlers-Danlos syndrome, bone mineral density variation, osteoporosis and Caffey disease ( 90 ). Mauri et al ( 91 ) identified compound heterozygous variants of COL1A1 (p.Met264Leu; p.Ala1083Thr) in 26 patients with PCG by whole-exome sequencing. Collagen protein is a core component of the extracellular matrix (ECM) of the TM, SC and lamina cribrosa, all of which are ocular tissues involved in the development of glaucoma.…”

Physiological function of myocilin and its role in the pathogenesis of glaucoma in the trabecular meshwork (Review)

“…MYOC is detected in the aqueous humor and MYOC mutations are the most common type of mutation in patients with glaucoma (10), accounting for 10% of juvenile-onset open-angle glaucoma (JOAG) (11) and 2-4% of adult-onset POAG (12). JOAG, unlike adult-onset POAG, has a close genotype-phenotype association with regard to myocilin mutations and glaucoma, and typical signs include high intra-ocular pressure (IOP) (13,14), severe optic nerve damage and earlier age at onset (usually <40 years) (15,16), which, if left untreated, results in severe visual impairment (17).…”