title: A novel mutation in transforming growth factor-beta induced protein (TGFβIp) reveals secondary structure perturbation in lattice corneal dystrophy.
abstract: BACKGROUND
  To describe mutations in the transforming growth factor-beta induced (TGFBI) gene in Asian patients with Bowman's membrane as well as stromal corneal dystrophies, and to elucidate their structural implications, using model peptides.
  
  
  METHODS
  Twenty-two unrelated Asian families were examined clinically including visual acuity testing and ocular examination with slit lamp biomicroscopy. Genomic DNA was extracted and the 17 exons of the TGFBI gene were amplified by PCR and sequenced bi-directionally. Biophysical techniques were used to characterise the wild type and mutant model peptides.
  
  
  RESULTS
  Molecular genetic analysis identified a variety of mutations in our patient series including a novel heterozygous C to A transversion mutation in exon 14 (c.1859C→A), resulting in a substitution of a highly conserved alanine residue by aspartic acid (p.A620D). Clinical presentation in the patient with the p.A620D included subepithelial scarring in addition to the linear branching opacities usually seen with lattice dystrophy. Using model peptides, we showed that A620D mutant peptide alters the secondary structure and conformational stability, and increased amyloid formation.
  
  
  CONCLUSIONS
  A novel mutation (A620D) in transforming growth factor-beta induced protein (TGFβIp) is described, expanding the repertoire of mutations in this protein. Using model peptides, we demonstrated that A→D substitution leads to perturbation of the secondary structure that may be responsible for the amyloid formation in lattice corneal dystrophy.
authors.affiliation: Singapore National Eye Centre, Singapore 168751, Singapore.
authors.forename: Rajamani
authors.initials: R
authors.lastname: Lakshminarayanan
authors.forename: Eranga N
authors.initials: EN
authors.lastname: Vithana
authors.forename: Shu-Ming
authors.initials: SM
authors.lastname: Chai
authors.forename: Shyam S
authors.initials: SS
authors.lastname: Chaurasia
authors.forename: Padhmanaban
authors.initials: P
authors.lastname: Saraswathi
authors.forename: Anandalaksmi
authors.initials: A
authors.lastname: Venkatraman
authors.forename: Camille
authors.initials: C
authors.lastname: Rojare
authors.forename: Divya
authors.initials: D
authors.lastname: Venkataraman
authors.forename: Donald
authors.initials: D
authors.lastname: Tan
authors.forename: Tin
authors.initials: T
authors.lastname: Aung
authors.forename: Roger W
authors.initials: RW
authors.lastname: Beuerman
authors.forename: Jodhbir S
authors.initials: JS
authors.lastname: Mehta
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000595:Amino Acid Sequence; D000682:Amyloid / Q000378:metabolism / Q000648:ultrastructure; D044466:Asian People / Q000235:genetics; D052160:Benzothiazoles; D050541:Bowman Membrane / Q000473:pathology; D002648:Child; D002942:Circular Dichroism; D015350:Contrast Sensitivity / Q000502:physiology; D003317:Corneal Dystrophies, Hereditary / Q000235:genetics* / Q000473:pathology; D003319:Corneal Stroma / Q000473:pathology; D018360:Crystallography, X-Ray; D016326:Extracellular Matrix Proteins / Q000235:genetics*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation; D016133:Polymerase Chain Reaction; D012029:Refraction, Ocular / Q000502:physiology; D013844:Thiazoles; D016212:Transforming Growth Factor beta / Q000235:genetics*; D014792:Visual Acuity / Q000502:physiology; D000099222:betaIG-H3 Protein
chemical_list: D000682:Amyloid; D052160:Benzothiazoles; D016326:Extracellular Matrix Proteins; D013844:Thiazoles; D016212:Transforming Growth Factor beta; D000099222:betaIG-H3 Protein; C009462:thioflavin T